Abnormalities in two shark species, the blue shark, Prionace glauca, and the school shark, Galeorhinus galeus (Elasmobranchii: Carcharhiniformes), from the Canary Islands, eastern tropical Atlantic

Abstract

A total of six abnormal embryos of shark species, five blue shark, Prionace glauca (Linnaeus, 1758), and one school shark, Galeorhinus galeus (Linnaeus, 1758), are herewith reported from the Canary Islands (eastern central Atlantic). Two P. glauca embryos showed two totally separated heads on one trunk (bicephalism), while the other three embryos had a single head with some duplicated parts, such as the mouth or the eyes (diprosopia). Galeorhinus galeus embryo showed cephalic abnormalities. Possible causes of these abnormalities are briefly discussed.

Teratological records in blue shark Prionace glauca embryos from the South-western Atlantic Ocean

“…Within the last two decades, reports of abnormalities in elasmobranch embryos have increased worldwide, and a wide variety of abnormal morphological conditions have been described. The reports come from a range of seas and oceans, including the Atlantic Ocean (Clark, 2002; Coelho & Erzini, 2006; Mancini et al ., 2006; Delpiani et al ., 2011; Zaera & Johnsen, 2011; Wagner et al ., 2013; Dos Santos & Gadig, 2014; Afonso et al ., 2016; Lamarca et al ., 2017; Ramírez-Amaro et al ., 2019; Prado et al ., 2020), Pacific Ocean (Goto et al ., 1981; Clark, 2002; Bejarano-Álvarez et al ., 2011; Galván-Magaña et al ., 2011; Hevia-Hormazábal et al ., 2011; Bejarano-Álvarez & Galvãn-Magaña, 2013; Muñoz-Osorio, et al ., 2013; Escobar-Sanchez et al ., 2014; Becerril-García et al ., 2017; Pastén-Marambio et al ., 2018; Rodriguez-Romero et al ., 2019), Mediterranean Sea (Saidi et al ., 2006; Bottaro et al ., 2008; Sans-Coma et al ., 2016), Caribbean (Ehemann et al ., 2016) and Indian Ocean (Moore, 2015).…”

“…The most frequently reported abnormalities are related to the anterior body region, such as: dicephaly (Galván-Magaña et al ., 2011; Rodriguez-Romero et al ., 2019), cyclopia (Bejarano-Álvarez & Galván-Magaña, 2013; Ramírez-Amaro et al ., 2019) and duplicate or absent structures (e.g. two mouths, Mancini et al ., 2006; missing gill slits, Saidi et al ., 2006).…”

Multiple morphological abnormalities in a blue shark Prionace glauca (Linnaeus, 1758) embryo from the Peruvian coast, southeast Pacific

“…This reports include albinism (e.g., Clark, 2002;Saïdi et al, 2006;Bottaro et al, 2008;Escobar-Sánchez et al, 2014), bicephaly (e.g., Galván-Magaña et al, 2011;Wagner et al, 2013), diprosopia (e.g., Mancini et al, 2006;Hevia-Hormazábal et al, 2011;Driggers et al, 2012), deformities in axial skeleton (e.g., Pastore & Prato, 1989;Heupel et al, 1999;Mancini et al, 2006), mummification (e.g., Rosa-Molinar et al, 1983;Sandoval-Castillo & Villavicencio-Garay-Zar, 2008) and even cyclopia (Bejarano-Álvarez & Galván-Magaña, 2013). Blue shark (Prionace glauca) is the shark species with the highest number of anomalies reported, which have been described by different authors (e.g., Goto et al, 1981;Mancini et al, 2006;Galván-Magaña et al, 2011;Hevia-Hormazábal et al, 2011;Bejarano-Álvarez et al, 2013;Ehemann et al, 2016;Rodríguez-Romero et al, 2018;Ramírez-Amaro et al, 2019).…”

“…On the other hand, it is known that morphological abnormalities registered in blue shark may be related to high embryo production (Mancini et al, 2006), varying from 28 to 54 embryos per litter, reaching a maximum record of 135 embryos (Compagno, 1984;Castro et al, 1999). In this species, uterus reduction due to a high number of embryos generates abnormal embryo development (Mancini et al, 2006;Ramírez-Amaro et al, 2019).…”

“…Current and previous reports about morphological anomalies shed light on the possible causes of these deformations in sharks (Ramírez-Amaro et al, 2019), but more studies about this topic are needed, especially in commercial relevant species.…”