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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Abstract. Two species of tilapia, Oreochromis mossambicus (Peters) and O. niloticus (L.), from five reservoirs in southern Sri Lanka as well as fish from a fish hatchery and laboratory stock were studied by starch gel electrophoresis at 18 enzyme loci, to determine the degree of mixing of the two species. Two reservoirs showed little or no mixing between O. mossambicus and O. niloticus, while two other reservoirs as well as the hatchery stock showed a high degree of mixing of the two species. The laboratory stock of O. niloticus also showed introgression of O. mossambicus alleles. The similarities of the local stocks to the original African as well as other Asian stocks is discussed.
Introgression
Hatchery
Oreochromis mossambicus
Sri lanka
Fish hatchery
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Nile tilapia
Broodstock
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An investigation into evolutionary history of four species of Tilapia species was carried out as a taxonomy tool to relate most tilapia species found within the Nigerian waters. These species are (Oreochromis niloticus, Tilapia zilli, Sarotherodon galilaeus, Sarotherodon melanotheron). Blood samples from the four species of tilapia were collected and preserved on Fast Technology for Analysis (FTA) cards for DNA extraction and PCR amplification. The various nucleotide sequences of the four Tilapia species found in the Mitochondria D-loop region were copied and aligned with the use of BioEdit and Mega 6.0 softwares. Three phylogenetic trees were drawn to show the evolutionary relationship amongst the four species of tilapia. The results indicated that Sarotherodon galilaeus and Sarotherodon melanotheron are sister texa and share a common ancestor with Oreochromis niloticus. Tilapia zilli is an out group which is the most distantly related to the three species (Oreochromis niloticus, Sarotherodon galilaeus Sarotherodon melanotheron). Tilapia zilli (Israel) and Tilapia zilli are sister texa and share a common ancestor in Tilapia sparmanii. The study also revealed ancestry relationship among other species of fish Cyprinus caprio and Clarias gariepinus formed a clade with the three tilapia species (Tilapia zilli, Tilapia zilli (Israel) and Tilapia sparmanii), which share an unknown but common ancestor.
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Oreochromis mossambicus
mtDNA control region
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Nile tilapia
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Tilapia is one of the commercially important fish in Malaysia as well as in other parts of the world. An understanding of monogenean infection dynamics in tilapia fish may assist us in searching for some intervention measures in reducing the loss of fish caused by parasitic diseases. The present study aimed (1) to compare infection level of monogeneans between the wild and cultured Oreochromis niloticus, and between the cultured O. niloticus and cultured red hybrid tilapia, and (2) to examine the spatial distribution of monogenean species over the gills of the different host species. From a total of 75 fish specimens, six species of monogeneans from two genera: Cichlidogyrus (C. halli, C. mbirizei, C. sclerosus, C. thurstonae, C. tilapiae) and Scutogyrus (S. longicornis) were identified. Data showed that the infection level of cultured O. niloticus was higher than that of the wild O. niloticus, however, the former was lower than that of the cultured red hybrid tilapia. Higher species richness of monogeneans was observed in the cultured red hybrid tilapia as compared to the others. Results for spatial distribution showed that the monogeneans have no preference on the left or right sides of the gills. However, C. halli, C. mbirizei, and C. tilapiae showed preferences on specific gill arches in the cultured O. niloticus and red hybrid tilapia. In general, the gill arch IV harboured the least number of monogeneans. The susceptibility of monogenean infection between the different types of tilapia is discussed.
Nile tilapia
Aquaculture of tilapia
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Oreochromis mossambicus
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Reliable estimates of morphometric traits are required for all traits of economic importance to predict response to selection, choose various breeding plans, estimate economic returns and to predict breeding values of stocks for selection.The present study was aimed at assessing the morphometric variation of tilapia fish (Oreochromis niloticus) from different populations.A total of two hundred samples from four populations that cut across two wild [Anantigha river (AN) and Ifiayong river (IF)] and two cultured [Unical fish farm (UN) and Domita fish farm (DM)] were used for the study with fifty samples from each population, respectively.A total of twenty morphormetric traits were measured on each fish.The data were transformed and subjected to multivariate analysis.Results obtained revealed that there were significant differences (P<0.05) in the morphometric traits of the different populations.Body weight was highest in the wild populations (AN =2.32 g; IF = 2.21 g).Correlation analysis revealed high and significant correlation coefficient between the measured traits, where the highest was observed from origin of the dorsal fin to the Original Research Articleinsertion of the pelvic fin (ODIP) and dorsal origin of the caudal fin to the ventral origin of the caudal fin (DCVC) with correlation coefficient of r= 0.955, P<0.01.Path coefficient analysis revealed that body depth, total length and posterior end of the dorsal fin to origin of the anal fin (PDOA) had the highest direct and positive contributions to the body weight of the fish with path coefficient values of 1.359, 0.943 and 0.673, respectively.Principal component analysis extracted four principal components (PC1 = 65.543%;PC2 = 10.869%;PC3 =7.364% and PC4 =1.327%) contributing to the observed variability among the populations.Hierarchical cluster analysis separated the tilapia fish samples into two major clusters, where fish samples from wild population were group majorly within the same cluster and samples from cultured population also grouped majorly within a common cluster.The findings suggest the strength of morphological traits in distinguishing tilapia populations as well as identifying the morphological traits with high contribution to the weight of tilapia fish which could be targeted for weight improvement.
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With increasing demand for improved farmed Nile tilapia (Oreochromis niloticus) fish seed, there is heightened demand for quality and proven broodstock by hatchery operators throughout the country and in the East African region. Uganda, fortunately, is endowed with vast natural Nile tilapia (Oreochromis niloticus) stocks in lakes Albert, Edward and George, as well as in Albert Nile River. To aquaculturally benefit from the different attributes of different stocks/strains, it is important to establish the existing strains in a manner that is phenotypically discernible where such differences are apparent. In this study, we used a suite of morphological traits to identify strains of Nile tilapia among 425 individuals sampled from the four major water bodies, lakes – Albert, Edward-George, Kyoga and Victoria. Morphological variation was investigated using multivariate approaches including principal component analysis, discriminant analysis and cluster analysis of 22 morphometric characters. These analyses indicated that there was high morphological variation among the different populations of Nile tilapia and the fish could be grouped into their respective sampled areas based on these morphological differences. Most of the variation (86.97%) was associated with the fish body size, the peduncle length and the interorbital distances. Findings imply that there are four major Nile tilapia strains in Ugandan waters that will be subjected to aquaculture performance evaluation before being used in the genetic improvement programme to produce improved Nile tilapia fish broodstock/seed for use in fish farming. Differences among populations may reflect genetic differences and/or environmental factors.Keywords: Morphometrics, Oreochromis niloticus, strain identification
Nile tilapia
Broodstock
Morphometrics
Aquaculture of tilapia
Hatchery
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Oreochromis mossambicus
Variation (astronomy)
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