Students hard at work on the "Mangrove Challenge"! (Sierpe River, SW Costa Rica)
III. Poison Dart Frog Basics
Poison-dart frogs are of the family Dendrobatidae. They grow to be between 2-5 cm in length and the males are often bigger and fatter than their female counterparts. In the wild, the frogs are often brightly colored with distinctive black patterns on their back. The bright colors serve as warning colors to predators and other organisms. Non-toxic species will be duller in color. They are diurnal, meaning they are active during the day and are very territorial. Wrestling between two males is commonly seen when territory is in question.
Less than 10% of all species of amphibians exhibit any parental care and poison-dart frogs exhibit extreme parental care (Herpetology 2001). The female will lay a small clutch, between 3 and 20 eggs. While the eggs are developing, the male usually guards the clutch which is in a warm shallow area of water. Then, at the appropriate time, the female will carry the hatched tadpoles on her back to a safer environment. She will continue to visit the tadpoles to feed them unfertilized eggs that are full of nutrients vital to their survival. (Poison Dart Frog 2006). Other species have different types of care. For example, the female will carry the tadpoles up into the canopy and deposit them on plant leaves that provide water in which the tadpole can further develop. Since there are multiple tadpoles in a clutch, the female might try to spread them out in different plants in order to increase the survival rate (Woodland Park Zoo 2001).
The poison dart frog requires certain factors in the environment. They prefer warm temperatures and high humidity, around 80%. These can be found in parts of Central and South America. Poison dart frogs are also found in Hawaii- but were introduced by humans (ThinkQuest 2006). The communities of amphibians, including Dendrobatids, are depleting in their natural habitat. This is due to the increasing pet trade and also habitat destruction in our world’s rainforests. Predators to these frogs are some species of snakes and large spiders that can withstand the toxic skin. Tadpoles of the species are more vulnerable to dragonfly larvae (Woodland Park Zoo 2001).
The community structure of poison dart frog species is very important. Often, the dart frogs are removing pests in the form of insects that are considered destructive to humans. Also, it is possible that the poison in the dart frogs could be beneficial in developing medicines to fight human disease (Woodland Park Zoo 2001).
IV. Poison Dart Frogs and Toxins
Not all poison dart frogs are extremely toxic. In fact, the two main genera that contain toxic species are the Dendrobates and the Phyllobates. The most toxic frog is the Phyllobates terribilis or golden dart frog (Poison Dart Frog 2006). It takes only 136 micrograms to kill a 150 lb. person- this is equivalent to 2-3 grains of table salt. Also, the frog can produce enough poison to kill 10 humans or 20,000 mice (Boston 2006). Luckily for humans, and animals alike, touching the frog will not immediately impair you. There would have to be contact and then entry into the system via blood or mucous in order to do any damage.
In the animal world, the predator might bite ignore the simple warning colors of the frogs and try to bite the frog only to come into contact with an unpleasant taste that is bitter and peppery. The reflex of most predators is to spit the frog back out and leave it alone. The frog can usually survive this brief encounter (ThinkQuest 2006). Other species that enjoy the dart frogs as a meal have adaptations to their toxic skin. The Rufous Motmot is presumed to have neutralizing capacity in its digestive system that allows consumption of the poisonous frog in the wild (Master 1999).
Poison dart frogs have their own role in the rainforest. They will consume many insects that negatively impact humans, specifically those that infest the crops. Also, they have been used to coat arrows for indian tribes native to Columbia. One shot will get the job done in killing the animal because within minutes the nerve damage will cause paralysis. This effective method of hunting is an ancient tradition of the local people (ThinkQuest 2006). Other positive impacts these little frogs have is that they can lead to possible medicinal treatments and therapies for humans. Since the toxins abundant in poison dart frogs affect nerves and heart muscles, the medicinal treatments could affect these pathways in the body. Scientists have revealed that batrachotoxin is not an immediate blocker of the nervous system and actually makes the heart muscle contractions stronger initially while the pumiliotoxin in Dendrobates could be a cardiac stimulant post heart attack. Using this knowledge, they might be able to positively utilize the toxin. In fact, the National Institute of Health is undergoing research and has used derivatives of the batrachotin for anesthetics in surgery (2006).
Other than the obvious poisonous aspect that poison dart frogs bring, there are other negative impacts on the ecosystem. Some organisms can mimic the warning colors that the poison dart frogs represent. If these fake toxic animals are not preyed upon, other species will have to find food elsewhere and possible be drained of their proper nutrients (Poison Dart Frog 2006).
Despite their tiny size, the poison dart frog is capable of a lot of damage. They maintain a small, but important role in their community. With human impact, their population is declining regardless of their value to humans through the consumption of many pests.
Comparing the positive and negative impacts that are known about poison dart frogs, one can assume that the possibilities of medicinal research outweigh any negative impacts that poison dart frogs have. Explorations in the fields involving these natural toxins is important for human development and further research will benefit the world of science.
*(2005). Frogs eat ants for poisonous protection. CHEMICAL & ENGINEERING NEWS, 83(33), 38-38.
*Boston, M. Osa Aventura. Mike’s Wildlife Articles of the Osa. Osa Safari: Jewels of the Forest. Accessed 5/12/06 at: http://www.lookout-inn.com/articles/jewels.php
*Dumbacher. (2004). Melyrid beetles (Choresine): A putative source for the batrachotoxin alkaloids found in poison-dart frogs and toxic passerine birds. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 101(45), 15857-15860.
*Herpetology, 3rd edition. 2001. Editors: Pough, Andrews, Cadle, Crump, Savitzky & Wells.
*Master. (1999). Predation by Rufous Motmot on black-and-green poison dart frog. WILSON BULLETIN, 111(3), 439-440.
*Patocka. (2000). Dendrobatidae frog poisons - Inspiration for bioorganic chemistry. CHEMICKE LISTY, 94(4), 230-233.
*ThinkQuest 2000. Poisonouse Plants and Animals: Poison Dart Frog. Accessed 5/12/06 at: http://library.thinkquest.org/C007974/2_2poi.htm
*Wikipedia contributors (2006). Alkaloid. Wikipedia, The Free Encyclopedia. Retrieved May 14, 2006 from http://en.wikipedia.org/w/index.php?title=Alkaloid&oldid=50938182
*Wikipedia contributors (2006). Poison dart frog. Wikipedia, The Free Encyclopedia. Retrieved May 14, 2006 from http://en.wikipedia.org/w/index.php?title=Poison_dart_frog&oldid=52793804.
*Woodland Park Zoo 6/2001. Animal Facts Sheet: Poison Dart Frog. Accessed 5/14/06 at: http://www.zoo.org/educate/fact_sheets/psn_frog.htm
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