Early development of Ensatina eschscholtzii: an amphibian with a large, yolky eggReportar como inadecuado

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, 1:6

First Online: 03 August 2010Received: 28 February 2010Accepted: 03 August 2010


BackgroundComparative analyses between amphibians, concentrating on the cellular mechanisms of morphogenesis, reveal a large variability in the early developmental processes that were thought to be conserved during evolution. Increased egg size is one factor that could have a strong effect on early developmental processes such as cleavage pattern and gastrulation. Salamanders of the family Plethodontidae are particularly appropriate for such comparative studies because the species have eggs of varying size, including very large yolky eggs.

ResultsIn this paper, we describe for the first time the early development from fertilization through neurulation of the plethodontid salamander Ensatina eschscholtzii. This species has one of the largest eggs known for an amphibian, with a mean ± SD diameter of 6 ± 0.43 mm range 5.3-6.9; n = 17 eggs. Cleavage is meroblastic until approximately the 16-cell stage fourth or fifth cleavage. At the beginning of gastrulation, the blastocoel roof is one cell thick, and the dorsal lip of the blastopore forms below the equator of the embryo. The ventral lip of the blastopore forms closer to the vegetal pole, and relatively little involution occurs during gastrulation. Cell migration is visible through the transparent blastocoel roof of the gastrula. At the end of gastrulation, a small archenteron spreading dorsally from the blastopore represents the relatively small and superficial area of the egg where early embryonic axis formation occurs. The resulting pattern is similar to the embryonic disk described for one species of anuran.

ConclusionsComparisons with the early development of other species of amphibians suggest that an evolutionary increase in egg size can result in predictable changes in the patterns and rate of early development, but mainly within an evolutionary lineage.

Electronic supplementary materialThe online version of this article doi:10.1186-2041-9139-1-6 contains supplementary material, which is available to authorized users.

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Autor: Andres Collazo - Ray Keller

Fuente: https://link.springer.com/

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