Development of the dendrobatid frog Colostethus machalilla

Abstract

To provide a developmental correlate with other frogs, we prepared a normal table of development for the dendrobatid, Colostethus machalilla and analyzed the morphology of its early development. This frog reproduces in captivity and deposits moderately sized eggs (1.6 mm in diameter) in terrestrial nests. The father guards the embryos until tadpole hatching. We divided development until hatching into 25 stages and implemented methods for in vitro culture of the embryos. The external and internal morphology of embryos were evaluated by observations in whole mount and in sections. Neural, notochord and somite specific antibodies were used to analyze gene expression patterns by immunostaining of embryos. Embryonic development of C. machalilla is slow and deviates from Xenopus laevis. In C. machalilla the elongation of the notochord, neural plate and somite formation occur after blastopore closure, possibly due to a delay in the dorsal convergence and extension movements. The gastrula of C. machalilla also deviates from X. laevis. The archenteron remains small until blastopore closure, where small cells accumulate at the blastopore lips. Simultaneously, the blastocoel roof thins until it becomes a monolayer of cells. Although C. machalilla does not form an embryonic disk, its thick blastopore lips resemble the embryonic disk of the marsupial frog Gastrotheca riobambae and represent an interesting deviation from the gastrulation pattern observed in X. laevis.

A comparative analysis of frog early development

“…Development of the neural tube and the morphology of the streams of cnc cells are conserved features of frog development and resemble the basic pattern observed in B. variegata (31,35). The cnc cell streams of G. riobambae and of foam-nesting frogs, however, are larger and more clearly defined than in X. laevis, C. machalilla (19,31), and E. tricolor (data not shown).…”

“…In embryos of G. riobambae, antigen 2G9 is expressed in the isthmus, rhombomeres 2 and 4, and rhombomeres caudal to rhombomere 5. It is also expressed in the streams of cnc and in the neural crest of the trunk as reported (31). The neural tube, the streams of cnc, and even numbered rhombomeres were clearly detected in tailbud embryos (st 17) of the foam-nesting frogs E. randi (Fig.…”

“…Expression of the neural cell adhesion molecule (NCAM) was used to recognize the neural tube and of antigen 2G9 for detection of the neural crest (29)(30)(31). In all of the analyzed species, the first expression of NCAM and of antigen 2G9 occurred in st-14 embryos (data not shown), and the expression became stronger in tailbud embryos (Fig.…”

“…Moreover, CE occurs after blastopore closure, as in G. riobambae but without formation of an embryonic disk. In contrast, elongation of the archenteron begins in the midgastrula (7,19,20). It is of interest to know whether the gastrulation pattern is altered in dendrobatid frogs with much larger eggs.…”

Diversidade ontogenética e desenvolvimento inicial nos anuros sulamericanos da família Cycloramphidae

“…Although the Neotropical frog fauna is the richest and most diverse, there have been embryological studies of only a few taxa of this fauna-i.e., repre sentatives of Dendrobatidae, Eleutherodactylidae, Hemiphracti dae, and Leiuperidae (Elinson and del Pino 1985, Townsend and Stewart 1985, Callery et al 2001, del Pino et al 2004, Desnitskiy 2004, Romero-Carvajal et al 2009). …”