The tiny Cuban frog, Eleutherodactylus orientalis, protects itself from predators by consuming toxin-laden oribatid mites and sequestering the toxins in its skin.

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Though many frogs accumulate chemicals in their skin for defense against pathogens and predators, the majority of those species synthesize the substances in their own bodies. In contrast, the tiny Cuban frog species Eleutherodactylus orientalis is among the few frogs that consume toxic alkaloid laden foods and sequester the compounds in the skin. Since the compounds are commandeered from prey, they are sometimes referred to as "cleptotoxins". These fat-soluble substances are very similiar to those secreted by the better- known poison-dart frogs. The frogs maintain immunity to the toxins due to a hypothesized difference in calcium channels in their muscle cells. An interesting aspect of E. orientalis is that it is potentially capable of selectively consuming species of mites that contain toxic alkaloids previously unknown to science. In fact, several prey species of mites that were once thought to not produce alkaloids were found to be consumed by the frogs for their alkaloid content. Whether the frogs actively seek out these alkaloid-bearing species or do so by random chance is still unknown.

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"Six pumiliotoxins and two indolizidines were found in E.[Eleutherodactylus] iberia, one of the smallest frogs in the world and characterized by a contrasting colour pattern for which we hypothesize an aposematic function…lipid-soluble alkaloids are taken up to an overwhelming extent with prey and then sequestered into specialized skin glands. Lipid-soluble alkaloids in amphibians occur in a wide variety, with over 800 compounds identified so far...these frogs contain lipophilic alkaloids of the same compound classes previously reported in other alkaloid-containing frog lineages." (Rodr?guez 2011:414-5).

"In E. orientalis, minor amounts of pumiliotoxin (PTX) 267C were detected...PTX 323A was the major alkaloid in both individuals, and several related compounds were present. In addition, two isomeric alkaloids of unknown structure were present in substantial amounts, here named 267 (1) and 267 (2)...These two alkaloids have an indolizidine core structure...Stomach content analyses of a total of seven adult specimens of E. iberia and E. orientalis identified mites as the major prey items of these miniaturized frogs. Oribatid mites, known as alkaloid sources for frogs in Central America, were well represented in the diet of these two species. Numerically, mites made up 66 per cent of the 35 prey items of E. orientalis, and 71 per cent of the 62 prey items of E. iberia." (Rodr?guez 2011:415).

"The diversity of species in tropical environments is overwhelming and extremely understudied, and no doubt many new mite species and their unknown life and natural histories await discovery...if alkaloids have not yet been detected in a genus, family or higher taxon...this does not necessarily exclude their occurrence in this taxon, especially when current knowledge is typically based on screening of a few species." (Vences 2011:557).

Journal article
Use of an Oligoribonucleotide Containing the Polypurine Tract Sequence as a Primer by HIV Reverse TranscriptaseJournal of Biological ChemistryJuly 26, 2002
L. Rodr guez-Rodr guez

Journal article
Defining frontiers in mite and frog alkaloid researchBiology LettersFebruary 23, 2011
M. Vences, S. Schulz, D. Poth, A. Rodriguez

Journal article
Discovery of skin alkaloids in a miniaturized eleutherodactylid frog from Cuba.The Royal SocietyRodr?guez A; Poth D; Schulz S; Vences M

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