Re: Leucistic Black Rats?

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Posted by patricia sherman on September 13, 2002 at 15:07:49:

In Reply to: Leucistic Black Rats? posted by Shinigami813 on September 12, 2002 at 15:54:19:

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.

Tricia

Follow Ups:

Tricia has a good point..........................more....... D Goudie 09/15/02 (2)
- Re: Tricia has a good point... patricia sherman 09/16/02 (1)
  - And THAT'S the way to do it!... Gerry Binczik 09/16/02 (0)