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Gonadal Changes of a Wild Freshwater Mud Eel, Monopterus Cuchia (ham.)in Spent Period

M. M. RAHMAN
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh

G. U. AHMED
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh

S. M. RAHMATULLAH
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh

Abstract/ Executive Summary:

Histology of the testes and ovaries of a wild freshwater mud eel, Monopterus cuchia (Ham.) was carried out to investigate the gonadal stage in spent condition during the month of September to November, 2003. In testes, secondary primordial germ cells, primary spermatogonium, some spermatogonia A, clone of spermatogonium B were seen. The clone of spermatogonium B was smaller than spermatogonia A, with light cytoplasm including a slightly dark round nucleus during the month of September. In October, numerous different shaped lobules having spermatogonia, spermatocytes and spermatids were seen but they were more distinct with cluster formation compared with the previous month. Reduced number of spermatogonia and degenerating cells were seen in November and they were thinly distributed creating wide gap among themselves . In ovary, polygonal shaped oocytes were seen during September. Ruptured follicular cells and broken parts of oogonia were hanging. Lipid droplets were present at the periphery of the cytoplasm during the period . The oogonia were shrunk with dense and irregular shape in October. Broken parts of the ruptured follicular cells of the oogonia were also hanging but large nucleolus with small peripheral nucleoli was seen during the period. In November , oogonia were also shrunk with thin , irregular shaped structure but broken parts of the ruptured follicular cells were scattered in the area resulting numerous empty spaces

Keywords: Spent period, Gonadal changes, Freshwater mud eel, Monopterus cuchia

Location: Mymensingh

Start Date: 01-09-2003

End Date: 30-11-2003

Program Area: Animal Health and Management

Commodity: Eel

Objectives:

The present study is to know the spawning period through observation of the particular stage of gonad of freshwater mud eel, M . cuchia.

Methodology:

The experiment was conducted in the Department of Aquaculture, Bangladesh Agricultural University, during September to November, 2003. Live fish were collected through a commercial dealer from Mymensingh region . The eels were carried in plastic bucket containing water. The fish were euthanized with 0.02% clove oil (Keene 1998) for individual measurement of total length to the nearest mm and total weight to the nearest g. For gonad collection, the fish were again killed by decapitation (Colombo and Grandi 1996). Gonad was dissected out from the body; total length and total weight of gonads were measured to the nearest mm and nearest O.1g, respectively . Small pieces from the anterior, central and posterior regions of gonads were fixed at 10% buffered formalin. Samples were processed for dehydration, clearing and infiltration by an automatic tissue processor (SHANDON Citadel 1000). The protocol used for dehydration, clearing and infiltration in different chemicals for various time frames was recorded. The samples were dehydrated in lower to higher concentrations of methylated spirit and alcohol, cleared in xylene and infiltered in melted paraffin wax. The samples were then embedded in steel molds and melted wax. Sections were cut at 6 µm by a microtome machine (Model: JUNG RM 2035 Leica. Germany) . The sections were placed properly over a water bath (40°C) and suitable one was taken on glass slides. The sections were then stained by using routine haematoxylin and eosin. After staining, sections were mounted with a drop of Canada balsam and covered by coverslips over the tissue of the slide. The slides thus prepared were studied under microscope and photographs were taken by a camera fitted with a photomicroscope (Olympus).

Source of Information: J. Asiat. Soc. Bangladesh, Sci. 31(1): 55-62, June 2005

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

In the present observation , both the gonads were lacking normal structure from histological point of view. However, comparatively improved gonadal structure was recorded in September and in other months the structures were deteriorating. It could be due to fact that August and September were months after breeding season (June and July), whereas, September and October were the spent period. The present observation, spent period of the mud eels starts after June i.e., from July onwards

Knowledge Management: Journal