Assessment of sperm storage across different reproductive modes in the elasmobranch fishes

The oviducal gland is a specialised region of the elasmobranch oviduct that is thought to be a site of sperm storage, among other functions. The phenomenon of female sperm storage in elasmobranchs has implications for the understanding of their reproductive ecology and the management of exploited populations, but relatively little information exists on its taxonomic extent. In the present study, oviducal glands from 29 different species, of varying reproductive modes, from the northern Indian and North East Atlantic oceans were examined using light microscopy for the presence of sperm. The organisation of the gland into four fundamental zones; club, papillary, baffle and terminal, was conserved across all species, with slight variations in relative zone volume due to reproductive mode. Spermatozoa observed within the oviducal gland were not limited to a particular reproductive mode or maturity stage. Although spermatozoa were most commonly encountered in the terminal zone tubules, in some species they were also encountered elsewhere in the gland. The storage of sperm may be a vital reproductive strategy for many species and furthering our taxonomic understanding of which species employ this strategy will help to better inform fisheries managers and protect exploited low reproductive species.