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Genetic resources for tilapia culture
373 morphisms as determined by chromomycin A3 (CMAS) staining. CMA3 appeared to stain both active and inactive NORs in salmonid fish. CMAS-NOR polymorphisms scored included average number of CMA3-NORs/cell, average total CMA3 band length/cell, chromosomal location of CMA3-NORs, size ofthe CMA3-NORs andpresence of adjacent Q bands. The size of chromosome bands was determined using a microcomputer-assisted image analysis system for chromosome measurement. The length of the short arm of chromosome 2 was measured in each cell and used as a standard for all other measurements. The six stocks could be divided into three groups: a Lake Superior group, a group originally from Lake Michigan and an eastern stock from Seneca Lake, New York. These three groups could be distinguished on the basis of differences in frequencies of isozyme alleles, frequencies of negatively staining Q band chromosome variants and in the total number of CMAS-NORs/cell. Each stock had a unique combination of CMA3-NOR banding variants.
Genetic resources for tilapia culture R.S.V. PULLIN’, J.M. MACARANAS’
and N. TANIGUCH13
‘ICLARM, P.O. Box 1501, Makati, Metro Manila (Philippines) 2iJniversity of the Philippines, Diliman, Quezon City (Philippines) “Dept. of Cultural Fisheries, Kochi University, Kochi 783 (Japan)
ABSTRACT Tilapia culture worldwide uses a small number of species and hybrids. The most important are Oreochromis aureus, 0. mossambicus, 0. niloticus, 0. spilurus, and various interspecific F, hybrid crosses which yield all or nearly all male progeny. There is lesser but significant interest in the culture of Tilapia rendalli, T. zillii, 0.andersonii and 0. macrochir. The red tilapias, a heterogenous group of hybrids, are also attracting attention. Despite worldwide interest in these tilapias, there are few reliable sources from which culturists can obtain founder stocks. Culture collections derived directly from founder stocks collected in Africa and checked by electrophoresis are maintained at only a few locations, for example, in Israel and the United Kingdom. Philippine and other Asian tilapia populations are currently being studied to assess their status, by electrophoresis, and their culture performance. There is disturbing evidence of interbreeding within captive populations. For example, 11 cultured populations in the Philippines, assumed to be 0. niloticus, are introgressed hybrids with 0. mossambicus. Using mean allelic frequency at six electrophoretic marker loci to estimate introgression, the range (values for least and most introgressed populations) was 0.067 rt 0.019 SE to 0.301% 0.054 SE. The mean genetic distance (Nei) between the 11 populations and Philippine 0. mossambicus is 0.2483 k 0.0058. Samples from single Taiwanese and Thai populations of 0. niloticus, kept for research, show negligible introgression: the corresponding mean allelic frequency was 0.012 +-0.009 SE for both and their mean genetic distance from Philippine 0. mossambicus was 0.3631 k 0.0058. Ongoing studies suggest that stable, well-characterized populations are rare throughout the Indo-Pacific. This emphasizes the need for the establishment of more culture collections to provide reliable material for research and production programs and the need for conservation of the wild tilapia resources of Africa and their habitats.
Genetic resources for tilapia culture R.S.V. PULLIN’, J.M. MACARANAS’
and N. TANIGUCH13
‘ICLARM, P.O. Box 1501, Makati, Metro Manila (Philippines) 2iJniversity of the Philippines, Diliman, Quezon City (Philippines) “Dept. of Cultural Fisheries, Kochi University, Kochi 783 (Japan)
ABSTRACT Tilapia culture worldwide uses a small number of species and hybrids. The most important are Oreochromis aureus, 0. mossambicus, 0. niloticus, 0. spilurus, and various interspecific F, hybrid crosses which yield all or nearly all male progeny. There is lesser but significant interest in the culture of Tilapia rendalli, T. zillii, 0.andersonii and 0. macrochir. The red tilapias, a heterogenous group of hybrids, are also attracting attention. Despite worldwide interest in these tilapias, there are few reliable sources from which culturists can obtain founder stocks. Culture collections derived directly from founder stocks collected in Africa and checked by electrophoresis are maintained at only a few locations, for example, in Israel and the United Kingdom. Philippine and other Asian tilapia populations are currently being studied to assess their status, by electrophoresis, and their culture performance. There is disturbing evidence of interbreeding within captive populations. For example, 11 cultured populations in the Philippines, assumed to be 0. niloticus, are introgressed hybrids with 0. mossambicus. Using mean allelic frequency at six electrophoretic marker loci to estimate introgression, the range (values for least and most introgressed populations) was 0.067 rt 0.019 SE to 0.301% 0.054 SE. The mean genetic distance (Nei) between the 11 populations and Philippine 0. mossambicus is 0.2483 k 0.0058. Samples from single Taiwanese and Thai populations of 0. niloticus, kept for research, show negligible introgression: the corresponding mean allelic frequency was 0.012 +-0.009 SE for both and their mean genetic distance from Philippine 0. mossambicus was 0.3631 k 0.0058. Ongoing studies suggest that stable, well-characterized populations are rare throughout the Indo-Pacific. This emphasizes the need for the establishment of more culture collections to provide reliable material for research and production programs and the need for conservation of the wild tilapia resources of Africa and their habitats.