by Obiebi Enifome Sonia
Snakes are elongated, legless, carnivorous reptiles of the suborder serpents that can be distinguished from legless lizards by their lack of eyelids and external ears. It is commonly believed that all snakes are venomous but that is an erroneous believes. Of all the 2700 known species of snakes only 300 are venomous. Most species are non venomous and those that have venom use it primarily to kill and subdue prey rather than for self defense. Some posses venom potent enough to cause painful injury or death to humans. Non venomous snakes either swallow prey alive or kill by constriction. (Joseph 1991) Snake venom is a highly modified saliva produced by snake’s special salivary gland. Snake venom is of a very proteinceous nature with protein constituting 90 percent or more of the venom’s dry weight. The nature of this venom was first established by Bonapate Lucien in 1843. Upon closer inspection it becomes clear that snake venom is no way a simple substance, it is a complex mixture of numbers of proteins, peptide, enzymes, toxins and non protein inclusions (Leon et al., 2011). The makeup of the toxins varies widely from one snake species to another, this allows for the great variety of different snake bite effects. The enzyme present in snake venom often aid in the digestion of prey animal which receives the snake bite, but some of these enzymes enhance or contribute to the toxic effect of the venom. Approximately 20 of these enzymes are known to be toxic. one of them cholinesterase is used to paralyze the snake’s prey by relaxing the victim muscles to the point where they can no longer be controlled properly. Another enzyme phosphodesterase leads to a negative cardiac reaction in victims, most notably a rapid drop in blood pressure. Hyaluronidase is one of the most dangerous enzymes absorbed more rapidly by victim. Others include phospholipase, phosphodiesterase, phosphomonesterase, L-amino acid oxidase, specific endopeptidase and non specific endopeptidase e.t.c. (wanaga and Suzuki 1979). These enzymes all co-operate in order to make the snake’s venom as effective as possible, though it should also be noted that no snake possess every single of these enzymes. On the average snake employ six to twelve of these enzymes in their venom. The dangerous mixtures present in snake venom intricate as they allow the snake to bring down their usual prey (and in some cases much larger creatures) with a single quick strike. EVOLUTION OF VENOMOUS SNAKES
Venomous snakes are a polyphyletic group of colubridae that includes all the family members of elapidae, viperidae and actractaspidae. Elapidae include cobras, kraits and coral snakes, the family viperidae has two subfamilies Rusell’s vipers such as saw snake vipers and crotalinae (pit vipers) and family actractaspidae. This lineage are believed to have originated in the Miocene but remains sparsely represented in the fossil record (Nilson and Andren 1997) (Rage 1997). Like their fossil record, scientific discussion concerning the evolutionary and selective forces responsible for shaping their venom are scant. Several studies have shown that the composition of snake venom is genetically controlled and thus subject to evolution via natural selection like any heritable trait (Jimenez-porras 1964), arid et al 1989)
CLASSIFICATION OF SNAKE VENOM
Snake venom are subdivided into three categories namely:
The neurotoxins is designed to attack the recipient’s neuron or nerve cells by interfering with membrane proteins and ion channels. They have the ability to inhibit ion movement across the cell membrane or communication between neurons across synapse. The typical effects of this toxin include the loss of motor skills, mental ability and even consciousness, sometimes depending on the dosage of the toxin, breathing difficulties or heart failure can result. (Bradbury and Deane, 1993). Examples of common...
Please join StudyMode to read the full document