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Histological Study of Gametogenesis in Endangered Mud Eel Monopterus Cuchia

MD. JAHANGIR ALAM
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh

Abstract/ Executive Summary:

In order to identify the processes of gametogenesis and to identify peak breeding season towards furnishing guidelines for induced breeding of an endangered fish species mud eel (Monopterus cuchia), an investigation was conducted for one year (March 2011 to February 2012) at the Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh. Samples of mud eel were collected from haor and beel areas of Mymensingh and Netrokona districts. The investigations included the observation of month-wise ovarian cycles of maturation, determination of the peak breeding season, identification of the process of gametogenesis and furnish guideline for conservation of this endangered fish species. Histological observation of ovary observed presence of undeveloped oocyte (UO), oogonium (O), early perinucleolar oocyte (EPNO), late perinucleolar oocyte (LPNO), previtellogenic oocyte (PVO), yolk vesicle (YV), yolk granule (YG), premature (PM) and mature (M) stages of oocytes during samples from different seasons. In this study, the mature stages of oocytes (PM and M oocytes) were found from April to June samples of ovary, indicating the spawning season of M. cuchia. These mature stages occurred high in proportion during late April to mid May samples indicating peak breeding season of this fish. In the breeding season, abdomen of female cuchia was round, swollen which was ready to spawn. The ovaries contained developing oocytes (UO, EPNO, and LPNO) from July to February, indicating spent and resting phases of ovary during these months. It is expected that the preliminary information generated on the gametogenesis of M. cuchia can serve as the base line information for further research on this fish with an aim of establishing the package of induced breeding and to manage and conserve from the endangered condition. This study provides the first detailed information about oogenesis of M. cuchia from the Sylhet basin of Bangladesh. It is expected that the information of this study can potentially be used for bringing a new high priced fish into aquaculture for supporting export earnings of the country in future.

Keywords: Gametogenesis, Endangered mud eel, Monopterus cuchia

Location: Faculty of Fisheries and Fisheries Field Laboratory Complex, Bangladesh Agricultural University, Mymensingh

Start Date: 00-03-2011

End Date: 00-02-2012

Program Area: Variety and Species

Commodity: Eel

Objectives:

a. To study gonadal histology of mud eel for identifying seasonal cycle of oocytes development during different seasons of the year;
b. To identify the breeding and peak breeding season of mud eel; and
c. To furnish guideline for induced breeding of this fish in captivity.

Methodology:

Experimental Site: Samples of mud eel were collected from Netrokona and Mymensingh districts. The catch of this species composed of collections from different haors and beels. Rearing of experimental fishes: The samples were reared in pond at backyard of Faculty of Fisheries and Fisheries Field Laboratory Complex, Bangladesh Agricultural University, Mymensingh. Common standard fish husbandry protocols were used for rearing these samples during the sampling period. The feeds such as live earthworm and trash fish were applied to fish at the rate of 3-5% body weight daily at evening. Collection of gonad sampling: For sampling of gonad, fish was captured from experimental pond. After anesthetizing using chloroform, ventral sides of the fish were cut opened from the anus towards the lower jaw by using scissors carefully. Then the muscles of the abdomen were cut from the anus towards the vertebral column vertically. Muscles, fat tissues, digestive organs and blood vessels were removed properly. After this the gonads were taken out by using forceps and scissors. Then the male and female fishes were identified by observing the gonads with naked eyes. The weight of the gonads was measured very carefully with the help of a sensitive portable electronic balance in gram. Then gonad samples were cut into small pieces by using scissors. Finally, the samples were preserved in Bouin’s fluid. Length and weight of fish were recorded prior to sampling. Sampling was done every month starting from March 2011 till February 2012. Histological observation of gonads: Just before dehydration, the preserved gonads were taken out from vials (kept in fixatives) and put into cassette. One testis and one ovary were put together into a cassette. Then dehydration process was carried out manually followed by clearing, infiltration, embedding, sectioning, staining, mounting and finally microscopic observation.

Source of Information: MS Thesis, Examination Roll No. 11Fish M JJ-12M, Semester: January- June, 2012, Registration No. 32526, Session: 2005-2006; Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

In the ovaries of M. cuchia, collected during March/11 to February/12, the following oocytes were observed: oogonia (O), early perinucleolar oocytes (EPNO), late perinucleolar oocyte (LPNO), yolk vesicle (YV), yolk granule (YG), premature (PM) and mature (M) stage. In this study, the mature stages of oocytes (PM and M) were observed from late April to June samples of ovary indicating breeding season of this fish. But highest mature stages were observed in late April and mid May indicating its peak breeding season.

Knowledge Management: Thesis