Effect of Short-Term Exposure to Mercuric Chloride on the Air-Breathing Catfish,Heteropneustes fossilis──Ⅱ.Scanning Electron Microscopic Study of the Gill

Alterations in the respiratory epithelium of gills of a catfish, Heteropneustes fossilis by the sublethal and lethal concentrations of HgCl2 have been observcd using scanning electron microscope. Fish exposed to 0.1 ppm shows a thin coat ot mucus, but the continuous layer of mucus is not retained in 0.3 ppm after 24 h of exposure. Epithelial cells of the gill filament are hyperplastic. Other changcs in the respiratory epithelium are contraction of epithelium, formation of interlamellar bridge and diminishing number of microridges. Massive destruction of the respiratory epithelium by deep lesions and sloughing of epithelial layer in 0.5 and 1.0 ppm solutions after 6-12 h of exposure apparently causes death to the fish. SEM observations are well in conformity with the findings made at light microscopic level

Estimation of Acute Toxicity of Ammonium Sulphate to the Fresh Water Catfish,Heteropneustes fossilis——Ⅰ.Analysis of LC_(50) Values Determined by Various Methods

The acute toxic effects of ammonium sulphate to fresh-water catfish, Heteropneustes fossilis (H.fossilis) have been studied by determining LC50 values with 95% confidence limits, by the graphic method, the logistic method, the Spearman and Karber method and the trimmed Spearman-Karber method. The trimmed Spearman-Karber method was found the most ideal for ammonium salt toxicity test. The flaws in the trimmed Spearman-Karber method are also discussed.

Effect of Short-Term Exposure to Mercuric Chloride on the Air-Breathing Catfish,Heteropneustes fossilis──Ⅰ.Light Microscopic Study of the Gill

Histopathological effects of sublethal (0.1, 0.2, 0.3 ppm) and lethal (0.5, 1.0 ppm)solutions of mercuric chloride (HgCl2) have been studied on the gills of the air breathing catfish, Heteropneustes fossilis at the intervals ranging from 6h to 15 days. Thickening of the epithelium, swelling and hyperplasia of the mucous cells, fusion of secondary lamellae, formation of interlamellar bridge and deposition of mucous over the entire surface are some noteworthy features of mercury poisoning in sublethal concentrations. Acute pathological manifestations are formation of subepithelial space, sloughing of the epithelial layer, hemorrhage and hypertrophy of the mucous cells. Causes and impact of these cellular alterations affecting survival of the fish have been discussed

Acute Toxic Effects of Mercuric Chloride on the Mucocytes of the Epithelial Lining of the Accessory Respiratory Organ and Skin of the Air Breathing Catfish Heteropneustes fossilis（Bloch）^1

Acute toxicity of 0.3 ppm mercuric chloride on the mucocytes of the branchial diverticulum and skin of Heteropneustes fossilis results in cyclic increases followed by decreases in the density, area occupancy and volume at different intervals of exposure. The alterations in the two tissues do not follow the same path perhaps due to different modes of action of the mercury salt: The skin comes under direct contact effects, while the branchial diverticulum may be affected by hormonal imbalance caused by a stress effect.

Histopathological Changes in the Epidermis of the Air Breathing Catfish Heteropneustes fossilis Exposed to Sublethal Concentration of Mercuric Chloride

Histopathological alterations induced by the sublethal concentration of (0.03 ppm) mercuric chloride solution on the epidermis of the fresh-water catfish Heteropneuates fossilis have been studied. It induces slow but significant histopathological changes in the various cellular components of the epidermis. It induces vacuolization, necrosis and pycnosis of the nuclei of the epithelial cells which subsequently shed. Loosening of epithelial cells of the outermost and middle layers following degeneration of the intercellular material and widened intercellular spaces is another important alteration. Prolonged mercury treatment also causes a gradual decrease in staining intensity for sulphated glycosaminoglycans in the outer border of the most superficial layer epithelial cells. The glandular elements (club cells and mucocytes) also get affected, showing cyclic degeneration followed by regeneration.

Piscicidal Effects of Terminalia arjuna Leaf,Bark and Fruit Extract on a Fresh Water Predatory Catfish,Heteropneustes fossilis

Piscicidal effects of several solvent extarcts(distilled water,50%ethanol,absolute ethanol and 80%methanol)of Terminalia arjuna leaves,barks and fruits were studied against a common fresh water predatory fish,Heteropneustes fossilis under laboratory conditions in terms of Behavior and mortality of fishes after 24 h.Fishes exposed to plant extracts showed agitating movement with quick surfacing,loss of balance,mucus secretion,and finally died.The LC50 values of distilled water,50%ethanol,absolute ethanol and 80%methanol extracts were found to be 311.726,236.141,183.541,478.794 ppm for leaves,117.894,96.998,38.990,304.193 ppm for barks and 1400.033,949.209,555.201,875.158 ppm for fruits,respectively.Chi-square values were found to be insignificant at P<0.05 in almost all plant extracts,indicating that observed and expected mortalities did not vary significantly in relation to doses,except 80%methanol extract of barks and absolute ethanol extract of fruits.The F-values of treatments were significant at P<0.01,except 80%methanol extract of fruits,in which F-values were insignificant in all replicates at P>0.01.Based on LC50 values,order of piscicidal activity followed the pattern,bark>leaf>fruit extracts.Order of piscicidal activity for the extracts was like absolute ethanol>50%ethanol>distilled water>80%methanol for leaf and bark,while for fruit extracts,trend was like absolute ethanol>80%methanol>50%ethanol>distilled water.

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.