Lack of Inheritance of Stumpbody and Taillessness in Channel Catfish

Channel catfish (Ictalurus punctatus) with the traits stumpbody and incomplete or absent caudal fin were mated with channel catfish having the same deformity and with channel catfish possessing normal body conformation. Progeny from these matings were compared to those from matings of normal fish. Most progeny from matings of deformed fish had normal body conformation and caudal fins, but 1% of the progeny of the stumpbody × stumpbody mating lacked all or part of the caudal fin. Apparently, these vertebral deformities of channel catfish have no genetic basis and likely result from environmentally induced congenital defects. Low expressivity and incomplete penetrance could be alternative explanations for the lack of expression of these traits in this experiment. Genes for these deformities may only be expressed under certain environmental conditions that were not present in this experiment.