Poison frogs less toxic when habitat degraded
October 2, 2006
A new study suggests habitat degradation may put some frogs at greater risk of predation by reducing their toxicity.
Clark says the research lends support to the idea that frogs could serve as a proxy for the overall health of an ecosystem.
"Frogs have been recognized as environmental indicators much akin to canaries in a coal mine," said Clark, lead author of the paper published in the October issue of Journal of Chemical Ecology. "Our research suggests that Malagasy poison frogs might also provide a measure for biological diversity."
"Poison frogs obtain their defensive skin alkaloids from their insect prey, and thus their alkaloid mixture reflects the local diversity of creatures they eat," she explained. "The study shows variation in alkaloid-toxin content of individual frogs to be greater among frogs collected in different places, and more importantly, frog individuals collected from a pristine forest consistently have a greater diversity of insect-derived toxins accumulated in their skin than do frogs from disturbed and fragmented forests. Since all the alkaloid chemicals that the frogs obtain from their diet vary so much in toxicity, the frogs with greater skin-alkaloid-diversity are more likely to be well defended against predators."
Clark and her colleagues also showed that a device for harvesting toxin samples from poison frogs, the nonlethal transcutaneous amphibian stimulator ("TAS"), is effective for collecting samples without harming local frog populations, an important finding given that frogs, especially in the forests of Madagascar, are increasingly endangered due to habitat loss and the emergence of a deadly fungal disease.
"The major cause of decline in frogs is the chytrid fungus, and it remains unknown whether any of the toxins sequestered from arthropods might protect poison frogs against this deadly fungus," Clark told mongabay.com. "There is much research still needed to fully understand poison frog ecology."
Study discovers why poison dart frogs are toxic
Poison poison dart frogs are small, colorful frogs found in the tropical forests of Central and South America. The brilliant coloration of these amphibians warns predators of their extraordinary toxicity -- the golden poison frog (Phyllobates terribilis) of Colombia is said to be lethal if held in one's hand. Scientists have long speculated on the origin of their toxins, but now, a new study published in the current issue of The Proceedings of the National Academy of Sciences reports that poison dart frogs, as well as the Mantella poison frogs of Madagascar, derive their toxicity from the ants they eat. Specifically, both groups are frogs are capable of storing ants' toxic alkaloid molecules in their glands without being harmed. Ants either synthesize these alkaloids themselves or acquire them from the plants on which they feed.
Amphibian extinction crisis requires unprecedented conservation response say leading scientists
The world's leading amphibian experts are calling for dramatic steps, including the formation of an Amphibian Survival Alliance (ASA), to prevent the massive extinction of amphibians worldwide. The proposal is set forth in the current issue of the journal Science. "Stopping further global losses of amphibian populations and species requires an unprecedented conservation response," write the 50 scientists who co-wrote the Science paper.
Climate change is killing frogs finds new research
The dramatic global decline of amphibians may be directly connected to global warming warns a new study published in the journal Nature. Looking at a group of frogs found in biodiversity hotspots in Central and South America, scientists found links between higher temperatures and frog extinctions caused by a skin fungus. The infectious skin disease—a type of chytrid fungus (Batrachochytrium dendrobatidis)—is now found in frog populations around the world and is the main suspect in the rapid disappearance of amphibians.
Toad on brink of extinction, scientists race to study amphibian for bioactive compounds
Under the bright florescent lights of the reptile house in the Bronx Zoo of New York, a colorful exotic toad makes its final stand. Once gathering by the thousands at the waterfalls of the Kihansi Gorge of Tanzania, the population of the Kihansi Spray Toad now stands at less than 200 individuals. The hasty construction of a desperately needed dam, built with good intentions by the World Bank, has relegated this species to the edge of existence. A decade ago the Kihansi Spray Toad thrived in its thoroughly unique habitat, the waterfalls of the Kihansi River, part of ecosystem that is one of only 25 Global Biodiversity Hotspots on the planet (Hotspots are regions noted for their extensive range of species in a very small area). The gorge is located in the Southern Udzungwa Mountains of South Central Tanzania, which possess the greatest biodiversity in all of Tanzania.
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