Genetic variation in lytic activities of blood serum from Nile tilapia and
genetic associations with survival and body weight
Jarunee Chiayvareesajja, Asst. Prof., D. of Aquatic Sci., F. of Natural Resources, PSU.
Knut H. Roed, D. of Morphology, Genetics and Aquatic Biology, Norwegian College of Veterinary
Medicine, Norway
Ambekar E. Eknath, International Center for Living Aquatic Resources Management (ICLARM),
Makati, Metro Manila, Philippines
Jodecel C. Danting, National Freshwater Fisheries Technology and Research Center, Bureau of
Fisheries and Aquatic Resources, Nueva Ecija, Philippines
Marietta P. De Vera, International Center for Living Aquatic Resources Management (ICLARM),
Makati, Metro Manila, Philippines
Hans B. Bentsen, Institute of Aquaculture Research, (AKVAFORSK), Norway
Corresponding e-mail : chjarune@ratree.psu.ac.th
Published : Aquaculture 1999, 175 : 49-62
Key words : genetic variation, lysozyme activity, spontaneous haemolytic activity,
genetic association, survival, body weight, Nile tilapia, Oreochromis niloticus
A study was carried out on lysozyme activity and spontaneous haemolytic (SH) activity of blood serum from 388 individuals of Nile tilapia (Oreochromis niloticus) coming from 42 full-sib groups within 21 paternal half-sib groups. The lysozyme activity was measured at both 15oC and 30oC incubation temperatures, whereas SH activity was measured at 30oC incubation temperature. Significant variation in lysozyme activity was detected between half-sib groups at 30oC incubation temperature, but not at 15oC incubation temperature and not for SH activity. Significant variation
was found between full-sib groups for all parameters. The estimated heritabilities of lysozyme acti-vity were relatively high (0.6-0.7) at 30oC incubation temperature and intermediate (about 0.3) at 15oC incubation temperature. The heritability estimate of SH activity was zero according to estimates based both on the sire component of vairance and on variance components from an individual animal model, whereas the estimate based on the dam component of variance was about 0.7 and highly sig-nificant. Survival and growth were recorded after a grow-out period of 120 days in individuals from a parallel set of samples from the same sib families. Significant negative correlations were found between least-squares means in the parallel sib groups for lysozyme activity and survival rates for both half-sib groups (r = -0.53; P = 0.01) and full-sib groups (r = -0.32; P = 0.04). No significant correlations were found between SH activity and survival rate nor between lytic activities and body weight at harvest.
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