DBT Colors and genetics

[Todd Stockwell]

The Stockton College page linked to another college page that had a tempting link on “terrapin genetics.” Unfortunately it isn’t active. Has anyone seen any recent genetic studies of dbts and/or any other attempts to explain their wide range in colors and patterns? And how closely they are actually related to graptemys? Genetic profiling is really hot in the rare farm animal breed conservation efforts. The first major studies were done on equines including color traits (because the money was there for horses). These genetic studies are really nailing down where modern surviving individual specimens of rare farm animals really fit and just how “old” some of the surviving strains really are (or aren’t). How far have turtle, and specifically dbt, genetic mapping projects gone to date? One of our list members mentioned observing a decrease in lighter colored dts in wild populations recently and mentioned that they might be more subject to predation in shallow water. So, let me ask the “dumb” question – why DO dbts have such variations from white to purple skin to blue to black, with spots, with concentric circles, etc.? Were the color variations that much more distinct and environmentally selected for prior to commercial transportaion and mixing of the subspecies? Are lighter dbts more subject to predation (as in Chun’s very unfortunate example?)? Why do the light specimens show up so frequently in wild populations (or do they)? What natural environments would select for the beautiful colors and patterns of dbts we see like the white skins and light shells? Can anyone with direct experience with the headstart programs tell us what percentage of hatchlings inherit the female’s color pattern? How much color and pattern variation is there in a clutch of eggs? Maybe some of our list members who have been successful at captive breeding and hatching can share observations? I am truly interested in the science of this, and I also am wondering what the ramifications are for selective captive breeding programs? To ask another “dumb” question, does selecting for certain colors and patterns in captive breeding of dbts produce high numbers of offspring that look like the parents or is there quite a spectrum from each mating? What colors and patterns are dominant and recessive? If turtles have good vision and use color patterns as part of their mating identification, how does this affect mating habits in dbts? Do they mix readily or tend to seek like-colored partners only? The questions on the “hybrids” might be answered by genetic profiles. Also, what about the “crosses” of macrospilota and other subspecies that sometimes seem to result in very outstanding and unique individual specimens? Is “crossing” of captive dbts to obtain unique colors and patterns a “bad” thing as long as there is never any intent to place the resulting animals back in the wild since there is only one species? I know this may stir up some debates, but I’m interested in hearing how those on this list devoted to captive husbandry of dbts see this issue? If there are places to look for these topics, then I’d be glad to get the citations and try to read up on it myself. However, I just haven’t seen much on this, but maybe I just don’t know where to look? Chun-Ming Chew wrote:

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