INDUCTION OF DIPLOID GYNOGENEIC LARVAE OF AFRICAN CATFISH, Clarias Gariepinus Burchell(1822)

Abstract

A simple and safe biotechnology genetic manipulation (GM) technique, gynogenesis, is employed in this study to produce all-female populations larvae of African catfish (Clarias gariepinus Burchell 1822). Eggs numbering 10010 in quadruplicates were induced by activating them with UV irradiated milt (UV irradiation at 30000 Wcm^-2 for 15 min) in a glass aquarium and then subjected to cold shock treatment at 2C for 20 min. The diploid and haploid control treatments were fertilized with normal and irradiated milt respectively to produce normal diploid and haploid embryos. Data on fertility, hatchability, and survival were monitored and recorded. The normal diploid control and haploid control treatments gave similar fertility (p<0.05) of 100% while gynogeneic treatment gave 72.5% with standard error of mean (SEM=3.9). The hatchability (p<0.05) gave 93%, 15% and 22% (SEM=10.7) for the normal diploid control, haploid control and gynogeneic treatments respectively. The survival (p<0.05) after one week for both normal diploid control and gynogeneic treatment recorded 91% and 13.25% (SEM=12.1) respectively while there was no fry that survived, even to swimming stage in the haploid group. The cytogenetic determination of the ploidy levels of the embryos was carried out by immersing the 1h posthatched embryos in 0.02% colchicine for 4 h, and later treated with diluted catfish serum 1:3 with 0.9% NaCl solution for 25 min, then in distilled water for 5 min, and stained with 20% Giemsa (Scharlau). Photomicrographic analysis of chromosome preparations gave the same chromosome number n = 562 for both normal diploid control and gynogeneic embryos while the haploid control have n = 282.