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Most frog species show little resistance to evaporative water loss (EWL), but some arboreal species are known to have very high resistances. We measured EWL and cutaneous resistance to evaporation (Rc) in 25 species of frogs from northern Australia, including 17 species in the family Hylidae, six species in the Myobatrachidae, and one each in the Bufonidae and the Microhylidae. These species display a variety of ecological habits, including aquatic, terrestrial, and arboreal specialisations, with the complete range of habits displayed within just the one hylid genus, Litoria. The 25 species measured in this study have resistances that range from Rc=0 to 63.1. These include low values indistinguishable from a free water surface to high values typical of "waterproof" anuran species. There was a strong correlation between ecological habit and Rc, even taking phylogenetic relationships into account; arboreal species had the highest resistance, aquatic species tended to have little or no resistance, and terrestrial species tended to have resistance between those of arboreal and aquatic frogs. For one species, Litoria rubella, we found no significant changes in EWL along a 1,500-km aridity gradient. This study represents the strongest evidence to date of a link between ecological habits and cutaneous resistance to water loss among species of frogs.

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The isolation and structures of two new cyclic hexapeptides and two new macrocyclic ethers from the aplousobranch ascidian Lissoclinum bistratum are described. Their structures were determined by two-dimensional NMR techniques. The hexapeptides, named bistratamide A and bistratamide B, differ only by the presence or absence of one double bond. They were tested for cytotoxicity toward human fibroblast and tumor cell lines and displayed similar toxicities to the octapeptides called patellamides from Lissoclinum patella. The peptides are found within the obligate algal symbiont Prochloron but clearly differ from peptides isolated from the same Prochloron of L. patella. The macrocyclic ethers isolated from L. bistratum are exceedingly potent in cytotoxicity. They have been named bistratenes A and B, and structures for these compounds are proposed.