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Endoparasitic Helminths of Tenualosa Ilisha in Bangladesh in Relation to Sex, Seasons and Habitat Type

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

Abstract/ Executive Summary:

Seasonal and sex wise occurrence of endoparasitic helminths were observed from sample collected round the year between January 2005 and December 2007. Some 2667 hilsa (male – 288 and female – 2379) were sampled from freshwater, brackish water and marine habitats. Fourteen species/genera of endohelminth parasites detected from hilsa were Faustula brevichrus, F. ilishii, F. gangeticus, Aphanurus stossichi, Lecithaster indicus, Ilisha parthenogenetica (plercercoid) , Otobothrium ilisha (plercercoid), Acanthosentis indica, A hilsai, Goezia bangladeshi, Capillaria sp., Hysterothylacium sp., Camallanus sp. and Porroceacum sp. Out of these 14 helminths, 6 (Faustula spp. Aphanurus stossichi, Lecithaster indicus, Ilisha parthenogenetica, Acanthosentis spp., and Goezia bangladeshi,) had the status of component para site (prevalence above 10%). Each species of component parasite has shown its own pattern of distribution over seasons and seasonal distribution of component parasites was found to be different between habitats of the hilsa. In freshwater, the spring and winter samples were found not significantly different from each other. But in summer and autumn, there was a significant difference among each other and between spring or winter. In brackish water mean parasite burden in spring was significantly different from other seasons. In marine hilsa the intensity of parasites in all the four seasons were different from each other. The female fishes were found to be more vulnerable to infection irrespective of the habitats of the host fish, though the differences were little.

Keywords: Hilsa, Helminths, Season, Host sex, habitat type

Location: Parasitology laboratory, Department of Zoology, University of Dhaka, Dhaka, Bangladesh.

Start Date: 00-01-2005

End Date: 00-12-2007

Program Area: Animal Health and Management

Commodity: Hilsa

Objectives:

To look into the seasonal and sex-wise occurrence of the component helminth parasites of T. ilisha collected from different rivers of Bangladesh which were ecologically different.

Methodology:

For the present investigation Tenualosa ilisha were collected from three different ecological habitats of Bangladesh waters like river (Chandpur 23° 14.40N 90° 40.73E, n=732 Aricha 23°46.10N 89°46.83E, n=624, Paksey 24° 04.46N 98° 02.15E, n=99 Sherpur24 °37.65N 91° 40.82E, n=110), estuaries (Patuakhali, 22°21.42N 90 °21.10E, n=21) Barguna, 22° 09.45N 90 ° 07.61E n=177 Bhola, 22 ° 43.10N 90°40.53E, n=154), Barishal 22 ° 42.23N 90° 22.49E n=127) and Sandwip 22 ° 30.56N 91° 42.78E, n=130)) and sea (Cox's Bazar 21° 25.09N 91° 59.97E, n=296 and Kuakata 21 ° 48.97N 90°07.32E, n=197). The Global Positioning System (GPS) readings were recorded by Trimble Navigation (Ensign GPS). A total of 2667 (male – 288 and female – 2379) fish were collected from January 2005 to December 2007. Fresh fish were collected from the fishermen on the spot as they collected fish except for the Cox’s Bazar sample. Frozen fish were collected from this site as the fishermen went out to the deep sea and come back after a week or more. The fish were dissected immediately to obtain the internal organs. The viscera of the fish were removed individually and put in 10% formalin in polyethylene bags with a label inside. Before they were dissected the weight, length and sex of each fish was recorded. The organs we re then brought to the Parasitology laboratory, Department of Zoology, University of Dhaka, Dhaka, Bangladesh. Extensive search was made for helminth parasites infecting the fish. All the parasites from each organ were sorted, cleaned and counted. They were preserved in 70% alcohol. Berland’s methods were used for staining and mounting. The trematode, cestode and acanthocephalan parasites 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 for measurements. Nematodes were cleaned and temporarily mounted in lactophenol for microscope study. A few viscera (5-10) were individually put in polyethylene bags and frozen in an icebox and brought to the laboratory from collection sites each time . Parasites obtained from such sample were used for aid in identification. Measurements were taken with the help of an ocular micrometer and a stage micrometer. The groups of successive samplings of each 3 month periods were considered to constitute a season for the purpose of this analysis. However, as there was no gap separating the seasons, this division was used to group the samples broadly into units for temporal comparisons. The seasons were designated as: Winter: November to January; Spring: February to April; Summer: May to July and Autumn: August to October.

Source of Information: Bangladesh J. Zool. 41(2): 153-163, 2013

Article Link (Online Journal): http://www.banglajol.info/index.php/BJZ/article/view/23317/16020

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

It could be concluded from the above results that each parasite species showed its own seasonal distribution pattern which is different in three different types of habitats. The female fish is more vulnerable to infection in all the three habitats.

Knowledge Management: Journal