Transient integumentary structures in Boana riojana (Anura, Hylidae) tadpoles

Abstract

Few studies focusing on embryos and/or tadpole skin morphology have described sensory transient organs whose morphological variation could indicate some taxonomical or functional correlations. We explore here some integumentary features of Boana riojana larvae that are rarely mentioned in tadpole descriptions. We provide histomorphological and SEM descriptions of the lateral line system, a series of evenly distributed unpigmented spots, and some symmetrical paired structures dorsal to the oral disc. The latter are previously unreported in any tadpole. Our descriptions reveal that the: 1) the number of lateral lines resembles those for most tadpoles, but with an unusual arrangement of stitches; 2) paired lateral spots are formed by ciliated cells dispersed in clusters unrelated to the lateral line system; and 3) upper-lip related structures are histomorphologically similar to the unpigmented spots. We discuss and suggest that integumentary transient structures in B. riojana represent traits that should be taken into account when describing tadpoles. This new information may help diagnose species and advance our understanding of tadpole ecomorphology and evolution.