Poison dart frog
|Poison dart frogs|
|Dendrobates azureus (top) and Dendrobates leucomelas|
|Subfamilies and genera|
|Distribution of Dendrobatidae (in black)|
Unlike many frogs, these are active during the day. They often have brightly-coloured bodies, which act as warning colouration. All dendrobatids are at least somewhat toxic. In the wild levels of toxicity vary greatly from one species to the next, and from one population to another. Many species are critically endangered.
Many poison dart frogs secrete alkaloid toxins through their skin. Alkaloids in the skin glands of poison frogs serve as a chemical defense against predation. They are able to be active alongside potential predators during the day. About 28 structural classes of alkaloids are known in poison frogs.
The most toxic of poison dart frog species is Phyllobates terribilis. As mentioned above, dart frogs do not make their own poisons, but keep (sequester) the chemicals from arthropod prey, such as ants, centipedes and mites. This is the diet-toxicity hypothesis. Because of this, captive-bred animals do not have significant levels of toxins: they are reared on diets that do not have the alkaloids used by wild populations. Nonetheless, the captive-bred frogs can store up alkaloids if they get an alkaloid-containing diet.
Most wild species are not lethal to their predators, but rather taste foul enough that frogs are released immediately. Despite the toxins used by some poison dart frogs, some predators can withstand them. One is the snake Leimadophis epinephelus, which has developed immunity to the poison.
Predation does influence the evolution of polymorphism, for example, in O. granulifera. Sexual selection has contributed to differentiation among the Bocas del Toro populations of Oophaga pumilio.
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