Chemical Ecology The Chemistry of Biotic Interaction (1995) / Chapter Skim
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The Chemistry of Poisons in Amphibian Skin
The Chemistry of Poisons in Amphibian Skin
Pages 17-28
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From page 17... ...
Another wide range of presumably defensive substances occur in marine invertebrates, including steroid and terpenoid sapogenins, tetrodotoxins, a variety of polyether toxins, and alkaloids (3, 41. Poisons also occur in terrestrial invertebrates and vertebrates, where they serve as chemical defenses by insects and other arthropods (5, 6)
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From page 18... ...
The water-soluble alkaloid tetrodotoxin occurs in newts of the family Salamandridae, toads of the brachycephalid genus Brachycephalus and the bufonid genus Atelopus, and now in one frog species of the dendrobatid genus Colostethus (12~. Lipophilic alkaloids have been found only in salamanders of the salamandrid genus Salamandra; in frogs of the dendrobatid genera Phyllobates, Dendrobates, Epipedobates, and Minyobates, the mantellid genus Mantella and the myobatrachid genus Pseudophryne; and in toads of the bufonid genus Melanophryniscus.
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From page 20... ...
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From page 22... ...
A bacterial origin for tetrodotoxin has been suggested, but such a source fails to explain the fact that one Central American species of toad of the genus Atelopus contains mainly tetrodotoxin; another Central American species contains mainly chiriquitoxin, which is a unique but structurally similar toxin; and yet another contains mainly zetekitoxin, which is another unique, probably structurally related toxin (see ref.
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From page 23... ...
, and their origin remains obscure in view of the relatively recent finding that frogs of the dendrobatid genera Dendrobates and Epipedobates, like Phyllobates, do not have skin alkaloids when raised in captivity (261. The distribution of the various alkaloids of amphibians is pertinent to any speculation as to their origin (see Table 1~.
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From page 24... ...
The decahydroquinolines are the third major class of dendrobatid alkaloids still known only from frog/toad skin. Decahydroquinolines occur in skin of all the frog/toad genera that have lipophilic alkaloids with the sole exception of the Australian myobatrachid frogs of the genus Pseudophryne that contain only (allo~pumiliotoxins and a series of indole alkaloids unique in nature to this genus of frogs namely, the pseudophrynamines (29~.
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From page 25... ...
Certainly, dendrobatid frogs of the dendrobatid genera Phyllobates, Dendrobates, and Epipedobates, which in the wild contain skin alkaloids, have highly efficient systems for accumulating selectively into skin a variety of dietary alkaloids (25, 341. A biological system for sequestration of alkaloids for chemical defense finds precedence in the transfer of pyrrolizidine alkaloids from plants via aphids to ladybug beetles (351.
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From page 26... ...
With regard to the frogs/toads from the Madagascan family Mantellidae, the Australian family Myobatrachidae and the South American genus Melanophryniscus of the family Bufonidae, which also contain many of the dendrobatid alkaloids, it is unknown whether sequestering systems are present or even whether captive-raised frogs will lack skin alkaloids. If such systems are present, then it is remarkable from an evolutionary standpoint that such unrelated lineages of toads/frogs have independently developed systems for sequestering alkaloids into skin glands from a diet of small, presumably noxious insects for use by the toad/frog in chemical defense.
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From page 27... ...
While it is possible that these are produced de nova or by symbiotic microorganisms, it appears more likely that they are sequestered by the amphibians from as yet unknown dietary sources.
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From page 28... ...
(1975) Tetrahedron Lett.
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