Behavioral Ecology Blog

(Sorry people, it is not god or the unnamed intelligent designer)

Hey guys, do you ever wonder about these things? I certainly did, but up until a few weeks ago, scientists didn’t really know.. It shoudn’t be too surprising to learn that the majority of the super-poison alkaloids come from their diets… The particulars though, are pretty cool.. Turns out, that Orbatid mites, like to one pictured on the right are the primary source of these chemicals…

Saporito et, al from Florida International University given us the details in a paper published in this months issue of PNAS.

Alkaloids in the skin glands of poison frogs serve as a chemical defense against predation, and almost all of these alkaloids appear to be sequestered from dietary arthropods. Certain alkaloid-containing ants have been considered the primary dietary source, but dietary sources for the majority of alkaloids remain unknown. Herein we report the presence of 80 alkaloids from extracts of oribatid mites collected throughout Costa Rica and Panama, which represent 11 of the 24 structural classes of alkaloids known in poison frogs. Forty-one of these alkaloids also occur in the dendrobatid poison frog, Oophaga pumilio, which co-occurs with the collected mites. These shared alkaloids include twenty-five 5,8-disubstituted or 5,6,8-trisubstituted indolizidines; one 1,4-disubstituted quinolizidine; three pumiliotoxins; and one homopumiliotoxin. All but the last of these alkaloid classes occur widely in poison frogs. In addition, nearly 40 alkaloids of unknown structure were detected in mites; none of these alkaloids have been identified in frog extracts. Two of these alkaloids are homopumiliotoxins, five appear to be izidines, four appear to be tricyclics, and six are related in structure to poison frog alkaloids that are currently unclassified as to structure. Mites are common in the diet of O. pumilio, as well as in the diets of other poison frogs. The results of this study indicate that mites are a significant arthropod repository of a variety of alkaloids and represent a major dietary source of alkaloids in poison frogs.