ManiRam Prasad

Toxicity of aqueous extract of Euphorbia tirucalli latex on catfish, Heteropneustes fossilis.

A four-day static renewal acute toxicity test was performed to determine the LC(50) value of aqueous extract of Euphorbia tirucalli latex for the freshwater fish, Heteropneustes fossilis. The LC(50) values, their upper and lower confidence limits and slope functions were calculated. The LC(50) values for aqueous extract of E. tirucalli latex at various exposure periods are 3.450 μl/L for 24 h, 2.516 μl/L for 48 h, 1.623 μl/L for 72 h and 1.315 μl/L for 96 h. The toxicity of aqueous extract of E. tirucalli latex exhibits a positive correlation between fish mortality and exposure periods. It is concluded that latex of E. tirucalli has higher piscicidal activity as compared with other synthetic pesticides, organophosphates and pyrethroids for the fish H. fossilis. Hence, adequate precautions must be exercised when E. tirucalli latex is being used near fish-inhabiting water reservoirs.

Effects of Euphorbia tirucalli latex on blood calcium and phosphate of the freshwater air-breathing catfish Heteropneustes fossilis

The effects of Euphorbia tirucalli latex on blood calcium and phosphate of Heteropneustes fossilis was investigated in this study. The fish were subjected to 0.8 of 96-h LC50 value of E. tirucalli latex (1.05 µL L−1) for 96-h in a short-term experiment and 0.2 of 96-h LC50 value (0.263 µL L−1) for 28 days in a long-term experiment. Fish were sacrificed after 24, 48, 72, and 96 h in the short-term experiment and after 7, 14, 21, and 28 days in the long-term experiment and blood samples were analyzed for calcium and inorganic phosphate. Acute exposure of E. tirucalli latex caused a progressive decrease in the calcium level after 48 h which persists till the close of the experiment. Phosphate levels remain unaffected till 48 h but after 72 h the levels exhibit a progressive decrease. Chronic E. tirucalli latex treatment provokes a decrease in calcium levels at day 7 continuing till the end of the experiment (28 days). The phosphate levels remain unaffected up to day 7, thereafter, levels decrease from 14 days till the end of the experiment.

Blood electrolytes of the freshwater catfish Heteropneustes fossilis in response to treatment with a botanical pesticide (latex of Euphorbia royleana)

The aim of the present study was to determine changes in blood electrolytes (calcium and phosphate) in the freshwater catfish Heteropneustes fossilis following short- and long-term exposure to latex of Euphorbia royleana. To investigate the effects of short-term exposure, fish were exposed to 80% of the 96-h LC(50) of E. royleana latex (2.47 mg/L) for 96 h. To assess the effects of long-term exposure, fish were exposed to 20% of the 96-h LC(50) of E. royleana latex (0.618 mg/L) for 28 days. Fish were killed after 24, 48, 72 and 96 h (short-term experiments) or after 7, 14, 21 and 28 days (long-term experiments). Blood samples were collected and sera were analyzed to determine calcium and inorganic phosphate levels. Serum calcium levels decreased progressively in H. fossilis after 48 h exposure to E. royleana latex. This decrease persisted until the end of the experiment (96 h). Serum inorganic phosphate levels in treated fish decreased progressively from 72 h. After 7 days exposure to E. royleana latex, decreased serum calcium levels were noted in H. fossilis that persisted until the end of the experiment. Serum phosphate levels were decreased in H. fossilis on days 21 and 28 of exposure to E. royleana latex. It is concluded that E. royleana latex alters the blood electrolyte content of the fish. The change in these electrolytes, particularly calcium levels, may cause disturbances in the normal vital physiological functions of the fish, its growth rate, and even its ability to survive in nature.

Influence of a botanical pesticide, azadirachtin, on ultimobranchial gland of the freshwater catfish Heteropneustes fossilis

Freshwater catfish, Heteropneustes fossilis, were subjected to 42 mg L−1 of azadirachtin for short-term exposure (96 h) and to 10.5 mg L−1 for long-term exposure (28 days). Six fishes were sacrificed on each time interval from control and experimental groups after 24, 48, 72, and 96 h in the short-term exposure and after 7, 14, 21, and 28 days in the long-term experiment. The calcium regulating endocrine gland, viz. the ultimobranchial gland, was fixed for histological studies. Up to 72 h of azadirachtin treatment, there was no histological alteration in the UBG (ultimobranchial gland) of H. fossilis. After 96 h exposure, the ultimobranchial cells stain feebly and the nuclear volume of these cells were slightly decreased. No histological alterations have been observed in the UBG cells up to 14 days following azadirachtin exposure. After 21 days, the cytoplasm of ultimobranchial cells was feebly stained and the nuclear volume exhibits a decrease. The nuclear volume of these cells was further decreased and the gland shows vacuolization and degeneration at certain places after 28 days azadirachtin treatment. Hence, it can be concluded that azadirachtin severely affects the physiology of calcium homeostasis in H. fossilis. Therefore, the botanical pesticides should be used carefully near aquatic reservoirs.

Nerium indicum, a botanical pesticide affects ultimobranchial gland of the catfish Heteropneustes fossilis

Heteropneustes fossilis were subjected to 11.27 mg L−1 (80% of 96 h LC50) and 2.81 mg L−1 (20% of 96 h LC50) of Nerium indicum leaf extract for short‐term and long‐term, respectively. After sacrificing the fish, blood was collected on 24, 48, 72, and 96 h in short‐term and after 7, 14, 21, and 28 days in long‐term experiment and analyzed for plasma calcium levels. Also, ultimobranchial glands (UBG) were fixed on these intervals. Serum calcium levels of H. fossilis exhibited a decline after 48 h following exposure to Nerium indicum leaf extract. This decrease continued till the end of the experiment (96 h). Ultimobranchial cells exhibited a decrease in the cytoplasmic staining response after 72 h following the treatment. The nuclear volumes of these cells were slightly decreased. These changes were exaggerated after 96 h following the treatment. Chronically exposed fish exhibited a decline in serum calcium levels of H. fossilis on day 14. The level progressively declined till the end of the experiment. Up to day 14 following the treatment there was no change in the histological structure of UBG. A decrease in the nuclear volume of ultimobranchial cells was noticed on day 21. Moreover, the cytoplasm of these cells displayed weakstaining response. The nuclear volume of these cells recorded a further decrease following 28‐day treatment. Also there was noticed vacuolization and degeneration at certain places. To the best of our knowledge, the effects of any botanical pesticides on fish UBG have not been reported yet.