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Genetic Variation of Three Populations of Indian Frog (hoplobatrachus Tigerinus) Revealed by Allozyme Marker

M. R. Islam
Department of Fisheries and Marine Science, Noakhali Science and Technology University, Sonapur, 3814, Bangladesh.

M. Belal Hossain
Department of Biology, FOS, University Brunei Darussalam, BE 1410, Brunei.

Abstract/ Executive Summary:

The Indian bullfrog, Hoplobatrachus tigerinus plays a significant role in maintaining the natural balance in the ecosystems. It plays an important role in controlling the various agricultural pests because of its omnivorous feeding habit. The aim of the present study was to know the genetic variation of H. tigerinus in three natural habitats. Samples collected from three districts of Bangladesh were analyzed with five enzymes (MDH, LDH, GPI, PGM and EST) in CA 6.1 buffer system for their genetic variation. Four polymorphic loci (Mdh-1, Est-1, Gpi-1 and Pgm) were interpretable in muscle with starch gel electrophoresis. Among the 5 presumptive loci, the mean proportion of polymorphic loci was observed 80, 80 and 60% in Rangpur, Khulna and Mymensingh populations, respectively. The highest mean number of allele per locus and mean proportion of heterozygous loci per individual were observed in the Rangpur population. The average observed heterozygosity (H_o) was 0.163 and expected heterozygosity (H_e) was 0.469. In pair-wise analysis, comparatively higher N_m value (5.507) was estimated between the Rangpur and Khulna populations corresponding lower level of F_ST value (0.043). The UPGMA dendrogram showed two clusters among the three Indian bullfrog populations. Rangpur and Khulna populations formed one cluster while Mymensingh population formed another cluster. The Mymensingh population separated from Rangpur and Khulna by a genetic distance of 0.177 whereas, the Khulna population is different from the Rangpur population by the genetic distance of 0.052. The results suggested that the considerable genetic distance is maintained among the natural H. tigerinus populations.

Keywords: Heterozygosity, Gel electrophoresis, Indian bull frog, Genetic variation, Bangladesh

Location: Mymensingh, Rangpur and Khulna districts

Start Date:

End Date:

Program Area: Variety and Species

Commodity: Frog

Objectives:

To identify the genetic variation of amphibian species (Hoplobatrachus tigerinus) in three different regions of Bangladesh

Methodology:

The experimental frogs (Hoplobatrachus tigerinus) were collected from the three different locations (Mymensingh, Rangpur and Khulna districts) of the country. Major part of the work was accomplished in the “Fisheries Biology and Genetics Laboratory”, Bangladesh Agricultural University, Mymensingh. A total of 20 specimens were collected from each region. The muscle and liver samples were taken from each individual and stored at -21°C until electrophoretic analysis.This experiment was performed by using allozyme markers through horizontal starch gel electrophoresis method. The enzymes analyzed, E.C. numbers, abbreviation of enzymes and the buffer system used for horizontal starch-gel electrophoresis. Electrophoresis was conducted using amine-citrate buffer (CA 6). After electrophoresis, the gel slices (about 1 mm thickness) were histochemically stained for different enzymes. Allelic frequencies were calculated directly from observed genotypes. The distribution of observed genotypes was calculated from the Hardy-Weinberg equilibrium using a chi-square (χ²) test for allozyme system. When the most common allele existed in a frequency of less than 0.95 at a given locus, it was regarded as polymorphic. The mean proportion of heterozygous loci per individual, mean proportions of polymorphic loci per population and average number of alleles per locus were calculated so as to show the extent of genetic variability for each population. Expected heterozygosity (He) and observed heterozygosity (Ho) was examined. Genetic distance (D) value was calculated by using Nei’s formula. Statistical analysis was performed by using SPSS (v.11).

Source of Information: International Journal of Zoological Research, 8(4): 150-156, 2012, ISSN 1811-9778

Article Link (Online Journal): DOI: 10.3923/ijzr.2012.150.156, URL: http://scialert.net/abstract/?doi=ijzr.2012.150.156

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The frog population collected from Rangpur showed comparatively higher mean proportion of polymorphic loci and mean proportion of heterozygous loci per individual, which was followed by Khulna population and lower values in Mymensingh population. The lower genetic variation in Mymensingh population might be due to mating of closely related individuals of same species i.e., inbreeding and/or small number of effective breeding population (Ne). So, the present study concludes that, still there exists considerable genetic variation among the natural H. tigerinus populations but this species were observed to be threatened in nature, their distribution had reduced over time and has become critically endangered in natural populations.

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