The Influence of the Albino Gene on Intraspecific Hybridization between Regular and Albino African Catfish

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Abstract:

This study investigates the influence of the albino gene on intraspecific hybridization between African Catfish and Albino Clarias gariepinus. Various aspects such as latency period, fecundity, fertility, hatchability, survival, growth performance, morphometric and meristic characteristics, as well as genetic characterization of parents and F1 generation offspring were examined. The experiment involved four mating combinations employing eight mature normal and albino Clarias gariepinus individuals, with an average body weight of 1.64 kg. The broodstock, sourced from Abdulfana fish farm Yola, were acclimatized for ten days and fed vital feed daily at 5% of their biomass. Ovaprim hormone was used for artificial breeding, administered at doses of 0.50 ml/kg for females and 0.25 ml/kg for males. Subsequent assessments included fertility and hatchability of the eggs using Randomized Complete Design (RCD) methodology, along with a long-term 18-month study of F1 and F2 generations that monitored weight, length, survival/mortality, and water quality parameters.

Gene characterization encompassed DNA extraction, electrophoresis, microsatellite marker selection, polymerase chain reaction (PCR) amplifications, and electrophoresis for PCR. Key findings revealed that female albino Clarias gariepinus displayed a longer latency period of 13.50 ± 0.22 hours at 27.50 ± 0.20°C and lower fecundity of 4032 ± 0.12, contrasting with normal Clarias gariepinus, which exhibited a shorter latency period of 12.00 ± 0.21 hours and higher fecundity of 7020 ± 0.23 at similar temperatures. Among mating combinations, NN♂ x NN♀ showed the highest fertility (44.79 ± 0.32%) and hatchability (72.6 ± 0.24%), while AA♂ x NN♀ had the lowest values (27.92 ± 0.31% and 46.3 ± 0.43%, respectively). In terms of weight gain, NN♂ x AA♀ had the highest mean gain (912.90 ± 0.00g), followed by NN♂ x NN♀ (900.75 ± 0.00g), while NN♀ x AA♂ and AA♂ x AA♀ had the lowest gains (893.88 ± 0.00g and 852.98 ± 0.00g, respectively). Survival rates varied, with crossed AA♂ x AA♀ displaying the highest (41.25 ± 0.00%), and NN♂ x AA♀ showing the lowest (12.50 ± 0.00%).

Morphometric analyses demonstrated that F1 generation exhibited greater head width, eye diameter, and occipital fontanelle measurements compared to their parents. Water quality parameters remained within acceptable ranges for tropical catfish cultivation. Genetic analyses unveiled two microsatellite loci for normal Clarias gariepinus (Cg01) and albino Clarias gariepinus (Cg02), with fragment sizes ranging from 0.92 to 1680 bp. Null allele frequencies were low for the parent stock and slightly higher for F1 generation. Allele analysis revealed heterozygosity for Cg01 and homozygosity for the second allele in Cg02. Homozygote excess was noted in Cg02 parents and F1 generation, showing a consistent 100% homozygosity rate for both normal and albino Clarias gariepinus. This study suggests that male and female Albino Clarias gariepinus can be effectively used by fish farmers to produce hybrids with superior survival rates and growth. Further research is recommended to explore the origins of distinctive traits in the F1 generation, such as skin characteristics, head width, eye diameter, and occipital fontanelle measurements.

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