Genetic variation within and between populations of hermaphroditic Bulinus truncatus tetraploid freshwater snails of the Albertine Rift, East Africa
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Genetic variability within and among Bulinus truncatus of the Albertine Rift freshwater bodies were assessed to investigate the degree of inbreeding and gene flow in the snail populations. The effect of ploidy on the genetic structuring of B. truncatus is also described. We characterized the genetic structure of seven B. truncatus populations from Lake Albert, Lake Kivu, and Katosho swamp in Tanzania using five polymorphic microsatellite loci. Genetic differentiation was quantified using pairwise FST values and Nei’s standard genetic distances. Different alleles were observed across all loci and genetic diversity was low although it varied greatly across populations; observed heterozygosity was, however, higher than the expected heterozygosity in three of the populations studied. Significant heterozygote deficiencies were observed coupled with significant linkage disequilibria in five populations for all the five loci examined in this study. We found significant genetic differentiation among the seven freshwater bodies; private alleles were observed across all loci indicating restricted or absence of gene flow between populations. Limited snail dispersal and the reproductive biology of B. truncatus are the major forces shaping the genetic variation observed. Low genetic variation within B. truncatus populations exposes them to a high parasite infection risk as predicted in the Red Queen hypothesis.
KeywordsBulinus truncatus Microsatellites Genetic structure Albertine Rift
We would like to thank the following departments for approval to collect snail samples: the National Centre for Research and Natural Sciences (C.R.S.N) for the permit to sample snails from Lake Kivu at Bukavu, the Tanzania Commission for Science and Technology (COSTECH) to sample at Lake Tanganyika, Kigoma and the National Council for Science and Technology, Uganda. This work was funded by the Danida through Mandahl-Barth Research Centre for Biodiversity and Health at Section for Parasitology, Health and Development, Faculty of life Sciences, University of Copenhagen, Denmark. Part of the field work at Lake Albert was supplemented by the EU-Schistosomiasis Control and Transmission grant (EU-CONTRAST: FP6 STREP contract no: 032203, http://www.eu.contrast.eu).
- Abdel-hamid, A.-H. Z., J. B. Molfetta, V. Fernandez & V. Rodrigues, 1999. Genetic variation between susceptible and non-susceptible snails to Schistosoma infection using random amplified polymorphic DNA analysis (RAPDS). Journal of Tropical Medicine of Sao Paulo 41(5): 291–295.Google Scholar
- Brown, D. S., 1980. Freshwater snails of Africa and their medical importance. Taylor and Francis, London.Google Scholar
- Brown, D. S., 1994. Freshwater Snails of Africa and Their Medical Importance, 2nd ed. Taylor & Francis, London.Google Scholar
- Burch, J. B., 1960. Chromosome numbers of schistosome vector snails. Parasitology 11: 449–452.Google Scholar
- Burch, J. B., 1967a. Chromosomes of intermediate hosts of human bilharziasis. International Journal of Malacology 5: 127–135.Google Scholar
- Burch, J. B., 1967b. Some species of the genus Bulinus in Ethiopia, possible intermediate hosts of schistosomiasis haematobia. Ethiopian Medical Journal 5: 245–257.Google Scholar
- Campbell, G., L. R. Noble, D. Rollinson, V. R. Southgate, J. P. Webster & C. S. Jones, 2010. Low genetic diversity in a snail intermediate host (Biomphalaria pfeifferi Krass, 1848) and schistosomiasis transmission in the Senegal River Basin. Molecular Ecology 19: 241–256.PubMedCrossRefGoogle Scholar
- Dundee, D. S., P. H. Phillips & J. D. Newsom, 1967. Snails on migratory birds. The Nautilus 80: 89–91.Google Scholar
- Goldman, M. A., P. T. LoVerde & C. L. Chrisman, 1980. Comparative karyology of the freshwater snails Bulinus tropicus and B. natalensis. Canadian Journal of Genetics and Cytology 22: 361–367.Google Scholar
- Nalugwa, A., T. K. Kristensen, S. Nyakaana & A. Jorgensen, 2010. Mitochondrial DNA variation in sibling species of the Bulinus truncatus/tropicus complex in Lake Albert, western Uganda. Zoological Studies 49: 515–522.Google Scholar
- Njiokou, F., C. Bellec, P. Jarne, L. Finot & B. Delay, 1993. Mating system analysis using protein electrophoresis in the self-fertile hermaphrodite species Bulinus truncatus (Gastropoda: Planorbidae). Journal of Molluscan Studies 59: 125–133.Google Scholar
- Page, R. D. M., 2001. TreeView32 v. 1.6.6. Distributed by the author [available on internet at http://taxonomy.zoology.gla.ac.uk/rod/rod.html].
- Patterson, C. M. & J. B. Burch, 1978. Chromosomes of pulmonate molluscs. Systematics, Evolution and Ecology 2A: 171–217.Google Scholar
- Rees, W. J., 1965. The aerial dispersal of Mollusca. Proceedings of the Malacological Society of London 36: 269–282.Google Scholar
- Satayathum, S. A., E. M. Muchiri, J. H. Ouma, C. C. Whalen & C. H. King, 2006. Factors affecting infection or reinfection with Schistosoma haematobium in coastal Kenya: survival analysis during a nine-year, school-based treatment program. American Journal of Tropical Medicine and Hygiene 75: 83–92.PubMedGoogle Scholar
- Yeh, F. C., R. C. Yang, J. Mao, Z. Ye & T. J. B. Boyle, 1999. PopGene Version 1.31. Microsoft Window-Based Freeware for Population Genetic Analysis. University of Alberta, Edmonton.Google Scholar
- Zakhary, K., 1997. Factors affecting the prevalence of schistosomiasis in the Velta region of Ghana. McGill Journal of Medicine 3: 93–101.Google Scholar