Lactate dehydrogenase isozyme pattern of the Mediterranean killifish Aphanius fasciatus (Teleostei, Cyprinodontidae)

Electrophoretic analyses of the tetrameric lactate dehydrogenase isozyme pa tterns of the endangered cyprinodontid fish Aphanius fasciatus were carried out. Organ and tissue samples of ten individuals of each sex were analysed by cellulose acetate electrophoresis and isoelectric focusing. Isozyme ele ctrophoretic patterns indicated that three LDH loci (Ldh-A, Ldh-B and Ldh-C ) were active and showed differential tissue expressions. No differences be tween sexes were observed. The Ldh-A and Ldh-B loci were expressed in all t issues analysed, and the A subunits possessed a net negative charge greater than B subunits. Heterotetramers including subunit A were not observed, bu t a complex heterotetramer banding pattern of subunits B and C was detected . On the basis of the staining intensity of the electromorphs, Ldh-A predom inated in all tissues analysed, with the exception of the liver, where Ldh- B predominated. Instead, Ldh-C was characterised by high relative anodal mo bility and was expressed only in the eye. Furthermore, at this locus two al leles were observed in specimens analysed. The LDH banding pattern of A. fa sciatus was consistent with that of advanced teleosts and it showed an inve rsion of the net negative charge of products of the Ldh-A and Ldk-B loci.