An investigation of maternal origin of morphometrically defined Tilapia species established in Sri Lanka
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Abstract:
Three species of tilapia viz; Oreochromis mossambicus, Oreochromis niloticus and Tilapia rendalli, are well established in Sri Lanka and significant in fresh water fishery. Introgressive hybridisation is common between certain tilapia species producing hybrids that can obscure the morphological boundaries between species and also have numerous negative effects on long-term fishery. Therefore an easy index for identification of tilapia species and their hybrids in the field, which is based on morphometry of tilapia fish is essential. However, such a morphological index substantiated by DNA based study is not available. The present investigation reports the most important morphometric characters for the identification of tilapia species in Sri Lanka. The maternal origin of selected individuals of such groups was determined using heteroduplex formation of PCR products of a part of control region of mitochondrial DNA (mtDNA) with the PCR product of the same region of an authentic O. mossambicus. The majority of individuals tested had maternal origin conforming to the present morphologically defined species, whereas a few (03) O. niloticus individuals had mossambicus maternal origin indicating hybridisation.Keywords:
Oreochromis mossambicus
Sri lanka
Aquaculture of tilapia
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Random amplified polymorphic DNA (RAPD) analysis was applied to the four-tilapia species (three genera): redbelly tilapia (Tilapia zillii), white tilapia (Sarotherodon galilaeus), blue tilapia (Oreochromis aureus) and Nile tilapia (Oreochromis niloticus). Twenty random primers – fifteen (10-mer) and five (20-mer) – were used to assay polymorphisms among three genera and between two species. Different RAPD fragment patterns were observed for different genera species. Results showed that there are great differences among the three genera of tilapia fish. Also, data demonstrated that RAPD markers are useful for the systematic investigation at the level of tilapia species.
Nile tilapia
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Oreochromis mossambicus
Aquaculture of tilapia
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Competitive interactions not only exist between invasive and native fish species but also between different invasive species, especially between those that have broad niche overlap. Nile tilapia (Oreochromis niloticus) and Redbelly tilapia (Tilapia zillii) are the most common invasive tilapia species in the rivers of South China. There may be specific factors that influence their competitive interactions and disturbance patterns, and temperature has been considered the most important factor. To study how temperature affects the distribution patterns and competitive interactions of these two invasive tilapia species, field surveys and laboratory experiments were conducted. Field surveys showed that latitude affected the ratio but not the biomass of all tilapia species. Nile tilapia was more abundant in the southern (warmer) sites, and Redbelly tilapia was more abundant in the northern (colder) sites. The distribution patterns of the two tilapia species were also related to latitude and minimum winter temperature. The results of the laboratory-based temperature experiments further confirmed that Redbelly tilapia can tolerate lower temperatures than Nile tilapia. However, the Nile tilapia were larger in field surveys, and laboratory experiments also showed that Nile tilapia are stronger competitors in warmer water because of their larger body size. Therefore, we suggest that the distribution patterns of these two invasive tilapia species were related to temperature conditions.
Nile tilapia
Aquaculture of tilapia
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Abstract Exotic cichlids, introduced to Asia during the second half of the twentieth century, contribute significantly to the reservoir fisheries in the region. The two major cichlid species, Oreochromis mossambicus (Peters) and O. niloticus (L.), tend to interbreed easily. In Sri Lankan reservoirs, introgressive hybridization of these two cichlids takes place. The reproductive biology of O. mossambicus, O. niloticus and their hybrids in three reservoirs in Sri Lanka was evaluated. An imbalance in sex ratio with male dominance was evident. The estimated fecundity for 20‐cm fish, using fecundity‐total length relationships for various populations, indicated that there was a decline in fecundity in hybrid forms. It is hypothesized that the long‐term effect of crosshybridization between the two cichlids might lead to a decline in fish yields in perennial reservoirs of Sri Lanka. The importance of the findings of the present study for the management of the reservoir fisheries in Asia is highlighted.
Cichlid
Oreochromis mossambicus
Dominance (genetics)
Sri lanka
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Oreochromis mossambicus
Variation (astronomy)
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The present work aims to produce a salinity tolerant fish through interspecific hybridization of Nile tilapia,Oreochromis niloticus × Red tilapia, Oreochromis sp. Growth performance, proximate body composition and feed utilization of the offspring produced of Nile tilapia, red tilapia and their diallelic interspecific hybridization under different salinity levels were evaluated and heterosis values were estimated for weight gain and specific growth rate. The results of most of the productive performance traits and heterosis values indicated a maternal effect and suggest that the hybrid of (♀ Red tilapia × â™‚ Nile tilapia) can be produced and reared at different salinity levels up to 32 ppt, as economic value compared to purebreds and reciprocal hybrid.
Key words: Salinity tolerance, Nile tilapia, red tilapia, productive performance, heterosis, interspecific hybridization.
Nile tilapia
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Abstract. The usefulness of isozyme and protein markers in identifying tilapia species and their hybrids is demonstrated Genetic characterization of Oreochromis niloticus populations from commercial farms, experimental stations, and government hatcheries in Luzon, Visayas and Mindanao in the Philippines indicates well-established introgression with O mossambicus Genetic differentiation of the O niloticus stocks, measured by Nei's genetic distance, was highly correlated with O mossambicus gene content The implications of these results for tilapia genetic improvement are discussed.
Introgression
Oreochromis mossambicus
Genetic distance
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Nile tilapia
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Leucaena
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