Gadadhar Dash

Ornamental fish goldfish,Carassius auratusand related parasites in three districts of West Bengal, India

The lucrative business of ornamental fish culture in West Bengal (Mainly in three districts-Howrah, North and South 24 Parganas) are facing loses due to the invasion of different ecto- and endo-parasites. The present study shows that the ornamental fish (Goldfish - Carassius auratus) are mainly affected with ecto-parasites like Ichthyophthirius sp., Dactylogyrus sp., Gyrodactylus sp., Argulus sp. and endo-parasites like Procamallanus sp. and Cucullanus sp. The intensity of infection is high in case of Ichthyophthirius sp. and the intensity of the infection is high in summer months when the temperature is high or moderately high. In cooler months the intensity of the infection is lower as because the parasites are unable to breed or scarcity of food particles.

Histopathological changes in Labeo rohita (Hamilton) fingerlings to various acclimation temperatures

Background: Histopathological changes induced by a rise in the acclimation temperature in advanced Labeo rohita (Hamilton) fingerlings were studied to understand their adaptive ability to thermal changes. The histopathological changes in relation to the thermal changes have been widely used as bioparameters in the evaluation of fish health. Materials and Methods: The six experimental temperatures that the fishes were exposed to were 32, 34, 36, 38, and 40oC for a period of 30 days each. The fishes kept at an ambient temperature of 29.3΁1.5oC were used as control. The major organs studied were gills, liver, kidney, and heart. No specific alterations were observed at control, 32, and 34oC. The organs were sampled at the end of 30 days exposure and histopathological changes of different organs were examined. Result and discussion: Different organs (gill, liver. Kidney and heart) show different histopathological changes in higher temperatures. However, adaptive and degenerative changes were found to occur at the higher temperatures of 36, 38, and 40oC. Conclusions: Changes of temperature can be tolerated by the fishes and it brings about adaptive physiological changes to compensate the effects of temperature. Significance: The study was helpful; to understand the adaptive mechanisms used by fishes with changes of environmental temperatures.

Parasitic prevalences in fresh water prawn Macrobrachium rosenbergii in north and south 24 Parganas districts of West Bengal

The occurrence of different freshwater prawn (Macrobrachium rosenbergii) parasites, found during the period from April to August 2007, was investigated in different freshwater wetlands of north and south 24 Parganas districts of West Bengal state in India. Eleven parasites - Zoothamnium, Epistylis, Gregarina, Amphileptus, Dileptus, Myxobolus, Chilodonella, Balladyna, Gozia, Rhabdochona, Indocucullanus, Procamallanus and Cucullanus - were found after examining 1,000 specimens of Macrobrachium rosenbergii of different-sized groups. The highest prevalence of the parasites was recorded in the size group of 81-85 mm and 136-140 mm. The intensity of ectoparasitic infection was observed to be high with an increase in size. The gills and the surface of the body were mostly infected. Endoparasites were found in the intestinal part, and mostly due to poor raw foods given to the prawns as their diets. The parasites get more shelter and space for them. The highest intensity of those parasites was found in the month of August due to favourable autumnal conditions, with little rain and favourable breeding time of the parasites. Stressed and weak prawns are more vulnerable to infestation under adverse environmental conditions.

Seasonal distribution of parasites in freshwater exotic carps of West Bengal, India

The study has been carried to find out the distribution of different parasites in Exotic carps with respect to different months and seasons. These were isolated and identified from the fishes sampled randomly from five fish markets, which were representing South 24 parganas district, West Bengal. During the study period ten different types of parasites were observed such as Trichodina sp, Chilodonella sp, Trichinella sp., Acanthocephala sp, Nematodes, Epistylis sp, Zoothamnium sp, Vorticella sp, developmental stages of eggs or parasites and some parasites (unidentified) among which most of the parasites were protozoan. Among all the parasites the most dominant were Trichodina sp, Chilodonella sp and Nematodes. Winter was the most vulnerable period to get parasitic infestation. During this period the water quality get deteriorated and the fishes were in stressed condition which favours the parasites to infest. Some parasites were found more during summer which favours their reproduction due to the availability of their intermediate host. In monsoon the temperature fluctuates which also favours growth of some parasites. During the study period Trichinella sp were found solely in Cyprinus carpio exclusively in winter.The protozoan parasites were most available during winter and these were the dominant parasites in exotic carps. These parasites were found mostly on gills and skin of the fishes where as nematodes were found in the intestine and body cavity of the fishes.

The use of antibiotics and disinfectants in the freshwater prawn (Macrobrachium rosenbergii) farms of north and south 24 Parganas districts of West Bengal

The freshwater prawn (Macrobrachium rosenbergii) farms and hatcheries of north and south 24 Parganas districts in West Bengal were surveyed for the details of antibiotics and disinfectants used for controlling the prawn diseases and pathogens. During the survey, 4antibiotics and four 4disinfectants were found to be used commonly by the farmers during a 12-month period of study. The chemicals used in the culture systems as antibiotics or disinfectants for the culture water, tanks, other utensils, and others have serious health hazards for both the cultured prawns and human beings. The study also indicates no herbal medicines, and probiotics are being used in prawn farms.

Histopathological alterations in the vital organs of Indian Major Carps with parasitic infestation in fish farms West Bengal, India

The study was conducted to investigate the histological changes of vital organs such as kidney, gills and brain with the mixed infestation of parasites in Indian Major Carps (IMC). The parasites such as Myxobolus spp., Thelohanellus spp., Trichodina spp., Dactylogyrus spp., Gyrodactylus spp. and Nematodes were observed in three IMC. Several histological alterations were observed in the kidney of Catla catla, Labeo rohita and Cirrhinus mrigala, which includes vacuolar degeneration in the epithelium of renal tubules, focal areas of necrosis, proliferation of bowman′s capsule and many cases the renal tubules lost its shape and canalculi formation was observed. The gills showed focal areas of necrosis, exacerbated swelling of gill arch, deposition of distinct black melanin pigmentation at the basal point of the gill arch, loss of primary and secondary lamellae, prominent vacuolar degeneration and formation of vacuoles. The presence of protozoan parasites in brain tissue resulted necrosis of the brain tissue, black pigmentation, vacuolization of myelin sheath of nerve fibers and common degenerative changes. Aims: To study histological changes of vital organs such as kidney, gills and brain with the mixed infestation of parasites in Indian Major Carps (IMC). Settings and Design: The organs fixed in 4% formalin are transferred to 50% ethyl alcohol and stored for further analysis. Materials and Methods: Histopathological analysis was made as described by Roberts. Statistical Analysis Used: Nil. Results: Described in text. Conclusions: The present study brings about conclusion that impact of mixed infestation of the parasites on their hosts was severe. Histopathological changes were observed in vital organs which might be due to toxins released by different parasites or physical damage of tissue with the presence of parasites.