Free Verse -- Sunday Morning Coming Down, Part 2 -- Nothing About The Bakken -- August 30, 2020

It's going to be one of those days, I can tell. I didn't take my meds. LOL. Where we go on the blog today is anyone's guess.

Can you believe this article was in Forbes. I said a couple of weeks ago that I needed to re-subscribe to Forbes. Memo to self. Subscribe. 

Turtles are key to tracing birds' "redness gene" back to the dinosaurs. Link here. Of all the animals out there, the one animal that continues to perplex biologists with regard to "where did they come from" and "how to classify them" are the turtles. This article may provide another connecting dot. From the linked article:

The gene responsible for red coloration and color vision in birds is also functional in turtles -- having arisen in a shared ancestor where it was probably used for color vision and possibly also for red coloration more than 250 million years ago

I recently wrote a piece about two elegant research papers that described how birds became red. Those papers, which were published side-by-side in the journal Current Biology, revealed that a gene-encoded enzyme, CYP2J19, converts yellow pigments obtained from the diet into red pigments, which red birds then use to color their feathers, bills and bare skin.

But manufacturing pigments for visual displays probably wasn't the original, ancestral, function for the "redness gene" because even birds that lack red coloring have a functional CYP2J19 "redness gene." In fact, it appears that CYP2J19 plays an important role in color vision. Specifically, CYP2J19 creates the red carotenoid pigments that are found in oil droplets within particular cone cells. These retinal cone cell pigments act as spectral filters to enhance color vision.

More:

Turtles are unique amongst reptiles because they have pigmented cone oil droplet, and their red oil droplet pigments also appear to be ketocarotenoids -- just as in birds. Like birds, turtles have excellent tetrachromatic color vision. Some turtle species, such as the painted turtles, Chrysemys picta, that are found throughout much of North America, have brilliant red pigments on their bodies, and this coloration appears to be acted on by sexual selection.

Where are turtles getting their red carotenoid pigments? Did the ability to manufacture ketocarotenoid pigments arise independently in birds and turtles? Or, as Dr. Mundy and his colleagues suspected, do birds and turtles share a genetic basis for ketocarotenoid synthesis? But if ketocarotenoid synthesis does have a shared genetic foundation in birds and turtles, which was the original function of CYP2J19; color vision or coloration?

Much more at the link. Archived.  

Sophia and I spend a lot of time watching and feeding the turtles at "Turtle Creek," Parr Park, Grapevine, TX. Per "bank-foot," this creek has more turtles than any other creek in the world. At least that's what I tell Sophia.

By the way, next project with Sophia: the night sky. There's a great app at the App Store for identifying night sky objects. Goal: identify a group of stars we can call "Barbie." Her own constellation. 

Oh, back to the original question: where did turtles come from; where do they fit in? From the linked article:

To answer this question, it was essential to look way back in time, back to that time when birds' and turtles' last common ancestor roamed the Earth. Thanks to newly-developed molecular and computer technologies, it was only recently found that turtles and archosaurs form a distinct clade (Archelosauria), independent from lizards, snakes and tuatara (lepidosaurs). Link here to wiki.

Archelosauria is a clade grouping turtles and archosaurs (birds and crocodilians) and their fossil relatives. Multiple sequence alignments of DNA and protein sequences and phylogenetic inferences showed that chelonians are the sister group to birds and crocodilians. Morever, there are about 1000 ultra-conserved elements in their genome that are unique to turtles and archosaurs, but which are not found in lepidosaurs (tuatara, lizards and snakes). Other genome-wide analysis also supports this grouping.

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