This post is chock full of animal oddity. It starts out with two creatures, one mammal and one reptile, that are odd not only because they are venomous, but because of new research into the evolution of their venom.
You might not think of a venomous reptile as odd, but the reality is that venom is really only an adaptation commonly seen in snakes. The other reptiles, including turtles, crocodilians and most lizards are totally non-venomous. The Mexican beaded lizard is one of the only two venomous lizards in the world (the other is its close cousin, the gila monster). Found in the desert ecosystems of the American southwest, Mexico and Central America, the Mexican beaded lizard doesn't inject its venom with a quick bite the way most venomous snakes do. Instead, it catches and holds a small mammal, reptile or bird in its strong jaws and then chews on it, allowing its venom to enter the prey's bloodstream through the wound. Not only is the Mexican beaded lizard odd because it's a venomous lizard, the method in which it envenomates its prey is odd too.
You might be surprised to learn that there are actually more venomous mammals than there are venomous lizards. The male platypus has sharp venomous spurs on its legs and several species of moles and shrews have venomous saliva. The northern short-tailed shrew is one of them. Found in the eastern and central parts of Canada and the United States, this little creature is classified as an insectivore, feeding on insects, snails and other invertebrates supplemented with seeds and fungi. Unlike many other tiny predators, however, the northern short-tailed shrew has the extra advantage of its venomous saliva, allowing it to tackle larger prey as well, including salamanders, mice, and even snakes!
The oddest thing of all, however, is the fact that although these two creatures are completely unrelated, new research shows that their venom evolved in the exact same way. What began in both species as a saliva enzyme with mild coagulant properties eventually, but totally independently, evolved into a toxic venom capable of incapacitating and even killing prey. Such similar evolutionary paths sometimes happen in closely related species but in species as vastly different as the Mexican beaded lizard and the northern short-tailed shrew, it is definitely odd.
http://www.flickr.com/photos/gillesgonthier/ / CC BY 2.0
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