Foetal deformities in a smooth-hound shark, Mustelus mustelus,from an oil exploited area in Angola

摘要

A smooth-hound shark, Mustelus mustelus (Linnaeus, 1758) caught off northern Angola had eight normally developed foetuses and one specimen with morphological abnormalities. This is the first teratologic embryonic deforma-tion recorded for the species, presenting large scoliotic, lordotic and kyphotic bends in the vertebral column. All fins were present but malformed, and the eyes were well developed. The specimen had five pairs of gill slits and embryonic teeth on the mandible. Records of such abnormalities are rare, and the deformation ratio increases with environmental contamina-tion.As the specimen was found in an extensive oil exploitation area the causality of the defects is discussed. Analyses of the toxic compounds in the sediments did not indicate pollution in the seabed, and selenium was the only compound found in relatively high levels (0.95μg/g) in the muscle tissue of the embryo. Selenium is a naturally occurring trace element, which may cause teratogenic deformities if taken in excess; however, there is no statistical evidence to link the deformity to oil exploitation. Still, the record is important as it contributes to assess the frequency of teratogenic deformities in sharks, and in the long run, the effects of toxic components on embryo development.