Bio Facts: Dart Frog, Blue Poison
Blue Poison Dart Frog
Bolivia, Puerto Rico, Costa Rica, Brazil, Colombia, Ecuador, Venezuela, Suriname, French Guyana, Peru, Panama, Nicaragua
Humid, tropical environments
Most species of poison dart frogs are small, sometimes less than 0.59 in (1.5 cm) in adult length, although a few are up to 2.4 in (6 cm) in length. They weigh about 0.07 ounces (2 g), depending on the size of the frog. Most are brightly colored, displaying aposematic (warning coloration) patterns to warn potential predators.
In the wild, 3 to 6 years; in captivity, 3 to 12 years
About 2 years
In the wild, they eat ants, mites and other small invertebrates; in the Zoo, they are fed
Varies by species
Poison dart frog (also dart-poison frog, poison frog or formerly poison arrow frog) is the common name of a group of frogs in the family Dendrobatidae which are native to Central and South America. Unlike most frogs, species are active during the day, and often exhibit brightly-colored bodies. Although all dendrobatids are at least somewhat toxic in the wild, levels of toxicity vary considerably from one species to the next, and from one population to another. Many species are critically endangered. These amphibians are often called “dart frogs” due to indigenous Amerindians’ use of their toxic secretions to poison the tips of blowdarts. In fact, of over 175 species, only three have been documented as being used for this purpose (curare plants are more commonly used), and none come from the Dendrobates genus, which is most characterized by the brilliant color and complex patterns of its members.
Unlike most other frogs, poison dart frogs are diurnal, rather than being primarily nocturnal or crepuscular. They tend to live on or close to the ground, as well as in trees up to 33 ft (10 m) above the ground.
Complex forms of sociality, territoriality, courtship, and parental care have evolved in many of these species. In all species for which there is data, tadpoles are carried on the back of the adult (sometimes the male, sometimes the female), usually from a terrestrial oviposition site to water. In several species of Dendrobates, the female carries tadpoles individually to the water-filled axils of bromeliads or tree holes, depositing a single tadpole into each crevice visited. The mother later returns, repeatedly, to each of her tadpoles, which have reduced beaks and denticles, and deposits unfertilized eggs for them to eat.
Aposematism is a secondary defense mechanism that warns potential predators of the existence of another primary defensive mechanism. The organism’s primary means of defense may include:
Unpalatability such as from the bitter taste arising from some insects such as the ladybird or tiger moth, or the noxious odor produced by the skunk, or:
Other danger such as the poison glands of the poison dart frog, the sting of a velvet ant or neurotoxin in a black widow spider.
In these particular examples, the organism advertises its capabilities via either bright coloration in the case of the ladybird, frog and spider; or by conspicuous stripes in the case of the skunk. Various types of tiger moths advertise their unpalatability by either producing ultrasonic noises which warn bats to avoid them, or by warning postures which expose brightly-colored body parts. Velvet ants have both bright colors and produce audible noises when grabbed (via stridulation), which serve to reinforce the warning.
The defense mechanism relies on the memory of the would-be predator; a bird that has once experienced a foul-tasting grasshopper will endeavor to avoid a repetition of the experience. One consequence of this is that aposematic species are often gregarious. Before the memory of a bad experience attenuates, the predator may have the experience reinforced through repetition, or else leave all the remaining and similarly colored prey alone and safe. Aposematic organisms often move in a languid fashion as they have little need for speed and agility. Instead, their morphology is frequently tough and resistant to injury thereby allowing them to escape once the predator gets a bad taste or sting before the kill.
A group of poison dart frogs is called an “army”.
Dart frogs are the focus of major phylogenetic studies, and undergo taxonomic changes frequently. Family Dendrobatidae was revised taxonomically in 2006 and contains 11 to 12 genera, with over 200 species.
Some poison dart frogs species include a number of conspecific color morphs that have emerged as early as 6,000 years ago. Therefore, species such as Dendrobates tinctorius can include color pattern morphs that can be interbred (colors are under polygenic control, while the actual patterns are probably controlled by a single locus). Differing coloration has historically misidentified single species as separate, and there is still controversy among taxonomists over classification.
Many poison dart frogs secrete lipophilic alkaloid toxins through their skin. As a result, they are able to be active alongside potential predators during the day. Dart frogs also do not synthesize their poisons, but sequester the chemicals from prey items, such as ants and mites. Because of this, captive-bred animals do not contain significant levels of toxins. Despite the toxins utilized by some poison dart frogs, there are some predators that have developed the ability to withstand them, including the Amazon ground snake (Liophis epinephelus).
Chemicals extracted from the skin of Epipedobates tricolor may be shown to have medicinal value. One such chemical is a painkiller 200 times as potent as morphine called epibatidine that has unfortunately shown to have unacceptable gastrointestinal side effects in humans. Secretions from dendrobatids are also showing promise as muscle relaxants, heart stimulants and appetite suppressants.
Allopumiliotoxin 267A is a toxin found in the skin of several poison frogs of the family Dendrobates. It is a member of the class of compounds known as allopumiliotoxins. Allopumiliotoxins, the most complex member of pumiliotoxin-A class (an alkaloid), have a wide range of biological activities, the full understanding of which has not been fully discerned due their incredible complexity and subsequent synthetic difficulties. The frogs produce the toxin by modifying the original version, pumiliotoxin 251D. It has been tested on mice and found to be five times more potent than the former version. It has been produced synthetically through a variety of different routes.
Batrachotoxins (BTX) are extremely potent cardiotoxic and neurotoxic steroidal alkaloids found in certain species of frogs (poison dart frog), Melyridae beetles, and birds. Batrachotoxin comes from the Greek words “batrachos” (βάτραχος), meaning frog, and “toxine” (τοξίνη), meaning poison. It was named by scientists John Daly and Bernard Witkop, who isolated the pure alkaloid and determined its structure and chemical properties. Its chemical formula is C31H42N2O6. More than 100 toxins have been identified from the skin secretions of members of the Dendrobatidae family of frogs, especially Dendrobates and Phyllobates. The most common use of this toxin is by the Noanamá Chocó and Emberá Chocó Indians of western Colombia for poisoning blowgun darts for use in hunting.
Poison darts are prepared by the Chocó Amerindians by first impaling a frog on a piece of wood. By some accounts, the frog is then held over or roasted alive over a fire until it cries in pain. Bubbles of poison form as the frog’s skin begins to blister. The dart tips are prepared by touching them to the toxin, or the toxin can be caught in a container and allowed to ferment. Poison darts made from either fresh or fermented batrachotoxin are enough to drop monkeys and birds in their tracks. Nerve paralysis is almost instantaneous.
Other accounts say that a stick siurukida (“bamboo tooth”) is put through the mouth of the frog and passed out through one of its hind legs. This causes the frog to perspire profusely on its back, which becomes covered with a white froth. The darts are dipped or rolled in the froth, preserving their lethal power for up to a year.
Epibatidine is an alkaloid that originally is found in the skin of a Epipedobates tricolor, a poison dart frog found in Ecuador. It was initially isolated by John Daly at the National Institutes of Health, and was found to be a powerful analgesic, about 500 times more potent than morphine. Because the natural source of epibatidine can only supply a small quantity, several laboratory syntheses have been developed.
Interestingly, this compound is not an opioid; instead, it is similar to nicotine and appears to act by binding and activating nicotinic acetylcholine receptors. While epibatidine may be too toxic to use in clinical practice, the compound represents a new lead in the drug design of new analgesics.
Of the tested epibatidine derivatives, Abbott Labs’ ABT-594 (Tebanicline) is the most promising reported to date. ABT-594 was discovered to be 50 times more potent than morphine, yet on animal tests, no paralysis or depression of muscle action was observed. It completed Phase II clinical trials in Europe, but while it showed clinical efficacy for treating neuropathic pain in humans it was dropped from further development due to unacceptable incidence of gastrointestinal side effects. Further research in this area is ongoing.
Histrionicotoxin is one of a number of related toxins found in the skin of poison frogs from the Dendrobatidae family, notably Dendrobates histrionicus. It is likely that as with other poison frog alkaloids, histrionicotoxin is not manufactured by the amphibians, but absorbed from insects in their diet and stored in glands in their skin.
Histrionicotoxin is a less powerful toxin compared to many of the other alkaloids found in poison frogs, however it has an unusual chemical structure and a distinct mechanism of action, acting as a potent non-competitive antagonist of nicotinic acetylcholine receptors, binding to a regulatory site on the delta subunit of the ion channel complex. It also has some affinity for sodium and potassium channels, although it is much less potent for these targets. The synthesis of histrionicotoxin and its various homologues is synthetically challenging and has been the subject of many different attempts.
Pumiliotoxin 251D is one of the toxins found in the skin of poison frogs from the Dendrobates, Epipedobates, Minyobates and Phyllobates and toads from the Melanophryniscus families. It is not manufactured by the amphibians, but absorbed through their insect-rich diet. It is extremely toxic to mosquitoes.
Pumiliotoxin 251D is a powerful toxin with several mechanisms of action, both blocking sodium and potassium channels in cells, and inhibiting calcium-dependent ATPase. Some poison frogs have the ability to convert pumiliotoxin 251D into allopumiliotoxin 267A, a more potent variant of the toxin.
Like many frog families, dendrobatids have also been affected by the worldwide decline in amphibian populations. Habitat loss (due to logging and farming) and predation by introduced species are the more common causes, but mostly the cutaneous chytridiomycosis has struck the dart frogs the hardest in the past 25 years. Zoos have tried to counteract this disease by treating captive frogs with an antifungal agent that is used to kill athlete’s foot in humans.
Jacksonville Zoo History:
The following species have been in the collection:
Blue Poison Dart Frog, Dendrobates azureus, is found in the forests surrounded by the Sipaliwini savannah, which is located in southern Suriname and Brazil. Dendrobates azureus is widely known as the Blue Poison Dart Frog or by its Tirio Indian name, Okopipi. It takes its species name from the fact that it is colored azure. Its range includes Suriname and Brazil. Its conservation status is IUCN – Threatened, Vulnerable to Extinction, and CITES – Appendix II. Blue Poison Dart Frogs (Dendrobates azureus) first arrived in 1991 to 1992, and returned in 2004. Probably the rarest of the six species that we have held at the zoo, this species recently bred here for the first time.
Green-and-black Poison Dart Frog, Dendrobates auratus, is native to Central America and northwestern parts of South America and was introduced to Hawaii. It is one of the most variable of all poison dart frogs next to Dendrobates tinctorius. It is considered to be of least concern from a conservation standpoint by the IUCN. The Green-and-Black Poison Dart Frog (Dendrobates auratus) was our first poison dart frog when it arrived in our collection in 1975 for a brief period. Since then the species has been on our inventory in 1989 to 1992, and again in 2004. Jacksonville has successfully bred this species several times.
Kokoe-pa Poison Dart Frogs (Dendrobates histrionicus) were part of the Jacksonville animal collection from 1989 to 1991.
Yellow-Banded or Bumblebee Poison Dart Frogs (Dendrobates leucomelas) were in the Jacksonville collection from 2004 to 2006.
Strawberry Poison Dart Frogs (Dendrobates pumilio) were briefly part of our Zoo’s collection in 1977.
Yellow-and-blue Poison Dart Frog, Dendrobates tinctorius, is also known as the dyeing dart frog. The species name, tinctorius, comes from the Latin, tingō, which means to “soak in dye’”. Indigenous tribes rub the skin of young parrots on this frog, which toxifys the bird’s skin causing the feathers to emerge in unnatural colors (the toxins “dye” the feathers). Its range includes Guyana, Suriname, Brazil, and nearly all of French Guiana. It is considered to be of least concern from a conservation standpoint by the IUCN. Yellow-and-Blue or Dyeing Poison Dart Frogs (Dendrobates tinctorius) first arrived in 1989 to 1991 and then returned to our collection in 2004.