Are juveniles full-scale replicas of adults? Evaluation of anuran special locomotion and digging adaptations during and after metamorphosis

Abstract

Many species of anurans display special mechanical abilities, such as excavation and climbing. The aim of this study is to investigate the development of traits that are associated with these special mechanical abilities, under the hypothesis that these structures attain their configuration during the juvenile stages of development. We examined specimens from four different species of Leptodactylidae and six species of Hylidae. For the digging behavior, we evaluated the progress of calcification in the anterior region of the skulls, as well as the development of the snout-ridge. To assess climbing ability, we examined the ossification rate, the variation in the shape of the phalanx, the progress of the offset angle, and the distance between the terminal phalanx and the penultimate phalange of finger IV. The ossification of the skull and phalanges, along with the development of the snout-ridge, progresses and reaches completion during the juvenile phase of ontogeny, suggesting that at the time of metamorphosis, individuals are not yet full-scale replicas of the adults. The shape and the mechanical characteristics of terminal phalanges are already established by the conclusion of metamorphosis, revealing intriguing distinctions among arboreal species with walking and jumping locomotion.