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Reptile reproduction, it turns out, is more flexible than our own. Whiptails, a girls-only species, can lay unfertilized eggs without the need for a male. And Komodo dragons have recently been discovered to perform parthenogenesis, or virgin birth, even though they are also capable of sexual reproduction.

But could a species of reptile--preferably a squamate or a crocodylomorph--be hermaphroditic? And no, I'm not talking about "sequential hermaphrodites", which are boys that are born girls. I'm talking about "simultaneous hermaphrodites", meaning that they carry both male and female sex organs and can fertilize both each other and themselves. In reptile physiology, is this sort of adaptation within the realm of possibility?

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  • $\begingroup$ Why would being a simultaneous hermaphrodite yield any different results from being an asexually reproducing female? No matter what, you end up with a near-clone. $\endgroup$
    – Zxyrra
    Mar 3, 2020 at 19:43
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    $\begingroup$ @Zxyrra - for all described options gametes still undergo meiosis shuffling, so no near clones. $\endgroup$
    – Willk
    Mar 3, 2020 at 19:44
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    $\begingroup$ Some fish are simultaneous hermaphrodites, for example the mangrove killfish Kryptolebias marmoratus or the painted comber Serranus scriba. So it is possible in vertebrates, although I don't know of any simultaneously hermaphroditic amniotes. $\endgroup$
    – AlexP
    Mar 3, 2020 at 20:02
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    $\begingroup$ If they can fertilize themselves unaided, evolution is either going to select away from simultaneous hermaphrodites in general (there are good reasons why sexual reproduction is generally dominant, namely the ability to adapt to changing conditions), select away from the ability to self-fertilize unaided in particular (evolution can only do so much about that, but it can at least make the anatomy awkward enough to keep it from really happening outside of intelligent intervention or a one-in-a-million fluke), or else leave you with a single-gender race like the Whiptail lizards you mention. $\endgroup$
    – Palarran
    Mar 3, 2020 at 21:45
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    $\begingroup$ @AlexP: The fish described are sequential, and there are three categories (MTF once, FTM once, or MTF-FTM cycle). Fish, Reptiles, and Birds have ZW sex chromosomes as opposed to the mammals XY, with the basic difference being that ZW is female and ZZ is male (where as XY system has XY male and XX female). The reasons why Incest is bad is probably why there aren't any true male-female simultaneous chromosomes. $\endgroup$
    – hszmv
    Mar 4, 2020 at 12:13

3 Answers 3

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Hermaphroditic reptiles can occur via axial bifurcation.

Axial bifurcation is a process in which an embryo splits along its axis early in its development. A complete split produces identical twins. A partial split results in a single individual with duplications.

Reptiles are more likely than mammals to undergo an axial bifurcation that produces a live individual; two headed snakes and turtles are rare but much more common than mammals with this condition.

I figured if a reptile could undergo axial bifurcation and have two heads, why not two sets of genitals? This would be less spectacular and more likely to evade notice, but case have been described. Described here are turtles from an article on axial bifurcation and teratology.

The Principal Diseases of Lower Vertebrates

Hermaphroditic sexual organs are of more obvious teratological interest. Risley (1941) reported on a specimen of Chrysemys picta marginata Agassiz which proved to be a complete hermaphrodite equipped with two testicles, a well-developed left oviduct, and nine oocytes in the right and thirty-two in the left testis. Another turtle (Mal.aelemys terrapin centrata Latreille) showed some degree of female pseudohermaphroditism. The juvenile animal was equipped with ovaries and an ovarian medullary tumour composed of testicular tissue.

This would also be a mechanism for a dragon to have 6 legs. I think it would necessarily have 2 tails as well.

The OP also wanted an individual which could fertilize itself. For a reptile such as is described here, the mechanics involved in that might be an obstacle.

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Yes it is completely possible there are already reptiles that occasional produce true hermaphroditic individuals.

Bothropoides insularis and Certain Pseudoficimia, both snakes, has 3 sexes one with both males and female sex organs, both sets of organs are slightly reduced than their counterparts but that could just be do to the spacial limitations of being a snake. Many are sterile but not all of them are.

source

You still need to come up with a reason it would be favored, but since it can exist, it could evolve and evolve further with the right pressures.

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    $\begingroup$ Downvotes without comment are unhelpful, folks. $\endgroup$
    – Starfish Prime
    Mar 4, 2020 at 13:28
  • $\begingroup$ That said; intersex conditions in the lanceheads are undersirable side effects of inbreeding in a small population and are generally infertile. Not sure about the Pseudoficimia, but certainly other flavours of reptile intersex conditions are generally associated with sterility, which isn't what the OP was after. $\endgroup$
    – Starfish Prime
    Mar 4, 2020 at 13:32
  • $\begingroup$ @StarfishPrime That is what flags are for. $\endgroup$
    – JohnWDailey
    Mar 4, 2020 at 14:08
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    $\begingroup$ @starfish, associated with sterility, but they are not always sterile, which means you have the conditions for it to continue to evolve if it was favored. Lots of favored traits start as undesirable side effects, which would define most mutations. $\endgroup$
    – John
    Mar 4, 2020 at 23:55
  • $\begingroup$ @John that's a reasonable point. $\endgroup$
    – Starfish Prime
    Mar 5, 2020 at 10:43
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The best I can offer is Haploids, which is common in many social colony insects (Ants, Bees, Termites (I think)). Males do not have a sex chromosome pair while females do. The queen can store the male sperm in a special organ and release it to fertilize the eggs based on the hive/colony's needs. If there is a low supply of workers, she will make more females... if she's all hot and bothered and needs to increase her collection of eye candy, she'll make more males. This leads to some bizarre family dynamics where all female drones are 3/4ths genetically related to their mother and 1/4th genetically related to their father while all male drones have no father and cannot have any sons. Unfertilized eggs will still hatch as males always.

Again, this isn't simultaneous Hermaphroditus, as it still takes two to tango, but it does provide a situation where mom can have Virgin Births so long as you accept that all those births will be men only.

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