Elasmobranchs through the Looking Glass

Claspers: male sharks; No claspers: female shark. Is this character enough to determine gender in elasmobranchs? While hermaphroditism has long been observed, recognized, and studied in many teleost fish species, this... [ view full abstract ]

Claspers: male sharks; No claspers: female shark. Is this character enough to determine gender in elasmobranchs? While hermaphroditism has long been observed, recognized, and studied in many teleost fish species, this reproductive condition in elasmobranchs – sharks and rays, is typically unusual. Here, we discuss the occurrence of intersexuality, the presence of both male and female sex characters, in the Bigeye Houndshark Iago omanensis and its potential implications on data used to inform fisheries management strategies. During landing site surveys along the northeastern coast of India, seven I. omanensis specimens (immature males) ranging in size between 40 and 60 cm total length, were collected and dissected. Externally, these specimens appeared to be immature males that were gravid (visible stomach bulge). Six out of seven males were gravid with pups present at different stages of development. Initial observations suggest these specimens exhibit basic intersexuality (a combination of both male and female reproductive characters) with the presence of fully developed female sexual organs. Over the past few decades, there have been increasing occurrences of intersexuality recorded in elasmobranchs. Fisheries monitoring data are often based on the external identification of species and the determination of sex ratios based on the presence or absence of claspers. With the increase in reports of intersexuals in a number of elasmobranch genera and species, there is a growing need to understand this phenomenon and its underlying causes. Without such an understanding, we risk under/ over-estimating sex ratios in routine fisheries sampling aimed at population modelling.