Structure, histochemistry, ultrastructure and seasonal variations of the male prostatic complex in the black Myotis bat, Myotis nigricans (Chiroptera: Vespertilionidae)

Abstract

Chiroptera are one of the most diverse orders of mammals and a unique group within Mammalia that posses a wide geographic distribution and considerable variability in reproductive strategies. The aims of the present study were to characterise the male prostatic complex of the bat Myotis nigricans (Vespertilionidae) and evaluate seasonal variations in the prostatic complex of M. nigricans specifically. Twenty-three sexually mature specimens (four sample groups: winter, spring, summer and autumn) were subjected to macroscopic, microscopic, morphometric and ultrastructural analyses. The reproductive accessory glands of M. nigricans were found to be composed of a multilobed complex associated with the urethra and a pair of inguinal bulbourethral glands. The complex was composed of three bilobed prostatic regions (ventral, dorsolateral and dorsal) with no ampullary gland and seminal vesicles. This pattern of lobulation is very similar to that described for the prostate of rodents; however, it differs from that of other mammals and even other families of bats (e.g. Phyllostomidae and Molossidae). Each prostatic region in M. nigricans has unique and distinctive characteristics, which synchronise to establish the main reproductive peak of the species in summer. The data also indicated an asynchrony in the activity of primary and secondary reproductive organs in the annual reproductive cycle of M. nigricans in São Paulo State, Brazil.

Morphological analysis of the male reproductive accessory glands of the bat Artibeus lituratus (Phyllostomidae: Chiroptera)

“…This variation is possibly due to its holocrine‐type of secretion, in which the entire cells are released in the lumen of the acini, together with their secretion. A similar histological pattern was observed in the ventral prostate of other bats (Beguelini et al, ; Christante et al, ; Martins et al, ; Negrin et al, ; Puga et al, ), indicating that this pattern was established early during the evolution of the prostatic complex in bats. However, studies of RAGs in other mammals did not show the presence of a holocrine gland in the complex, which shows that this pattern is possibly exclusive to bats.…”

“…This morphology seems to be the typical arrangement of the dorsal prostate in bats (Beguelini et al, ; Christante et al, ; Martins et al, ; Negrin et al, ; Puga et al, ) and is very similar to the morphology of the ventral prostate of Rodentia (Rochel et al, ). However, its PAS‐negative secretion differs from the PAS‐positive secretion observed in the dorsal region of other bat species (Beguelini et al, ; Christante et al, ; Martins et al, ; Negrin et al, ; Puga et al, ). This indicates a variation in the composition of the secretion in A. lituratus , which seems to be more protein than glycosidic.…”

“…Although the presence of seminal vesicles was proposed for species of bats from other families, such as Pteropodidae (Danmaigoro et al, ; Fard & Ghassemi, ; Krutzsch, ), Miniopteridae (Krutzsch & Crichton, ), Molossidae (Krutzsch & Crichton, ), and Vespertilionidae (Gadegone & Sapkal, ), the absence of seminal vesicles is not exclusive to A. lituratus . Its absence was also reported in other species of phyllostomid bats (Martins et al, ; Puga et al, ), as well as in bats from other families, such as Hipposideros speoris (Hipposideridae – Pal, ), Molossus molossus (Molossidae – Christante et al, ), Myotis nigricans (Vespertilionidae – Negrin et al, ), Noctilio albiventris (Noctilionidae – Beguelini et al, ), Rhinolophus capensis (Rhinolophidae – Bernard, ), and Rhynchonycteris naso (Emballonuridae – Beguelini et al, ). This demonstrates that this gland is absent in the Phyllostomidae family, as well as, possibly, in other bat families.…”

“…Recent studies have indicated marked morphological and functional variability of these glands in bats, including the fusion of prostatic lobes in some species; a lobulated pattern, very similar to that observed in rodents, in others; and the absence of a seminal vesicle (Beguelini, Góes, Rahal, Morielle‐Versute, & Taboga, ; Beguelini et al, ; Christante et al, ; Martins et al, ; Negrin et al, ; Puga, Beguelini, Morielle‐Versute, Vilamaior, & Taboga, ; Puga et al, ). In view of the great variation observed in these glands in bats, together with the lack of a description of these glands in one of the most important and representative bat species in Brazil, this study aims to analyze and characterize the composition, anatomy, histology, histochemistry, and ultrastructure of the male RAGs in the bat, Artibeus lituratus (Phyllostomidae: Chiroptera).…”

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

“…They become hypertrophied and secretory with granular columnar epithelium in synchrony with the elevated testicular steroid cycle and involuted with cuboidal epithelium and agranular cytoplasm in the inactive testicular state in number of bat species, Nactyla noctula (Racey, 1974); Pipistrellus dormeri (Gadegone & Sapkal, 1983); Taphozous melanopogon and Miniopterus (Gadegone et al, 1995); Brachyphylla cavemarum (Krutzsch & Nellis, 2006); Hipposideros lankadiva (Gadegone et al, 2005); Brachyphylla cavemarum (Puga et al); Myotis negricans (Negrin et al, 2014) and Eidolon helvum (Danmaigoro et al, 2014). Similar cyclical changes in the histology of the bulbo-urethral gland of Rousettus have been reported in the present study.…”