Toxic effects of native poison dart frogs (Dendrobatidae) in Costa Rica (#1/Final)

This topic submitted by Jill Elder ( elderjb@miamioh.edu) at 7:12 PM on 5/18/06.

QUICKTIME MOVIE: Just Click on the Image--A really funny encounter of a human and bear fighting over a salmon fish!

Tropical Field Courses -Western Program-Miami University


I. Introduction
Poison dart frogs (Dendrobatidae), native to Costa Rica, provide a unique role in the community because of their toxic capabilities. Also, understanding the general chemistry of the toxins present in animals will help to better associate poison dart frogs with their impact on surrounding species and the environment.
Many species of animals, including some amphibians and reptiles contain poison or venom that can protect them naturally. Two common classes of toxins, pumiliotoxin and batrachotoxin are prominent in these species. These classes of toxins generally affect the nervous system and heart muscle activity. Other animals can have different classes of toxins that affect their victims in similar nerve dulling means.
The family Dendrobatidae has 9 genera but the two most toxic genera are the Dendrobates and the Phyllobates. These species can be studied in order to further investigate their toxic potential and its impact on humans.

II. Toxins
In general, the classes of toxins that are found in most animals and their skin are alkaloids. An alkaloid is a complex organic compound containing nitrogen. They are commonly derived from amino acids, and originate from alkines which explains the bitter taste. Some common amphibian alkaloids are batrachotoxins, pumiliotoxins, histrionicotoxins, gephyrotoxins and epibatidines (Patocka 2000). With the exception of the pumiliotoxins, all affect the nervous system through Na+ channel blocking and recepting. The pumiliotoxin affects cardiac muscle activity (Patocka 2000, Alkaloid 2006).
In amphibians, these toxins are found in the skin secretions. Scientists have been able to find ways to use different forms- fresh or fermented- and both are satisfactory.
The toxins in the poison dart frog can be classified as neurotoxins, or nerve poisons. Sometimes the skin toxins affect the victim in different ways, just local irritation can occur but other extreme effects are hallucinations and vasoconstriction which can result in increased blood pressure (ThinkQuest 2006).
Although the warning colors of the poison dart frog generally keeps predators away, some species are not affected by the poisonous skin. A few snake and bird species can prey upon these tiny frogs and do not have any damage. Sometimes, spiders that are trying to prey upon the poison dart frogs will die because of the poison. They are often attracted by the beautifully colored skin and before they realize it, the toxin has already contacted them and they become a snack for the frog (ThinkQuest 2006).
The toxicity of these frogs is not produced in the frog itself but rather derived from the food that they eat, specifically ants that they further metabolize (2005). These ants could acquire the poison from their diets from various plants. These plants are also commonly used for current medicinal purposes and research (Alkaloid 2006). Another finding indicates that a family of beetles Melyridae with high levels of batrachotoxins are a frequent dietary source for poison darts (Dumbacher 2004).


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).

V. Conclusion
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.

Works Cited

*(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


Next Article
Previous Article
Return to Topic Menu


Here is a list of responses that have been posted to your discussion topic...

Important: Press the Browser Reload button to view the latest contribution.

If you would like to post a response to this topic, fill out this form completely...

Response Title:
Author(s):

E-Mail:
Optional: For Further Info on this Topic, Check out this WWW Site:
Response Text:


DOWNLOAD the Paper Posting HTML Formating HELP SHEET!

We also have a GUIDE for depositing articles, images, data, etc in your research folders.


Article complete. Click HERE to return to the Pre-Course Presentation Outline and Paper Posting Menu. Or, you can return to the course syllabus

  • Tropical Marine Ecology of the Bahamas and Florida Keys
  • Tropical Ecosystems of Costa Rica
  • Site NAVIGATION--Table of Contents

    Listen to a "Voice Navigation" Intro! (Quicktime or MP3)

    Google
    Search WWW WITHIN-SITE Keyword Search!!

    WEATHER & EARTH SCIENCE RESOURCES

    TROPICAL ECOSYSTEM FIELD COURSES

    Hays' Marine Ecology Images and Movies Ohio Bird Photo Collection | Tropical Bird Collection | Costa Rica Image Collection | Edge of the Farm Conservation Area | Hays' Tarantula Page | Local Watershed Fish Studies| Wildflowers, Arthropods, ETC in SW Ohio | Earth Science Resources | Astronomy Links | Global Change | Marine Ecology "Creature Study Guide" |

    OTHER ACADEMIC COURSES, STUDENT RESEARCH, OTHER STUFF

    | Educational Philosophy | Discovery Labs: Moon, Geologic Time, Sun, Taxonomy, Frisbee | Project Dragonfly | Vita |Field Course Postings | Student Research Postings | Nature/Science Autobiography | Environmental Programs at Miami University

    TEACHING TOOLS & OTHER STUFF

    Daily Necessities: Macintosh Resources |Search Engines | Library Resources|Server Stats| Family Album | View My Schedule | View Guestbook | Western College "Multimedia Potpourri"


    It is 2:03:57 AM on Saturday, December 16, 2017. Last Update: Wednesday, May 7, 2014