Abstract

Embryonic development is highly variable in different salamander species, even within the same genus. Also variable are the breeding and egg laying patterns of those different species. Previous studies have found variation in aspects of embryonic development, but could not isolate whether these differences likely were due to differences in breeding season, nesting habitat, or egg attendance. Both species in my study were known to be late summer and early fall breeders. All embryos observed were collected in Arkansas, where the species breed in similar ponds. Ambystoma opacum is a terrestrial egg laying species that practices parental care by covering and staying near the eggs after they are laid. Ambystoma annulatum is an aquatic egg laying species that lacks the practice of parental care entirely. I observed the embryos of each species over time in a lab setting to assess variation in development. Survivorship, time to hatching, stage at hatching, and mass at hatching were all recorded for analysis. It was predicted that some significant differences would be found in the development, eliminating the possibility that breeding season is the primary cause for variation in embryonic development. The results of the study confirmed this with A. opacum having a higher age, stage, and mass at hatching. This confirmation allows us to examine more closely the relationship of terrestrial breeding and parental care to these traits in embryonic development, as well as the differing effects of aquatic breeding and the lack of parental.

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