Heterochrony during skeletal development of Pseudis platensis (Anura, Hylidae) and the early offset of skeleton development and growth

FABREZI, MARISSA; GOLDBERG, JAVIER

JOURNAL OF MORPHOLOGY

Wiley-Blackwell

Lugar: New Jersey, US; Año: 2009 vol. 270 p. 205 - 220

0362-2525

The aquatic, frog Pseudis platensis, has a giant tadpole, long developmental time, and dissociated metamorphic events that include later offset of larval somatic morphologies. Moreover, when the tadpole metamorphoses, the young frog is nearly the size of an adult, suggesting that this species has low rates of postmetamorphic growth. Herein, we study the development of the skeleton during larval development up to the end of metamorphosis—denoted by the complete lost of the tail in P. platensis. Our study revealed heterochronic differences in skeletal development compared to that of most anurans; these involve the complete differentiation of skull bones and the extensive ossification of the postcranial skeleton before completion of metamorphosis. The skull of metamorphosing P. platensis has an ossified sphenethmoid and a fully formed plectral apparatus, thus differing with regard to the pattern observed in most anurans in which both developmental events take place during the postmetamorphic life. Despite the fact that the iliosacral articulation and the urostyle are present at the end of metamorphosis as in most anurans, ossification/calcification of carpus, tarsus, and limb epiphyses during metamorphosis of P. platensis suggests that the postcranial skeleton lacks postmetamorphic growth. This study also includes a discussion of the pattern of development of the plectral apparatus, which allows us to propose a new hypothesis regarding pars externa plectri homology.