New report of malformations in blue shark embryos (Prionace glauca) from the western coast of Baja California Sur, Mexico

Abstract

Four new malformations observed in blue shark embryos in the western coast of Baja California Sur, Mexico are reported in this study. The embryos of blue shark samples were obtained on board the industrial fishing boat ‘Damasta’; the organisms were frozen and transferred to CIBNOR Fish Ecology Laboratory where the corresponding measurements were taken and malformations observed. The first malformation was the presence of one nostril in two female embryos that showed short and crushed snouts. The second one was observed in a female with two jaws and the middle portion of the column trunk in screw-shape. The third one was an embryo with dicephaly, two separate vertebral columns, two first dorsal fin pairs, absence of the second dorsal fin, five pelvic fins and two joint caudal fins. The fourth malformation observed was an embryo with incomplete development and undifferentiated sex. Malformations are still a mystery and also an object of study because they affect different organisms, not only sharks but also fish. It is highly relevant to know the causes and perform further studies to understand if the origin is either genetic or anthropogenic.

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

“…However, similar reports in the South Atlantic Ocean are less frequent in comparison with the North Atlantic Ocean. In both the Atlantic and Pacific Oceans, the most commonly reported malformations for this species at this stage of development are diprosopia (usually two heads) and twisted vertebral columns (Mancini et al ., 2006; Bejarano-Álvarez et al ., 2011; Galván-Magaña et al ., 2011; Hevia-Hormazábal et al ., 2011; Ehemann et al ., 2016; Lamarca et al ., 2017; Pastén-Marambio et al ., 2018; Rodriguez-Romero et al ., 2019; Ramírez-Amaro et al ., 2019; Kanagusuku et al ., 2020). In this study, we report the second embryo with a kind of cyclopia for the South-western Atlantic Ocean (Ferreira et al ., 2002).…”

“…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).…”

“…Another factor that can be affecting the malformation presence is environmental degradation or pollution (Goto et al, 1981;Ferreira et al, 2002;Rosa et al, 2004;Mancini et al, 2006). In this context, some studies have been reported presence of high levels of heavy metals (e.g., Hg) ( Barrera-García et al, 2012;Rodríguez-Romero et al, 2018) and genetic alterations related with initial stages of development (Mancini et al, 2006;Rodríguez-Romero et al, 2018). Although the lack of information about the causes of anomalies, an explanation for some individual reported in this study who did not survive after birth, could be related with difficulties in swimming, feeding and avoiding predators in these individuals (Mancini et al, 2006;Rodríguez-Romero et al, 2018).…”