Observations of sperm storage in some deep-sea elasmobranchs

Abstract

The presence of sperm storage was evaluated in several deep-sea elasmobranchs (Centrophorus squamosus, Centroselachus crepidater, Deania calcea, Brochiraja spinifera, Brochiraja asperula, Apristurus ampliceps, A. exsanguis, A. garricki and A. sinensis), all considered at risk to the impacts of fishing in New Zealand. Biological measurements of reproductive organs (e.g. follicle size and number, oviducal gland size, uterus width and gonad weight) were recorded in addition to conventional macroscopic maturity assessment measures. Histology was conducted on a sample of oviducal glands to investigate the occurrence of sperm storage. Sperm storage was confirmed in three of the nine species: Centroselachus crepidater, Centrophorus squamosus and Brochiraja asperula. To the best of our knowledge, these are the first observations of sperm storage for these genera, and the first in the family Centrophoridae. Sperm storage was observed in macroscopically mature females and also in some females considered macroscopically as maturing. The female reproductive tract may regress substantially between reproductive events to the extent that a mature fish is mis-classified as maturing, and would be consistent with long periods of resting between reproductive events. Alternatively, it is equally possible that aggrieve male mating behaviour results in premature copulation of maturing females. We summarise published occurrences of sperm storage in chondrichthyans, and conclude that sperm storage is most likely ubiquitous in chondrichthyans, and an adaptive benefit to traumatic mating behaviour, that may also be adaptive to low fish densities in the relatively unproductive environment of the deep-sea.