Adaptations for Life in Tree Holes by Rhacophorid Tadpoles from Thailand

Abstract

Larvae of two species of rhacophorids are reported from tree holes in Thailand. One, referred to Theloderma stellatum, has a body nearly as wide as long and a denticle formula of 1:3+3/1+1:11. Internally, it has large branchial baskets with many rows of dense gill filters, but only two filter cavities. It has secretory cells in its branchial food traps, but they are not arranged in ridges. Its buccal musculature is slight. The larva of the second species, referred to Philautus (cf. carinensis) has a truncated snout, anteriorly directed mouth, denticle formula I/O, and unusually shaped beaks with the upper portion concave but serrations confined to the lower. It has huge buccal musculature. In this form all branchial structures associated with suspension feeding, and respiratory gill filaments, are absent. Both larvae have large, anteriorly placed glotta, which are evidently adaptations for aerial respiration. The Theloderma has a peculiar mosaic of feeding structures associated with dietary extremes of microphagy and macrophagy. Its gut contents consist of both large and small food items. The Philautus larva has features of an obligate macrophagous larva. From its gut contents it appears to eat only frog eggs. Certain arboreal tadpoles for the New World tropics, e.g., Hyla zetecki and others, resemble these Philautus tadpoles in form and diet. No analog of larval Theloderma stellatum is yet known from the American tropics.