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Rapid venom evolution can also be explained by the arms race between venom-targeted molecules in resistant predators, such as the opossum, and the snake venom that targets the molecules. Scientists performed experiments on the opossums and found that multiple trials showed replacement to silent substitutions in the von Willebrand factor ( vWf ...
Virginia opossums can vary considerably in size, with larger specimens found to the north of the opossum's range and smaller specimens in the tropics. They measure 33–55 cm (13–22 in) long from their snout to the base of the tail, with the tail adding another 25–54 cm (9.8–21.3 in).
This adaptation seems to be unique to the Didelphini, as their closest relative, the brown four-eyed opossum, is not immune to snake venom. [47] Similar adaptations are seen in other small predatory mammals such as mongooses and hedgehogs .
The immunity was initially thought to come from an immune response leading to the production of antibodies, but in fact it comes from toxin-neutralizing proteins found in opossum serum. [7] [8] These proteins are produced by the opossum prior to any encounter with a venomous snake, thus this immunity is not learned but inherited. [7]
The common opossum (Didelphis marsupialis), also called the southern or black-eared opossum [2] or gambá, and sometimes called a possum, is a marsupial species living from the northeast of Mexico to Bolivia (reaching the coast of the South Pacific Ocean to the central coast of Peru), including Trinidad and Tobago and the Windwards in the Caribbean, [2] where it is called manicou. [3]
An older snake may shed its skin only once or twice a year, but a younger, still-growing snake, may shed up to four times a year. [18] The discarded skin gives a perfect imprint of the scale pattern and it is usually possible to identify the snake if this discard is reasonably complete and intact.
A Virginia opossum (Didelphis virginiana) playing dead A barred grass snake (Natrix helvetica) playing dead. Apparent death [a] is a behavior in which animals take on the appearance of being dead. It is an immobile state most often triggered by a predatory attack and can be found in a wide range of animals from insects and crustaceans to ...
The venom of the fer-de-lance is so potent that didelphine opossums (i.e., opossums like the Virginia opossum), which are normally immune to the venom of pit vipers and rattlesnakes, are still capable of succumbing to the venom of this snake. This is especially the case if the opossum is not fully grown (and thus the venom is more concentrated ...