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photo compliments of Dr. Shin Sugiyama
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John Daly, a researcher
for the National Institute of Health, was the first to conduct an intensive
study on the Epipedobates tricolor. Daly and his associates began
to collect poison dart frogs from the Ecuadorian highlands in 1974.
It was during one of their first missions to South America that Daly and
his fellow researcher, Charles Myers, of the American Museum of Natural
History, realized the true danger that the toxic secretions posed.
Although Myers and Daly took great precautions when conducting their research,
always wearing protective clothing and taking care to burn the protective
gear immediately after contamination with the toxin, the scientists were
not confronted with its true power until they woke up one morning to find
the bodies of several animals near the area where their clothes had been
burned the night before. (Bainbridge, 1989) They concluded that the deaths
of these animals had resulted from the ingestion of the frog toxin that
remained This event led Daly to pronounce that the potency of the
“secretions made strychnine look like table salt” (Bainbridge, 1989).
Even in the wake of this occurrence, and the associated knowledge that
it elucidated, the first studies conducted on Epipedobates tricolor and
several other species of poison dart frogs were extremely primitive and
especially risky.
In an effort to determine the relative virulence of the toxins emitted
by various species the scientists agitated the frogs, causing them to secrete
the toxin, and then touched the frogs skin with their tongues. The
observations recorded in the study indicate that species of mild toxicity
produced a bitter taste, followed closely by numbness of the tongue and
tightening in the throat (Bainbridge, 1989). This method could not
be used with all species of frogs, however, because the more deadly species
- such as the Phyllobates terribilis - can secrete enough poison
to bring about the deaths of multiple humans (Bainbridge, 1989). This simple
test was not as dangerous as it may seem, though, for most dart frog toxins
are only deadly upon entering the bloodstream (Turkington, 1999).
However, the most potent toxins do quickly give rise to significant irritation,
including blistering and swelling (Turkington, 1999).
Photo compliments of Jesper Hansen
Upon returning to the United
States with their sample species, Daly and his coworkers determined that
the secretions contained an alkaloid material which elicited a straub-tail
response - the raising and arching of the tail in mice injected with the
substance - characteristic of opiods (Strong, 1998). Shortly after
this discovery, Daly was forced to stop his research, for a period of more
than ten years, due to the introduction of an international treaty banning
the collection of the Epipedobates tricolor (Strong, 1998).
During this ban, Daly attempted to raise the frogs in captivity.
Unfortunately, he soon realized that the secretions rapidly lost their
analgesic effects and formed the hypothesis that the poison resulted as
a byproduct of some indigenous substance ingested in the wild (Moffet,
1995). The actual substance was not determined until 1997 when Daly
and other NIH researchers released the finding that the frogs build up
high levels of the alkaloid in their skin by eating a huge number of ants,
which also contain the deadly chemicals in small amounts. The more
ants eaten by the frogs, the greater the amount of alkaloid present in
their skin and the greater their overall toxicity. (Current Science, 1997)
Photo compliments of Reto
Siegenthaler
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