Occurrence of an Intersexual Blacktip Shark in the Northern Gulf of Mexico, with Notes on the Standardization of Classifications for This Condition in Elasmobranchs

Abstract

An intersexual Blacktip Shark Carcharhinus limbatus with a testis, immature female reproductive tracts (embedded), and claspers was caught in the Gulf of Mexico. Histology of the single gonad revealed that all stages of spermatogenesis were occurring; however, the absence of ovaries and a male duct system suggests that neither sex would have been functional in this individual. Intersexuality has been reported in 17 families and 36 species of elasmobranchs. The degree to which the different sexes are present in a given individual is often difficult to categorize by normal hermaphroditic standards, as this is typically an anomalous presentation in elasmobranchs. Therefore, this report provides three categories for classification (basic, incomplete, and complete intersexuality) to standardize terminology and allow for more precise comparisons to be made among elasmobranch examples. Basic intersexuals have gonadal tissue of only one sex and a combination of other male and female characters with neither or only one sex being complete. Incomplete intersexuals have gonadal tissue of both sexes and a combination of other male and female characters; however, neither or only one sex is complete. Complete intersexuals have claspers as well as gonadal tissue and tracts for both sexes. The majority of the reported intersexual elasmobranchs, including the shark described here, are basic intersexuals. Received September 30, 2012; accepted April 17, 2013

Occurrence of an Intersexual Pacific Spadenose Shark Scoliodon macrorhynchos from the Southern Taiwan Strait

“…As this intersexual specimen had claspers as well as gonadal tissue and tracts for both sexes, it can be classified as a complete intersexual (Hendon et al 2013). …”

“…The histological analysis of the ovotestis revealed that the testicular tissue consisted of spermatocytes at different stages of spermiogenesis (Figure 2), including late-stage spermatids that were considered to be mature (Chen et al 1999;Lam 2009), and the ovarian portion showed maturing ova (Figure 2), which was enlarged and contained a high density of yolk granules (Teshima 1981;Lam 2009). As this intersexual specimen had claspers as well as gonadal tissue and tracts for both sexes, it can be classified as a complete intersexual (Hendon et al 2013).…”

“…The maturity stages of the reproductive tracts of both sexes were judged according to Stehmann (2002). The classification standard of Hendon et al (2013) was used to define which type of intersexuality applied to this specimen. To compare with the intersexual specimen, the same measurements were recorded for three normal, mature (similar size with the intersexual specimen) and three normal, immature specimens of each sex.…”

“…The vast majority of elasmobranchs (sharks and rays) are considered gonochoristic (Compagno 1990); nevertheless, intersexuality has been occasionally documented in this group. Based on the research of Hendon et al (2013), according to the degree to which the different sexes are present in a given individual, intersexuality in elasmobranchs can be classified into three types (basic, incomplete, and complete). Basic intersexuality has gonadal tissue of only one sex and a combination of other male and female characteristics with neither or only one sex being complete.…”

First record of second‐generation facultative parthenogenesis in a vertebrate species, the whitespotted bambooshark Chiloscyllium plagiosum

“…The externally male specimen was further dissected to verify its male sex as abnormities and hermaphroditism is also known to occur in diverse lineages of sharks (Yano & Tanaka, 1989;Iglésias et al, 2005;Ribeiro-Prado et al, 2009;Costa et al, 2013;Hendon et al, 2013). The dissection was documented at different stages using a Panasonic digital camera DMC-TZ26 (www.panasonic.com).…”