Morphological correlates of subaerial existence in leptodactylid tadpoles associated with flowing water

Tadpoles of the Brazilian leptodactylid frog genera Cycloramphus and Thoropa are characterized by having extremely depressed bodies and elongated, nearly finless tails. In this paper we describe internal oral features of Cycloramphus duseni, Thoropa miliaris, and Thoropa petropolitana larvae. These tadpoles are similar internally. Although they are considered "stream adapted" by some authors, they are found on steep, wet, rocky surfaces often near, but not directly in, streams. Internally they differ from typical stream larvae in having less buccal papillation, having an exposed glottis, and lacking secretory ridges on the branchial food traps. These are features that they share with other subaerial tadpoles, be they semiterrestrial or arboreal. Elongated tadpoles associated with streams appear more adapted for avoiding currents than living within them. Extreme elongation in tadpoles characterizes a fossorial way of life.