Portrait of the Grass Snake (72)
|Natrix natrix (Grass Snake) [in Turk. Yarı Sucul Yılan, Küpeli Yılan] (Old Female)|
Today another two posts from two different POV –lateral & top - of the Grass Snake showing its head scalation and colouration details, and especially its sticked out bifurcated tongue.:) [please see attached WS too:) to see the amazing tongue from relatively top POV] since it is really very vital organ for snakes and also some lizards.
TFL & Cheers,
©Bayram GÖÇMEN, All Rights Reserved.
Please see my first post of this harmless and funny beauty to read more about it. Here I would like to give more detailed info on the olfactory sense of reptiles.
Jacobson’s organ, a second kind of olfactory chamber, is well developed in snakes and some lizards.
For many vertebrates, vision is the most vital of all the senses, followed generally by hearing. In most reptiles, however, chemical sensitivity is as vital as vision, or more so. As in other vertebrates, olfaction is mediated by the paired nasal organs, which open to the exterior through the nostrils. Olfactory receptors are located in these nasal passages, where a stream of air flows over them during ventilation of the lungs or during pumping movements of the throat, which may have a “sniffing” function. Olfactory receptors are generally more varied than other receptors, and many are highly specific for chemical stimuli.
In more advanced lizards -such as those in the family Varanidae (Monitor Lizards)- and snakes, however, additional mediators of chemical sensitivity are the paired vomeronasal (Jacobson’s) organs, a second kind of olfactory chamber called as “the vomeronasal or Jacobson’s organ”, is a pair of blind-ended cavities opening into the oral cavity, which are at the anterior extremity of the roof of the mouth, close to the nasal organs. In Varanids, this is associated with this characteristic is a shift in the morphology and deployment of the tongue, which is used mainly to pick up nonvolatile molecules and to convey them to the vomeronasal organs. There is an associated shift from insectivory to carnivory. In snakes, which may be derived from a varanid-like ancestor, these shifts have been carried to an even greater extreme.
In general, the nasal organs are sensitive to airborne or volatile chemicals, whereas the vomeronasal (Jacobson’s) organs are sensitive to substrate-borne or nonvolatile chemicals. Jacobson’s organs are lacking in crocodilians and are poorly developed in many other reptiles.
1. Budak, A. & Göçmen, B. (2005). Herpetology. Ege Üniversitesi Fen Fakültesi Kitaplar Serisi, No. 194, Ege Üniversitesi Basimevi, Bornova-Izmir, 226 pp. [2nd Edition, 2008].
2. Grzimek, B., (2003). Grzimek’s Animal Life Encyclopedia, Second Edition Volume 7 Reptiles Schlager Group Inc. 571 pp.