Saturday, February 6, 2010

Red-eared Slider

We are all familiar with the ability of some species of chameleons to change their coloration to match their background or their mood.  Alas, the poor turtle has to hope that its carapace color matches its habitat's color- or does it?  Research has recently demonstrated their ability to change their melanization, similar to chameleons and squid, although being turtles, this is slower like everything else done at a turtle pace.

John W. Rowe and colleagues from Alma College in Michigan,used gravid female midland painted turtles and red-eared sliders from the wild in a study of coloration.They collected eggs and then kept half the hatchlings in control groups on either black or white substrate, for 160 days.  The other groups were kept on either black or white substrates for 80 days, then switched to the other color substrate.  They measured the color changes on the carapace and head of the animals with a spectrometer.
After 80 days, the colors were the same in the control and study groups.  After 160 days, the controls had their same color while the study groups who had moved to the opposite color substrate were changing color to match their latest background.  More details are covered in Natural History magazine.
 Red-eared sliders are a common turtle found all over Missouri.  They tend to live in muddy bottoms of ponds and rivers and are less common in our gravel based Ozark streams.  They have a tendency to develop progressive darkening (melanism) when they grow old, covering both the yellow stripes on the carapace and their red ears.
If you are of my generation- which few are- you will recall when you could buy a small plastic turtle island with a baby red-eared slider at Woolworth's Five and Dime.  (Have I lost some of you yet?)  You would raise them on turtle food, clean the island when Mom insisted, and hopefully remember to put them back on their island.  Fortunately for the turtles, the discovery that they could carry and transmit Salmonella led to outlawing their sale.
There are still come companies breeding them for sale in Europe and Asia.  Just like pot-bellied pigs, when they get bigger and no longer cute, they are released in the wild where they are able to out-compete native species.  This may sound somewhat familiar if you think of kudzu, thistle, and the English sparrow.  It is interesting to think that our red-eared slider is now an invasive species on other continents!

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