A Taxonomic Survey of Female Oviducal Glands in Chondrichthyes: A Comparative Overview of Microanatomy in the Two Reproductive Modes

Abstract

Oviducal glands (OGs) are distinct expanded regions of the anterior portion of the oviduct, commonly found in chondrichthyans, which play a key role in the production of the egg in-vestments and in the female sperm storage (FSS). The FSS phenomenon has implications for understanding the reproductive ecology and management of exploited populations, but little information is available on its taxonomic extent. For the first time, mature OGs from three lecithotrophic oviparous and four yolk-sac viviparous species, all considered at risk from the fishing impacts in the central western Mediterranean Sea, were examined using light microscopy. The OG microanatomy, whose morphology is generally conserved in all species, shows differences within the two reproductive modalities. Oviparous species show a more developed baffle zone in respect to viviparous ones because of the production of different egg envelopes produced. Among oviparous species, Raja polystigma and Chimaera monstrosa show presence of sperm, but not sperm storage as observed, instead, in Galeus melastomus and in all the viviparous sharks, which preserve sperm inside of specialized structures in the terminal zone.

Ontogenetic Shifts in Body Morphology of Demersal Sharks’ Species (Order: Squaliformes) Inhabiting the Western-Central Mediterranean Sea, with Implications for Their Bio-Ecological Role

“…A similar situation has also been observed in other demersal sharks such as the zebra shark ( Stegostoma fasciatum Hermann, 1783), for which it has been hypothesized that the progressive elongation of the body might be functional to create more room in the thoracic cavity for the development of the reproductive organs [ 38 ]. However, given the absence of significant discrepancies in linear measurements between sexes described in the present study, and also considering the higher space requirement that females’ reproductive organs (and, even embryos in viviparous species [ 39 , 40 ]) generally necessitate with respect to males’, the need for extra room for the reproductive organs’ development as a main cause of body elongation in the species investigated here seems unlikely to be a driving factor in their ontogenetic growth. Nonetheless, considering that it has often proven difficult to draw a conclusion on whether there are differences or not between sexes [ 12 ], this hypothesis should be investigated further before being completely rejected.…”

Contrast‐enhanced computed tomography and cross‐sectional anatomy of the trunk in the brownbanded bamboo shark (Chiloscyllium punctatum)

“…Although Selachimorpha share the same basic coelomic organs, the positions and shape of the organs are expected to be different depending on the external morphology. In addition, the reproductive modes of Selachimorpha have been grouped into two major categories: oviparity and viviparity (Marongiu et al, 2021). The appearance of female reproductive organs is considered to differ depending on the reproductive modes.…”

Ontogenetic changes in the tyrosine hydroxylase immunoreactive preoptic area in the small-spotted catshark Scyliorhinus canicula (L., 1758) females: catecholaminergic involvement in sexual maturation

“…In this context, in the Mediterranean Sea, among 88 chondrichthyan species (Otero et al, 2019 ), more than half (at least 53%) are threatened because of overfishing (Dulvy et al, 2016 ). In this sense, understanding the overall process of reproduction would be useful for assessing the population status of these species (Marongiu et al, 2021 ) by investigating male–female interactions, physiology, biochemistry, and anatomy (e.g., Storrie et al, 2008 ; Jordan et al, 2021 ).…”