Ontogenia musculoesquelética craniana na família Phyllomedusidae com ênfase no gênero Phasmahyla (Anura: Phyllomedusidae)

Abstract

There are currently 67 species of Phyllomedusidae comprising eight genera. The genus Phasmahyla is endemic to the Atlantic Forest and currently comprises eight species. One of the main characteristics of the species of the genus is the distinct morphology of their tadpoles, which have oral discs facing the back, in a funnel-shaped structure (i.e., umbeliforms oral discs), used in the collection of particles that are on the water surface (neustonic guild). This study aimed to describe comparatively the ontogeny of musculoskeletal cranial morphology in Phasmahyla jandaia, Pithecopus ayeaye and Phyllomedusa burmeisteri, in order to contribute with new interpretations of cranial variations within the Phyllomedusidae family. Tadpoles between stages 26 and 44 were cleaned and stained and them were analyzed regarding their cranial musculoskeletal morphology. P. jandaia has several features in common with P. ayeaye and P. burmeisteri, as well as other species in the Phyllomedusidae family, including the larval synapomorphies known for the family. On the other hand, P. jandaia differs from other species mainly in the rostral region of the chondrocranium, due to characters associated with the umbeliform oral disc of this species. The most striking features of the P. jandaia chondrocranium include the dorsal surface suprarostral cartilage; short trabecular horns; Meckel's and infrarostral cartilages positioned dorsally; long articular process of the palatoquadrate with slight dorsal inclination; thin palatoquadrate muscle process and robust ceratohyal with less prominent anterior processes and posteriorly directed lateral processes. Regarding the cranial musculature, the main differences of P. jandaia in relation to the other two species and other Phyllomedusidae are the more developed mandibulolabialis fibers, the more robust interhyoideus and the supensorioangularis muscle fibers restricted to the lower half of the palatoquadrate muscle process. Concerning the cranial musculoskeletal ontogeny, some characters related to the dorsal oral disc of P. jandaia were observed, such as the presence of the buccal funnel and mandibulolabialis retained until stage 42; anterior projection of the lower mandible in stages 42 and 43 and a slight anterodorsal inclination of the premaxilla in stages 43 and 44. The data from the present study corroborate the information available for other Phasmahyla species, which indicate that the dorsal orientation of the suprarostral cartilage and the lower jaw rotation may be synapomorphies for the Phasmahyla genus. In addition to these, we emphasize that the condition of the mandibulolabialis, interhyoideus and supensorioangularis muscles, as described above, may be unique for the Phasmahyla genus. Finally, we discuss the convergence aspects between neustonic tadpoles from different anuran lineages.