Changes in membrane carbohydrates distribution associated to epididymal sperm maturation during the prolonged sperm storage period of Corynorhinus mexicanus bat (Chiroptera: Vespertilionidae)

Abstract

The Corynorhinus mexicanus bat provides an interesting experimental model for the study of epididymal sperm maturation because after testicular regression, this bat stores sperm in epididymal cauda for several months. Earlier research conducted by our group suggested that sperm maturation in this specie must be completed in the caudal region of the epididymis, although the precise factor linked with this phenomenon is unknown. Therefore, the aim of this work was to analyze changes in the distribution of N-acetylglucosamine and/or sialic acid, Fucose and Mannose carbohydrates in different membrane domains of sperm cells as they change from the caput to the cauda of the epididymis, as well as, their changes in different dates of capture. The sperm cells present a redistribution of N-acetylglucosamine and/or sialic when they arrived in the caudal region (September 11), but after storage until October 22 the distribution of N-acetylglucosamine and/or sialic acid changed. Mannose residues were found predominantly towards the acrosome during their entry into and transit through the three regions of the epididymis. The flow cytometry assay indicated that fluorescence intensity due to the presence of of N-acetylglucosamine and/or sialic acid on the sperm decreases as the sperm pass through the epididymal duct and as storage time in the cauda goes on. The Mannose fluorescence intensity, decreased in corpus and cauda from September 24 to October 8, though no differences appeared on the latter date. The presence of Fucuse was corroborated only by flow cytometry. In conclusion, the carbohydrate distribution on sperm membrane can be considered as part of the process of epididymal sperm maturation and is associated with the phenomenon of prolonged sperm storage that is characteristic of this specie. This adaptation allows the males to synchronize with the period of receptivity of the females, and then, carry out the matings.

Participation of apoptotic markers in the process of maturation and elimination of spermatozoa in the epididymis of the Corynorhinus mexicanus bat

“…However, that study was conducted with a species characterized by continuous reproduction in which epididymal sperm maturation ends before the spermatozoa reach the caudal region. Our results did not show this behavior, as externalization was lower in the cauda region, perhaps reflecting the observation that the spermatozoa of C. mexicanus are not fully mature when they reach the cauda (Cervantes et al, 2008;Rodríguez-Tobón et al, 2020, 2016, as occurs in other species (Lewis &John Aitken, 2001 andSullivan &Mieusset, 2016), however, EPS are present in the Mating phase. The spermatozoa have to remain in the cauda to complete their maturational process (James et al, 2020).…”

“…A total of 12 adult male bats were capture for study. The selection criteria used to identify sexually‐mature individuals have been published previously (Kunz & Anthony, 1982; León‐Galván et al, 2005 and Mendoza‐Sánchez et al, 2023) The selection criteria for sexually mature individuals included complete closure of the metacarpophalangeal epiphyses of the fourth finger of the hand (Kunz & Anthony, 1982) and evidence of spermatozoa in the caudal region of the epididymis, which can be seen scrotal, with bulbous appearance and whitish in tone (Arenas‐Ríos et al, 2005; León‐Galván et al, 2005; López‐Wilchis, 1989; Mendoza‐Sánchez et al, 2023 and Rodríguez‐Tobón et al, 2016, 2020).…”

“…An incision was made in the pelvic‐ventral region to extract the epididymides. Both organs from each individual were measured with a vernier weighed on an analytical balance, then dissected into three anatomical regions ( caput, corpus , and cauda ) according to the procedure described previously ( Cervantes et al, 2008; Mendoza‐Sánchez et al, 2023 and Rodríguez‐Tobón et al, 2016, 2020). In the cephalic region can find the union with the efferent ducts; the corpus, is very narrow and the cauda, is the most robust region of the three, it is clearly identified, since the curvature of the vas deferens marks the point where this region begins.…”

“…Standard methods were used to evaluate the sperm parameters, largely following the laboratory manual for the examination and processing of human semen (WHO, 2010), but with adaptations for the type of sample analyzed in the study (León‐Galván et al, 2005 and Rodríguez‐Tobón et al, 2016, 2020) The parameters of sperm motility, viability and concentration were recorded.…”

“…In continuously reproducing species such as the rat, it is very difficult to determine whether apoptotic markers are involved in sperm death or possibly in epididymal sperm maturation. However, the reproductive pattern of the bat C. mexicanus has been characterized with great detail through histological, physiological and biochemical studies that have made it possible to distinguish the specific times and the different stages through which sperm passage during its transit and storage in the epididymis, before, during and after the copulation period (Cervantes et al, 2008; Rodríguez‐Tobón et al, 2016, 2020). This knowledge helps to elucidate the role of apoptotic markers in sperm maturation and elimination processes.…”