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In Anabas Testudineus (bloch, 1792) from a Polluted Beel of Bangladesh

Aminul Islam Bhuiyan
Department of Zoology, University of Dhaka, Dhaka-1000, Bangladesh

Jannatul Bushra
Department of Zoology, University of Dhaka, Dhaka-1000, Bangladesh

Osman Ghani
Department of Zoology, University of Dhaka, Dhaka-1000, Bangladesh

Abstract/ Executive Summary:

Abundance and distribution of the endoparasitic helminths in Anabas testudineus (collected from a polluted water body) was analyzed. Out of 50 fish observed, 42 (84%) were parasitized by at least one species. Five metazoan endoparasites, one trematode (Neopecoelina saharanpuriensis) and four nematodes (Ascaridida sp., Contracaecum sp., Camallanus anabantis and C. pearsei) were recorded. Prevalence was higher in female (90%) hosts than males (75%). A significant positive correlation was observed between the standard length of the host and the abundance for parasites except Ascaridida sp. Nematodes were the more prevalent group (72%) than trematodes (48%). No parasitic species was observed as central species category; three parasites (N. saharanpuriensis, Ascaridida sp. and Contracaecum sp.) were considered as secondary and Camallanus spp. as satellite species. All nematode parasites showed aggregated distribution pattern and the trematode showed random distribution pattern. Interspecies association between two species of parasite was low.

Keywords: Endoparasitic helminths, Anabas tstudineus, Koi, Abundance

Location: Taiwabpur Beel, Board Bazaar, Ashulia industrial area, Dhaka, Bangladesh

Start Date: 00-04-2012

End Date: 00-10-2012

Program Area: Animal Health and Management

Commodity: Koi/Climbing

Objectives:

To determine in Anabas Testudineus (Bloch, 1792) from a Polluted Beel of Bangladesh.

Methodology:

The present study was conducted to investigate the parasites of host fish Anabas testudineus collected from Taiwabpur Beel, Board Bazaar, Ashulia industrial area, a branch of Turag River (23⁰52'N - 90⁰24'E) during April-October, 2012. The water quality parameters of the sampling site were pH ranged of water was 6.14-8.79, hardness was high (300-1816 mg/l), turbidity level was 12.31-97.2 NTU, DO was quite low (0.76-7.1 mg/l), BOD was 0.7-4.65 mg/l and CO₂was 0-15.5 mg/l. The average width and depth of the river were 400m and 10m respectively. Fifty koi fish (A. testudineus) were collected from local fishermen from its habitat as live and were immediately brought to the Parasitology Laboratory of the Department of Zoology, University of Dhaka for investigation. Sample size of each month was not equal since we could not collect same number of fish each month. However, month wise sample size was: April- 9, May- 12, June- 12, July- 10, August- 4 and September- 3 fishes. Investigation on helminth parasites: The examination was aimed to determine endoparasitic helminth infection of A. testudineus. Length, weight, sex and organ wise infections of fish by each parasite species were recorded. Length and sex of hosts were noted before autopsy. All parasites from each organ were sorted, cleaned and counted and then preserved in 70% alcohol. Standard methods were used for staining and mounting. Under the dissecting microscope two species of Camallanus (C. anabantis, C. pearsei) looked similar. The morphological characteristics became apparent only when the parasites were studied under high magnification using a compound microscope. That is why these two species have been referred to as Camallanus spp. for calculation. One nematode, Ascaridida could not be identified to species level, therefore referred as Ascaridida sp. Calculation and data analysis: To describe the structure of the infra- and component-communities, parasites’ abundance, prevalence and intensity were calculated according to Bush et al. (1997). The methods used here was to describe general features of parasite infra-communities (prevalence, abundance, and intensity) and component community. Component community structure was described in two ways: traditional descriptors (e.g. mean abundance and mean intensity) and community similarity. Measurement of dominance, species richness and evenness were followed by standard definitions given by Begon et al. (1996). Status of distribution: The classification was done according to the importance value of a parasite species for the community as- Central species = present in more than 66.6%; Secondary species = present 33.3%-66.6% and Satellite species = lower than 33.3% of the total number of fish analyzed (Bush and Holmes 1986). 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. Evenness and equitability: The density of community depends on the number of species and the evenness. So an attempt was made to quantify the evenness component of the parasite diversity in the community. Three indices as Heip (1974) evenness index (Eh), Hill (1973) evenness index (EH) and Modified Hill’s ratio (E'H) were used to determine species evenness. Modified Hill’s ratio (E'H) is preferred over EH (Alatalo 1981) as it has a clearly desirable property for an evenness index. 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 (Zar 1996). Existence of association: Jaccard's index (Jaccard 1908) was used to compare the presence/absence of two parasite species occurring in the same host at a time. For determining the probable variation of infection in relation to host sex with abundance of parasite species Mann-Whitney ‘U’ test was conducted (Mann and Whitney 1947). The analysis included only component parasite species i.e. whose prevalence was greater than 10% (Bush et al. 1990). Community structure of parasites has been determined as a function of host size and sexes. Statistical tests were conducted by using SPSS 16.0 software package. Statistical significance level adopted was p ≤ 0.05.

Source of Information: Bangladesh J. Zool. 42(1): 1-10, 2014

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Achievement/Findings:

In the present study, host size was not always positively correlated with the prevalence and abundance of the parasite species, while at the infra-community level the total number of parasite individuals, in addition to their diversity and richness, generally presented positive relationships with host size. The presence of relationship between abundance and prevalence with the host’s standard length might due to the presence of relationship between endoparasitic diversity and the body length of the host samples under analysis indicated that fish’s growth rate did not vary according to their habitat. This fact indicates homogeneity in their increasing of body length during their life cycle and thus permits the uniform recruitment of the species of endoparasites throughout their life. As pointed out by Poulin (2000), these patterns cannot be generalized because in many host-parasite species systems the correlations are positive but weak and insignificant. Also ontogenetical changes in feeding behavior might influence parasite prevalence and abundance in the different host size classes (Saad-Fares and Combes 1992). Infection in relation to host’s sex: In the specimen (50 fishes), 30 were female and 20 were male of which 27 (90%) female and 15 (75%) male fishes were infected. According to the Mann-Whitney ‘Z(U)’ test it was found that intensity of infection and parasite abundance was not significantly (p>0.05) affected to the host’s sex. The insignificant values with regard to host sex from Mann-Whitney test evidenced that the ecological relationships (occupation of habitat and diet) are similar among males and females. Same results have been obtained for other species of freshwater fishes (Janovy and Hardin 1988). Moreover, Poulin (1996) stated that high testosterone levels can cause immune-suppression in males and could lead in some cases to males suffering more from parasites than do females, although many parasite surveys have reported no significant differences in infection abundance and prevalence between female and male hosts.

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