Evaluation of protein fractions of indigenous clariid fish species (Clarias gariepinus and Heterobranchus bidorsalis) and their reciprocal hybrids

Abstract

Electrophoresis of myofibrillar and sarcoplasmic muscle proteins of African catfish: Clarias gariepinus, Heterobranchus bidorsalis and their reciprocal hybrids in South-West Nigeria was carried out to reveal the similarities and dissimilarities among species in order to aid the selection of suitable strains for aquaculture that could lead to production of new varieties of fishes to alleviate the problem of short supply of fast growing quality fish seeds. The study was aimed at analyzing the muscle protein profiles of C. gariepinus, H. bidorsalis and their reciprocal hybrids. Sixteen juveniles fish samples (comprising four samples from each mating combinations) artificially propagated and reared for sixteen weeks were analysed electrophoretically. Myofibrillar and sarcoplasmic fractions were prepared by homogenizing 150 mg of fish muscle in 1.5mL of rigor buffer containing 10 mM Trismeleates, 60 mMKCl, 5 mMMgCl2,1 nM EDTA. Extracts were centrifuged in a tube at 10,000 g for 5 min at 4°C. The resultant pellets (myofibrilla) and supernatant (sarcoplasmic) were separated using 12.5% Sodium Dodecyl-Sulphate Polyacrylamide Gel Electrophoresis (ID SDS-PAGE). The relative concentration of individual protein bands were analysed using TotalLab™ 1D software. The individual protein bands in the electrophoregram were identified in relation to their molecular weights. A total of eleven and seven protein bands were resolved in myofibrilla and sarcoplasmic fractions, respectively. The 5th band with Molecular Weight (MW) of 52.23 kDa of the myofibrilla electrophoregram distinguished C. gariepinus from H. bidorsalis while the 3rd band with MW 119.04, 4th band with MWs 101.49 and 102.13; 8th band with MWs 29.24 and 29.39 kDa distinct the pure breeds from the hybrids. However, in sarcoplasmic fraction, the 3rd and 5th bands with MWs 92.11 kDa and 54.28 kDa, respectively distinguished the hybrids in the while the 7th band with MW 41.67 kDa distinct the pure breeds. Therefore, this research will serve as a bridge between the existing gaps of information available on the muscle protein profile of C. gariepinus, H. bidorsalis and their reciprocal hybrids and the study identifies the proteomic classification of clariid species with the aim of enlightening fish researchers and aquaculturist on the characterization of broodstock selection for successful breeding exercise.