Reptile & Amphibian Forums

While I, like most of you, am convinced of the brattler hoax it did raise an interesting question in my mind. Many folks jumped on the "hoax" bandwagon because they believe (and it may be true) that an egg-laying species can't hybridize with a live-bearer.

I got to pondering that logic and have a few observations and/or questions. First rattlesnakes are not truly viviparous they are ovoviviparous ... they incubate unshelled eggs in their oviducts and give birth to live young in individual birthsacks. This condition is intermediary in the evolutionary path from oviparity to viviparity, and at least one member of the family Viperidae retains the ancestral condition of oviparity, the bushmaster.

Some oviparous animals (documented at least in alligators and snakes) can delay oviposition until the embryo is fairly well developed. Smooth green snakes in the northern extent of their range have been known to "hold" their eggs until they are within a month of hatching. There are environmental factors that may account for this "behavior", but the main thing of interest is that oviparity in reptiles may not be a rigid construct.

So what genetic mechanisms exist to preclude an oviparous animals and an ovoviviparous animal from reproducing? I don't know. I do know that there is reportedly a species of Lacerta in Europe that is a "live-bearer" in the northern portion of its range, but in the south, where the climate is warm enough to incubate eggs it is an egg-layer.

So here's a question ... is anyone aware of two relatively closely related snakes ... same genus would be nice ...one of which is an egg-layer and the other of which is a live-bearer? I am in no way a proponent of mutts, however I would be very interested to see if the two reproductive strategies actually preclude hybridization.

Anyway ... I think, for now, the stronger biological argument against the brattler might be odds of successfully hybridizing across two Families. $.02 Steve

Actually, I've got a copy of a research paper running around somewhere concerning a single species (a lizard - not a snake) in the Old World somewhere where some populations are live bearers and some populations are egg bearers. When they crossbred the populations, the mothers that were supposed to lay eggs, laid eggs and vice versa. The F1 generation, when bred together, typically laid very thin shelled eggs that were retained for a little longer than expected. Soooo, they were intermediate, but eggs COULD hatch from the F1 cross.

I might be able to find the reference at my office if necessary. Email me if you want me to try and find it because you plan to run it down at a University library or something.

KJ

To my knowledge no hybridization experiements have been carried out on these.. but they are examples of closely related snakes with different reproducion modes-

Eryx muelleri- West African sand boa- egg layer
Eryx colubrinus and conicus- Kenyan and rough scaled sand boas- live bearers

Cerastes cerastes- desert horned adder- egg layer
Cerastes vipera- Cleopatra's asp, Avicenna viper, Sahara sand adder- livebearer.

The sand boas lay thin shelled eggs that hatch in 14 days. No one even knew they laid eggs until 1998. Eryx jayakari also lays eggs, but I guess isn't considered as closely related to the other Eryx species. I could do this experiment myself since I have both muelleri and colubrinus, but am wondering about the ethics.
Cerastes cerastes lays classic snake eggs but is otherwise almost impossible to tell apart from vipera (except that some cerastes have horns).

Ok, these are good points to the possibility of the two breeding. However, don't rattle snakes eat other snakes? How would a bull protect itself? And doesn't the aggressiveness of the rattler make this union a high improbability? just another veiw . . .

Rattlesnakes don't eat other snakes as a habit. They actually GET eaten by kingsnakes. And wild rattlers probably aren't any more aggressive than wild bullsnakes (I'm sure there are people here with more firsthand experience in that than I)...

But that's kind of beside the point, a rattler and a bullsnake matng would be like a dog and a pig mating. They're just not enough alike to produce any offspring. They're in two completely different snake families, ect. ect.

Boas and pythons can not even breed (some examples on the hybrid forum) and seem more closely related than colubrids and crotalids. Andy
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Andy Maddox
Houston Herp Key
The Reptizone

Who are you who can say it's ok to live through me? Alice In Chains

Yup... A Brattler really is as likely a cross as a Jackalope... People just think snakes are all similar because none of them have legs.
Last I read, no one was really sure which group of snakes is the closest relatives of the vipers... I'm kind of curious about that myself.

Some biological and physiological differences that would make this highly improbable at best:

1. Differences in the pheremones that snakes emit during the breeding season. It is doubtful at a Rattlesnake would recognize those of a Bullsnake as breeding signals and vice-versa.
2. Chemical barriers. This would probably prevent the sperm of one penetrating the protein coating of the eggs of the other. This is one of nature's safeguards against this sort of thing happening.
3. Fertilization and the start of embryo development is, in a lot of ways, like fitting the pieces of a giant complex jigsaw puzzle together genetically. It would be like taking half of the pieces of one jigsaw puzzle together with half the pieces of another totally different one and trying to piece together one puzzle that makes sense. If the sperm was, in fact, able to penetrate the egg it would be doubtful that the genetic code of the two snakes could be sorted out to form the "blueprint" for the embryo.

These are all valid points and provide a stronger case as to why these two species probably could not hybridize. All of these characteristics are attributable, at least in part, to the genetic differences inherent in the 2 species ... not to the mere fact that one is oviparous and the other ovoviparous.

The point I was "dancing" around is that oviparity and ovoviparity are not necessarily "fixed" points on a continuum of reproductive strategies. There appears to be some plasticity in these traits ... begging the question about the genetic control. Hence the question as to whether these two different reproductive "conditions" would preclude hybridization. I would be willing to bet (not a lot, but some) that in cases where the taxa were closely related the possibility of successful hybridization would be possible.

BTW eastern rattlesnakes, as you are probably aware are fall breeders and only reproduce biennially ... it would be pretty difficult for spring breeding pine snakes to "hook up" with one of our EDB's or Cbrakes ...

SteveB