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Abstract

Post-metamorphic growth and the reproductive cycle of the eastern narrowmouth toad (Gastrophryne carolinensis) were studied from 204 individuals collected during the April August 1989 activity season in a two-county area of northeastern Arkansas near the northwestern edge of the species' geographic range. Late summer metamorphs require a full growing season before they can reproduce as they approach their second year of life. The oldest individuals may be at least five years old. By late April, gonadal cycles of adults had commenced; the males were producing sperm, and some of the females were gravid. Fertility of both sexes increased during the season and peaked in June. Males remained fertile through August, but only two gravid females were found after June indicating that adults were physiologically capable of breeding for a period longer than weather conditions were acceptable for oviposition. Neither clutch size nor ovum diameter increased with female body size. Disparity of body size and clutch characteristics throughout the brief breeding season could be explained by deposition of partial clutches. The growth, maturity, and gonadal cycle of this species at the northern edge of its range are similar to findings in southern populations, and climate, not changes inbreeding physiology, constrain breeding at this northern site.

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