| Golden poison frog | |
|---|---|
 | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Amphibia |
| Order: | Anura |
| Family: | Dendrobatidae |
| Genus: | Phyllobates |
| Species: | P. terribilis |
| Binomial name | |
| Phyllobates terribilis | |
Thegolden poison frog (Phyllobates terribilis), also known as thegolden dart frog orgolden poison arrow frog, is apoison dart frogendemic from the rainforests ofColombia. The golden poison frog has become endangered due tohabitat destruction within its naturally limited range. Despite its small size, this frog is considered to be the most poisonous extant animal species on the planet.
The golden poison frog was described asPhyllobates terribilis in 1978 by herpetologists Charles W. Myers and Borys Malkin as well as biochemist John W. Daly;[3] the species nameterribilis is a reference to the deadly toxins present in the skin secretions of this species.[2] Myers' research was based on hundreds of specimens collected on an expedition to the Quebrada Guangui and La Brea regions of the Colombian rainforest, and a breeding colony of 18 frogs established at theAmerican Museum of Natural History.[2][4]
The golden poison frog isendemic to humid forests of the Pacific coast ofColombia in theCauca andValle del Cauca Departments in the Chocó Rainforest.[3][5] The optimal habitat of this species is therainforest with high rain rates (5 m or more per year), altitudes from sea level to 200 m elevation, temperatures of at least 26 °C, and relative humidity of 80–90%.[citation needed] It is known only from primary forest. The eggs are laid on the ground; the males transport thetadpoles to permanent pools.[1] Its range is less than 5,000 square km; destruction of this habitat has contributed toP. terribilis becoming an endangered species.[6]
The golden poison frog is the largest species of thepoison dart frog family, and can reach a weight of nearly 30 grams with a length of 6 cm as adults.[7] Females are typically larger than males.[4] The adults are brightly colored, while juvenile frogs have mostly black bodies with two golden-yellow stripes along their backs. The black fades as they mature, and at around 18 weeks of age the frog is fully colored.[4] The frog's color pattern isaposematic (a coloration to warn predators of its toxicity).[8] Despite their common name, golden poison frogs occur in four main color varieties or morphs:[9][10][11]
The yellow morph is the reasonPhyllobates terribilis has the common name golden poison frog. These frogs can be pale yellow to deep, golden yellow in color. YellowPhyllobates terribilis specimens are found in Quebrada Guangui, Colombia.[12]
The largest morph ofPhyllobates terribilis exists in the La Brea and La Sirpa areas in Colombia; despite the name "mint green" these frogs can be metallic green, pale green, or white.[2][12]
Orange examples ofPhyllobates terribilis exist in Colombia, as well. They tend to be a metallic orange or yellow-orange in color, with varying intensity. They have been observed living near yellow specimens in Quebrada Guangui, Colombia, and it is unclear to what extent these represent an individual subpopulation or locality distinct from the yellow morph.[2]
The orange blackfoot morph is a captive bred line established by Tesoros de Colombia, a Colombian company that aims to reduce poaching of wild dart frogs by breeding rare species and flooding the pet trade with low cost animals to decrease the value of wild specimens to poachers.[10] This morph is golden yellow to a deep orange. They have dark markings on their feet, throat, vent, and rump that range from distinct black to nearly absent or speckled grey.[10]
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The frog is normallydiurnal; golden poison frogs live evenly spaced without forming larger congregations.[9]
This species is an unspecialized ambush hunter; an adult frog can eat food items much larger in relation to its size than most other dendrobatids.[9][13] The main natural sources of food ofP. terribilis are the ants in the generaBrachymyrmex andParatrechina, but many kinds of insects and other smallinvertebrates can be eaten, specificallytermites andbeetles, which can easily be found on the rainforest floor.[citation needed] Tadpoles feed on algae, mosquito larvae, and other edible material that may be present in their environment.[citation needed]
Males advertise to receptive females with a trilling call.[citation needed] Golden poison frogs are notable for demonstrating tactile courtship duringreproduction, each partner stroking its mate's head, back, flanks, and cloacal areas prior to egg deposition.[14] The eggs are fertilized externally. The golden poison frogs lay their eggs on the ground, hidden beneathleaf litter.[15] Once the tadpoles emerge from their eggs, they stick themselves to the mucus on the backs of their parents. The adult frogs carry their young into the canopy, depositing them in the pools of water that accumulate in the centre ofbromeliads and water-filled tree holes.[16][14] The tadpoles feed on algae and mosquito larvae in their nursery.
Golden poison frogs are so toxic that adult frogs likely have few – if any – predators.[4] The snake speciesLeimadophis epinephelus has shown resistance to several frog toxins including batrachotoxin, and has been observed to eat juvenile frogs without ill effects.[2]
The golden poison frog is one of the most poisonous animals on the planet; these frogs produce deadly alkaloidbatrachotoxins in their skin glands as a defense against predators.[16][17] To become poisoned a predator generally must attempt to consume the frog, although this species is so toxic that even touching an individual frog can be dangerous.[16] This extraordinarily lethal poison is very rare. Batrachotoxin is found only in three poisonous frogs fromColombia (all genusPhyllobates), a fewbirds fromPapua New Guinea, and four Papuan beetles of the genusChoresine in the familyMelyridae.[18][19] Batrachotoxin affects thesodium channels of nerve cells. While it is unknown how the frog avoids poisoning itself, other species of poisonous frogs have been demonstrated to express a "toxin sponge" protein in blood plasma, internal organs, and muscle that binds and sequesters the toxin so as to prevent autointoxication.[20]
Batrachotoxin binds to, and irreversibly opens, thesodium channels of nerve cells leaving themuscles in an inactive state of contraction, which can lead to paralysis,heart fibrillation,heart failure, and death.[21] The average dose carried will vary between locations, and consequent local diet, but the average wild golden poison frog is generally estimated to contain about onemilligram of poison, enough to kill between 10 and 20 humans, or up to two African bull elephants.[22][16] Smaller doses have been shown to causeseizures,salivation,muscle contractions,dyspnoea and death in mice: the subcutaneous LD50 is just 0.2 μg/kg, although low doses such as 0.01 μg/kg and 0.02 μg/kg may be lethal.[17] Myerset al. estimate that the lethal dose for humans is between 2.0 and 7.5 μg.[17]
Golden poison frogs appear to rely on the consumption of smallinsects or otherarthropods to synthesize batrachotoxin; frogs kept in captivity fed on commercially available feeder insects will eventually lose their toxicity, and frogs bred in captivity are considered non-toxic.[9][4] It is not clear which prey species supplies the potent alkaloid that gives golden poison frogs their exceptionally high levels of toxicity, or whether the frogs modify another available toxin to produce a more efficient variant, as do some of the frogs from the genusDendrobates.[22] Scientists have suggested the crucial prey item may be a smallbeetle from the familyMelyridae. At least one species of these beetles produces the same toxin found in golden poison frogs. Their relatives in Colombian rainforests could be the source of the batrachotoxins found in the highly toxicPhyllobates frogs of that region.[19][23]
Golden poison frogs are a very important frog to the local indigenous cultures, such as theEmberá andCofán people in Colombia's rainforest.[4] The frog is the main source of the poison in the darts used by the natives to hunt their food. The Emberá people carefully expose the frog to the heat of a fire, and the frog exudes small amounts of poisonous fluid. The tips of arrows and darts are soaked in the fluid, and remain deadly for two years or longer.[13]
The golden poison frog is a popularvivarium subject due to its bright color and bold personality in captivity.[10][11][9] Despite its dangerous toxicity in the wild, captive specimens raised without their natural food sources are non-toxic in captivity.[11] Due to their small range in the wild, poaching for the pet trade formerly represented a serious threat to the survival of the species. Due to efforts of frog breeders like Tesoros de Colombia, captive bred frogs are now widely available for the pet trade. As these specimens are legal, non-toxic, healthier, and less expensive when compared to poached animals, the demand for illegally obtained wild caught specimens has decreased.[10] Today, theIUCN estimates that the majority of golden poison frogs sold for the pet trade are legally produced from captive lines, and estimates the threat from collection for the pet trade to be small.[1]
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