Category: All Posts Page 146 of 149

Yes, it’s true. A “third eye” does exist, not only in the ancient Hindu literature and the new age imagination, but in birds, amphibians, reptiles, fish, lampreys, and hagfishes. We’re talking about the pineal gland, a small organ located on top of the brain, just underneath the surface of the skull. Although it doesn’t have visual capabilities in the image-forming sense, it is intrinsically photosensitive, responding to light signals without any help from the lateral eyes. (Mammals, including humans, have a pineal gland too…but it has lost the ability to detect light).

You can see the parietal eye on top of this anole’s head (it’s the tiny circle in the middle). The pineal gland can’t be seen externally, but it’s just posterior to the parietal eye and right underneath the surface of the skull. Photo credit: TheAlphaWolf, License:Creative Commons Attribution-Share Alike 3.0 Unported

Anoles, and some other lizards, actually have two “third eyes,” one being the pineal gland, and the other being the parietal eye, which can be seen in the picture above.

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The sequencing of the genome of the  green anole (Anolis carolinensis) is a landmark in the age of genomics, and a highpoint in the annals of anole studies.  It is the first complete genome sequence of a reptile, and a great step forward in the development of comparative genomics. Results are already coming in: Matthew Fujita, Scott Edwards and Chris Ponting have a paper in press in Genome Biology and Evolution, using an earlier release of the anole genome, showing that the green anole genome lacks the large guanine-cytosine rich regions (called isochores) that are characteristic of birds and mammals. Is this lack unique to the green anole, or a feature of some larger group? We don’t know, of course, because the green anole is the first non-avian/non-mammalian amniote to be sequenced, but it is a hint of new things to come. As Rich Glor put it in his commentary here at Anole Annals,

Fujita et al.’s work  is a good example of the insight offered by comparative genome sequencing; as the number of available genomes expands, this work is sure to continue to challenge overly simplistic assumptions about genome architecture and evolution derived from biased sampling of the tree of life.

Green Anole, Anolis carolinensis, New Orleans, LA. Note the expanded subdigital toepads.

So why was an anole chosen to be the first reptile sequenced? The short answer is that, among a small group of candidate species of reptiles announced by the NIH in May of 2005, the response of the biological community favored the green anole over the garter snake. But the longer answer includes why the community preferred the green anole: it has long been the subject of diverse physiological, behavioral, ecological, and other  studies (a “model” organism in the functional biology sense), and, more importantly, anoles in general have been favored and favorable materials for a diverse array of physiological, behavioral, ecological, evolutionary, and zoogeographic studies over many decades. The goal of this post is to review a bit of the rich history of anole studies to provide some background on why so many researchers have found anoles to be vastly interesting animals.

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and who doesn’t?

http://dusttracks.com/2011/08/20/the-green-anole-is-the-hero-the-sweet-tea-is-the-salvation/

Caribherp is a website devoted to all herpetologic matters West Indian. It describes itself as follows:

Caribherp contains information on amphibians and reptiles of the Caribbean Islands (West Indies). It serves as a checklist of what occurs in the region as well as a quick identification guide to the species. Approximately 2000 images and maps, and selected frog calls (sounds), are presented along with an integrated open-access journal, Caribbean Herpetology. The journal accepts color images and video and currently publishes brief communications on individual species—later volumes will include full research articles. The species accounts can be sorted in many ways. Maps of the Caribbean, both current and historical, can be found on a separate site, Caribmap. Multimedia essays related to conservation issues on Caribbean islands are on a third site, Caribnature.

The poster above and a similar one can be obtained here on the “Resources” page.