Archosaur Lungs

Posted by tigerhawkvok on January 20, 2010 12:45 in dinosaurs , evolution , biology , herpetology

Just a quick update, before I head to Indiana to visit Purdue and my friend Jessica. I realize I missed yesterday's tetrapod, but I prefer to postpone a week and post a better update rather than a very breif post every week (look forward to sea snakes next week).

In this week's science, there is a paper describing unidirectional airflow in alligator lungs, strongly suggesting that this formerly "avian-style lung" is in fact an archosaurian synapomorphy. That is to say, this paper gets as close as a single paper can get to outright saying that this is a mechanism that helped nonavian dinosaurs get so large. Archosaurs just keep being awesome.

On somewhat related news, I think I'll try to put up a few evolutionary YouTube videos. Rather than a pure bash-on-creationist style, though, it'll be focused on describing particular evolutionary lineages and evidence. We'll see how that works out, though I need to become much more familiar with movie editing software.

Chytrid fungus in plethodontid salamanders

Posted by tigerhawkvok on December 18, 2009 16:47 in General , biology , research , misc science , herpetology

Yes, I know I failed on the Tuesday Tet. I know what it will be (and will be a double-feature next week), but I couldn't bring myself to do a short entry without some research first.

Also, the entry on the basal theropod (DOI 10.1126/science.1180350) will be coming. More importantly though, I wanted to note that my good friend Sara Weinstein had her first paper published in Copeia today. You can view the abstract at asihcopeiaonline.org ("An Aquatic Disease on a Terrestrial Salamander: Individual and Population Level Effects of the Amphibian Chytrid Fungus, Batrachochytrium dendrobatidis, on Batrachoseps attenuatus (Plethodontidae)" DOI: 10.1643/CH-08-180). I'll post a nice summary of it in an few days, also. Hopefully that will be somewhat illuminating, as I've known about this project (and helped a little bit) for 3-4 years now!

Now, I just need to get myself in gear and get *my* paper out. 9 months is just embarassing.

Ensatina, Taricha, and TTX Resistance

Posted by tigerhawkvok on June 19, 2009 03:17 in evolution , biology , herpetology

Rather than a longish comment on Rachael's latest post, I thought I'd write up a brief entry on Ensatina.

First, the picture:

Ensatina eschscholtzii eschscholtzii

Ensatina eschscholtzii eschscholtzii, or Monterey subspecies of E. escscholtzii. The "Monterey Salamander", found near Monterey, CA.

Ensatina are an interesting species of salamander in that they are a "ring species", or, they have a sequence of morphotypes that gradually change regionally, and these morphotypes overlap but do not interbreed. There are two terminal morphotypes that are too distantly related to be capable of interbreeding (see Wikipedia's discussion of the subject). The beauty of ring species is that they provide a living sample of speciation and evolution.

In particular, Ensatina in the Bay Area differ from the Monterey morphotype in that they are very morphologically similar to the non-terrestrial stage of Taricha torosa, which are highly toxic to ingest. The tetrodotoxin they produce is a neurotoxin that is potent enough to kill most vertebrates (though some Thamnophis (Garter snakes) have evolved modified sodium channels to enable consumption of them as prey items; see this paper and others for more) (DOI: 10.1007/s10886-005-1345-x). Thus, Ensatina in the Bay Area mimic Taricha presumably to avoid predation.

For those of you curious about the diagnostic differences, an Ensatina is generally smoother than a Taricha, with more prominent costal grooves (the grooves along the side), has nasolabial grooves, and has a constricted base at its tail. The Monterey specimen here lacks the yellow eyes of Taricha, though the Bay Area ecomorph has eyes that are quiet similar to those of Taricha.

Suggested Thamnophis/Taricha studies: