Guilds of Anuran Larvae: Relationships among Developmental Modes, Morphologies, and Habitats

Anurans show a distinct dichotomy among the sources of energy used during larval growth and development, endotrophy and exotrophy. This distinction allows more exact definitions of direct development, ovoviviparity, viviparity, and related terms. Endotrophic larvae, whether as a non-hatched embryo or a free-swimming, non-feeding tadpole, gain immediate developmental nutrition solely from parental sources, most frequently from the yolk allotted to each egg during vitellogenesis. Exotrophic larvae are always free-swimming, feeding tadpoles and orally consume numerous sources of energy not derived from a parent. The morphology of exotrophic tadpoles is surveyed with an emphasis on oral structures. Speculative scenarios and hypotheses concerning the functions of the various morphologies and the relationship of trophic structures to the ecology of the tadpoles are offered. Larval morphology and behavior permit the recognition of six developmental guilds of endotrophic larvae and 18 ecomorphological guilds of exotrophic larvae; these guilds are fully characterized.