Seasonal venom
A study found that in certain venomous species there is a correlation with the season and venom yield. There was no effect of food consumption, molting, and pregnancy on the yield of the venom, which excluded these as factors for the increase in yield. It is believed that the temperature is the main factor for this correlation. During summer the venom yield is highest and during winter the venom yield is lower. The Northern Mojave rattlesnake (Crotalus scutulatus scutulatus) was found to have the highest venom yield in spring/summer conditions and the maximum venom yield during the hottest summer conditions. Another study done on the Southern Pacific rattlesnake (Crotalus oreganus helleri) found higher venom yield from July to October. I have not covered venomous mammals in my blog yet, but one venomous mammal only produces its venom during mating season. This mammal is the Platypus (Ornithorhynchus anatinus) and will only use its venom in the Spring while breeding. The Platypus possesses a spur on their hind leg that is connected to glands in the pelvic region and is believed to be used to fight off other males.
Belov, K. Gombert, S. King, G. Mofiz, E. Morgenstern, D. Morris, K. Papenfuss, A. Renfree, M. Temple-Smith, P. Warren, W. Whittington, C. Wong, E. (2012), 'Proteomics and Deep Sequencing Comparison of Seasonally Active Venom Glands in the Platypus Reveals Novel Venom Peptides and Distinct Expression Profiles', Molecular & Cellular Proteomics, Vol. 11, Iss. 11, Pgs. 1354-1364.
Bosisio, A. Egen, N. Gregory-Dwyer, V. Righetti, P. Russell, F. (1986), 'An isoelectric focusing study of seasonal variation in rattlesnake venom proteins', Toxicon, Vol. 24, Iss. 10, Pgs. 995-1000.
Thursday, 1 May 2014
Fang structures
There are three known fang structures found in snakes. In this blog I will list and explain a little about them. This article correlates with the venom gland article that I did because the Opisthoglyphous fangs are typically associated with the Colubridae family, which is believed to be the oldest family. The Solenoglyphous fangs are associated with the Viperidae family, which is believed to be the newest family and also has the most complicated venom apparatus.
Opisthoglyphous fangs: These fangs are mostly found in the Colubridae family. The fangs are typically angled backwards and grooved. For rear-fanged snakes to envenomate they have to move the prey to the back of its mouth to pierce with its fangs. The hunt of larger prey is much harder for snake species with this type of fangs and usually catch small prey.
Proteroglyphous fangs: The snakes with these fangs exhibit shortened maxillae with enlarged fangs pointing down and slightly backwards. A hollow syringe-like structure is found within the fangs that encompasses the venom channel completely. Snakes with this fang type are known to yield the most toxic venom of all snakes and usually associated with neurotoxins. Some species have another modification on this fang allowing them to spit the venom in a predators eyes (Spitting Cobra).
Solenoglyphous fangs: These fangs are only found within the Viperidae family. These fangs have hollow, hinged fangs that are situated anteriorly in the oral cavity. This fang type if the most sophisticated venom delivery apparatus. Each maxilla is reduced to a core that is supporting a single hollow fang. These fangs can reach a size of 55 mm and are folded against the palate when the mouth is closed. Solenoglyphs are known to produce mainly haemotoxins and cardiovascular toxins.
Mackessy, S. (2009), 'Handbook of Venoms and Toxins of Reptiles'. New York: CRC press, Pgs. 5-12.
There are three known fang structures found in snakes. In this blog I will list and explain a little about them. This article correlates with the venom gland article that I did because the Opisthoglyphous fangs are typically associated with the Colubridae family, which is believed to be the oldest family. The Solenoglyphous fangs are associated with the Viperidae family, which is believed to be the newest family and also has the most complicated venom apparatus.
Opisthoglyphous fangs: These fangs are mostly found in the Colubridae family. The fangs are typically angled backwards and grooved. For rear-fanged snakes to envenomate they have to move the prey to the back of its mouth to pierce with its fangs. The hunt of larger prey is much harder for snake species with this type of fangs and usually catch small prey.
Proteroglyphous fangs: The snakes with these fangs exhibit shortened maxillae with enlarged fangs pointing down and slightly backwards. A hollow syringe-like structure is found within the fangs that encompasses the venom channel completely. Snakes with this fang type are known to yield the most toxic venom of all snakes and usually associated with neurotoxins. Some species have another modification on this fang allowing them to spit the venom in a predators eyes (Spitting Cobra).
Solenoglyphous fangs: These fangs are only found within the Viperidae family. These fangs have hollow, hinged fangs that are situated anteriorly in the oral cavity. This fang type if the most sophisticated venom delivery apparatus. Each maxilla is reduced to a core that is supporting a single hollow fang. These fangs can reach a size of 55 mm and are folded against the palate when the mouth is closed. Solenoglyphs are known to produce mainly haemotoxins and cardiovascular toxins.
Mackessy, S. (2009), 'Handbook of Venoms and Toxins of Reptiles'. New York: CRC press, Pgs. 5-12.
An evolutionary hypothesis of snake fangs
One hypothesis for the evolution of snake fangs is that the fangs did not evolve initially for the use of venom, but for swallowing. It is believed that snake fangs evolved from posterior maxillary teeth. The elongation of these teeth increased the effectiveness of swallowing for snakes. The teeth are able to swing through a longer retraction arc than other maxillary teeth allowing the snake to swallow more at one time. It is believed that after this that two separate evolutionary lineages took place. The first, the use of the elongated maxillary teeth for the use of swallowing (Xenodon and Heterodon snakes). The second, the elongated maxillary teeth for the use of venom usage (Viperidae family).
Kardong, K. (1979), 'Protovipers and the evolution of snake fangs', Evolution, Vol. 33, No. 1, Pgs. 433-443.
One hypothesis for the evolution of snake fangs is that the fangs did not evolve initially for the use of venom, but for swallowing. It is believed that snake fangs evolved from posterior maxillary teeth. The elongation of these teeth increased the effectiveness of swallowing for snakes. The teeth are able to swing through a longer retraction arc than other maxillary teeth allowing the snake to swallow more at one time. It is believed that after this that two separate evolutionary lineages took place. The first, the use of the elongated maxillary teeth for the use of swallowing (Xenodon and Heterodon snakes). The second, the elongated maxillary teeth for the use of venom usage (Viperidae family).
Kardong, K. (1979), 'Protovipers and the evolution of snake fangs', Evolution, Vol. 33, No. 1, Pgs. 433-443.
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