Biochemical and immunological markers for the discrimination of three Tilapia species: T. zillii Gervais T. guineensis Bleeker and T. dageti Thys v.d. Audenaerde (Pisces: Cichlidae) from West Africa

Abstract

General muscle proteins and parvalbumins of Tilapia dageti (Thys van den Audenaerde), T. guineensis (Bleeker) and T. zillii (Gervais) (Pisces, Cichlidae) which occur sympatrically in Ghana were subjected to various electrophoretic and immunological assays, and erythrocytes of the species underwent agglutination tests. These investigations aimed to identify species-specific markers, as discrimination of the three closely related species based on morphology has been difficult. A positive agglutination reaction of T. zillii erythrocytes with the soy bean lectin distinguished this species from the other two. Allozyme screening of general muscle proteins revealed loci at which the three species were monomorphic and fixed for different alleles. Polyacrylamide gel electrophoresis and isoelec-trofocussing of parvalbumins revealed species-specific protein profiles for the three tilapias. Immunoelectrophoresis and Western blot tests of parvalbumins with an antiserum to T. guineensis parvalbumins also produced species-specific band patterns. The results offer alternative options for the unambiguous identification of the investigated species as well as of closely related organisms in general. This is a prerequisite for the study, conservation or breeding of any species.