Poisonous dwarf frogs

There are four types of poisonous frogs known to secrete lipid‑soluble alkaloids derived from their food. The discovery of these skin alkaloids in a fifth species in Cuba could provide new clues to these amphibians’ evolution.Amphibians accumulate a variety of compounds in their skins, many of which act as a defence against microorganisms and predators. Of these compounds, 800 have been identified as lipid-soluble alkaloids; but despite the wide variety, the alkaloids occurrence is restricted to a small but diverse group of frog species.

During fieldwork in Cuba studying dwarf frogs, the odour of dissected specimens reminded researchers of alkaloid-containing species and so they tested the skins using GC-MS. Analysis revealed the presence of eight alkaloid compounds, some of which researchers also found in mites and ants that the frogs had eaten.¹

Previous studies have noted correlations between alkaloids in the skin, small body size, small prey and colourful skin to warn predators but the order these traits evolved in has been unclear. However, dietary sources for these alkaloids, as suggested by this research, favours a scenario where the frogs specialized in smaller prey first, which then lead to them becoming poisonous.

1. A. Rodriguez et al., Biol. Lett., 6 (2010).

This story originally appeared in The Column. Click here to view that issue.