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Triploidy Induction and Growth Performance of Hybrid Catfish (clarias Macrocephalus × C. Gariepinus)

Parven A.
Assistant Professor
Department of Agribusiness, Atish Dipankar Science and Technology, Dhaka-1212, Bangladesh

Gallardo, G. W.
Associate Professor
Marine Science and Fisheries, Sultan Qaboos University, Oman

Abstract/ Executive Summary:

Cold shock and heat shock were evaluated for their efficacy as methods of manipulating ploidy in hybrid catfish (C. macrocephalus × C. gariepinus). The most effective method of inducing triploidy was cold shock at 6^oC applied of 25 min which resulted in 87% triploidy with 48% fry survival rate from fer tilization to two weeks rearing period. Both of thermal shock treatment initiated 3 minutes after water activation. Co ld shock treatment for 30 min or more caused total mortality of embryos. Heat shock at 40^oC for 1 min resulted 42% triploidy with fry sur vival of 42%. Flow cytometry analysis was used to assess the ploidy level of diploid and triploid larvae in both experiments with blood samples. In growth experiment, growth of triploid was higher than control but lower than the cold shocked (6^oC 25 min) diploid fry, with the survival rate ranging between 63 - 73% in all treatments after 16 weeks of rearing period. Triploid fish were 15% larger than control; while shocked diploid was 27% larger than control.

Keywords: Cold shock, heat shock, triploidy, embr yo, mortality, Flow cytometry , triploid, shocked diploid, control .

Location: The experiments were conducted in National aquaculture Genetic Research Institute (NAGRI), AARM hatchery and the Aquaculture research facility at the Asian Institute of Technology, Thailand.

Start Date:

End Date:

Program Area: Animal Health and Management

Commodity: Cat fish

Objectives:

To know the optimum combination of temperature and duration in triploidy induction along with the hatching, survival of the triploid and shocked dipoloid catfish.

Methodology:

The brood fish was collected from Testhong farm. The size of the female brood stock was 200-250 g size/fish and the age of about 1 year. The male brood stock was 3 - 5 kg size/fish and the age of about 2-3 year. For female; first injection was given as ½ of pituitary gland per kg fish; second injection was decided as one pituitary gland per kg fish. One kilogram of fish was injected with 1 ml of solvent requirement. Females were stripped after 8 hours of the second injection and placed into a bowl. Males usually cannot strip and was sacrificed to collect sperm for 1 minute Dry method (eggs and sperm mixed together before the water was added) were followed in fertilization. Clean water was added and stirred for a few minutes and drained water. This will be repeated for 3 times.

Immediately after fertilization and before they began to adhere, the fertilized eggs were distributed into the strainer by using micropipette.1 micro - liter of eggs were distributed in 3 Petri dishes and counted to take an idea about the total amount of eggs present in each strainer. A minimum of 320 eggs was subjected to cold shock at 2^oC, 4^oC and 6^oC that started 3 min after water activation of the eggs and lasted for 10, 20 and 25 minutes shock duration. The eggs from other females were heat shocked at 38^oC, 40^oC and 42^oC starting at 3 min after water activation with the shock duration of 1 min, 2.5 and 4 min. There were 3 replicates of each treatment. Time of hatching was dependent on water temperature. The normal water temperature was about 30.2^oC, the time from fertilization until hatching was ~ 24 hour. Fertilization rate was calculated based on the number of white eggs, which were considered not fertilized. Thirty (30) hours after insemination, hatchlings were counted and the hatching rate was calculated as the relative percentages of the initial eggs were fertilized and incubated. After 24-30 h rs, the percentages of normal and deformed larvae and of nondeveloped eggs were calculated and found that there were no deformed larvae. Survival rate was assessed two (2) weeks after hatching.

The optimum rate of temperature and duration for triploidy induction was determined by considering two factors: The highest rate of triploidy induction and the maximum survival rate from hatching to 15 days rearing period. 6^oC 25 min and 40^oC gav e the highest triploidy rate. So, these treatments were used for the growth experiment. 100 females and 6 males were used to induce triploidy at 6 and 40^oC. A large number of eggs were used for the shock induction. After hatching, hatchlings were reared for 35 days to let them grow enough to collect the blood sample. Sufficient amount of blood was required to determine the triploidy and cold and heat shocked diploid fry. At 6^oC 25 min sufficient amount of triploid and shocked diploid fry were found. At 40^oC 1 min no triploidy fry were found. There were three replicates in each treatment. So, there were twelve tanks in this experiment. The fry were reared in large concrete tank with water recirculation systems and the fry were feeding with live and frozen Moina sp. 8 times/day.

Source of Information: International Journal of Fisheries and Aquatic Studies 2014; 1( 6 ): 151 - 162, Retrieve from: http://www.fisheriesjournal.com/archives/2014/vol1issue6/PartC/141.pdf

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The experiment reported in this paper show that the tripod can be successfully i nduced in hybrid catfish through the use of cold shock rather than using the heat shock at proper condition. This work concludes that cold shock at 6^oC 25 min applied to hybrid catfish eggs, give the highest triploidy rate and also cold shock longer than 30 min caused total mortality in hybrid catfish. The study suggests that the The effects of cold shock treatment on other cellular process require further study and also observe the effect of temperature in 5, 7, 8 and 10^oC in triploidy induction. Grow - out performance of triploidy hybrid catfish or the hybrid shocked diploid catfish could be determined to determine the utility for Aquaculture. FCR for triploid and cold shocked diploid fry can be measured in the next experiment.

Knowledge Management: Journal