Ultrastructure of the Secretory Epithelial Cells of the Bulbo-Urethral Glands (Cowper's gland) in the Indian Fruit Bat, Rousettus leschenaulti (Desmarest) During the Reproductive Cycle

Abstract

SUMMARY:The present paper describes the ultrastructural characteristics of the bulbo-urethral gland (Cowper' glands) of the Indian fruit bat, R. leschenaulti during sexually inactive-breeding cycle. Cyclic histological changes during the seasonal breeding quiescence cycle are not well marked. There are no marked differences. The ultrastructural characteristic of the secretory epithelial cells of BulboUretrhal Gland gland have been studied during different phases of reproductive cycle. The secretory epithelial cells are characterized by the well-developed rough endoplasmic reticulum, extensive developed complexus golgiensis (Golgi apparatus) and mitochondria. Mitochondria with lamellate cristae are dispersed in the cytoplasm. Three different types of secretory granules can be identified on the basis of electron density. These granules are not of different types but they represent the different stages of granule maturation. The secretory products of bulbo-urethral gland of bat are released into lumen both by apocrine and merocrine modes. The functional significance of the secretions of the bulbo-urethral glands in reproduction is discussed.

Histology, ultrastructure, and seasonal variations in the bulbourethral gland of the African straw‐colored fruit bat Eidolon helvum

“…Thus, there was maximal secretory activity in the bulbourethral gland of E. helvum during the rainy (breeding/mating) season, while the activity was minimal during the dry (non-breeding/nonmating) season. Similar significant cyclical changes during seasons were reported in temperate and neotropical bats (Krutzsch, 2000;Krutzsch & Nellis, 2006;Nerkar et al, 2017). The result suggests that the bulbourethral gland epithelial cells of E. helvum became hypertrophied and highly secretory during the rainy season, probably in synchrony with the elevated testosterone and testicular activities during the mating season.…”

“…The occurrence and position of the bulbourethral gland in E. helvum and its morphological organization into lobules of secretory simple columnar epithelial cells are similar to other bats and mammals (Adebayo et al, 2015;Akbari, Kianifard, & Babaei, 2018;Konig & Liebich, 2004;Krutzsch & Nellis, 2006;Martins et al, 2015;Nerkar et al, 2017;Puga, 2011). Presence of well-developed RER, Golgi complexes and mitochondria in the principal cells suggests that the cells are involved in the synthesis and secretion of protein materials.…”

“…The two different types of secretory vesicles encountered in the principal cells may represent different phases of maturation of the secretory products. Discharge of the products by merocrine and microapocrine modes is similar to other mammals (Abou-Elmagd & Wrobel, 1989;Adebayo et al, 2015;Badia et al, 2006;Nerkar et al, 2017;Rochel et al, 2007). The PASpositive secretions indicate presence of neutral mucins, which may provide an alkaline slimy environment to protect against acidic urine residues and also serve to lubricate both the male and female reproductive tracts for the spermatozoa.…”

“…The baso‐lateral in‐foldings of the principal cells may be related to active ion transport, which may modify the secretions of the cell by selective transfer of ions across the basal plasma membrane as has been described in the secretory cells of salivary glands (Dünker & Aumüller, 2002). More so, Nerkar et al (2017) reported that the basal membranes of the principal cells of the bulbourethral gland of Rousettus leschenaultii were usually straight but in‐foldings were occasionally observed. Dense cells encountered besides the principal cells in the bulbourethral gland of E. helvum appear to be unique to this species.…”

“…The paired bulbourethral glands, in the order Chiroptera, are located extra‐abdominally on either side of the base of the penis (Krutzsch, 2000; Nerkar, Gujar, & Gadegone, 2017). With ~1,386 known species worldwide (Burgin, Colella, Kahn, & Upham, 2018), the order Chiroptera is the second largest mammalian order after rodents making up ~22–25% of all known mammalian species (Mickleburgh, Hutson, & Racey, 1992; Tudge, 2000; Wilson & Reeder, 2005).…”