Literature Review: Snake Fangs Continued

So, I got interested by Deseray's presentation of snake fang evolution, especially the one article where they tracked embryonic development of fang cells, and wanted to dig in some more. So here I am, for the first time realizing the usefulness of work citing and reading the actual paper she presented on. And what they did to determine the development of those fangs are quite fascinating!

Vonk, F. K. (2008). Evolutionary origin and development of snake fangs. Nature, 454(7204), 630-633.

To access the paper: http://www.nature.com/nature/journal/v454/n7204/pdf/nature07178.pdf

and supplemental information containing more data: http://www.nature.com/nature/journal/v454/n7204/extref/nature07178-s1.pdf

From the lab species list we learned that there are hinged-fanged venomous snakes (Crotalidae), erect-fanged venomous snakes (Elapidae), and rear-fanged snakes (Dipsadidae). The question of if , or how, different types of snake fangs relate to their venomous properties popped into my head.

Apparently, snakes can 1) non-fanged 2) front-fanged, 3) rear-fanged, and 4) front AND rear fanged!

As you can see from this phylogeny, both the erect-fanged venomous Elapidae and the hinged-fanged venomous Crotalidae that we've learned are FRONT-fanged. All the other snake groups we covered in lab-- Dipsadidae, harmless living bearing Natricidae, and harmless egg-laying Colubridae--have rear-fanges. So regardless of a snake being "harmless" or not, it can still have fangs. There's only one group that does not have fangs of any sort, and that's Boidae. All snakes have teeth though, so watch out!

 

I modified their diagram comparing the fangs of 4 groups of snakes:

As you can see, all fangs, regardless of types, are located on the UPPER jaw. They also found that the fangs are always located on the maxilla portion of tooth-bearing bones, colored in red.

 

They tracked the growth of the "odonthogenic band"--a band of tooth forming epithelial tissues that forms a dental lamina that later becomes the teeth--and came up the following models that I modified and labeled: (green indicates front portion of the ondonthogenic band, and orange indicates back)

The two venomous groups both have regression in the development of the rostral portion of their teeth, and the none-fanged non-venoumous group and rear-fanged non-venomous group show similarities developing the front portion first then the back.

 

The final interest for these biologists are always about phylogeny and evolution, which I'm not interested in, but here's what they came up with:

 

Continuous dental development with no subregions (Boidae) is ancestral, differentiation of 2 subregions came next with posterior regressions (front fang), venom gland, and then loss of anterior dental development.

 

The reason I am very interested in this research has more to do with the technologies that are applied. Through the marking of cells, coloring the images, 3-D modeling, the research, to me combined science and art, and achieved more than supporting a proposed phylogeny.

 

A suggestion for improvement from reading the article. It could be helpful, for illustration and comparison purposes, to use the same species for the demonstration of skeletal structures and dental development, and organize the snake groups in the same order for the two illustrations. Currently the skeletal illustration lacks a representative from Colubridae, and the dental development diagrams lacks one from Naricidae.

 

Thanks to Desseray.