Viperidae
Taxonomy and Evolution
The Viperidae, commonly known as vipers, are a family of venomous snakes found in most parts of the world, excluding Antarctica, Australia, New Zealand, Madagascar, Hawaii, various other isolated islands, and north of the Arctic Circle. They are represented by 37 known genera and about 360 species. The family Viperidae is divided into two subfamilies: Viperinae (true vipers) and Crotalinae (pit vipers).
The evolution of vipers is closely tied to the evolution of their venom. The venom of vipers has been found to have evolved through a process of gene duplication followed by accelerated evolution of the proteins produced by the duplicated genes. This process has led to the development of a wide range of toxins, each targeting different physiological processes, such as blood coagulation, nerve transmission, and muscle contraction.
Characteristics
Vipers are characterized by a pair of long, hollow, venom-injecting fangs. These fangs are attached to movable bones in the upper jaw, allowing the snake to control when and how much venom is injected. Vipers also possess a sophisticated venom delivery system, which includes venom glands and muscles that squeeze the venom out of the glands and into the fangs.
Vipers have a wide range of body sizes, from the tiny hump-nosed viper (Hypnale hypnale) at just 30 cm in length, to the bushmaster (Lachesis muta), which can reach lengths of up to 3 meters. Despite this range in size, all vipers share a relatively stocky build, with short, stout bodies and broad, triangular heads.
Behavior and Ecology
Vipers are predominantly solitary animals and are most active during the night. They are ambush predators, often lying in wait for prey to come within striking distance. Their diet primarily consists of small mammals, birds, and other reptiles. Some species, like the Gaboon viper (Bitis gabonica), have been known to consume prey larger than themselves.
Vipers have a range of reproductive strategies. Some species are oviparous, laying eggs that hatch outside the mother's body. Others are viviparous, giving birth to live young. In some species, the young are independent from birth, while in others, the mother provides some level of postnatal care.
Venom
Viper venom is a complex mixture of proteins and enzymes, designed to immobilize and digest prey. The venom varies greatly in its effects, but it is generally hemotoxic, attacking the circulatory system and disrupting blood clotting. Some viper venoms also contain neurotoxins, which affect the nervous system, and cytotoxins, which damage cells and tissues.
The potency of viper venom varies between species and even between individuals within a species. However, all viper venoms are potentially lethal to humans if not treated promptly. Antivenom is available for many species, but not all, and rapid access to medical treatment is crucial in the event of a bite.
Conservation
Many viper species are threatened by habitat loss and degradation, as well as persecution due to fear and misunderstanding. Some species are also over-collected for the pet trade. Conservation efforts for vipers include habitat protection, education programs to reduce human-snake conflict, and captive breeding programs for critically endangered species.