Report on fetal mummification in the scalloped hammerhead shark Sphyrna lewini

Abstract

This study describes the fetal mummification process in two embryos of a 310 cm total length scalloped hammerhead shark Sphyrna lewini caught in southeastern Brazil, in December 2017. Fourteen embryos were observed in total, in which two males in the left uterus presented different stages of mummification. Both mummified embryos were covered by an exudate (i.e., a mucous substance), indicating a hematic mummification process. All embryos were at the placentotrophic stage of development, indicating that they were close to parturition. An intrinsic characteristic is suggested as possible etiology for this condition, such as umbilical torsion, because both embryos were at different sizes and, therefore, at different development stages.

Re‐evaluation of reproductive cycle and fecundity of finetooth sharks Carcharhinus isodon (Valenciennes 1839) from the Northwest Atlantic Ocean, with new observations on ovarian cycle and reproductive endocrinology of biennially reproducing sharks

“…One aspect of C. isodon reproduction that was observed in this study but not previously reported was an unexpectedly high rate of EED, which was observed in 11% of pregnant females examined. Although embryo death consistent with that observed in this study ( i.e ., the presence of infertile eggs and/or malformed, growth‐retarded or “mummified” embryos) has been previously reported in other shark species (Clark & von Schmidt, 1965; Martins et al ., 2020; Parsons, 1993; Randall, 1977; Rosa‐Molinar & Williams, 1983; Sandoval‐Castillo & Villavicencio‐Garayzar, 2008; Smale & Goosen, 1999; Springer, 1960), the factors that lead to such phenomena remain largely unknown. Nonetheless, irrespective of its causes, embryo loss can have negative effects on population growth in sharks.…”

“…It is also noteworthy that EED was more common in large females. This is a phenomenon that has not been reported in earlier studies focusing on EED in other shark species ( e.g ., Martins et al ., 2020; Rosa‐Molinar & Williams, 1983; Sandoval‐Castillo & Villavicencio‐Garayzar, 2008); nonetheless, it has been observed in some domestic species such as pigs (Borges et al ., 2005) and horses (Noakes et al ., 2009) although its causes remain unclear (Lefebvre, 2015). Nonetheless, this was believed to be responsible for the lack of a significant positive relationship between maternal size and brood size.…”

“…e., the presence of infertile eggs and/or malformed, growth-retarded or "mummified" embryos) has been previously reported in other shark species (Clark & von Schmidt, 1965;Martins et al, 2020;Parsons, 1993;Randall, 1977;Rosa-Molinar & Williams, 1983;Sandoval-Castillo & Villavicencio-Garayzar, 2008;Smale & Goosen, 1999;Springer, 1960), the factors that lead to such phenomena remain largely unknown. Nonetheless, irrespective of its causes, embryo loss can have negative effects on population growth in sharks.…”