penis and hemipenis
Yehudah Werner
>>
> Technically, all reptiles have 'hemipenes', or in the case of
> chelonia one 'hemipene'. This is because a true penis contains a
> closed urethra, the reptile versions do not. Sperm is introduced into
> the female via grooves on the surface of the hemipene. The organ is
> not used for urination. This is a useful distinction for us vets, as
> a lacerated/ damaged hemipene may be surgically removed without
> worrying about maintaining a patent urethra as in mammals. Aren't
> reptiles marvellous?!
>
> Sharon
>
>
> ********************************************************
> Sharon Redrobe
> NVS / Exotic Species Vet
> Small Animal Clinic
> Edinburgh University
> Edinburgh
> EH9 1QH
> UK
>
> Phone 00 44 131 650 6074
> Fax 00 44 131 650 6577
> email SP...@lab0.vet.ed.ac.uk
> Smile- people will wonder what you have been up to..
Well, Sharon, I suspect I know what you have not been up to. Or has evolution
really progressed that quickly? When I learned comparative anatomy in the 50's,
the copncept hemipenis meant not "not proper penis" but "half penis" because
the two did (though not simultaneously) the work of one; the penis of turtles
was not homologous to the mammalian one, and not to the squamate hemipenis; the
crocodilian penis was not homologous with any of these. Each group had evolved
its own intromittent organ separately from the penis-less cloaca, which persists
in Sphenodon and most birds (ducks and relatives having evolved their own
penis) - so it isn't so illuminating to say that most amniotes have a penis.
Also, female mammals used to be able to urinate without the urethra
running the length of the penis. I admit I have not searched the literature
for urination in de-penissed males.
Won't you come to the 5th International Congress of Vertebrate
Morpholog, Bristol (UK), July (97) ?
Cheers, Yehudah
P.S. Smile: When in the 60's I taught vertebrate morphology to freshmen
and gave an "American" (multiple choice) exam, one co-ed opined that all
mammals have duplex penises. No comment.
Prof.Y.L.Werner
Dept. ESE
Hebrew Univ.
91904 Jerusalem
Israel
Sharon Redrobe
Now I am confused....
> When I learned comparative anatomy in the 50's,
> the copncept hemipenis meant not "not proper penis" but "half penis" because
> the two did (though not simultaneously) the work of one
I did not say it was a proper penis, I said it was NOT a proper penis
like a mammal one...
> so it isn't so illuminating to say that most amniotes have a penis.
I said that* mammals* have a penis (they are amniotes but not all
amniotes are mammals....)
> Also, female mammals used to be able to urinate without the urethra
> running the length of the penis. I admit I have not searched the literature
> for urination in de-penissed males.
In some female mammals the urethra opens into the distal vagina, in
others it has a separate orifice. When
you amputate the penis in a mammal the urethra must be identified and
maintained- the animal is left with a hole. Sometimes a new urethral
orifice is made in the proximal penis if the end is damaged/ blocked,
but this is beside the point.
In my original comment I meant that as the snakes, lizards, chelonia,
crocs etc do not have a copulatory organ with a urethra within it
then it is not termed 'penis' but hemepene. I thought that the term
'hemepene' was derived from the fact that its was essentially a
'half' penis (structurally or functionally or both)
> Won't you come to the 5th International Congress of Vertebrate
> Morpholog, Bristol (UK), July (97) ?
Maybe we should meet up as (hopefully) we will make more sense to
each other face to face rather than over the ether!!!
Keith Benson
Yehudah Werner wrote:
which persists
> in Sphenodon and most birds (ducks and relatives having evolved their own
> penis)
Lets not forget Ratites! (ostriches, kimi, emus etc!)
- so it isn't so illuminating to say that most amniotes have a penis.
> Also, female mammals used to be able to urinate without the urethra
> running the length of the penis.
Actually Yehudah - they still do! ;)
Keith
Mason Meers
On Thu, 6 Feb 1997, Sharon Redrobe wrote:
> In my original comment I meant that as the snakes, lizards, chelonia,
> crocs etc do not have a copulatory organ with a urethra within it
> then it is not termed 'penis' but hemepene. I thought that the term
> 'hemepene' was derived from the fact that its was essentially a
> 'half' penis (structurally or functionally or both)
Don't worry. Some of us actually understood you the first time. It
wasn't as difficult as it's being made. If I may be so bold... I
believe Dr. Werner was simply trying to make the point that hemepene, as
you described their distribution, are not homologous. Some would argue
that terminology for anatomical structures should be strictly tied to
homology, in which case we'd have to invent a new term for the
"hemepenis-like" copulatory organ of each of these groups. ...not a
concept I'd like to teach in a freshman zoology course.
Mason B. Meers
Mason B. Meers
Johns Hopkins, SOM
Functional Anatomy & Evolution
*Please direct all flames to my flame-retardant address below:
mme...@welchlink.welch.jhu.edu