Influence of rainfall and temperature on the spermatogenesis of Leptodactylus macrosternum (Anura: Leptodactylidae)

Abstract

In the semi-arid environment, the reproductive success of anurans depends on adaptations in their life cycle, which synchronizes with ideal environmental conditions to maximize the number of offspring. In this study changes in the histological and morphometric aspects of the testes of Leptodactylus macrosternum Miranda-Ribeiro, 1926 are characterized, to evaluate the influence of rainfall and temperature on them. Specimens were collected at Horto Florestal Olho d’Água da Bica -HFOB (06°49'20‘S, 36°15'85‘W) area, municipality of Cuité, state of Paraíba, Brazil. Search for specimens was active, happened at night, and amounted to 15 days from January to December 2013. The densities of spermatids (primary and secondary), sperm and area of the seminiferous locules of the testes were registered. The influence of climate variables (rainfall and temperature) on the density of primary and secondary spermatids, sperm and locular area were verified using Simple Linear Regression. Primary spermatids had the lowest density in July (57.90 ± 51.54 mm2), with a peak in November (300.32 ± 117.35 mm2); secondary spermatids had the lowest density in December (287.87 ± 79.05 mm2), with a peak in May (135,727.00 ± 301.13 mm2); sperm was in the lowest density in July (237.37 ± 121.10 mm2), with a peak in June (2,270.45 ± 602.62 mm2) and the locular area had the lowest density in December (40,292.9 ± 8,174.20 µm2) and highest density in June (338,875.01 ±2,262.10 µ m2). A notable decrease in sperm density was evident between June and July. That, associated with the observation of a larger locular area in June, allowed us to identify as June as the peak of spermatogenesis and the following month as the most potentially reproductive. The density of secondary spermatids(r = 0.02), sperm (r = 0.21) and locular area (r = 0.01) showed dependency on rainfall whereas only sperm (r = 0.09) showed dependency on temperature. Therefore, we can state that the reproductive cycle of L. macrosternum is potentially continuous, with a reproductive peak in July.