Redescription of Physalaemus barrioi (Anura: Leiuperidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

THE TADPOLE of PHYSALAEMUS MOREIRAE (ANURA: LEIUPERIDAE)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Comparing the tadpoles of Hyla geographica and Hyla semilineata

External morphology, internal oral anatomy, and chondrocranial anatomy were examined for tadpoles of Hyla geographica from the Amazon rainforest, Brazil, and Hyla semilineata from the Atlantic rainforest, Brazil. Here, we provide morphological larval data to help diagnose these closely related species. Scanning electron microscopy analysis of buccal morphology showed the most distinctive features between these species: the distance between the lingual papillae in the buccal floor of H. geographica is three times greater than that distance in H. semilineata, and the relative size of the lingual papillae in H. geographica is less than half their size in H. semilineata. Although the chondrocranium of both species is identical, and the external morphology of the larvae of both taxa is very similar, they differ greatly in size at most developmental stages. A multivariate analysis of covariance, corrected for stage and size, also showed a significant difference between morphometric measurements of the two species. These differences support the existence of two separate taxa.

Análises de sequências ontogenéticas do crânio imaturo de Pipa arrabali: implicações filogenéticas e ecológicas

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Comparative morphology of pond, stream and phytotelm-dwelling tadpoles of the South American Redbelly Toads (Anura: Bufonidae: Melanophryniscus)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Analysis of BMP signalling through the receptor type IA in embryogenesis using conditional gene inactivation in mice

Although bone morphogenetic proteins (BMPs) were initially identified for their potent bone-inducing activity, their precise roles in processes of endochondral and intramembranous bone formation are far from being clear. Tissue-specific loss-of-function experiments using the BMP receptor type IA (BMPR-IA) are particularly attractive since this receptor is thought to be essential for signaling by the closely related BMPs -2, 4, and 7. To ablate signaling through this receptor during chondrogenesis, we have generated transgenic mice expressing Cre recombinase under the control of the collagen type II (Col2a1) gene regulatory sequences. Mice lacking BMPR-IA function in chondrocytes display a number of skeletal abnormalities, including defects in bones of the chondrocranium, abnormal dorsal vertebral processes, scapulae with severe hypoplasia of dorsal elements, and shortening of the long bones. Alterations in the growth plate of long bones in mutants suggest that BMPR-IA is not required for early steps of the chondrocyte specification, but is rather important in regulation of terminal differentiation. Molecular analysis revealed noticeable downregulation of the Ihh/Ptch signalling pathway, decreased chondrocyte proliferation rate and deregulation of hypertrophy. ^ In order to elucidate the role of BMP signalling in development of the limb and intramembranous ossification, we have used mice expressing Cre recombinase under control of the Prx1 (MHox) regulatory elements (M. Logan, pers comm.). Cre activity was found in those mice in the developing limb bud mesenchyme, as well as in a subset of cranial neural crest cells. Prx1-Cre-induced conditional mutants display prominent defects in distal limb outgrowth, as well as ossification defects in a number of neural crest-derived calvarial bones. Intriguingly, mutant limbs displayed alterations in patterning along all three axes. Molecular analysis revealed ectopic anterior Shh/Ptch signalling pathway activation and expression of some Hox genes. Observed loss of Msx1 and Msx2 expression in the progress zone correlates with downregulation of Cyclin D1 and decreased distal outgrowth. Abnormal ventral localization of Lmx1b-expressing cells along with observed later morphological abnormalities suggest a novel role for BMP signalling in establishment or maintaining of the dorso-ventral polarity in the limb mesoderm. ^