Friday, October 17, 2008
"Bug-eyes" in Trans-Pecos Ratsnakes, an evolutionary adaptation
This doesn't happen often, but sometimes I talk to people who are laboring under the myth that "bug-eyes" in Trans-Pecos Ratsnakes is a result of captive inbreeding. This is well-documented for leucistic Pantherophis obsoletus lindheimeri, but for Bogertophis, nothing could be further from the truth.
Trans-Pecos Ratsnakes are fossorial during the day and 100% nocturnal otherwise. In other words, they're constantly in complete darkness -- in fact, in the wild, they absolutely shun light. "Bug-eyes" is an evolutionary adaptation to this lifestyle. And bug-eyes is not only seen in TPRSs -- it, as a physical trait, has convergently evolved in many unrelated taxa of animals with similar nocturnal habits. Owls, Leaf-tailed Geckos of the genus Uroplatus (among many other gekkonids), tarsiers, Red-eyed Tree Frogs, and the list goes on and on. Another example of "bug-eyes" in completely nocturnal snakes is Gray-banded Kingsnakes. Their lifestyle is much more fossorial and nocturnal than most Lampropeltis, and so they have those bulging eyes, which is a disharmonic trait for a kingsnake species.
And there is no deleterious allele in subocs that causes extra or excessive "bug-eyedness" when subocs are inbred. In fact, of the 115 subocs in my facility, some of the most bug-eyed are from parents that were caught hundreds of miles apart -- the furthest thing from inbreeding.
So, in conclusion, though "no bug eyes" might be a selling point for leucistic Texas Rats, it's not desirable, healthy, or normal to have a TPRS without them!
I mean, can you imagine someone selling a tarsier on the "selling point" that it has "NO bug eyes!"? 
Have a great weekend, all.
