Morphological abnormalities in skates and rays (Chondrichthyes) from off southeastern Brazil

In this paper, the authors report morphological abnormalities observed in six species of skates and rays from off southeastern Brazil, between 2005 and 2008 as follows: the rio skate, Rioraja agassizi (Muller and Henle, 1841); the spotback skate, Atlantoraja castelnaui (Ribeiro, 1907); the eyespot skate, A. cyclophora (Regan, 1903); the pelagic stingray, Pteroplatytrygon violacea (Bonaparte, 1832); the roughtail stingray, Dasyatis hypostigma (Santos and Carvalho, 2004); and the shortnose guitarfish, Zapteryx brevirostris (Muller and Henle, 1841). The abnormalities observed included pectoral fins non-adherent to the head; incomplete pectoral fin, anophthalmia, and presence of a single clasper. The percentage of abnormal specimens ranged from 0.1 to 1.3. Potential causes of the abnormalities probably occurred during embryonic development, for instance pectoral fins had failed to fuse together in front of the head in early development. Additionally, unfavorable  environmental conditions cannot be excluded, such as the role of chemical pollutants playing a role in embryonic development of skates in egg cases.