ABSTRACT
Aims: To reveal the genetic variability of wild and captive populations of the Indian major carp, mrigal (Cirrhinus cirrhosus) based on microsatellite DNA markers analysis. Study Design: Three rivers namely the Halda, the Padma and the Jamuna were selected under wild population category and three hatcheries such as Brahmaputra Hatchery of Mymensingh, Raipur Government Hatchery, Luxmipur, and Sonali Hatchery, Jessore were selected under the captive population category. Place and Duration of the Study: Department of Fisheries Biology and Genetics, Bangladesh Agricultural University, Mymensingh from July 2005 to June 2008. Methodology: DNA was extracted from fin clips of a total of 180 fish, 30 from each of the six populations. Five microsatellite markers MFW1, MFW2, MFW17, Barb54 and Bgon22 were amplified by polymerase chain reaction for each DNA sample and resolved on denatured polyacrylamide gel and visualized by silver nitrate staining. Results: Three of the five loci were found to be polymorphic in all the six populations. The observed (HO) and expected heterozygosity (HE) ranged from 0.233 to 0.633 and 0.406 to 0.664 respectively. The FIS values ranged from 0.032 to 0.635 indicating deficiency in heterozygosity. Except the Raipur Hatchery stock, the other five populations showed nonconformity to Hardy- Weinberg Expectation at least in one locus. Significant population differentiation was observed between the Halda-Jamuna, Jamuna-Brahmaputra Hatchery, Jamuna-Raipur Hatchery and the Padma-Raipur Hatchery population pairs. The UPGMA dendrogram based on genetic distances resulted in two major clusters: the Halda river and the Raipur Hatchery population were in one cluster and the remaining four populations were in the other cluster. Conclusion: The study, as a whole, revealed low levels of genetic variation in terms of allelic richness and heterozygosity in the three major rivers and three selected hatchery stocks of C. cirrhosus in Bangladesh.
ABSTRACT
The hilsa shad, Tenualosa ilisha (Clupeidae, Clupeiformes) is an important anadromous clupeid species from the Western division of the Indo-Pacific region. It constitutes the largest single fishable species in Bangladesh. Information on genetic variability and population structure is very important for both management and conservation purposes. Past reports on the population structure of T. ilisha involving morphometric, allozyme and RAPD analyses are contradictory. We examined genetic variability and divergence in two riverine (the Jamuna and the Meghna), two estuarine (Kuakata and Sundarbans) and one marine (Cox's Bazar) populations of T. ilisha by applying PCR-RFLP analysis of the mtDNA D-loop region. The amplified PCR products were restricted with four restriction enzymes namely, XbaI, EcoRI, EcoRV, and HaeIII. High levels of haplotype and gene diversity within and significant differentiations among, populations of T. ilisha were observed in this study. Significant F ST values indicated differentiation among the river, estuary and marine populations. The UPGMA dendrogram based on genetic distance resulted in two major clusters, although, these were subsequently divided into three, corresponding to the riverine, estuarine and marine populations. The study underlines the usefulness of RFLP of mtDNA D-loop region as molecular markers, and detected at least two differentiated populations of T. ilisha in Bangladesh waters.