The spermatogenic process of the common vampire bat Desmodus rotundus under a histomorphometric view

Abstract

Among all bat species, Desmodus rotundus stands out as one of the most intriguing due to its exclusively haematophagous feeding habits. However, little is known about their spermatogenic cycle. This study aimed at describing the spermatogenic process of common vampire bats through testicular histomorphometric characterization of adult specimens, spermatogenic production indexes, description of stages of the seminiferous epithelium cycle and estimative of the spermatogenic process duration. Morphometrical and immunohistochemical analyzes for bromodeoxiuridine were conducted under light microscopy and ultrastructural analyzes were performed under transmission electron microscopy. Vampire bats showed higher investment in gonadal tissue (gonadosomatic index of 0.54%) and in seminiferous tubules (tubulesomatic index of 0.49%) when compared to larger mammals. They also showed a high tubular length per gram of testis (34.70 m). Approximately half of the intertubular compartment was found to be comprised by Leydig cells (51.20%), and an average of 23.77x106 of these cells was found per gram of testis. The germline cells showed 16.93% of mitotic index and 2.51% of meiotic index. The overall yield of spermatogenesis was 60% and the testicular spermatic reserve was 71.44x107 spermatozoa per gram of testis. With a total spermatogenesis duration estimated at 37.02 days, vampire bats showed a daily sperm production of 86.80x106 gametes per gram of testis. These findings demonstrate a high sperm production, which is commonly observed in species with promiscuous mating system.

Reproductive functions in Desmodus rotundus: A comparison between seasons in a morphological context

“…Overall, the histology of testicular parenchyma in D . rotundus observed herein was similar to that previously described in this species by Morais et al [ 28 ]. Likewise, no differences in morphological parameters between dry and rainy seasons were observed in testis of Sturnira lilium , another phyllostomid species widely distributed in Brazil [ 7 ].…”

“…Interestingly, our data of daily sperm production in D . rotundus were lower compared to the findings reported by Morais et al [ 28 ]. This probably occurred because the methodology adopted in the present study considers only the number of testicular homogenized-resistance spermatids heads (HRSH) in order to calculate sperm production.…”

“…The HRSH are considered viable cells, and they would probably become sperm in the end of spermatogenic cycle [ 54 ]. Conversely, the methodology used by Morais et al [ 28 ] is based on the round spermatids count in histological testis sections in stage 1 of the seminiferous cycle, regardless of cell loss. There is no other reason that could explain the differences observed for daily sperm production in both techniques.…”

“…Daily sperm production (DSP) was assessed dividing the number of spermatids at stage 19 by 4.8, which represents the number of days that spermatids are present in the seminiferous epithelium. According to Morais et al [ 28 ], each seminiferous epithelium cycle of D . rotundus has about 8.23 days and elongated spermatids are present in 58.43% of this cycle.…”

“…Despite the information available on the reproductive behavior of this species, little is known about its male reproductive physiology. Some studies have focused on its spermatogenesis [ 28 ] and structural features of the testis and epididymis [ 29 – 31 ]. Nevertheless, no studies were found evaluating seasonal influences on male reproductive parameters of these bats.…”