Abstract
Due to the scarcity of information about patterns of spermatogenesis in bats, this study aimed to provide information on the testicular activity of the bat Sturnira lilium along the annual seasons. Thus, a series of morphometrical and stereological analyses were made using the testes of adult S. lilium in order to achieve a better understanding of the sperm production dynamics. Light and transmission electron microscopy analyses were performed in testicular fragments of animals captured during dry and rainy seasons. The testes followed the pattern of organization described for other mammals, and there were no morphological differences between organs collected either in dry or in rainy seasons. Each tubular cross-section in stage 1 was made of 0.5 type-A spermatogonia, 4.4 primary spermatocytes in preleptotene/leptotene, 3.7 in zygotene, 11.9 in pachytene, 35.6 round spermatids and 8.5 Sertoli cells. The mitotic and meiotic indexes were 15.4 and 2.9 cells, respectively, while the spermatogenesis yield was 68.7 cells. The testicular sperm reserves was 37.61×106 cells, and daily sperm production per gram of testis averaged 209.68×106 cells, both highest averages occurring in the rainy season. S. lilium male bats have a continuous reproductive pattern, high spermatogenesis yield and low support capacity by the Sertoli cells.
Highlights
Bats show a diverse range of reproductive strategies, their reproductive skills are directly related to individual body condition, which makes the availability of food a determining factor for the onset of the reproductive cycle in these animals [1,2,3].The bat Sturnira lilium
Morphometry and stereology The present study provides valuable data for better understanding of the reproductive biology of the order Chiroptera, with emphasis on morphometry and stereology apllied to spermatogenesis, since only one previous study regarding the theme has been published so far [22]
The gonadosomatic index (GSI) found for Sturnira lilium corroborates the idea of polygyny, since it was approximately 1.6 times lower than the observed in other polygynous species, such as Molossus molossus and Artibeus lituratus [22,23], 5.4 times higher than that observed in animals essentially monogamous as the crab-eating fox Cerdocyon thous [24], or the optional monogamic maned wolf Chrysocyon brachyurus [25]
Summary
Bats show a diverse range of reproductive strategies, their reproductive skills are directly related to individual body condition, which makes the availability of food a determining factor for the onset of the reproductive cycle in these animals [1,2,3].The bat Sturnira lilium The frugivory is highly beneficial for many plants, especially those from the Solanaceae family, which are of great ecological and economic importance. Bats inhabiting temperate or tropical regions show seasonal reproductive pattern, some species may not be restricted to it [1,3,4]. In Brazil, S. lilium exhibits bimodal polyestry, with two breeding seasons per year: in October and March [4,7]. These months correspond to the beginning and end, respectively, of the rainy season, which comprises the Spring and Summer [8]. Some studies have related the reproductive activity of females, including pregnancy and lactation, to the rainy season [8,9,10]
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