Variation in the growth and development of the hind limbs in frogs of the genus Telmatobius (Anura: Telmatobiidae).

There are remarkable interspecific differences in the sizes of the larvae of Andean frogs of the genus Telmatobius. This size variation seems to be associated with the duration of the larval stage and may affect the hind-limb morphology in Telmatobius. Larval, juvenile, and adult Telmatobius rubigo and T. oxycephalus were examined to determine the variation in relative sizes of hind-limb elements, their growth patterns during postmetamorphic life, and skeletal ontogeny. The results showed that the proportionately shorter hind limbs of T. rubigo relative to those of T. oxycephalus are associated with the protracted development and ossification of hind limbs during the prolonged larval life of T. rubigo. Postmetamorphically, the hind limbs grew faster than the body in juveniles of both species in contrast to the relative growth rates of the hind limbs and bodies of the adults. The growth phase of juvenile T. rubigo seems shorter than that of juvenile T. oxycephalus; possibly, this heightens the difference in the relative lengths of hind limbs after metamorphosis. Temperature affects the effects of thyroid hormone on growth and development, and T. rubigo lives at much higher, colder elevations than does T. oxycephalus. It is not clear whether the developmental differences described here are plastic (i.e., environmentally induced) or genetically fixed in each species.