Poison dart frog
|Poison dart frogs|
|Dendrobates azureus (top) and Dendrobates leucomelas|
|Subfamilies and genera|
|Distribution of Dendrobatidae (in black)|
Unlike most frogs, these are active during the day. They often have brightly-coloured bodies, which act as warning colouration. Although 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. Blue poison dart frogs are poisonous because they eat ants and other small insects that have toxins in their bodies. If an animal eats the frog, it will become very sick.
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, and they are therefore 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. It is argued that dart frogs do not synthesize their poisons, but sequester the chemicals from arthropod prey items, such as ants, centipedes and mites – the diet-toxicity hypothesis. Because of this, captive-bred animals do not possess significant levels of toxins as they are reared on diets that do not contain the alkaloids sequestered by wild populations. Nonetheless, the captive-bred frogs retain the ability to accumulate alkaloids when they are once again provided 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 have developed the ability to withstand them. One is the snake Leimadophis epinephelus, which has developed immunity to the poison.
Dart frogs are the focus of major phylogenetic studies, and undergo taxonomic changes frequently.  Family Dendrobatidae was revised taxonomically in 2006 and contains 12 genera, with about 170 species.
Predation may have influenced the evolution of polymorphism in O. granulifera, while sexual selection appears to have contributed to differentiation among the Bocas del Toro populations of Oophaga pumilio.
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