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Community Structure Analysis of Endoparasitic Helminths of Anabas Testudineus (bloch, 1792) from a Fresh Water Body of Bangladesh

AMINUL ISLAM BHUIYAN
Department of Zoology, University of Dhaka, Dhaka 1000, Bangladesh

MD OSMAN GHANI
Department of Zoology, University of Dhaka, Dhaka 1000, Bangladesh

JANNATUL BUSHRA
Department of Zoology, University of Dhaka, Dhaka 1000, Bangladesh

Abstract/ Executive Summary:

Community structure of the parasites of Anabas testudineus was analyzed collected from a fresh water body, Turag River at Diabari, Mirpur point of Dhaka, Bangladesh. Out of 50 A. testudineus fish observed, 36 (72%) were parasitized by at least one species of helminth endoparasites. Six metazoan endoparasites were recorded: two trematodes (Allocreadium minutum, Neopecoelina saharanpuriensis) and four nematodes (Ascaridida sp., Gnathostoma spinigerum, Contracaecum sp., Paragendria wallagonia). Prevalence was higher in female (81.25%) hosts than male (55.56%). Nematode was more prevalent group (70%) than trematode (62%). All parasite species were accounted as secondary species category; no central or satellite species accounted in the sample. A significant positive correlation was observed between the standard length of the host with the prevalence and abundance of all parasites in this sample fishes. Two parasites (A. minutum and Ascaridida sp.) showed typical over-dispersed distribution pattern and other four parasites (N. saharanpuriensis, G. spinigerum, Contracaecum sp. and P. wallagonia) showed random distribution pattern. Interspecies association between two species of parasite was moderately strong. The host’s sex did not affect the parasite diversity and abundance.

Keywords: Endoparasite, Anabas, Community structure, Component community, Infra community

Location: Beribadh area of Turag River at Diabari, Mirpur, Dhaka

Start Date: 00-04-2012

End Date: 00-10-2012

Program Area: Animal Health and Management

Commodity: Aquatic animal

Objectives:

1. To extend the knowledge about the endoparasitic fauna of Anabas testudineus, through determining its parasite diversity at component and infra- community structure level, and to analyze the possible influence of host sex and standard length and others from a fresh water body of Bangladesh.

Methodology:

The present study was conducted by investigation of parasites of host fish Anabas testudineus collected from Beribadh area of Turag River at Diabari, Mirpur, Dhaka, Bangladesh (23°52?N- 90° 24?E) during April-October, 2012. One attempt was made each month to collect fish but we could collect fish during months of April (n=12), May (n=10), September (n=7) and October (n=21). Fish were not available during rest of the months. Fifty A. testudineus individuals were collected from local fishermen during the study period. Sample fishes were collected from its habitat water as live and immediately brought to the parasitology laboratory of the Department of Zoology, University of Dhaka for investigation. The river body’s average width and depth are 400m and 10m respectively. Investigation on helminth parasites: The examination was aimed to determine endoparasitic helminths infection of A. testudineus. Length, sex and organ wise infections of fish by each parasite species were recorded. Length and sex of hosts were noted before autopsy. Extensive search was made for helminth parasites infecting the fish using Leica Zoom 2000 Dissecting Microscopes. All parasites from each organ were sorted, cleaned, counted and then were preserved in 70% alcohol. The trematodes were stained in acetic carmine for 2-3 hours depending on size of specimens. After staining, the worms were washed in 70% alcohol to which a few drops of glacial acetic acid were added. Then they were cleaned and temporarily mounted in lactophenol. Nematodes were cleaned and temporarily mounted in lactophenol for microscope study. Berland method was used for staining and mounting. Species identification was done by using taxonomic keys. Two nematodes, Ascaridida and Contracaecum could not be identified to species level, therefore referred as Ascaridida sp. and Contracaecum sp. Calculation and data analysis: To describe the structure of the infra- and componentcommunities, data was related to parasite abundance, prevalence and intensity were calculated. The methods used here to describe general features of parasite infra-communities (prevalence, abundance, and intensity) and component community. Component community structure of parasite was described in two ways: traditional descriptors (e.g. species richness, mean abundance and mean intensity) and community similarity. Measurement of dominance, species richness and evenness also followed standard definitions. Status of distribution: The classification of the species was done according to the importance value for the community as Central species = present in more than 66.6%; Secondary species = present between 33.3% to 66.6% and Satellite species = lower than 33.3% of the total number of fish analyzed. Dispersion indices: Two criteria namely Green’s dispersion index (GI) (Green 1966) and index of dispersion (DI) were used to evaluate the dispersion pattern of parasite species. Dispersion index was tested using statistical‘d’ as most of the parasite species did not follow theoretical Poisson distribution series. Distribution of parasites was classified as aggregated when d > 1.96; regular when d < –1.96 and random when d < 1.96. Diversity indices: Simpson diversity index (λ) was determined for the sample and for infinite population Simpson unbiased estimator () and Shannon's index of diversity (H´) were used. Evenness and equitability: Three indices were used to determine species evenness. Correlation: Pearson linear correlation coefficient (r) and Spearman’s rank correlation coefficient (rs) were computed to determine possible correlations between the host’s standard length with the prevalence and abundance of each parasite species respectively. Existence of association: Jaccard index detects the existence of association between species for measuring the degree of association. It always contains a value between 0 to 1 and as the value approaches to 1, indicates the association between species is high. For determining the probable variation of infection in relation to host sex with abundance of parasite species, Mann-Whitney ‘U’ test was conducted. The analysis included only component parasite species i.e. whose prevalence was greater than 10%. Community structure of parasites has been determined as a function of host habitats, sizes, sexes. Statistical tests were conducted by using XLSTAT 2011 (Kruskal-Wallis test) and SPSS 16.0 (Pearson linear correlation, Spearman’s rank correlation and Mann-Whitney ‘U’ test) software package. The statistical significance level adopted was p ≤ 0.05.

Source of Information: J. Asiat. Soc. Bangladesh, Sci. 40(1): 67-77, June 2014

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

In the present study, host size was always positively correlated with the prevalence and abundance of the parasite species. The presence of relationship between abundance and prevalence with the host’s standard length might be due to the presence of relationship between endoparasitic diversity and the body length of the host sample under analysis indicated that fish’s growth rate might help in the process of equal recruitment of different parasite species in their habitat. This fact indicates homogeneity in their increase in body length during their life cycle and thus permits the uniform recruitment of the species of endoparasites throughout their life.

Knowledge Management: Journal