Morphological characteristics of the gastrula in Ceratophrys stolzmanni (Anura: Ceratophryidae)

Abstract

The gastrula morphology of Ceratophrys stolzmanni (the Pac-man frog) was studied. Its eggs, whose diameter at the beginning of the gastrulation process is 2.2 mm in diameter, develop rapidly. The gastrulation process requires five hours approximately. The embryos were fixed and analyzed in whole-mount, in bisections, and vibratome sections. The eggs of C. stolzmanni were pigmented, as in Xenopus laevis, but their size was bigger. The gastrula morphology of C. stolzmanni is similar to the one described for Ceratophrys ornata (the argentine horned-frog) by other authors. The late gastrula and early neurula stages, studied with vibratome sections stained for cell nuclei, revealed lack of endoderm covering both the posterior notochord and the somites found on this region. This region is called the GRP (Gastrocoel roof plate) and it plays a major role in the development of the left-right axis in amphibians. In this work the GRP of C. stolzmanni was characterized at the morphological level.