We studied the pattern of annual reproductive activity in the Andean dendrobatid frog Ranitomeya virolinensis by comparing age–sex structure of the population, morphology, and morphometry of gonad among months and between seasons. The focal population is found in a mountain habitat with a bimodal pattern of rains, which suggests a seasonal pattern of reproduction, as has been observed in other Neotropical frogs. Mature and reproductive females and males were collected during the entire year and their reproduction is continuous. Sexual maturity was reached in both sexes near 16.0 mm snout–vent length (SVL); females are significantly larger than males. The diameter of the ovary and of the largest follicles did not show significant differences among months or between seasons. Clutch size in all mature females was only one egg per oviposition event; however, the simultaneous presence of advanced vitellogenic follicles with the oviductal egg suggests that females produce several clutches with short inter-clutch intervals. Testes of all mature males had seminiferous tubules with cysts of all spermatogenic stages and free spermatozoa in the lumen in each month we sampled. The size of testes did not differ among months or between seasons. Therefore, the ability to produce ova and spermatozoa is continuous throughout the year in this species. Because juveniles in the smallest size classes were observed in all months, we assume that reproduction is continuous. The continuous reproductive activity of R. virolinensis is likely favored by its semi-terrestrial mode of reproduction, in an environment where direct resources for reproduction, such as moist ground for oviposition and phytotelmata for rearing tadpoles, are available despite a seasonal rainfall pattern.
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Vol. 2010 • No. 2