Were Ichthyosaurs Ovoviviparous, or Viviparous?

[Peter Nyikos]

All books on paleontology that go into detail about Ichthyosaurs agree that
they gave live birth: the fossil evidence for that is overwhelming.

The only ones I've found that discuss what happens before the live birth
are Romer's 1945 text, and Colbert's 1955 _Evolution_of_the_Vertebrates_,
which agree that they were ovoviviparous. Colbert writes:

So it is evident that these reptiles were ovoviviparous -- that they retained the egg within the body until it was hatched, as do some modern lizards and snakes. [*ibid*, p. 162]

In contrast, Carroll only has a photo of a fossil of an ichthyosaur giving live birth,
but no mention in the running text about it. The third edition of Benton's text
also makes no mention of the issue.

Wikipedia's entry simply claims they are viviparous and references an 1846
[NOT 1946] article by J.C. Pearce for it.

In a case of the left hand not knowing what the right hand is doing (and vice versa),
the entry on viviparity broadens the meaning of the term and distinguishes
four different varieties
among extant animals, giving examples of each kind. One of them is ovoviviparity,
which it seems to want to demote to a variety of oviparity.
https://en.wikipedia.org/wiki/Viviparity


Of course, it is difficult if not impossible to decide whether ichthyosaurs were
viviparous or ovoviviparous. It could even depend on the genera.
It is conceivable that some soft tissues could be found preserved in some
Konservat-Lagerstätten.
Either bits of fossilized egg membrane (or shell??) or something like an umbilical cord
could tip the scales heavily one way or the other.


Does anyone here have any ideas for other (probably much weaker)
evidence for one form or the other?


Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of South Carolina
http://people.math.sc.edu/nyikos

[John Harshman]

It seems unlikely that any sort of evidence could be preserved. It also
seems unlikely that an ovoviviparous ichthyosaur would have hard-shelled
eggs. Whatever evidence did Romer use for his claim? Phylogenetic
bracketing, perhaps?

[erik simpson]

Evidence for viviparity in ichthyosaurs having appeared in land-living ancestors:

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0088640
https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0088640&type=printable (open access)

[Peter Nyikos]

On Friday, August 26, 2022 at 11:37:49 AM UTC-4, erik simpson wrote:
> On Friday, August 26, 2022 at 6:39:46 AM UTC-7, peter2...@gmail.com wrote:
> > All books on paleontology that go into detail about Ichthyosaurs agree that
> > they gave live birth: the fossil evidence for that is overwhelming.
> >
> > The only ones I've found that discuss what happens before the live birth
> > are Romer's 1945 text, and Colbert's 1955 _Evolution_of_the_Vertebrates_,
> > which agree that they were ovoviviparous. Colbert writes:
> >
> > So it is evident that these reptiles were ovoviviparous -- that they retained the egg within the body until it was hatched, as do some modern lizards and snakes. [*ibid*, p. 162]
> >

> > In contrast, Carroll [1988] only has a photo of a fossil of an ichthyosaur giving live birth,

Two copies of the same article, as far as I could tell.

Unfortunately, the authors' argument for viviparity is very weak.
The following seems to be as close as they try to come:

Viviparity in extant reptiles is known only among squamates. Despite the traditional four-step evolutionary model from lecithotrophy to placentotrophy, squamate reproductive strategies are almost bimodally divided between oviparity (egg laying), including cases of egg retention up to limb-bud stage, and viviparity involving functional placentation [2], with few intermediate forms [22]. Therefore, viviparity seems to evolve simultaneously with functional placentation in squamates [23]. Given these observations, it would be reasonable if viviparity in Chaohusaurus involved a degree of placentation. However, this inference cannot be tested directly with fossil evidence because the soft tissue is not preserved.

[22] is linked to a mere abstract via Google Scholar, while "View Article" just takes us back
to the article itself! The same goes for [23].

My time today for posting is limited, so for the moment I have to fall back on Wikipedia,
specifically the link I gave earlier, https://en.wikipedia.org/wiki/Viviparity and the following:

https://en.wikipedia.org/wiki/Ovoviviparity

Unfortunately, this gives no reptilian examples, while the other website only has this:

"Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae)."

There is a link for "vipers," but its talk of their reproduction only takes us back to
https://en.wikipedia.org/wiki/Viviparity


Looks like we need to borrow a term from chess for this kind of frustration:

"Draw by perpetual check" :)

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--

Univ. of South Carolina at Columbia
http://people.math.sc.edu/nyikos

[erik simpson]

I knew I'd seen something about this and I found the paper in my collection of PDFs. Checking online, it's
still there as I cited. Both cite are the same, one (potentially?) paywalled.

From the paper "squamate reproductive strategies are almost bimodally divided between oviparity (egg laying), including
cases of egg retention up to limb-bud stage, and viviparity involving functional placentation, with few
intermediate forms." (Refences cited in the paper)

The Wiki entry does suggest caution with the use of the term ovoviviparity as "poorly and inconsistently defined, and may be obsolete.
This term has been redefined and more commonly referred to as oviparous egg retention or prolonged egg retention."

So yeah, ichthyosaurs aren't squamates, and there's no evidence of egg retention, but I don't see any need to
be frustrated. Again, from the paper: "Given these observations, it would be reasonable if viviparity in Chaohusaurus

[Peter Nyikos]

I've found myself with a bit of unexpected free time, but even so,
this might be my last post to s.b.p. until Monday.

In your reply, Erik, you are repeating two subsets of what is in the following paragraph.

> > Viviparity in extant reptiles is known only among squamates. Despite the traditional four-step evolutionary model from lecithotrophy to placentotrophy, squamate reproductive strategies are almost bimodally divided between oviparity (egg laying), including cases of egg retention up to limb-bud stage, and viviparity involving functional placentation [2], with few intermediate forms [22]. Therefore, viviparity seems to evolve simultaneously with functional placentation in squamates [23]. Given these observations, it would be reasonable if viviparity in Chaohusaurus involved a degree of placentation. However, this inference cannot be tested directly with fossil evidence because the soft tissue is not preserved.
> >
> > [22] is linked to a mere abstract via Google Scholar, while "View Article" just takes us back
> > to the article itself! The same goes for [23].
> >
> > My time today for posting is limited, so for the moment I have to fall back on Wikipedia,
> > specifically the link I gave earlier, https://en.wikipedia.org/wiki/Viviparity and the following:
> >
> > https://en.wikipedia.org/wiki/Ovoviviparity
> >
> > Unfortunately, this gives no reptilian examples, while the other website only has this:
> >
> > "Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae)."

The frustration I talk about below is inability to find out whether some vipers
are viviparous and others are ovoviviparous.

> >
> > There is a link for "vipers," but its talk of their reproduction only takes us back to
> > https://en.wikipedia.org/wiki/Viviparity
> >
> >
> > Looks like we need to borrow a term from chess for this kind of frustration:
> >
> > "Draw by perpetual check" :)

> I knew I'd seen something about this and I found the paper in my collection of PDFs. Checking online, it's
> still there as I cited. Both cite are the same, one (potentially?) paywalled.
>
> From the paper "squamate reproductive strategies are almost bimodally divided between oviparity (egg laying), including
> cases of egg retention up to limb-bud stage, and viviparity involving functional placentation, with few
> intermediate forms." (Refences cited in the paper)

This is the first subset that I mentioned above.

>
> The Wiki entry does suggest caution with the use of the term ovoviviparity as "poorly and inconsistently defined, and may be obsolete.
> This term has been redefined and more commonly referred to as oviparous egg retention or prolonged egg retention."

With reptiles there does not seem to be any problem, because AFAIK the live offspring are miniatures
[roughly speaking, like with us humans] of their parents.

Not so with mammals, though: marsupials and even some placentals have their live births in a stage
like the late embryo or early fetus of humans.

A similar problem comes with amphibians, whether the live birth is of the larval or of the adult form. Both forms are found:

The young of some ovoviviparous amphibians, such as Limnonectes larvaepartus, are born as larvae, and undergo further metamorphosis outside the body of the mother. Members of genera Nectophrynoides and Eleutherodactylus bear froglets, not only the hatching, but all the most conspicuous metamorphosis, being completed inside the body of the mother before birth.
-- https://en.wikipedia.org/wiki/Ovoviviparity

>
> So yeah, ichthyosaurs aren't squamates, and there's no evidence of egg retention,

...the alternatives being the following:

Histotrophic viviparity: the zygotes develop in the female's oviducts, but find their nutriments by oophagy or adelphophagy (intra-uterine cannibalism of eggs or sibling embryos in some sharks or in the black salamander Salamandra atra).
Hemotrophic viviparity: nutrients are provided by the female, often through some form of placenta. In the frog Gastrotheca ovifera, embryos are fed by the mother through specialized gills. The skink Pseudemoia entrecasteauxii and most mammals exhibit a hemotrophic viviparity.
Placental viviparity is arguably the most highly developed form of viviparity. Placental mammals, including humans, are the best-known example, but adaptations in some other animals also have incorporated this principle or close analogies. Other examples include some species of scorpions[5] and cockroaches,[6][7] certain genera of sharks and snakes, and velvet worms.
https://en.wikipedia.org/wiki/Viviparity

More frustration: I have no clue as to where the author draws the line between Hemotrophic viviparity and Placental viviparity.
There is a link for the latter -- just click on "Placental viviparity" -- but it is utterly useless for that purpose:

"Placentas are a defining characteristic of placental mammals, but are also found in marsupials"
https://en.wikipedia.org/wiki/Placenta
...which strongly contradicts "most mammals exhibit a hemotrophic viviparity." [See above.]

Now, I've known about many different kinds of mammalian placentas for decades,
with varying degrees of inte]rpenetration and whether they are choriovitelline [marsupials]
or chorioallantoic [most placentals but NOT primates, where the allantois is vestigial]
and this heightens my frustration.

> but I don't see any need to be frustrated. Again, from the paper: "Given these observations, it would be reasonable if viviparity in Chaohusaurus
> involved a degree of placentation. However, this inference cannot be tested directly with fossil evidence because the
> soft tissue is not preserved."

This is the second subset of what I quoted, and is why I find vipers so frustrating.
For all I know, they might be mostly viviparous [which would make the inference "reasonable"]
or all ovoviviparous [which would make the inference almost untenable, given the variety of vipers].


You aren't contributing anything to the on-topic discussion in this second post of yours, Erik.

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--

Univ. of South Carolina in Columbia
http://people.math.sc.edu/nyikos

[Peter Nyikos]

On Friday, August 26, 2022 at 6:32:49 PM UTC-4, Peter Nyikos wrote:

> You aren't contributing anything to the on-topic discussion in this second post of yours, Erik.

Minor technical exception: you completed the three-line description of Ovoviviparity in
https://en.wikipedia.org/wiki/Viviparity
of which I had posted the first sentence.

[Sight Reader]

Wasn’t there something about reptile eggs needing to breathe or something? I supose amphibian eggs can be underwater; are reptile eggs the same way?

[erik simpson]

You're contributing what I see as a substantial digression into Mammalia. As for vipers, "squamate reproductive

strategies are almost bimodally divided between oviparity (egg laying), including cases of egg retention up to limb-bud stage,

and viviparity involving functional placentation". I don't understand what's frustrating.

[erik simpson]

On Friday, August 26, 2022 at 3:47:42 PM UTC-7, thesigh...@gmail.com wrote:
> Wasn’t there something about reptile eggs needing to breathe or something? I supose amphibian eggs can be underwater; are reptile eggs the same way?

Once laid, eggs certainly do need to breathe (egg shells allow for this). I'm not sure what goes on in "retained" eggs.

[Peter Nyikos]

On Friday, August 26, 2022 at 7:16:18 PM UTC-4, erik simpson wrote:
> On Friday, August 26, 2022 at 3:42:40 PM UTC-7, peter2...@gmail.com wrote:
> > On Friday, August 26, 2022 at 6:32:49 PM UTC-4, Peter Nyikos wrote:
> >
> > > You aren't contributing anything to the on-topic discussion in this second post of yours, Erik.

> > Minor technical exception: you completed the three-line description of Ovoviviparity in
> > https://en.wikipedia.org/wiki/Viviparity
> > of which I had posted the first sentence.

> You're contributing what I see as a substantial digression into Mammalia. As for vipers, "squamate reproductive
> strategies are almost bimodally divided between oviparity (egg laying), including cases of egg retention up to limb-bud stage,
> and viviparity involving functional placentation". I don't understand what's frustrating.

The fact that the claim could be wrong [see reasoning below], and thus being used fallaciously to support
viviparity in ichthyosaurs, which is at the exact resonant center of this thread.

I guess the shortness of the post attracted you like a magnet, causing you
to miss out on the original post, including the following reasoning:

___________________________ first excerpt from the original post_________________

> but I don't see any need to be frustrated. Again, from the paper: "Given these observations, it would be reasonable if viviparity in Chaohusaurus
> involved a degree of placentation. However, this inference cannot be tested directly with fossil evidence because the
> soft tissue is not preserved."

This is the second subset of what I quoted, and is why I find vipers so frustrating.
For all I know, they might be mostly viviparous [which would make the inference "reasonable"]
or all ovoviviparous [which would make the inference almost untenable, given the variety of vipers].

======================== end of first excerpt =======================

And here is why the "Given" is seriously affected:

######################## second excerpt from the original post #####################

> From the paper "squamate reproductive strategies are almost bimodally divided between oviparity (egg laying), including
> cases of egg retention up to limb-bud stage, and viviparity involving functional placentation, with few
> intermediate forms." (Refences cited in the paper)

This is the first subset that I mentioned above.

************************************************************ end of second excerpt
from
https://groups.google.com/g/sci.bio.paleontology/c/X2eRy1wQf8U/m/4I_chwJ8AQAJ
Re: Were Ichthyosaurs Ovoviviparous, or Viviparous?

And, lest your memory fail you between the first repost and the second, compare:

"make the inference almost untenable, given the variety of vipers".

and
> "almost bimodally, ... with few intermediate forms."


Capice?

Peter Nyikos
Professor, Dept. of Mathematics

Univ. of South Carolina -- standard disclaimer--
http://people.math.sc.edu/nyikos

[John Harshman]

On 8/26/22 5:12 PM, Peter Nyikos wrote:
> On Friday, August 26, 2022 at 7:16:18 PM UTC-4, erik simpson wrote:
>> On Friday, August 26, 2022 at 3:42:40 PM UTC-7, peter2...@gmail.com wrote:
>>> On Friday, August 26, 2022 at 6:32:49 PM UTC-4, Peter Nyikos wrote:
>>>
>>>> You aren't contributing anything to the on-topic discussion in this second post of yours, Erik.
>
>>> Minor technical exception: you completed the three-line description of Ovoviviparity in
>>> https://en.wikipedia.org/wiki/Viviparity
>>> of which I had posted the first sentence.
>
>> You're contributing what I see as a substantial digression into Mammalia. As for vipers, "squamate reproductive
>> strategies are almost bimodally divided between oviparity (egg laying), including cases of egg retention up to limb-bud stage,
>> and viviparity involving functional placentation". I don't understand what's frustrating.
>
> The fact that the claim could be wrong [see reasoning below], and thus being used fallaciously to support
> viviparity in ichthyosaurs, which is at the exact resonant center of this thread.

If you want to find about whether the claims in that paper are wrong,
you should consult the references cited to support the claims. In this
case that would seem to be references 2 and 22.

> I guess the shortness of the post attracted you like a magnet, causing you
> to miss out on the original post, including the following reasoning:
>
> ___________________________ first excerpt from the original post_________________
>
>> but I don't see any need to be frustrated. Again, from the paper: "Given these observations, it would be reasonable if viviparity in Chaohusaurus
>> involved a degree of placentation. However, this inference cannot be tested directly with fossil evidence because the
>> soft tissue is not preserved."
>
> This is the second subset of what I quoted, and is why I find vipers so frustrating.
> For all I know, they might be mostly viviparous [which would make the inference "reasonable"]
> or all ovoviviparous [which would make the inference almost untenable, given the variety of vipers].

Apparently, "ovoviviparous" is ambiguous and not a useful term.
Apparently, retention of the eggs until hatching (or birth, if you
prefer) requires maternal nourishment of the eggs, at least in squamates.

> ======================== end of first excerpt =======================
>
> And here is why the "Given" is seriously affected:
>
> ######################## second excerpt from the original post #####################
>
>> From the paper "squamate reproductive strategies are almost bimodally divided between oviparity (egg laying), including
>> cases of egg retention up to limb-bud stage, and viviparity involving functional placentation, with few
>> intermediate forms." (Refences cited in the paper)
>
> This is the first subset that I mentioned above.
>
> ************************************************************ end of second excerpt
> from
> https://groups.google.com/g/sci.bio.paleontology/c/X2eRy1wQf8U/m/4I_chwJ8AQAJ
> Re: Were Ichthyosaurs Ovoviviparous, or Viviparous?
>
> And, lest your memory fail you between the first repost and the second, compare:
>
> "make the inference almost untenable, given the variety of vipers".
> and
>> "almost bimodally, ... with few intermediate forms."

The second quote would seem to entail that the first quote is wrong.
Have you tried looking at the cited references? Have you searched for a
review of squamate viviparity?

Here's one: https://rep.bioscientifica.com/view/journals/rep/147/1/R15.xml

Abstract: Squamate reptiles (lizards and snakes) are an ideal model
system for testing hypotheses regarding the evolution of viviparity
(live birth) in amniote vertebrates. Viviparity has evolved over 100
times in squamates, resulting in major changes in reproductive
physiology. At a minimum, all viviparous squamates exhibit placentae
formed by the appositions of maternal and embryonic tissues, which are
homologous in origin with the tissues that form the placenta in therian
mammals. These placentae facilitate adhesion of the conceptus to the
uterus as well as exchange of oxygen, carbon dioxide, water, sodium, and
calcium. However, most viviparous squamates continue to rely on yolk for
nearly all of their organic nutrition. In contrast, some species, which
rely on the placenta for at least a portion of organic nutrition,
exhibit complex placental specializations associated with the transport
of amino acids and fatty acids. Some viviparous squamates also exhibit
reduced immunocompetence during pregnancy, which could be the result of
immunosuppression to protect developing embryos. Recent molecular
studies using both candidate-gene and next-generation sequencing
approaches have suggested that at least some of the genes and gene
families underlying these phenomena play similar roles in the uterus and
placenta of viviparous mammals and squamates. Therefore, studies of the
evolution of viviparity in squamates should inform hypotheses of the
evolution of viviparity in all amniotes, including mammals.

Here's another: https://pubmed.ncbi.nlm.nih.gov/21573966/

There are more, but you can google.
> Capice?

This would be a better discussion if you didn't resort to condescension
so early into it.

[Peter Nyikos]

On Friday, August 26, 2022 at 6:47:42 PM UTC-4, thesigh...@gmail.com wrote:
> Wasn’t there something about reptile eggs needing to breathe or something? I supose amphibian eggs can be underwater; are reptile eggs the same way?

No. In fact, turtles always lay their eggs on land, and some will go to great distances to do it:

Turtles, including sea turtles, lay their eggs on land, although some lay eggs close near water that rises and falls in level, submerging the eggs. While most species build nests and lay eggs where they forage, some travel miles. The common snapping turtle walks 5 km (3 mi) on land, while sea turtles travel even further; the leatherback swims some 12,000 km (7,500 mi) to its nesting beaches.[13][85]
https://en.wikipedia.org/wiki/Turtle#Eggs_and_hatchlings

This makes sea turtles highly vulnerable to humans with a taste for turtle eggs,
and the fact that beaches are such a popular destination makes the situation worse.

Here in South Carolina, signs are posted telling people not to
disturb turtles in the process of laying eggs, nor to dig on the beaches
at designated areas that are known to be favored for egg laying.


Back to the differences: the very thing that separates amniotes
from amphibians is the extraembryonic members [1], of which the chorion and amnion
keep the embryo from drying out. Hence common snapping turtles seem
to specifically want to get away from water, as the quote from Wikipedia above suggests.

[1] In this context, "membrane" is a mis-translation of the Latin "membranum"; granted,
the amnion is a membrane in the usual sense of the word.

I've been wondering for a long time about something that the Wiki excerpt
addresses with:

"some lay eggs close near water that rises and falls in level, submerging the eggs."

So it looks like some turtle eggs are dependent on water to some extent.

Here is what I've been wondering about. With few exceptions, turtles
(snapping turtles are a well known exception) have soft-shelled eggs, and
perhaps it is important for the ground in which they are laid to remain moist.

Or perhaps not for some species; perhaps some also need a drying-out period, like low tide on the beach.

Does anyone reading this know more about this?

[Sight Reader]

Sorry everyone, Mr. Slow here again (I’m the one for whom the saying, “He who laughs last did not get the joke” was invented)

Anyway, would it be correct to summarize the above as saying that reptiles evolved from true “egg laying” to simply keeping eggs within the body until they “hatched” several times within their history? I guess that would make the difference between external egg laying and viviparous birth more of continuum than a hard line.

Would it be possible for something like Ichthyosaur eggs to evolve “backwards” from a hard reptilian shell egg back to goopy, unshelled, caviar-like blobs of jelly?

[Peter Nyikos]

On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
> On 8/26/22 5:12 PM, Peter Nyikos wrote:
> > On Friday, August 26, 2022 at 7:16:18 PM UTC-4, erik simpson wrote:
> >> On Friday, August 26, 2022 at 3:42:40 PM UTC-7, peter2...@gmail.com wrote:
> >>> On Friday, August 26, 2022 at 6:32:49 PM UTC-4, Peter Nyikos wrote:
> >>>
> >>>> You aren't contributing anything to the on-topic discussion in this second post of yours, Erik.
> >
> >>> Minor technical exception: you completed the three-line description of Ovoviviparity in
> >>> https://en.wikipedia.org/wiki/Viviparity
> >>> of which I had posted the first sentence.
> >
> >> You're contributing what I see as a substantial digression into Mammalia. As for vipers, "squamate reproductive
> >> strategies are almost bimodally divided between oviparity (egg laying), including cases of egg retention up to limb-bud stage,
> >> and viviparity involving functional placentation". I don't understand what's frustrating.
> >
> > The fact that the claim could be wrong [see reasoning below], and thus being used fallaciously to support
> > viviparity in ichthyosaurs, which is at the exact resonant center of this thread.

> If you want to find about whether the claims in that paper are wrong,
> you should consult the references cited to support the claims. In this
> case that would seem to be references 2 and 22.

[2] doesn't even use the term "ovoviviparous". It could, of course, be paraphrased
somewhere, but it's getting late and so I'm postponing this project for the weekend,
which means reporting on anything relevant on Monday or Tuesday.

As for [22], what I posted on that earlier was preserved in the post that neither Erik
nor you have shown any sign of having read, preferring the small correction which
followed it almost immediately.

[repost from uncorrected post]

> > [22] is linked to a mere abstract via Google Scholar, while "View Article" just takes us back
> > to the article itself! The same goes for [23].

[end of repost]

I'll try to Google them on ResearchGate, like I did the reference you gave me next, but the
same thing applies that applies above.

> > I guess the shortness of the post attracted you like a magnet, causing you
> > to miss out on the original post, including the following reasoning:
> >
> > ___________________________ first excerpt from the original post_________________
> >
> >> but I don't see any need to be frustrated. Again, from the paper: "Given these observations, it would be reasonable if viviparity in Chaohusaurus
> >> involved a degree of placentation. However, this inference cannot be tested directly with fossil evidence because the
> >> soft tissue is not preserved."
> >
> > This is the second subset of what I quoted, and is why I find vipers so frustrating.
> > For all I know, they might be mostly viviparous [which would make the inference "reasonable"]
> > or all ovoviviparous [which would make the inference almost untenable, given the variety of vipers].

> Apparently, "ovoviviparous" is ambiguous and not a useful term.
> Apparently, retention of the eggs until hatching (or birth, if you
> prefer) requires maternal nourishment of the eggs, at least in squamates.

What is the reasoning/reference behind "Apparently"?

> > ======================== end of first excerpt =======================
> >
> > And here is why the "Given" is seriously affected:
> >
> > ######################## second excerpt from the original post #####################
> >
> >> From the paper "squamate reproductive strategies are almost bimodally divided between oviparity (egg laying), including
> >> cases of egg retention up to limb-bud stage, and viviparity involving functional placentation, with few
> >> intermediate forms." (Refences cited in the paper)
> >
> > This is the first subset that I mentioned above.
> >
> > ************************************************************ end of second excerpt
> > from
> > https://groups.google.com/g/sci.bio.paleontology/c/X2eRy1wQf8U/m/4I_chwJ8AQAJ
> > Re: Were Ichthyosaurs Ovoviviparous, or Viviparous?
> >
> > And, lest your memory fail you between the first repost and the second, compare:
> >
> > "make the inference almost untenable, given the variety of vipers".
> > and
> >> "almost bimodally, ... with few intermediate forms."

> The second quote would seem to entail that the first quote is wrong.
> Have you tried looking at the cited references? Have you searched for a
> review of squamate viviparity?

There has been too little time for that. The whole topic of this thread came
as a brainstorm as I was lying awake this morning around 6 am.
Until then the issue had never occurred to me.

>
> Here's one: https://rep.bioscientifica.com/view/journals/rep/147/1/R15.xml
>
> Abstract: Squamate reptiles (lizards and snakes) are an ideal model
> system for testing hypotheses regarding the evolution of viviparity
> (live birth) in amniote vertebrates. Viviparity has evolved over 100
> times in squamates, resulting in major changes in reproductive
> physiology. At a minimum, all viviparous squamates exhibit placentae
> formed by the appositions of maternal and embryonic tissues, which are
> homologous in origin with the tissues that form the placenta in therian
> mammals. These placentae facilitate adhesion of the conceptus to the
> uterus as well as exchange of oxygen, carbon dioxide, water, sodium, and
> calcium. However, most viviparous squamates continue to rely on yolk for
> nearly all of their organic nutrition. In contrast, some species, which
> rely on the placenta for at least a portion of organic nutrition,
> exhibit complex placental specializations associated with the transport
> of amino acids and fatty acids. Some viviparous squamates also exhibit
> reduced immunocompetence during pregnancy, which could be the result of
> immunosuppression to protect developing embryos. Recent molecular
> studies using both candidate-gene and next-generation sequencing
> approaches have suggested that at least some of the genes and gene
> families underlying these phenomena play similar roles in the uterus and
> placenta of viviparous mammals and squamates. Therefore, studies of the
> evolution of viviparity in squamates should inform hypotheses of the
> evolution of viviparity in all amniotes, including mammals.

Thanks, that may be the first paper I look up.

> Here's another: https://pubmed.ncbi.nlm.nih.gov/21573966/
>
> There are more, but you can google.
> > Capice?
>
> This would be a better discussion if you didn't resort to condescension
> so early into it.

This from someone who has treated me with gratuitous condescension
in talk.origins for almost a dozen years, and in sci.bio.paleontology for about
half as long, with two completely contrasting breaks: Thrinaxodon (later nym: Oxyaena) almost
destroying s.b.p with relentless crazy spam, and what I call the Oasis
of Civilization Period, which lasted from mid-2015 to early 2018.

But, on a less aggressive note, the discussion seemed to have
died out until you and Sight Reader came along.


Peter Nyikos

[John Harshman]

On 8/26/22 6:28 PM, Sight Reader wrote:
> Sorry everyone, Mr. Slow here again (I’m the one for whom the saying, “He who laughs last did not get the joke” was invented)
>
> Anyway, would it be correct to summarize the above as saying that reptiles evolved from true “egg laying” to simply keeping eggs within the body until they “hatched” several times within their history?

Apparently not, based on the literature I've seen. There are 108
evolutions of viviparity in squamates, but every one of them involves
more than just keeping the eggs inside.

> I guess that would make the difference between external egg laying and viviparous birth more of continuum than a hard line.
>
> Would it be possible for something like Ichthyosaur eggs to evolve “backwards” from a hard reptilian shell egg back to goopy, unshelled, caviar-like blobs of jelly?

Simple enough. Eggs only get their shells as they pass through the
oviduct. That whole thing could be suppressed with a few mutations.

[John Harshman]

On 8/26/22 7:04 PM, Peter Nyikos wrote:
> On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
>> On 8/26/22 5:12 PM, Peter Nyikos wrote:
>>> On Friday, August 26, 2022 at 7:16:18 PM UTC-4, erik simpson wrote:
>>>> On Friday, August 26, 2022 at 3:42:40 PM UTC-7, peter2...@gmail.com wrote:
>>>>> On Friday, August 26, 2022 at 6:32:49 PM UTC-4, Peter Nyikos wrote:
>>>>>
>>>>>> You aren't contributing anything to the on-topic discussion in this second post of yours, Erik.
>>>
>>>>> Minor technical exception: you completed the three-line description of Ovoviviparity in
>>>>> https://en.wikipedia.org/wiki/Viviparity
>>>>> of which I had posted the first sentence.
>>>
>>>> You're contributing what I see as a substantial digression into Mammalia. As for vipers, "squamate reproductive
>>>> strategies are almost bimodally divided between oviparity (egg laying), including cases of egg retention up to limb-bud stage,
>>>> and viviparity involving functional placentation". I don't understand what's frustrating.
>>>
>>> The fact that the claim could be wrong [see reasoning below], and thus being used fallaciously to support
>>> viviparity in ichthyosaurs, which is at the exact resonant center of this thread.
>
>> If you want to find about whether the claims in that paper are wrong,
>> you should consult the references cited to support the claims. In this
>> case that would seem to be references 2 and 22.
>
> [2] doesn't even use the term "ovoviviparous". It could, of course, be paraphrased
> somewhere, but it's getting late and so I'm postponing this project for the weekend,
> which means reporting on anything relevant on Monday or Tuesday.

Perhaps 2 doesn't use it because it's not a useful term.

> As for [22], what I posted on that earlier was preserved in the post that neither Erik
> nor you have shown any sign of having read, preferring the small correction which
> followed it almost immediately.
>
> [repost from uncorrected post]
>>> [22] is linked to a mere abstract via Google Scholar, while "View Article" just takes us back
>>> to the article itself! The same goes for [23].
> [end of repost]

You may have to find the actual paper. Donk't your university resources
work for that?

You have to start letting go of ancient grievances if you actually want
to discuss the science.

[erik simpson]

He can't help it. I'm not going to continue with such an edgy exchange.

[Glenn]

I'm sure John will make a note of that.

[Sight Reader]

On Friday, August 26, 2022 at 8:04:19 PM UTC-6, peter2...@gmail.com wrote:
> But, on a less aggressive note, the discussion seemed to have
> died out until you and Sight Reader came along.

Oh no! Sorry… I didn’t mean to start a flame war! (tries to hide his poisonous keyboard behind his back…)

[erik simpson]

No cause to be sorry, or even concerned. As you've gathered, Peter is a man of very strong opinions, very
forcefully expressed on a very broad range of subjects. He's been here for a long time, and some of this ideas
are very controversial. As a result, discussions often become contentious. Some posters here (and on talk.origins)
get along with him better than others. Stick around, and you'll see why. Open mind, and all that. Unfortunately, it's
been years since any professional paleontologists or even people on that track have been regular participants.
Everybody here is an amateur of whatever grade. John is the closest, as an ornithogist and systematist, Some of the
rest may have advanced degrees in something, but for the most part interest is all we've got in common.

[John Harshman]

You forget Pandora, who admittedly isn't as regular as some.

[jillery]

You are way too charitable. None of of the characteristics you
describe above inform my responses to the peter's posts.

[erik simpson]

Indeed I did. I don't know who Pandora is, or what his/her qualifications are, but I'd be interested to know.
BTW, I described you as a "systematist". Is that correct or would "phylogeneticist" be more accurate? Both?
Christine Janis has also appeared, very irregularly and rarely, but certainly a "pro".

[erik simpson]

There are other characteristics of Peter's than I mentioned, but thesightreader is new here, so my
description is as anodyne as I could make it. If he (thesightreader) lingers long enough, he'll become
fully aware of them anyway. I don't find communicating directly with Peter is instructive or amusing
enough to make it worth the effort.

[John Harshman]

I'd say that "phylogeneticist" is a subset of "systematist", so either
would be fine.

[Peter Nyikos]

On Friday, August 26, 2022 at 9:28:12 PM UTC-4, thesigh...@gmail.com wrote:
> Sorry everyone, Mr. Slow here again (I’m the one for whom the saying, “He who laughs last did not get the joke” was invented)
>
> Anyway, would it be correct to summarize the above as saying that reptiles evolved from true “egg laying” to simply keeping eggs within the body until they “hatched” several times within their history? I guess that would make the difference between external egg laying and viviparous birth more of continuum than a hard line.

If you are referring to hard-shelled eggs, Harshman pointed out that it only takes a few mutations
to get rid of the hard calcium carbonate shell. But that's only the beginning of a complicated web
of possible stages (with a number of surprises along the way) to what Wikipedia calls "Placental viviparity".
If you have access to the following webpage, take a look at Figure 5, which ends with an *early* stage in that web:

https://www.researchgate.net/publication/233720256_Squamate_reptiles_as_model_organisms_for_the_evolution_of_viviparity

If by "viviparous birth" you only mean "live birth," you can stop in the middle of Figure 5. But if you
want more, you could have a long haul ahead of you.

>
> Would it be possible for something like Ichthyosaur eggs to evolve “backwards” from a hard reptilian shell egg back to goopy, unshelled, caviar-like blobs of jelly?

Yes, see above. But a more fundamental question arises:

Did any ichthyosaur ancestor lay hard shelled eggs?

In fact, did any non-archosaur lay hard shelled eggs, including those living today?

Crocodilians are non-avian archosaurs, and they do lay hard shelled eggs, according to
https://en.wikipedia.org/wiki/Crocodile

But although a recent study has put ichthyosaurs closer to archosaurs
than they were thought to be before, they are still rather remote from them phylogenetically.


Peter Nyikos

[Daud Deden]

On Friday, August 26, 2022 at 9:39:46 AM UTC-4, peter2...@gmail.com wrote:
> All books on paleontology that go into detail about Ichthyosaurs agree that
> they gave live birth: the fossil evidence for that is overwhelming.
>
> The only ones I've found that discuss what happens before the live birth
> are Romer's 1945 text, and Colbert's 1955 _Evolution_of_the_Vertebrates_,
> which agree that they were ovoviviparous. Colbert writes:
>
> So it is evident that these reptiles were ovoviviparous -- that they retained the egg within the body until it was hatched, as do some modern lizards and snakes. [*ibid*, p. 162]
>

> In contrast, Carroll only has a photo of a fossil of an ichthyosaur giving live birth,

> but no mention in the running text about it. The third edition of Benton's text
> also makes no mention of the issue.
>
> Wikipedia's entry simply claims they are viviparous and references an 1846
> [NOT 1946] article by J.C. Pearce for it.
>
> In a case of the left hand not knowing what the right hand is doing (and vice versa),
> the entry on viviparity broadens the meaning of the term and distinguishes
> four different varieties
> among extant animals, giving examples of each kind. One of them is ovoviviparity,
> which it seems to want to demote to a variety of oviparity.
> https://en.wikipedia.org/wiki/Viviparity
>
>
> Of course, it is difficult if not impossible to decide whether ichthyosaurs were
> viviparous or ovoviviparous. It could even depend on the genera.
> It is conceivable that some soft tissues could be found preserved in some
> Konservat-Lagerstätten.
> Either bits of fossilized egg membrane (or shell??) or something like an umbilical cord
> could tip the scales heavily one way or the other.
>
>
> Does anyone here have any ideas for other (probably much weaker)
> evidence for one form or the other?
>
>

> Peter Nyikos
> Professor, Dept. of Mathematics -- standard disclaimer--

> University of South Carolina
> http://people.math.sc.edu/nyikos

Cf sea snakes?

[Sight Reader]

On Monday, August 29, 2022 at 11:07:40 AM UTC-6, peter2...@gmail.com wrote:
> If you have access to the following webpage, take a look at Figure 5, which ends with an *early* stage in that web:
>
> https://www.researchgate.net/publication/233720256_Squamate_reptiles_as_model_organisms_for_the_evolution_of_viviparity

Dang, I *SO* want to read this thing, but I’m getting absolutely slaughtered at school (to the point that I’m not sure I can make it to the end of the semester without quitting).

> Did any ichthyosaur ancestor lay hard shelled eggs?
>

Oh dang, I never considered this. I assumed their ancestors would be reptiles and therefore lay hard shells, but I never considered whether there might have been reptiles that DIDN’T lay hard shell eggs!

[Peter Nyikos]

I've been so busy this month, Daud, that I only had time to look up
this good suggestion of yours this weekend.

> Cf sea snakes?

The wikipedia entry on them seems to have them pigeonholed:

Except for a single genus, all sea snakes are ovoviviparous; the young are born alive in the water where they live their entire lives.[9] In some species, the young are quite large, up to half as long as the mother.[7] The one exception is the genus Laticauda, which is oviparous; its five species all lay their eggs on land.[9]
https://en.wikipedia.org/wiki/Sea_snake#Reproduction

And the following definition of "ovoviviparous" is completely unambiguous:

"Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop inside eggs that remain in the mother's body until they are ready to hatch."
...
"Ovoviviparous animals are similar to viviparous species in which there is internal fertilization and the young are born alive, but differ in that there is no placental connection and the unborn young are nourished by egg yolk; the mother's body does provide gas exchange."
--https://en.wikipedia.org/wiki/Ovoviviparity
last edited on 15 July 2022, at 07:33 (UTC).

Earlier on this thread, there were some claims about "ovoviviparous" being
ambiguous, but they were based on a Wikipedia entry that was last edited on
23 May 2022, at 16:25 (UTC): https://en.wikipedia.org/wiki/Viviparity

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--

University of So. Carolina at Columbia
http://people.math.sc.edu/nyikos

[Peter Nyikos]

On Tuesday, August 30, 2022 at 8:26:31 PM UTC-4, thesigh...@gmail.com wrote:
> On Monday, August 29, 2022 at 11:07:40 AM UTC-6, peter2...@gmail.com wrote:
> > If you have access to the following webpage, take a look at Figure 5, which ends with an *early* stage in that web:
> >
> > https://www.researchgate.net/publication/233720256_Squamate_reptiles_as_model_organisms_for_the_evolution_of_viviparity
> Dang, I *SO* want to read this thing, but I’m getting absolutely slaughtered at school (to the point that I’m not sure I can make it to the end of the semester without quitting).

I'm very sorry to hear about this. Has the situation improved any this month?

> > Did any ichthyosaur ancestor lay hard shelled eggs?
> >
> Oh dang, I never considered this. I assumed their ancestors would be reptiles and therefore lay hard shells, but I never considered whether there might have been reptiles that DIDN’T lay hard shell eggs!

Considering that reptiles evolved from amphibians [cladistic conventions notwithstanding],
whose eggs are invariably very soft shelled (if a thin membrane counts as a shell), it could be
that hard shelled eggs are a relatively recent development.

Be that as it may, my reply to Daud a few minutes ago throws the question in my thread
title back into the realm of mystery: we don't have any evidence of there being a hard
shelled egg in ichthyosaurs, and so they could have been anywhere on the spectrum
between ovoviviparity and placental viviparity. See the two Wikipedia webpages
for the definitions:

https://en.wikipedia.org/wiki/Ovoviviparity

https://en.wikipedia.org/wiki/Viviparity

Unfortunately, I have not found a place where hemotrophic viviparity
is clearly separated from placental viviparity. The second entry linked
above is almost completely useless for this.

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--

University of So. Carolina in Columbia
http://people.math.sc.edu/nyikos

[Peter Nyikos]

> On 8/26/22 7:04 PM, Peter Nyikos wrote:
> > On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:

> >> Apparently, "ovoviviparous" is ambiguous and not a useful term.
> >> Apparently, retention of the eggs until hatching (or birth, if you
> >> prefer) requires maternal nourishment of the eggs, at least in squamates.
> >
> >
> > What is the reasoning/reference behind "Apparently"?

You didn't answer this, even though you used the word twice.

Did you use any reference besides the following?

https://en.wikipedia.org/wiki/Viviparity

See my replies to Daud and The Sight Reader earlier today as to some reasons why this
reference is suspect. It says this by way of fueling your first "Apparently":

"Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae). However, the term is poorly and inconsistently defined, and may be obsolete.[4]

[4] is a 2000 article by Daniel A. Blackburn, *proposing* a change in the terminology:
https://www.researchgate.net/publication/233720323_Classification_of_the_Reproductive_Patterns_of_Amniotes

Blackburn proposed the term "lecithotrophy" to nutrition being provided exclusively by yolk,
with "lecithotrophic oviparity" synonymous with the definition of "oviparity" in the Wiki entry:

"Five modes of reproduction have been differentiated in animals[3] based on relations between zygote and parents. The five include two nonviviparous modes: ovuliparity, with external fertilisation, and oviparity, with internal fertilisation. In the latter, the female lays zygotes as eggs with a large yolk; this occurs in all birds, most reptiles, and some fishes.[4]

Note the reference to [4] again, but Blackburn defines "oviparity" simply as "egg-laying." So it is unclear
whether Blackburn's proposal has been widely adopted.


Peter Nyikos

[John Harshman]

On 9/26/22 6:18 PM, Peter Nyikos wrote:
>> On 8/26/22 7:04 PM, Peter Nyikos wrote:
>>> On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
>
>>>> Apparently, "ovoviviparous" is ambiguous and not a useful term.
>>>> Apparently, retention of the eggs until hatching (or birth, if you
>>>> prefer) requires maternal nourishment of the eggs, at least in squamates.
>>>
>>>
>>> What is the reasoning/reference behind "Apparently"?
>
> You didn't answer this, even though you used the word twice.

Afraid I don't remember. If I recall, however vaguely, there was a
review of viviparity in squamates that reported the egg to be nourished
from outside during "pregnancy". Didn't I cite anything?

[Peter Nyikos]

On Monday, September 26, 2022 at 10:01:49 PM UTC-4, John Harshman wrote:
> On 9/26/22 6:18 PM, Peter Nyikos wrote:
> >> On 8/26/22 7:04 PM, Peter Nyikos wrote:
> >>> On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
> >
> >>>> Apparently, "ovoviviparous" is ambiguous and not a useful term.
> >>>> Apparently, retention of the eggs until hatching (or birth, if you
> >>>> prefer) requires maternal nourishment of the eggs, at least in squamates.
> >>>
> >>>
> >>> What is the reasoning/reference behind "Apparently"?
> >
> > You didn't answer this, even though you used the word twice.

> Afraid I don't remember. If I recall, however vaguely, there was a
> review of viviparity in squamates that reported the egg to be nourished
> from outside during "pregnancy". Didn't I cite anything?

You did, and here it is:

https://rep.bioscientifica.com/view/journals/rep/147/1/R15.xml

HOWEVER, try as I might, I found no mention of sea snakes, even though
I gave names of genera and higher taxa that encompassed the ones
said to be ovoviviparous here:

https://en.wikipedia.org/wiki/Sea_snake#Reproduction

And your second "Apparently" has a big hole in it right here.

See whether you can do any better with it, or with the
other reference you gave:
https://pubmed.ncbi.nlm.nih.gov/21573966/

> > Did you use any reference besides the following?
> >
> > https://en.wikipedia.org/wiki/Viviparity
> >
> > See my replies to Daud and The Sight Reader earlier today as to some reasons why this
> > reference is suspect. It says this by way of fueling your first "Apparently":
> >
> > "Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae). However, the term is poorly and inconsistently defined, and may be obsolete.[4]
> >
> > [4] is a 2000 article by Daniel A. Blackburn, *proposing* a change in the terminology:
> > https://www.researchgate.net/publication/233720323_Classification_of_the_Reproductive_Patterns_of_Amniotes
> >
> > Blackburn proposed the term "lecithotrophy" to nutrition being provided exclusively by yolk,
> > with "lecithotrophic oviparity" synonymous with the definition of "oviparity" in the Wiki entry:
> >
> > "Five modes of reproduction have been differentiated in animals[3] based on relations between zygote and parents. The five include two nonviviparous modes: ovuliparity, with external fertilisation, and oviparity, with internal fertilisation. In the latter, the female lays zygotes as eggs with a large yolk; this occurs in all birds, most reptiles, and some fishes.[4]
> >
> > Note the reference to [4] again, but Blackburn defines "oviparity" simply as "egg-laying." So it is unclear
> > whether Blackburn's proposal has been widely adopted.

By the way, Blackburn uses "lecithotrophic viviparity" to give exactly the same unambiguous definition
that the following entry gives to "ovoviviparity":

https://en.wikipedia.org/wiki/Ovoviviparity

[For the definition, see my reply to Daud yesterday.]

Peter Nyikos
Professor, Dept. of Mathematics

University of So. Carolina -- standard disclaimer--
http://people.math.sc.edu/nyikos

[John Harshman]

On 9/27/22 6:01 AM, Peter Nyikos wrote:
> On Monday, September 26, 2022 at 10:01:49 PM UTC-4, John Harshman wrote:
>> On 9/26/22 6:18 PM, Peter Nyikos wrote:
>>>> On 8/26/22 7:04 PM, Peter Nyikos wrote:
>>>>> On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
>>>
>>>>>> Apparently, "ovoviviparous" is ambiguous and not a useful term.
>>>>>> Apparently, retention of the eggs until hatching (or birth, if you
>>>>>> prefer) requires maternal nourishment of the eggs, at least in squamates.
>>>>>
>>>>>
>>>>> What is the reasoning/reference behind "Apparently"?
>>>
>>> You didn't answer this, even though you used the word twice.
>
>> Afraid I don't remember. If I recall, however vaguely, there was a
>> review of viviparity in squamates that reported the egg to be nourished
>> from outside during "pregnancy". Didn't I cite anything?
>
> You did, and here it is:
>
> https://rep.bioscientifica.com/view/journals/rep/147/1/R15.xml

That's the reasoning, then. Read the paper.

> HOWEVER, try as I might, I found no mention of sea snakes, even though
> I gave names of genera and higher taxa that encompassed the ones
> said to be ovoviviparous here:
>
> https://en.wikipedia.org/wiki/Sea_snake#Reproduction
>
> And your second "Apparently" has a big hole in it right here.

Take it up with the authors. Or perhaps you could look at the references
they cite for viviparity in squamates. It is a review article, after
all. It never gives a list of taxa.

> See whether you can do any better with it, or with the
> other reference you gave:
> https://pubmed.ncbi.nlm.nih.gov/21573966/

That's just the abstract, and I have no access to the full article.
Perhaps you do, and can look up the reference for "108 times". But in
either case the information you seek would likely be in the references,
not in the review articles.

>>> Did you use any reference besides the following?
>>>
>>> https://en.wikipedia.org/wiki/Viviparity
>>>
>>> See my replies to Daud and The Sight Reader earlier today as to some reasons why this
>>> reference is suspect. It says this by way of fueling your first "Apparently":
>>>
>>> "Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae). However, the term is poorly and inconsistently defined, and may be obsolete.[4]
>>>
>>> [4] is a 2000 article by Daniel A. Blackburn, *proposing* a change in the terminology:
>>> https://www.researchgate.net/publication/233720323_Classification_of_the_Reproductive_Patterns_of_Amniotes
>>>
>>> Blackburn proposed the term "lecithotrophy" to nutrition being provided exclusively by yolk,
>>> with "lecithotrophic oviparity" synonymous with the definition of "oviparity" in the Wiki entry:
>>>
>>> "Five modes of reproduction have been differentiated in animals[3] based on relations between zygote and parents. The five include two nonviviparous modes: ovuliparity, with external fertilisation, and oviparity, with internal fertilisation. In the latter, the female lays zygotes as eggs with a large yolk; this occurs in all birds, most reptiles, and some fishes.[4]
>>>
>>> Note the reference to [4] again, but Blackburn defines "oviparity" simply as "egg-laying." So it is unclear
>>> whether Blackburn's proposal has been widely adopted.
>
> By the way, Blackburn uses "lecithotrophic viviparity" to give exactly the same unambiguous definition
> that the following entry gives to "ovoviviparity":
>
> https://en.wikipedia.org/wiki/Ovoviviparity
>
> [For the definition, see my reply to Daud yesterday.]

The name you attach is much less interesting than the description of the
situation.

[erik simpson]

Just as a general remark, "unambiguous definitions" in life sciences is as elusive a concept
as any other unqualified statement. Precision of definitions is great, but life itself is so messy
that exceptions always show up, or have been hanging around. Even "species" defies precision
or would leave out or include embarrassing exceptions. Ovip[various letters] is probably just
another example where clarity can't be achieved with a single word.

[Peter Nyikos]

This general remark ignores the specific example under question. You have
nothing to say about any possible ambiguities in the definition of ovoviviparity given here:

"Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop inside eggs that remain in the mother's body until they are ready to hatch."
...
"Ovoviviparous animals are similar to viviparous species in which there is internal fertilization and the young are born alive, but differ in that there is no placental connection and the unborn young are nourished by egg yolk; the mother's body does provide gas exchange."
--https://en.wikipedia.org/wiki/Ovoviviparity
last edited on 15 July 2022, at 07:33 (UTC).

> Precision of definitions is great, but life itself is so messy
> that exceptions always show up, or have been hanging around. Even "species" defies precision

That's not a good use of "even," nor is it a good example of an exception.

> or would leave out or include embarrassing exceptions. Ovip[various letters] is probably just
> another example where clarity can't be achieved with a single word.

It can if it is defined in the right way. Your last sentence conveniently ignores the above definition,
which I showed to Daud in my reply to him yesterday.


Peter Nyikos

Professor, Dept. of Mathematics -- standard disclaimer--

University of So. Carolina at Columbia
http://people.math.sc.edu/nyikos

PS Here is a much better example: try to show that the word "objective," which Harshman
keeps applying to cladistic classification, is NOT an exception to the general claims
that you have made so confidently above.

I predict you won't even try.

[Peter Nyikos]

It's been six days, and my prediction at the end is holding up. The default assumption in
cases like this is that Erik has no good comeback that is aimed at rehabilitating his claims.

Short specific comments in this case follow below.

Harshman has not responded to this "assignment".

> > > > > Did you use any reference besides the following?
> > > > >
> > > > > https://en.wikipedia.org/wiki/Viviparity
> > > > >
> > > > > See my replies to Daud and The Sight Reader earlier today as to some reasons why this
> > > > > reference is suspect. It says this by way of fueling your first "Apparently":
> > > > >
> > > > > "Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae). However, the term is poorly and inconsistently defined, and may be obsolete.[4]
> > > > >
> > > > > [4] is a 2000 article by Daniel A. Blackburn, *proposing* a change in the terminology:
> > > > > https://www.researchgate.net/publication/233720323_Classification_of_the_Reproductive_Patterns_of_Amniotes
> > > > >
> > > > > Blackburn proposed the term "lecithotrophy" to nutrition being provided exclusively by yolk,
> > > > > with "lecithotrophic oviparity" synonymous with the definition of "oviparity" in the Wiki entry:
> > > > >
> > > > > "Five modes of reproduction have been differentiated in animals[3] based on relations between zygote and parents. The five include two nonviviparous modes: ovuliparity, with external fertilisation, and oviparity, with internal fertilisation. In the latter, the female lays zygotes as eggs with a large yolk; this occurs in all birds, most reptiles, and some fishes.[4]
> > > > >
> > > > > Note the reference to [4] again, but Blackburn defines "oviparity" simply as "egg-laying." So it is unclear
> > > > > whether Blackburn's proposal has been widely adopted.

> > > By the way, Blackburn uses "lecithotrophic viviparity" to give exactly the same unambiguous definition
> > > that the following entry gives to "ovoviviparity":
> > >
> > > https://en.wikipedia.org/wiki/Ovoviviparity
> > >
> > > [For the definition, see my reply to Daud yesterday.]
> > > Peter Nyikos
> > > Professor, Dept. of Mathematics
> > > University of So. Carolina -- standard disclaimer--
> > > http://people.math.sc.edu/nyikos

Erik introduced his claim here:

> > Just as a general remark, "unambiguous definitions" in life sciences is as elusive a concept
> > as any other unqualified statement.

This statement was rendered vacuous by the following remarks of mine.

> This general remark ignores the specific example under question. You have
> nothing to say about any possible ambiguities in the definition of ovoviviparity given here:
> "Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop inside eggs that remain in the mother's body until they are ready to hatch."
> ...
> "Ovoviviparous animals are similar to viviparous species in which there is internal fertilization and the young are born alive, but differ in that there is no placental connection and the unborn young are nourished by egg yolk; the mother's body does provide gas exchange."
> --https://en.wikipedia.org/wiki/Ovoviviparity
> last edited on 15 July 2022, at 07:33 (UTC).


> > Precision of definitions is great, but life itself is so messy

> > that exceptions always show up, or have been hanging around. Even "species" defies precision.

> That's not a good use of "even," nor is it a good example of an [alleged] exception.

> > or would leave out or include embarrassing exceptions. Ovip[various letters] is probably just
> > another example where clarity can't be achieved with a single word.

> It can if it is defined in the right way. Your last sentence conveniently ignores the above definition,
> which I showed to Daud in my reply to him yesterday.
>
>
> Peter Nyikos
> Professor, Dept. of Mathematics -- standard disclaimer--
> University of So. Carolina at Columbia
> http://people.math.sc.edu/nyikos

Here is what Erik has no good comeback for:

> PS Here is a much better example: try to show that the word "objective," which Harshman
> keeps applying to cladistic classification, is NOT an exception to the general claims
> that you have made so confidently above.
>
> I predict you won't even try.

This prediction put Erik between a rock and a hard place. He has to choose between
loyalty to Harshman and rehabilitating his comments. By his silence, he has chosen loyalty.


Peter Nyikos

[erik simpson]

You can inerpret silence any way you like. I interpret my silence, at least in this case, as simply indicating disinterest.

[Peter Nyikos]

The on-topic lesson from the largely personal exchange below is that
the Wikipedia entry on Ovoviviparity seems to be an effort to
rescue the term "ovoviviparous" from its misuse by so many researchers
in the past century. In this way, we can use the term (or one of its shortened spellings)
instead of the less familiar and more cumbersome "lecithotrophic viviparity."

https://en.wikipedia.org/wiki/Ovoviviparity
Excerpt:
Criticisms and disuse
A lack of a rigidly defined term resulted in widespread misuse of the term ovoviviparity in the biological literature.[7] Ovoviviparity has been used to describe delayed forms of egg-laying reproduction as well as live-bearing species that provide maternal nutrients but do not use a placenta. [7] This widespread misuse of the term has led to confusion over what earlier authors meant when using the name. Modern practice has seen the disuse of ovoviviparity in favour of the more specific definitions of lecithotrophic and matrotrophic oviparity and viviparity.[8]

The above notwithstanding, the entry on sea snakes used the term "ovoviviparity" and linked the above webpage.

Back to a little bit of the personal:

> You can inerpret silence any way you like. I interpret my silence, at least in this case, as simply indicating disinterest.

That's Harshman's favorite face-saving fallback too.

From time to time you claim that you are bored with me, but you always come back
sooner or later with personal attacks, especially when I say some nice things about Glenn to you or John.

Aren't you glad I didn't say a nice thing about JTEM the last time I mentioned him to you?


Peter Nyikos

[John Harshman]

If you would just stop with the crap, people might be more interested in
having real discussions with you. As it stands, the nonsense is a
deterrent, as is the tendency to reply to bits 4 or 5 levels deep.

[erik simpson]

Asking Peter to stop with the crap is like asking him not to exhale.

[Peter Nyikos]

On Tuesday, October 4, 2022 at 1:13:20 PM UTC-4, erik simpson wrote:
> On Tuesday, October 4, 2022 at 10:08:00 AM UTC-7, John Harshman wrote:
> > On 10/4/22 9:43 AM, Peter Nyikos wrote:

> > > The on-topic lesson from the largely personal exchange below is that
> > > the Wikipedia entry on Ovoviviparity seems to be an effort to
> > > rescue the term "ovoviviparous" from its misuse by so many researchers
> > > in the past century. In this way, we can use the term (or one of its shortened spellings)
> > > instead of the less familiar and more cumbersome "lecithotrophic viviparity."

This on-topic talk was too tame for Harshman, who made a transparently
phony excuse for not getting involved in it below; and you mindlessly
followed him, Erik.

> > > https://en.wikipedia.org/wiki/Ovoviviparity
> > > Excerpt:
> > > Criticisms and disuse
> > > A lack of a rigidly defined term resulted in widespread misuse of the term ovoviviparity in the biological literature.[7] Ovoviviparity has been used to describe delayed forms of egg-laying reproduction as well as live-bearing species that provide maternal nutrients but do not use a placenta. [7]

The non-misuse meaning is that there is no exchange of nutrients through the (soft) shell, but only gas exchange.
See direct quote out of the linked webpage below.

> > > This widespread misuse of the term has led to confusion over what earlier authors meant when using the name. Modern practice has seen the disuse of ovoviviparity in favour of the more specific definitions of lecithotrophic and matrotrophic oviparity and viviparity.[8]"

> > >
> > > The above notwithstanding, the entry on sea snakes used the term "ovoviviparity" and linked the above webpage.

https://en.wikipedia.org/wiki/Sea_snake#Reproduction


And now, back to Ichthyosaurs. They were the most exclusively marine reptiles of the Mesozoic,
just as sea snakes in one subfamily are the most exclusively marine reptiles of the Cenozoic.
So it's a bit suggestive [but no more] that, just as those sea snakes are ovoviviparous,
so too the ichthyosaurs might have been.

If either you, Erik, or John shows some interest, I can talk about a fascinating
example that probably spans Mesozoic and Cenozoic: there are several
lines of evidence that coelacanths are, and have been for a long time, ovoviviparous.

Here is that definition again:

For many months after you instigated the destruction of what I call
the s.b.p. 2015 -early 2018 oasis of civilization, Harshman's usual
practice was to do unmarked deletia of personal criticism to
focus on the on-topic material. Here he is doing just the reverse,
and pretending to speak in the name of "people".

As it stands, the "crap" is what he is really interested in here.

> > As it stands, the nonsense is a deterrent, as is the tendency to reply to bits 4 or 5 levels deep.

The on-topic part above was 0 levels deep, so this is transparent nonsense
by Harshman.

> > > From time to time you claim that you are bored with me, but you always come back
> > > sooner or later with personal attacks, especially when I say some nice things about Glenn to you or John.
> > >
> > > Aren't you glad I didn't say a nice thing about JTEM the last time I mentioned him to you?
> > >
> > >
> > > Peter Nyikos
> Asking Peter to stop with the crap is like asking him not to exhale.

Harshman asking you to stop with the crap when you unleashed
it in early 2018 was unthinkable for him;
that's why what I call the s.b.p. oasis of civilization no longer exists.

The same applies to you asking Harshman to stop with the crap whenever he
unleashes it. That is why, early in 2019, you kept mum as he kept aggressively alleging
that I was speaking nonsense about subduction into deep ocean trenches,
yet repeatedly neglected to explain why it was supposed to be nonsense.

So far from thinking about asking him to stop, you and Oxyaena were emboldened
by it to get more aggressive on another issue, culminating in a post where
Oxyaena said she would contact my employers. That made me
decide to boycott her for the rest of 2019. And since you had
been working hand in glove with her in her attacks up to that point,
I included you too.

One reason I didn't include Harshman was that he had been
playing "good cop" to your and Oxyaena's "bad cops,"
saying that the insults Oxyaena and [IIRC] you were heaping on me were
inappropriate, "even against someone like Peter."

Another was that, with each new post, his unsupported claims about
what I said about subduction got more and more muted.

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--

Univ. of So. Carolina at Columbia
http://people.math.sc.edu/nyikos

[John Harshman]

On 10/4/22 2:07 PM, Peter Nyikos wrote:

> And now, back to Ichthyosaurs. They were the most exclusively marine reptiles of the Mesozoic,
> just as sea snakes in one subfamily are the most exclusively marine reptiles of the Cenozoic.
> So it's a bit suggestive [but no more] that, just as those sea snakes are ovoviviparous,
> so too the ichthyosaurs might have been.
>
> If either you, Erik, or John shows some interest, I can talk about a fascinating
> example that probably spans Mesozoic and Cenozoic: there are several
> lines of evidence that coelacanths are, and have been for a long time, ovoviviparous.

Sure. What do you have? I presume here that your definition is gas
exchange across the shell, but no nutrients.

[Peter Nyikos]

On Tuesday, October 4, 2022 at 6:45:58 PM UTC-4, John Harshman wrote:
> On 10/4/22 2:07 PM, Peter Nyikos wrote:
>
> > And now, back to Ichthyosaurs. They were the most exclusively marine reptiles of the Mesozoic,
> > just as sea snakes in one subfamily are the most exclusively marine reptiles of the Cenozoic.
> > So it's a bit suggestive [but no more] that, just as those sea snakes are ovoviviparous,
> > so too the ichthyosaurs might have been.
> >
> > If either you, Erik, or John shows some interest, I can talk about a fascinating
> > example that probably spans Mesozoic and Cenozoic: there are several
> > lines of evidence that coelacanths are, and have been for a long time, ovoviviparous.

In fact, *Rhabdoderma*, another candidate for ovoviviparity, is from the Paleozoic.

> Sure. What do you have? I presume here that your definition is gas
> exchange across the shell, but no nutrients.

Yes.

I'm busy in talk.origins and other s.b.p. threads for probably the rest of the week,
but I intend on Monday to go deep into details in a great book on *Latimeria,*
the living coelacanth and AFAIK the only known Cenozoic coelacanth.
It is by Keith S. Thompson, titled _Living Fossil: The Story of the Coelacanth_ .

For now, I'll just quote something about that Paleozoic coelacanth.

"The Carboniferous fossils that Schultze had described as free-living yolk sac larvae were from a genus, (*Rhabdoderma*) that may have lived in brackish waters rather than the sea. In this case (if the water was less saline than the body tissues) it is possible that ovoviviparity was not needed, but economy of hypotheses suggests the strong likelihood that this genus was ovoviviparous also." [p. 199]

The rationale for this "strong likelihood" would seem to be that
the yolk sac, being still attached to the free-swimming young, creates the
presumption that there had been enough yolk all the way to birth
to dispense with any maternal nutrients in addition.

The alternative hypothesis, that the yolk sac was only a partial
source of nutrition, is less economical, as the author puts it.

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--

University of So. Carolina in Columbia
http://people.math.sc.edu/nyikos

[Trolidan7]

Double checking.

For oviparous reptiles, birds, and monotremes, The shell of
an amniote egg is secreted onto an egg during the process of laying.

Therefore an egg that is not laid will have no shell?

Is it possible for a blood vessel in a closed circulatory
system to be able to exchange oxygen with a tissue outside
of a blood vessel without also being able to exchange nutrients?

[John Harshman]

Nope. This "process of laying" can take days, as the egg moves down the
oviduct. All that's needed is for the finished egg to skip that last
step of leaving the mother's body.

> Is it possible for a blood vessel in a closed circulatory
> system to be able to exchange oxygen with a tissue outside
> of a blood vessel without also being able to exchange nutrients?

Yes, totally. Oxygen and CO2 diffuse more easily than most other molecules.

[Trolidan7]

However there is such a thing called 'lymph', and cells need
nutrients as well as oxygen.

Can blood vessels modulate the amount of sugar sent to tissues,
and not just fluid? Can it sort larger sacchararides and protiens
from smaller ones? To what extent?

Regularly fluids, with edema and other processes, cross through
blood vessels. Red blood cells do not cross through blood vessels,
but white blood cells do. This makes the color of the interior
of the vessels generally different from the exterior.

When fluids perfuse outside of blood vessels, that undergoes
a word change, and it is called 'lymph', or some times 'edema'
potentially resulting in 'swelling'. That name change produces
the idea that it is a vastly different substance inside the
blood vessels rather than outside, but that idea may potentially
be questionable in a lot of ways.

I do not think that is sophistry on the part of biologists.
These color differences were able to be noticed before the
existence of microscopes.

[Peter Nyikos]

Here is where you came in, Trolidan7:

> Double checking.
>
> For oviparous reptiles, birds, and monotremes, The shell of
> an amniote egg is secreted onto an egg during the process of laying.

AFAIK this applies only to hard shells, like bird shells. [John, do you know differently?]
Monotreme eggs have soft shells, through which even some nutrients
can reach the embryo throughout the pregnancy. This was a big surprise for me, which I found out
late in September from a 2000 article by Daniel G. Blackburn. He calls this
form of reproduction "Matrotrophic viviparity." A more recent article by him about this is here:

Blackburn, Daniel (2015). "Evolution of Vertebrate Viviparity and Specializations for Fetal Nutrition: A Quantitative and Qualitative Analysis". Journal of Morphology. 276 (8): 961–990. doi:10.1002/jmor.20272. PMID 24652663. S2CID 549574.
cited in:
https://en.wikipedia.org/wiki/Ovoviviparity

> Therefore an egg that is not laid will have no shell?

Not to my knowledge. There may however be a difference in terminology,
whereby what I call "soft shells" above are called "membranes" as long
as the egg is within the parental body. [In sea horses, this is the brood pouch of the male!]

> Is it possible for a blood vessel in a closed circulatory
> system to be able to exchange oxygen with a tissue outside
> of a blood vessel without also being able to exchange nutrients?

John answered this one with Yes.

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--

[Trolidan7]

On 10/9/22 11:58 AM, John Harshman wrote:

When I look up the words 'closed circulatory system' in Wikipedia
it gives three examples - annelids, some molluscs, and vertebrates.

Since two are protostomes and one is a deuterostome I am guessing
that is not based upon phylogenetics.

Now in cephalopods, I am thinking that the copper metalloprotein
that carries oxygen is not contained within any cells inside a
cell membrane, rather it is within a blood matrix. I am not sure
if the oxygen bound copper diffuses across the blood vessel or not.

Now in vertebrates in general, hemoglobin resides inside red blood
cells. For oxygen to get inside the cells in tissues outside of
blood vessels I am thinking it has to do the following.

Go outside the red blood cell into the extracellular fluid of
the blood in the vessel.

Travel outside the fluid of the blood vessel into the fluid
outside of the blood vessel (sometimes called lymph or other
tissue fluid)

Then go inside of the cells receiving oxygen. There in some
circumstances it might bind with myoglobin for storage before
metabolic use.

During all of this time, both oxygen, nitrogen, and carbon
dioxide remain dissolved in an aqueous solution. They never
go into the gas state. If something like this happens, this
is called the 'bends' (or decompression sickness). This is
generally suppressed because if it becomes too widespread
it can lead to problems with circulation.

Basic question.

In the closed circulatory system of vertebrates, how do
white blood (immune, not red blood) cells go from the
blood vessels into tissues outside of the blood stream
when they undergo some form of damage or infection? Do
they open up small passages in the walls of the blood
vessels and then close them afterward? Are there gaps
that allow them to go through?

How does oxygen or carbon dioxide pass through a blood
vessel? Does it go inside of the cell membranes of the
cells making up the blood vessel walls themselves and
pass through the cells to get inside and outside of the
blood vessels? Does it go through small gaps between
the cells of the blood vessels without passing into and
out of the cells themselves that make up much of the
blood vessel tissues?

Then after that the oxygen or carbon dioxide when then
have to pass through the extracellular fluid of the
tissue before being taken up by the cells in the tissue.

[John Harshman]

I doubt that small, uncharged molecules notice whether they're going
through a cell membrane or not. I'm pretty sure travel is by passive
diffusion, not active transport.

[Trolidan7]

O2 has no polar or non-polar side.

A cell membrane is a bilayer generally composed of lipid molecules
along with glycerols and other materials. The lipid has a non-polar
tail that has affinities for other non-polar materials and a polar
side is attracted toward the aqueous polar inside and outside of the
membrane.

A cell membrane also has a lot of pores in them that open or close
to allow certain substances in or out. The sodium, potassium, and
calcium channels specific for certain types of ions are some examples.

It might be that CO2 could be different from O2, but you are in
essence saying that all of O2 at least passes through the cell membranes
of the cells of the blood vessels on both sides, and when immune cells
exist the bloodstream they in essence open small doors between the
blood vessel cells, and close those doors behind them?

I was thinking there were regular gaps between the blood vessel cells,
and lymph was formed from a persistent regular leakage from the blood
vessels into the intercellular fluid outside of the blood vessels.
Perhaps that was wrong.


adheres to non-polar fats and a polar (carboxylic acid) side.

[Trolidan7]

On 10/12/22 2:33 PM, John Harshman wrote:

I have several more questions about the lymphatic versus the
regular blood circulatory systems that I may have been mistaken
about before.

1, The direction of flow of the lymphatic system is opposite
the flow of the blood circulatory system. Is that correct?

That means that when lymph empties into the regular blood system
at the exit to the lymphatic system, possible backflow of blood
into the lymphatic ducts is stopped by the valves in the lymphatic
system. Since there are many valves in the lymph system, just like
in the blood vessels, failure of one valve will not mean that the
lymph system is not filled because there are many valves within it?

2. I read that in some reptiles there are 'lymph hearts'. Is that
in only some reptiles? Which ones? How about birds? How about
monotremes or marsupials? I am thinking that in mammals it is all
skeletal muscles and the fact that the lymph vessels have valves
that make the lymph flow only one way. It does not need to flow
very fast.

3. I remember reading once that mammals have mature red blood cells
with no nucleus. Other vertebrates do not and will retain a nucleus
in mature red blood cells. Why would you think that is so? Small
blood vessels in small animals in the Mesozoic? Resistance to virus
infections of the blood? Something else?

[Glenn]

"Inside the air sacs, oxygen moves across paper-thin walls to tiny blood vessels called capillaries and into your blood. A protein called haemoglobin in the red blood cells then carries the oxygen around your body. At the same time, carbon dioxide that is dissolved in the blood comes out of the capillaries back into the air sacs, ready to be breathed out."

https://www.blf.org.uk/support-for-you/how-your-lungs-work/oxygen-and-blood

> >Does it go inside of the cell membranes of the
> > cells making up the blood vessel walls themselves and
> > pass through the cells to get inside and outside of the
> > blood vessels? Does it go through small gaps between
> > the cells of the blood vessels without passing into and
> > out of the cells themselves that make up much of the
> > blood vessel tissues?
> >
> > Then after that the oxygen or carbon dioxide when then
> > have to pass through the extracellular fluid of the
> > tissue before being taken up by the cells in the tissue.
> I doubt that small, uncharged molecules notice whether they're going
> through a cell membrane or not. I'm pretty sure travel is by passive
> diffusion, not active transport.

You doubt? Or you're pretty sure? Which is it?

[John Harshman]

Actually, O2 is a polar molecule, but not very polar.

> A cell membrane is a bilayer generally composed of lipid molecules
> along with glycerols and other materials.  The lipid has a non-polar
> tail that has affinities for other non-polar materials and a polar
> side is attracted toward the aqueous polar inside and outside of the
> membrane.
>
> A cell membrane also has a lot of pores in them that open or close
> to allow certain substances in or out.  The sodium, potassium, and
> calcium channels specific for certain types of ions are some examples.
>
> It might be that CO2 could be different from O2, but you are in
> essence saying that all of O2 at least passes through the cell membranes
> of the cells of the blood vessels on both sides, and when immune cells
> exist the bloodstream they in essence open small doors between the
> blood vessel cells, and close those doors behind them?

I don't know how the immune cells get around, but presumably they don't
go through the epithelial cells but around them.

CO2 is a non-polar molecule, and in fact it's known to diffuse somewhat
more easily than O2.

> I was thinking there were regular gaps between the blood vessel cells,
> and lymph was formed from a persistent regular leakage from the blood
> vessels into the intercellular fluid outside of the blood vessels.
> Perhaps that was wrong.

It's been a while since I thought about cellular physiology, and you
might more profitably consult a text.

[John Harshman]

No idea.

> That means that when lymph empties into the regular blood system
> at the exit to the lymphatic system, possible backflow of blood
> into the lymphatic ducts is stopped by the valves in the lymphatic
> system.  Since there are many valves in the lymph system, just like
> in the blood vessels, failure of one valve will not mean that the
> lymph system is not filled because there are many valves within it?

Again, no idea.

> 2. I read that in some reptiles there are 'lymph hearts'.  Is that
> in only some reptiles?  Which ones?  How about birds?  How about
> monotremes or marsupials?  I am thinking that in mammals it is all
> skeletal muscles and the fact that the lymph vessels have valves
> that make the lymph flow only one way.  It does not need to flow
> very fast.

I don't know that either. I do know that a lot of lymph circulation
happens because of the contraction of body muscles.

> 3. I remember reading once that mammals have mature red blood cells
> with no nucleus.  Other vertebrates do not and will retain a nucleus
> in mature red blood cells.  Why would you think that is so?  Small
> blood vessels in small animals in the Mesozoic?  Resistance to virus
> infections of the blood?  Something else?

I don't think anyone knows that one. Mammals are no smaller than
reptiles, so I can't see your first explanation being valid. Are mammal
erythrocytes even smaller than reptilian ones? Could they carry more
oxygen per cell? No idea.

[Trolidan7]

I am sorry. This is a complex phenomenon that might occur on
many different microscalar levels. Just the right reference
search may not necessarily produce omniscience.

[Peter Nyikos]

I've been busy on other threads last week and am trying
to catch up on this one.

On Wednesday, October 12, 2022 at 5:13:40 PM UTC-4, Trolidan7 wrote:
> On 10/9/22 11:58 AM, John Harshman wrote:
> > On 10/9/22 9:57 AM, Trolidan7 wrote:

> >> Is it possible for a blood vessel in a closed circulatory
> >> system to be able to exchange oxygen with a tissue outside
> >> of a blood vessel without also being able to exchange nutrients?
> >
> > Yes, totally. Oxygen and CO2 diffuse more easily than most other molecules.

> When I look up the words 'closed circulatory system' in Wikipedia
> it gives three examples - annelids, some molluscs, and vertebrates.
>
> Since two are protostomes and one is a deuterostome I am guessing
> that is not based upon phylogenetics.

That is a very safe bet.

> Now in cephalopods, I am thinking that the copper metalloprotein
> that carries oxygen is not contained within any cells inside a
> cell membrane, rather it is within a blood matrix.

What is your source for this? The Wikipedia comment on this looks
like a case of too many cooks spoiling the broth:

"Unlike the hemoglobin in red blood cells found in vertebrates, hemocyanins are not confined in blood cells but are instead suspended directly in the hemolymph."
https://en.wikipedia.org/wiki/Hemocyanin

However, the link to hemolymph takes one to a page where one sees:
"Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod (invertebrate) body, remaining in direct contact with the animal's tissues."

This leaves me up in the air as to where the hemocyanin in cephalopods is confined.
On the other hand, some mollusks and some annelids have true hemglobin.
Most annelids have the hemoglobin in the plasma, but a few species,
including *Glycera*, contain it in red blood cells.

>I am not sure
> if the oxygen bound copper diffuses across the blood vessel or not.

I doubt it: if you look at the picture in the one wikipedia link I gave,
hemocyanins are quite complicated, unlike the gases you talked about below.

> Now in vertebrates in general, hemoglobin resides inside red blood
> cells. For oxygen to get inside the cells in tissues outside of
> blood vessels I am thinking it has to do the following.
>
> Go outside the red blood cell into the extracellular fluid of
> the blood in the vessel.

The plasma, in other words. There is an interplay between the
oxygen and carbon dioxide that influences the red blood
cells to give up their bound oxygen. Strangely, one of the best
biology textbooks (_Biology_, by Campbell, Reece et al)
spends a lot of time on the technical details of this but says
essentially nothing about how the oxygen is then delivered
to the cells.

>
> Travel outside the fluid of the blood vessel into the fluid
> outside of the blood vessel (sometimes called lymph or other
> tissue fluid)
>
> Then go inside of the cells receiving oxygen. There in some
> circumstances it might bind with myoglobin for storage before
> metabolic use.
>
> During all of this time, both oxygen, nitrogen, and carbon
> dioxide remain dissolved in an aqueous solution.

Yes, but the red blood cells need to take up about 90% of the oxygen for
there to be enough stored oxygen in the blood vessels.

> They never go into the gas state. If something like this happens, this
> is called the 'bends' (or decompression sickness). This is
> generally suppressed because if it becomes too widespread
> it can lead to problems with circulation.
>
> Basic question.
>
> In the closed circulatory system of vertebrates, how do
> white blood (immune, not red blood) cells go from the
> blood vessels into tissues outside of the blood stream
> when they undergo some form of damage or infection? Do
> they open up small passages in the walls of the blood
> vessels and then close them afterward? Are there gaps
> that allow them to go through?

White blood cells are like amoebas: they can greatly
change their shapes to squeeze between cells in the capillaries.
Red blood cells are comparatively rigid.

However, they do drastically change their shape in people with
the sickle cell trait. In the altered sickle cell form, the cell
can no longer take in oxygen. In heterozygous individuals,
the change to this form usually happens only when a malaria parasite invades the cell.
Then the parasite dies due to oxygen starvation.

In homozygous individuals, the change can be stimulated a lot
more easily, and the result is sickle cell anemia.

I mention all this because this shows how diffusion of oxygen
across cell membranes needs to be supplemented by the hemoglobin
molecule being in the right location for easy takeup.

> How does oxygen or carbon dioxide pass through a blood
> vessel? Does it go inside of the cell membranes of the
> cells making up the blood vessel walls themselves and
> pass through the cells to get inside and outside of the
> blood vessels? Does it go through small gaps between
> the cells of the blood vessels without passing into and
> out of the cells themselves that make up much of the
> blood vessel tissues?

I think the latter process contributes a lot more,
but I am not sure.

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--

Univ. of So. Carolina in Columbia
http://people.math.sc.edu/nyikos