Protein polymorphism and genetic variation in the catfish Synodontis schall (Bloch-Schneider, 1801) and S. serratus (Ruppel, 1829) from the White Nile (Sudan)

Abstract

Protein polymorphism and allelic variation were investigated in the blood of the cat¢sh, Synodontis schall (Bloch-Schneider,1801) and S. serratus (Ruppel,1829) from three localities along the White Nile. The ¢rst sampling locality at khartoum, the second at Jebel Aulia Dam, 45 km south of khartoum and the third locality was 45 km southward along the White Nile. Seventeen gene loci were identi¢ed in separating 13 enzymes and proteins. Nine loci were polymorphic and eight were monomorphic in the two species. Two alleles were observed for each polymorphic locus. Except for serum albumin (ALB Ã ) and erythrocyte glucose phosphate isomerase (GPI-1 Ã ), all corresponding allozymes in the two species revealed similar mobilities and separation patterns. Serum albumin (ALB Ã ) was monomorphic with a molecular weight of 67 kd in S. schall and 60^62 kd in S. serratus. Glucose phosphate isomerase (GPI-1 Ã ) was polymorphic in S. schall, but monomorphic in S. serratus. A contingency (w 2 ) test shows signi¢cant interspecies heterogeneity in allele frequency at (haemoglobin (HB Ã )), (6-phosphogluconate dehydrogenase (6PGD Ã )) and (superoxide dismutase (SOD Ã )) but none of the other polymorphic loci. Average heterozygosity was (0.26) for both species and the genetic distance between the two species was (0.22).