Continuous spermatogenesis in the lizard Sceloporus bicanthalis (Sauria:Phrynosomatidae) from high elevation habitat of Central Mexico

Sceloporus bicanthalis is a viviparons lizard that inhabits high altitude temperate zone habitats in Mexico. Our histological observations indicate that adult males exhibit spermatogenesis and spermiogenesis throughout the year; no seasonal differences were found in testes mass, height of epididymal epithelial cells, and number of layers of spermatogonia, primary and secondary spermatocytes, and spermatids. Seminiferous tubules exhibited slight, but statistically significant, seasonal variation in diameter. Continuous spermatogenesis and spermiogenesis of S. bicanthalis differ from the cyclical pattern exhibited by most species of lizards and from lizard species sympatric with S. bicanthalis. Continuous reproductive activity of males of S. bicanthalis, and maturation at a relatively small size, is associated with a female reproductive activity in which vitellogenic or pregnant females are present in the population during all months of the year. As a consequence, males can encounter potential mates as soon as they mature.