Why did the flatfish's eye move from one side to the other?
brian0918
divinely guided... by Picasso... but my question is as follows:
The common explanation I've seen for its evolution is:
1. Taking to the sea floor, it was natural for the flatfish to rest on
its side.
2. With one eye stuck in the ground, it was at a disadvantage.
3. Yadda yadda yadda
4. Result: Its bottom eye moved around to the top.
The problem is in step 3. It is unlikely that the bottom eye suddenly
appeared on top within a couple generations. So, how about those
transitional species: what was the evolutionary advantage to having an
eyeball offset by a couple millimeters, but still stuck in the ground?
The only solution I can think of is that since there was no advantage
to eyeballs shifted only slightly (but still stuck in the mud), all the
various transitional species thrived together equally, and it wasn't
until one of the strains had their bottom eyeball shifted up above the
sea floor that natural selection actually started to occur--sort of a
"delayed natural selection". It would be interesting to find fossils of
transitional species in which the bottom eye socket is shifted all over
the place: 3 millimeters toward the spine, 5 mm toward the tail, 10 mm
toward the mouth, etc.
Anyone have some input?
Bobby D. Bryant
--
Bobby Bryant
Austin, Texas
brian0918
Thanks for that brilliant reasoning... Now if only all of evolution was
goal-oriented. Then our lives would have purpose.
Kaskir
explanation than the "delayed" natural selection. If having both eyes
on the same side of the head is an advantage to the fish, it means that
it is eating better (at least), thus making his development faster and
his reproductive abilities multiplied. In such a scenario, weird little
mutants would quickly take over healthy (although highly inefective)
"normies". It follows then that a gradual transition might not have
been necesary but that a single mutant individual might have been
highly succesful with the ladies. OR a highly succesful lady produced
enough eggs to allow for a stable population to develop, and lady fish
produce a LOT of eggs, especially fat old succesful lady fish.
Given the mechanisms of speciation, a small, isolated and
highly succesful population might just be able to reverse migration
patterns and populate wider areas with their "one side eyed" weirdos.
What's more, the tendency of some species of delicious flat fish to
have the eyes on either side, while other species can be distinguish by
the side on which the eye lies could point to parallel independent
evolutions of the same trait. That's another extral cool point to our
mouth watering friends.
In the other hand, I do agree that it would be SO cool to
find a fish with a real functioning eye near the tail. That would be
either the smartest fish ever or the most stupid one. In either case, I
don't think it would last long as a species. For one, smart fish don't
finish first, indeed they rarelly finish at all surrounded by huge
predators that invested their evolutionary stock into WMDs such as
longer, nastier more effective teeth. Then you have to consider that
fish are generally not social creatures (schools are agrupations
without social assigments [as of yet]), so if I was smart fish I would
kill myself from boredom itself (another argument for goldfish
stupidity?). Then of course, stupid fish usually swim themselves into
sleeping predators mouths while merrily singing:
"Hello mister big fish
I'm your little cleaner shrimp,
would like some buuuutter
with your morning snack"
Here is to mankind never singing such song... Salud!
brian0918
would probably rule out one or two "freak fish" who suddenly appeared
with two eyes on the same side of their heads. In other words, the fact
that the bones show twisting, rather than an extra eye socket where
there normally isn't one, is indicative of a gradual shift in position,
rather than a single gene which mutated to give "2 eyes" where there
used to be 1.
Pip R. Lagenta
wrote:
>"To get on the other side. "
>
>Thanks for that brilliant reasoning... Now if only all of evolution was
>goal-oriented. Then our lives would have purpose.
To hold our pants up.
>
--
內躬偕爻,虜,齯滌`偕爻,虜,齯滌`偕爻,虜,齯滌`偕爻,虜,齯滌`偕爻,
Pip R. Lagenta Pip R. Lagenta Pip R. Lagenta Pip R. Lagenta
�虜,齯滌`偕爻,虜,齯滌`偕爻,虜,齯滌`偕爻,虜,齯滌`偕爻,虜,齯滌
-- Pip R. Lagenta
President for Life
International Organization Of People Named Pip R. Lagenta
(If your name is Pip R. Lagenta, ask about our dues!)
<http://home.comcast.net/~galentripp/pip.html>
(For Email: I'm at home, not work.)
Kaskir
fish. That is, all, ALL flat fish are born with eyes in their normal
positions. To be completely clear, as they leave the egg, baby flat
fish has one eye in every side of his two sided head. Then the
migration occurs and as you can read in every bio book with decent
images on it (some even have x-ray pictures that look sweet) the bones
twist and the eye socket moves into position. This could be interpreted
as a repetition of the evolution of the fish, however this would be as
wrong as assuming that because all vertebrate enbrios look alike at
some point in their development therefore thats the way we evolve
"upwards" to human beings proposition.
In any case, mine was just another proposition for a pathway of
evolution, this might have affected one or two species, that developed
into families, but there are many other ways. Again, I agree with you
in that finding such evolutionary evidence would be cool, however I
have to warn you that you sound a bit creationist by asking for fossils
to be discovered. Fossils are the exception, not the rule. In order to
make a fossil, the most rigoruos environmental cirscunstances have to
happen at the right moment, which is why we don't find fossils every
spring when digging to plant our new seasonal oak tree.
brian0918
would be cool, however I have to warn you that you sound a bit
creationist by asking for fossils
to be discovered. Fossils are the exception, not the rule."
Yes, I know all about how improbable fossil formation is. I didn't ask
for fossils, I said it would be "interesting to find fossils"....
Kaskir
trying to provide with another plausible explanation and somehow it
came out all confrontational.
nickm...@gmail.com
LOL!
nickm...@gmail.com
juvenile flatfish swim right-side up, and as they mature their eye
begins to twist around as the lay on their sides.
Possible factors that may have facilitated the evolution of eye
migration:
* even a slight, incomplete eye migration might help fish for the
period of time when they are just beginning to settle on the bottom,
and when they are just beginning to lift
* slight eye migration might have initially been useful when the
flatfish was swimming in the open water, even if not useful while on
the bottom. Presumably swimming flatfish are near the seafloor anyhow,
so any eye facing straight down might be less useful than one that
twists to the side a bit
* the eye migration feature might have gotten going with the assistance
of nongenetic organismal behavior, e.g. if the fish is constantly
twisting its lower eye sideways and forwards to see better, or even
twisting its head slightly, then mutations that developmentally
enhanced the effect this might be preserved. Canalization or some
such.
[googles on flatfish evolution]
Well, there is obviously more to it than the above, because evidently a
few flatfish species (7 out of 550) are POLYMORPHIC for which side,
left or right, becomes "up". This implies some kind of semi-random
symmetry-breaking device that can go either way and can pull either eye
to the new "top", and also pigment the correct side. It could just be
the fish picks whichever side it prefers, and then developmental
mechanisms respond to an environmental signal like gravity or light.
But anyway, there are some really cool pictures here:
http://ceratostoma.bms.bc.ca/cbergstr/starry%20flounder%20info%20Page%208.htm
Mitchell Coffey
wrote:
>"To get on the other side. "
>
>Thanks for that brilliant reasoning... Now if only all of evolution was
>goal-oriented. Then our lives would have purpose.
Evolution isn't goal-oriented, but my life has purpose. Why does
you're live's purpose depend on the particulars of evolutionary
mechanisms?
Mitchell Coffey
Steven J.
brian0918 wrote:
> Of course, there is no doubt that the evolution of the flatfish was
> divinely guided... by Picasso... but my question is as follows:
>
> The common explanation I've seen for its evolution is:
>
> 1. Taking to the sea floor, it was natural for the flatfish to rest on
> its side.
> 2. With one eye stuck in the ground, it was at a disadvantage.
> 3. Yadda yadda yadda
> 4. Result: Its bottom eye moved around to the top.
>
> The problem is in step 3. It is unlikely that the bottom eye suddenly
> appeared on top within a couple generations. So, how about those
> transitional species: what was the evolutionary advantage to having an
> eyeball offset by a couple millimeters, but still stuck in the ground?
>
symmetrical like other fish, with an eye on each side of their skull,
and after they lie down on the seafloor, their skull continues to grow,
but in an asymetric and "deformed" manner, so that both eyes end up on
the same side.
Now, this suggests that a smaller change in skull development, one
that, when the fish was mature, caused an eye to be just a few
millimeters displaced, might indeed be beneficial. Flatfish are ambush
predators, lying still and camoflaged on the bottom, and attacking when
prey draws near. A fish could do this, with eyes on opposite sides of
its head, but it might alert the prey if it moved to check out
approaching prey with both eyes. If it could do this while moving
*less*, it would alert the prey less often, and eat better for less
effort, and have more energy to devote to making babies. So one can
imagine (yes, this is a just-so story, but I hope it addresses your
specific question) that selection pressure existed even for slight
modification in the direction of the both-eyes-on-one-side mature
skull.
>
> The only solution I can think of is that since there was no advantage
> to eyeballs shifted only slightly (but still stuck in the mud), all the
> various transitional species thrived together equally, and it wasn't
> until one of the strains had their bottom eyeball shifted up above the
> sea floor that natural selection actually started to occur--sort of a
> "delayed natural selection". It would be interesting to find fossils of
> transitional species in which the bottom eye socket is shifted all over
> the place: 3 millimeters toward the spine, 5 mm toward the tail, 10 mm
> toward the mouth, etc.
>
> Anyone have some input?
-- Steven J.
Ross Langerak
"Steven J." <stev...@altavista.com> wrote in message
news:1145164117....@z34g2000cwc.googlegroups.com...
Another possibility along the same line, is that the bottom eye could be
used to spot food on the seafloor. If the bottom eye were located more
toward the front, and therefore nearer the mouth, the flounder would have an
easier time finding food on the bottom. Once the eye had reached the front
of the skull, the binocular vision would have made it a better hunter, and
it could have changed its behavior to take advantage of its new abilities.
brian0918
ourselves, which is really just another way of saying, "screw it, I'm
going to live my life according to someone or something else's
principles."
hersheyhv
The following is speculation and should be treated as such. If you
look at the eyes of other ambush (pounce) predators, such as anglerfish
and groupers in the sea and cats on land, you notice that the eyes are
often placed so as to be able to triangulate distance to their prey.
For a suction predator, this would be an important survival technique.
This is not necessarily the case in chase predators that can move their
head from side to side.
The flat fish ancestor probably did not have the option of hiding in
bush or weeds or corals, but had to hide in plain sight on a flat plane
site in clear waters. And it also had the body of many fish, flat
dorsal/vertical which is useful for swimming with a tail that moves
horizontally. Unlike the grouper or anglerfish, it's initial forays
into ambush predator probably involved twisting its body flat to the
surface, but trying, as much as possible to keep both eyes above for
triangulation. This obviously is not an optimal state, but it could
suffice to hide the ancestor *sufficiently* such that fish with this
imperfect ability (initially largely behavioral) to lie as flat as is
possible with a head that was somewhat twisted to the vertical still
did better (in terms of *net* energy acquisition) than active hunting
in this environment with its long sight lines. A prey is less likely
to see a motionless bump on the plain than the rapidly moving predator.
This then would allow subsequent selection for fish that could lay
their heads *flatter* on the surface, perhaps in association with
selection of prey to recognize the twisted partially hidden predator
and avoid it (i.e., an arms race between recognizing the predator and
predator camoflauge). With eyes somewhat naturally set forward and
close together, it would not take a large initial change in bone
structure to have the effect of allowing *some* forward and upward
vision from the lower eye. allowing the head to lie flatter.
The crucial genetic innovation would involve the (environmental?)
triggers that allowed the breaking of symmetry. But other organisms
have such triggers that allow such asymmetry, so that is not a
make-or-break novelty.
Mike Painter
Why assume that it was natural for it to rest on it's side? Certainly there
are any number of fish that lay in wait from the bottom where this is not
the case. Some of them even partially bury themselves in the sand (The flat
fish tend to be almost completely burried with only the hard to see eyes in
the clear) but have the advantage of being able to wait in rocky cover.
Note also that the fish starts out in a normal configuration, the eye
migrates after birth.
Danniel Soares
The intermediates with the eye in the middle of the way to the other
side had the advantage of swimming closer to the soil than fishes that
had yet perfect symmetry.
With perfect symmetry, was likely that the eye would be near the widest
part of the body, and at the same time, more at the "new" bottom side,
more prone to rub and harm in the soil.
The fish had to swim a bit over the soil to avoid harming the eye while
rubing it against sand and stones, thus was more visible to prey and
predators.
As it moves "up" or to the front of the head, it goes to a body part
that is slightly narrower, and the fish is less prone to damage the eye
while swimming even nearer to the soil, and can swim more freely and
quickly in this situation. It improves as more closer to the top or
front of the had the eyes migrate.
When the eye reaches the edge of the body, then it will probably
migrate a bit more now under the selective advantages of the reacquired
vision of that eye.
Von R. Smith
The other posters have it all wrong. The eye gradually migrated
*through* the skull to get to the other side. The advantage was
enlightenment through introspection. Buddhism only tells half the
story: truly enlightened individuals emerge out the other side of
Nirvana to be reborn as flatfish.
Danniel Soares
the eye in the first steps, and then as the eye reaches nearly the
other surface of the head, it is again selected for vision...
jobu
growth, or something else?
thechick...@gmail.com
jillery
wrote:
To get to the other side?
--
I disapprove of what you say, but I will defend to the death your right to say it.
Evelyn Beatrice Hall
Attributed to Voltaire
Bob Casanova
appeared in talk.origins, posted by
thechick...@gmail.com:
>;)
Because the chicken had the "road" thing locked up?
--
Bob C.
"The most exciting phrase to hear in science,
the one that heralds new discoveries, is not
'Eureka!' but 'That's funny...'"
- Isaac Asimov
Gary Hurd
> Of course, there is no doubt that the evolution of the flatfish was
> divinely guided... by Picasso... but my question is as follows:
>
> The common explanation I've seen for its evolution is:
>
> 1. Taking to the sea floor, it was natural for the flatfish to rest on
> its side.
> 2. With one eye stuck in the ground, it was at a disadvantage.
> 3. Yadda yadda yadda
> 4. Result: Its bottom eye moved around to the top.
>
There is a modestly easy physical process for the various "flaties" to grow asymmetrically. One skeletal side grows less than the other. The faster growing side is the "top" and the slower is the "bottom." The pattern is most obvious looking at the skull, but the entire skeleton follows the same asymmetric growth. Top side ribs are even larger than bottom ribs.
Evolution does not anticipate advantage. There was not a fish one day that thought, "I'll freak my DNA into a biased skeletal growth and lay on sandy mud." Rather, multiple species had what seems a weakening of a genetic switch. They grew lopsided and it worked for them. These species are not even all closely related as they belong to multiple families.
(I just checked some old notes- I have dissected about 10 species).
I suggest;
Matt Friedman
2008 "The evolutionary origin of flatfish asymmetry" Nature volume 454, pages 209–212
And a less technical version;
The Improbable—but True—Evolutionary Tale of Flatfishes, NOVA May 7, 2014
https://www.pbs.org/wgbh/nova/article/flatfish-evolution/