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Induction of Mitotic and Meiotic Gynogenesis and Production of Genetic Clones in Rohu, Labeo Rohita Ham.

M.G. Hussain
Freshwater station, Bangladesh Fisheries Research Institute, Mymehsingh-2201, Bangladesh

M.S. Islam
Freshwater station, Bangladesh Fisheries Research Institute, Mymehsingh-2201, Bangladesh

M.A Mazid
Freshwater station, Bangladesh Fisheries Research Institute, Mymehsingh-2201, Bangladesh

M.B. Tanu
Freshwater station, Bangladesh Fisheries Research Institute, Mymehsingh-2201, Bangladesh

SM. Rahman
Freshwater station, Bangladesh Fisheries Research Institute, Mymehsingh-2201, Bangladesh

S.C. Mahata
Freshwater station, Bangladesh Fisheries Research Institute, Mymehsingh-2201, Bangladesh

Abstract/ Executive Summary:

Studies were undertaken to produce genetic clones derived from all homozygous mitotic gynogenetic individuals In rohu, Labeo rohita Ham. In view of this, attempts were made to interfere with the normal functioning of the spindle apparatus during the first mitotic cell division of developing eggs using heat shocks, ther·e by leading to the induction of mitotic gynogenetic diploids in the F₁ generation. Afterwards, viable mitotk gynogenetic alevins were reared and a selected mature female fish was used to obtain ovulated eggs which were fertilized later with UV-irradiated milt. Milt was diluted with Cortland1s solution and the sperm concentration was maintained at 1 08/ml. The UV· irradiation was carried out for 2 minutes at the intensity of 200 to 250 W/cm² at 28± 1°c. The optimal heat shock of 40^oc for 2 minutes applied at 25 to 30 minutes a.f. was used to induce mitotic gynogenesis in fisrt (F₁) generation and at 3 to 5 minutes a.f. to induce meiotic gynogenesis in the second (F₂) generation. The results obtained are presented and the light they shed on the timing of the mitotic and meiotic cell division in this species is discussed.

Keywords: L. rohita, Gynogenesis, Genetic clones

Location: Freshwater Station, Bangladesh Fisheries Research Institute

Start Date: 00-00-1995

End Date: 00-00-1995

Program Area: Variety and Species

Commodity: Carp fish

Objectives:

The present work was undertaken and the trials were aimed at the production of mitotic gynogens as a first step and secondly meiotic gynogens for the development of clonal lines in Labeo rohita Ham.

Methodology:

Origin of broodtosck and induced breeding -The gonadal materials, eggs and sperm, used in this study were obtained from different mature broods of L. rohita maintained under hatchery programmes of the Freshwater Station, Bangladesh Fisheries Research Institute, Mymensingh, Bangladesh. The broods were induced with carp pituitary extracts through intramuscular injections (twice, six hourly) and after 11 to 12 hours the milt and eggs were collected by stripping. UV-irradiation of milt -The milt was kept under refrigerated condition at 4 c for a few minutes. The milt was then diluted at 1 :100 to 1 :200 times with refrigerated physiological saline solution, Cortland's, solution with pH 7.2 to 7.5 and samples from this were checked for motility of sperm. Then the concentration of sperm from samples were determined and maintained at a concentration of about 108 ml-1 by further dilution. The diluted milt was spread out on to a plastic petridish and a fine film was made with a thickness of about 0.5-1.0 mm. This sperm solution was exposed to ultraviolet (UV) irradiation under a short wave UV-Iamp (Model · UVBGL-58; Multiband-254/366 NM). The intensity of UV-irradiation was optimized at 200-250 ~W/cm 2 applied for 2 minutes at 28±1 ⁰c and the irradiated sperm was kept in a refrigerator controled at 4°c. The irradiated sperm was then used to inseminate the eggs. Based on the preliminary experiment these parameters were fixed for subsequent trails. Induction of gynogenesis (both mitotic - and meiotic) - All the treatment batches of eggs were fertilized with UV-irradiated milt except the control eggs which were fertilized with untreated, diluted milt. The recently stripped eggs fertilized with UV-irradiated sperm were poured into an incubator jar of 6 litre capacity with a water flow rate at 1 litre/minute at a 0 temperature of 26±1 c for normal development. Heat shocks designed to interfere with the first mitotic cell division of these eggs were initiated from 1 0 minutes up to 50 minutes a.f. to determine the window at which treatment can properly be applied. The experimental parameters used to interfere with the first mitosis were at a late heat shock of 40° c for 2 minutes, applied at 20 to 40 minutes after fertilization with 2.5 minutes intervals. These parameters were also used as optimal for the retention of second polar body in producing meiotic gynogens by early shocks,. 3 to 5 minutes a.f. Egg incubation and karyotyping - The temperature for incubation of eggs was always maintained at 26±1 °c. The rates of fertilization, hatching success of eggs and survival of spawn were recorded. The hatching of normal larvae was considered as the primary criterion for estimating the success of induced diploidization. The karyotypes of samples from treated and untreated groups were determined by the techniques. Production of genetic clones - The survivors of two batches of the induced mitotic gynogens attained an average weight of 1.8 and 1.9 kg in their second year of life and they were all female. Among them, only a single mature female was selected and this brood was used in the production of induced meiotic gynogens. The protocol for induction of meiotic gynogenesis is described above.

Source of Information: Bangladesh J. Fish. Res., 1(2):01-07, 1997

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The optimal heat shock of 40^oc for 2 minutes applied at 25 to 30 minutes a.f. was used to induce mitotic gynogenesis in fisrt (F₁) generation and at 3 to 5 minutes to induce meiotic gynogenesis in the second (F₂) generation. The results obtained are presented and the light they shed on the timing of the mitotic and meiotic cell division in this species is discussed.

Knowledge Management: Journal