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Karyotype Analysis of Clarias Gariepinus ,c. Batrachus and Their Hybrid

G. KlBRIA
Department of Zoology, University of Dhaka, Dhaka-1000, Bangladesh.

G.B. SUF
Department of Zoology, Univrsity of Dhaka, Dhaka-1000, Bangladesh.

M. KHATUN
Department of Botany, University of Dhaka, Dhaka-1000, Bangladesh

SHEIKH SHAMIMUL ALAM
Department of Botany, University of Dhaka, Dhaka-1000, Bangladesh

Abstract/ Executive Summary:

Karyotypes of Clarias gariepinus and C. batrachus were compared with that of their hybrid. The somatic chromosome number a nd centromeric formulae of these taxa were found to be (i) 2n = 56 and 18m+16sm + 10st + 12t in Clarias gariepinus; (ii) 2n = 50 and 21m + 14sm + 5st + 10t in C. batrachus and (iii) 2n = 53 and 19m + 16sm + 7st + 11t in their hybrid . Heteromorphicity in respect of length and centromeric type was found in each taxon. The hybrid possessed an intermediate karyotypic feature in comparison to their parents. The chromosomes of hybrid did not assemble in pair as they have two different genomes obtained from two different species. Therefore, the karyotype analysis confirmed the interspecific hybrid status.

Keywords: Cat fish, Karyotype, Clarias gariepinus, C. batrachus

Location: Department of Zoology, University of Dhaka, Dhaka

Start Date:

End Date:

Program Area: Animal Health and Management

Commodity: Cat fish

Objectives:

In this study, the karyotypes of an assumed hybrid (Clarias gariepinus x C. batrachus) and its parents were compared to justify the hybrid status cytogenetically.

Methodology:

The live specimens of Clarias gariepinus (African magur) and C. batrachus (Asian magur) weighing 80-120 g were collected from the fish markets in Dhaka city. However, their hybrids were obtained from Fisheries Reseach Institute (FRI), Mymensingh. They were reared in the aquarium. Fishes were injected intraperitoneally with 0 .1% colchicine (2 ml per 100 g weight) and left in well aerated aquaria for 3 hours. The fishes were then dissected to remove kidney and gills. These were minced in 1% sodium citrate and allowed to hypotonize for 30 - 40 minutes at room temperature. The cell suspension was centrifuged at 2000 rpm for 10 minutes. The supernatant liquid was decanted and cell mass was fixed by adding freshly prepared Carnoy's fluid (1 : 3, acetic acid : alcohol) for 20 minutes and then centrifuged again. The centrifuge procedure was repeated for 3 - 4 times at 20 minutes intervals. The final suspension was dropped on well cleaned dry slides and heated on a flame for 5 - 6 seconds. The air-dried slides were stained in 6 % Giemsa at pH 6.8 for 10 - 15 minutes. The photography was made using an Olympus (C. 35 AD. 2, Japan) research microscope. Chromosomes were classified following a modified method of Levan et al.

Source of Information: Dhaka Univ. J. Biol. Sci. 10(2): 145-149, 2001 (July)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The hybrid possessed an intermediate karyotypic feature in comparison to their parents. The chromosomes of hybrid did not assemble in pair as they have two different genomes obtained from two different species. Therefore, the karyotype analysis confirmed the interspecific hybrid status.

Knowledge Management: Journal