Re: leucistic tx vs. leucistic black rat

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Posted by patricia sherman on October 26, 2002 at 14:04:25:

In Reply to: leucistic tx vs. leucistic black rat posted by favoritemistake on October 21, 2002 at 01:18:54:

I'm reposting a response that I originally posted about six weeks ago to a similar query.

Leucistic black rat snakes supposedly do exist, but they're controversial. Some people believe that it is a naturalllu occuring morph, others allege that they have an infusion of leucy Texas rat genes. Although leucism is a much rarer anomaly than are amelanism and anerythrism, as far as I know, it is an anomaly that can possibly occur in any species. It is just so rare, that it draws a lot of attention when it is seen.

Elaphe o. obsoleta is very closely related to E. o. lindheimeri, and it well may be the case that the leucism in E. o. o. did originally occur spontaneously. Unfortunately, because the two subspecies are so similar to each other, there's no easy way of being sure. Perhaps DNA analysis could settle the question, but I doubt that anyone owning a leucy black is likely to have it done. It is a costly procedure, and the owner may be disappointed if it proved that the snake was an intergrade.

As to the bug-eyedness, this is a defect that is "linked" to the leucy gene (it occurs on the approximately the same chromosomal locus). Never having bred leucy blacks, I can't tell you whether or not it is known in them, but see no reason why it wouldn't occur unless the foundation stock were test-bred to ensure that they didn't carry the bug-eyed gene. In the Texas rats, it may be that the bug-eyed gene is passed through some of the normals (in whom it isn't expressed). For instance, a pair of normals het for leucy may have inherited it from the leucy parent/s. In mating such a het pair, one could theoretically produce babies that were homo for the normal colour AND homo for bug-eyes, but their eyes wouldn't be buggy because they lacked the leucy gene. The only way of proving it, would be to mate that "normal" to a bug-eyed leucy, and see if half the progeny were leucy.

If none of the progeny were leucy, then the "normal" parent would be homozygous for that colour. If half the progeny were leucy, then the normal parent would be proven to be heterozygous. If all of those leucy progeny expressed the trait, then the normal parent would be proven homozygous for it. If only half of the leucy progeny were bug-eyed, then the normal parent would be a het for bug-eyes. In the best possible scenario, none of the leucy progeny would be bug-eyed, and the normal parent would be proved to be a non-carrier.

Now, as to your question about temperament differences. I'd have to say that each snake is an individual, and there are no hard and fast rules about this. I have a leucy TX rat female that is extremely calm and gentle. I also have several very black obsoletas that are of like nature. I have a normal TX that is a little firebrand. One of my 15-yr-old parent obsoletas (the female) is also quite snappish. Occasionally, even the calmest will catch you off-guard and strike at you, but usually it is foreseeable (either the snake is very hungry, or you surprised and scared it).

Sizewise, there is equal variability in both subspecies. My lindheimeri pair are both growing impressively. With my yearling obsoleta sibling-pair, the male is such a husky thing that I've named him Goliath, but his sister is several inches shorter, and only 3/5ths his weight. Of the two-yr-old sibling-pair, the female is a foot shorter and weighs only 2/5ths the weight of the male, but that isn't a fair comparison, since he was the biggest baby in that clutch and she was the runt. With my son's pair from the same clutch, his female is about 3/4ths the weight of his male which is only marginally smaller than my male. Generally, the males show more length and girth than the females of like age, but my leucy TX female is the thickest of all of them. As a general rule, all members of the E. o. complex are a fair but longer and more slender than E. guttata of similar age/weight.

Tricia

:How do these 2 stack up as far as length, girth, attitude, color (does one have less little specks of color than the other). I was planning on a tx, but now the black rats caught my eye. Please give me your opinions. Thanks

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