Toxic effects of cypermethrin and alphamethrin on reproduction and oxidative metabolism of the freshwater snail, Lymnaea acuminata

Effects of sublethal exposure to cypermethrin and alphamethrin on the reproductive physiology and oxidative metabolism of the freshwater snail, Lymnaea acuminata, were studied. Sublethal exposure to both pyrethroids caused increases in the numbers of egg masses and eggs at all concentrations, but the survival rate of the snails was significantly reduced 28 days after of hatching. Both pyrethroids altered the oxidative metabolism in hepatopancreas and ovotestis tissues of the snails. Stress conditions result in less availability of oxygen and in turn less ATP production in tissues, adversely affecting oxidative metabolism and reproduction in L. acuminata.     

Alterations in carbohydrates and the protein metabolism of the harmful freshwater vector snail Lymnaea acuminata induced by the Euphorbia tirucalli latex extract

To know the short- as well as long-term effect of aqueous latex extracts of Euphorbia tirucalli on carbohydrate and protein metabolism, the snail Lymnaea acuminata was exposed to sublethal doses of 0.37 and 0.55 mg/L for a 24-h and 0.20 and 0.31 mg/L for a 96-h exposure period. Significant (P<0.05) alterations in the glycogen, pyruvate, lactate, total protein, and free amino acid level, as well as in the activity of enzyme lactic dehydrogenase, succinic dehydrogenase, cytochrome oxidase, protease, aspartate aminotransaminase, and alanine aminotransaminase were observed in the nervous, hepatopancreatic, and ovotestis tissues of the freshwater vector snail L. acuminata exposed to sublethal doses of E. tirucalli latex extract. The alterations in all biochemical parameters were significantly (P<0.05) time and dose dependent. After the 7th day of the withdrawal of treatment, there was significant (P<0.05) recovery in glycogen, pyruvate, lactate, total protein, and the free amino acid level and in the activity of the lactic dehydrogenase, succinic dehydrogenase, cytochrome oxidase, protease, aspartate aminotransaminase and alanine aminotransaminase enzymes in all three of the studied tissues of the snail, which supports the view that the plant product is safe for use as a molluscicide for the control of harmful freshwater vector snails in the aquatic environment.     

Toxic and sublethal effects of carbaryl on a freshwater catfish,Mystus vittatus (Bloch)

The effects of carbaryl (1-naphthalenyl methylcarbamate), commonly used in agricultural operations, have been studied with reference to survival, behavior, food intake, growth, and conversion efficiency of the catfishMystus vittatus. At a concentration of 32.5 ppm, carbaryl caused 100% mortality within 24 hr; the 72 hr LC₅₀ was 17.5 ppm. At concentrations of 12.5 ppm and below, it caused no mortalities within 72 hr. But such sublethal concentrations accelerated the swimming activity and increased the frequency of opercular beats. The latter response was dose-dependent. These behavioral changes were the immediate response to the toxicant and were indicators of possible stress. A 27-day exposure to sublethal concentrations of carbaryl led to a decrease in feeding rate and growth rate. The latter decreased from 10.15 mg/g/day (freshwater) to 2.84 mg/g/day (12.5 ppm). The reduced growth and conversion efficiency may be due to the expenditure of more energy for the purpose of maintenance. Therefore, the insecticide is considered to be a metabolic Stressor.     

Phorate and mexacarbate induced changes in enzymes of the snail,Lymnaea acuminata

The snailLymnaea acuminata, vector of the liver flukesFasciola hepatica andFasciola gigantica, was exposed to 40% and 80% LC₅₀ doses of the pesticides 12/24 mg/L phorate (O,O-diethylS-(ethylthio) methyl phosphorodithioate) and 2.5/5.0 mg/L of mexacarbate (4-dimethylamino)-3,5-dimethylphenyl methyl carbamate) for 24 or 48 hr. These pesticides, although considered to be antiacetylcholinesterase agents, inhibited alkaline phosphatase and enhanced the activity of acid phosphatase in hepatopancreas, mantle, intestine, and foot of the snail. Trypsin activity in the alimentary canal of the snail was also inhibited. Discontinuation of pesticide treatment resulted in partial recovery in mexacarbate-treated animals while in phorate-treated animals the effect of the pesticide was largely irreversible.     

Reduction of growth and haemolymph Ca levels in the freshwater snail Lymnaea stagnalis chronically exposed to cobalt

The ecological risk assessment and the development of water-quality criteria for Co are currently still hampered by insufficient knowledge about the toxicity of Co to freshwater organisms. A relevant group of organisms, for which no toxicity data with Co are available, is the class of the herbivorous pulmonate freshwater snails, which fulfil a pivotal role in the consumption and decomposition of aquatic plants and epihyton. We measured the growth rate of the pond snail Lymnaea stagnalis chronically exposed for 28 days to a series of Co concentrations. The no observed effect concentration (NOEC) and the lowest observed effect concentration (LOEC) for growth rate were 26 and 79 microg Co/L, respectively. Growth rate of snails exposed to 79 microg Co/L and higher concentrations was more impaired in the final 2 weeks of exposure than in the first 2 weeks of exposure. The reduced growth rate at 79 microg Co/L was accompanied by a reduced concentration of Ca in the haemolymph at the end of the exposure. Possible mechanisms of toxicity of Co to snail growth were suggested to be an impairment of Ca uptake and homeostasis and/or feeding inhibition. Although additional research is needed to investigate the relative importance of these mechanisms, as well as the interrelatedness between them, the toxicity data currently presented can assist in risk assessment and water-quality criteria development.     

Nonylphenol polyethoxylate adjuvant mitigates the reproductive toxicity of fomesafen on the freshwater snail Lymnaea stagnalis in outdoor experimental ponds

The influence of nonylphenol polyethoxylates (NPEO), formulated as the adjuvant Agral 90, on the effects of the diphenyl ether herbicide fomesafen in the pond snail Lymnaea stagnalis was investigated, with particular attention to the reproductive performances and underlying energetic and hormonal processes. Separate short-term exposures to low concentrations of fomesafen and fomesafen-Agral mixture were performed in the laboratory. Outdoor experimental ponds (mesocosms) were used for long-term exposures to higher chemical concentrations. At the concentrations used in the studies, NPEO were known as nontoxic in L stagnalis. Fomesafen was mixed with the adjuvant in the 3:7 ratio recommended for agricultural uses (nominal herbicide concentrations of 22 and 40 microg/L in laboratory and mesocosm, respectively). In mesocosms, multiple application of fomesafen, leading to maximal herbicide concentrations of 60.33 +/- 2.68 microg/L in water, resulted in reduced number of egg masses and altered glycogen metabolism in contaminated snails. These changes, as well as affected steroid-like levels in fomesafen-exposed snails, support the hypothesis of impaired neuroendocrine functions. When Agral 90 was added to the herbicide, results obtained in mesocosms showed that the adjuvant softened the impact of fomesafen. In mesocosms treated with the fomesafen-Agral mixture, significantly lower herbicide levels were found in the water (30.33 +/- 14.91 microg/L at the end of the contamination period). Consequently, internal exposure of the snails to fomesafen was reduced when the herbicide was mixed with the adjuvant. Mitigation of the effects of fomesafen by the adjuvant may therefore result from nonionic surfactant activity of NPEO that prevented fomesafen from reaching the snails.     

Long-term effects of Depo-Provera on carbohydrate and lipid metabolism

Long-term effects of injection Depo-Provera (depo-medroxyprogesterone acetate) on carbohydrate and lipid metabolism were studied in 157 women who were treated continuously for a mean duration of 43.3 months. The patients were matched with 162 controls for race, age, parity and height. Glucose tolerance was impaired with higher intolerance at longer duration. Glucose areas were significantly higher at 48 and 60 months of injection. Insulin levels were also significantly decreased at 30 minutes and increased at 150 minutes but the area was normal. Triglycerides were initially decreased, being significant at 36 months (p less than 0.001) and returned to normal at 60 months while cholesterols were significantly higher at 24 and 36 months (p less than 0.05) and 60 months (p less than 0.001). In view of these findings, Depo-Provera may have an advantage over oral pills on a short term basis as there are less alterations in carbohydrate and lipid metabolism.     

Zinc sensitivity of a freshwater snail,Lymnaea luteola L., in relation to seasonal variations in temperature

Bulletin of Environmental Contamination and Toxicology -     

Implanon contraceptive implants: effects on carbohydrate metabolism

The objective of the study was to assess the possible differences in effects of Implanon and Norplant implants on carbohydrate metabolism. This is a 2-year open randomized study of 80 implant (Implanon and Norplant) acceptors. Oral glucose tolerance test (OGTT) was performed before implant insertion and at 6, 12, and 24 months after implant insertion. Glycosylated hemoglobin A(1)C was measured in fasting samples and plasma samples during OGTT were tested for glucose and insulin levels. There was a significant increase in the area under the curve for both glucose and insulin during OGTT within each group with increasing duration of use. However, there was no significant change in the fasting plasma glucose values. There was no significant difference in the carbohydrate parameters between the two groups during implant use, except for a minimal but statistically significant rise in fasting glycosylated hemoglobin A(1)C levels at 24 months in the Implanon group. Both implants appear to induce mild insulin resistance but no significant change in serum glucose levels. These alterations in carbohydrate metabolism should have no clinical significance in healthy women.     

Mercuric chloride intoxication in freshwater prawn. I. Effect on carbohydrate metabolism

The effects of mercuric chloride on the glycogen content of various tissues and on the hemolymph glucose level of freshwater prawns, Macrobrachium lamarrei (M. Edwards), have been studied. Mercuric chloride depleted the glycogen content of different tissues. The hemolymph glucose level was decreased within 24 hr and later increased significantly up to 72 hr. Further, a remarkable decrease in glucose level was observed after 96 hr. The possible cause of disturbance in carbohydrate metabolism in relation to mercury intoxication is briefly discussed.     

Impact of phosphamidon on the carbohydrate metabolism of a freshwater prawn, Macrobrachium lamarrei

The effects of a lethal (96 hr LC50) and two sublethal (40 and 80% of 96 hr LC50) doses of phosphamidon on hepatic and muscle glycogen values and blood glucose level of a freshwater prawn, Macrobrachium lamarrei (H. Milne Edwards), have been studied. Pesticide exposure depleted the glycogen values in both tissues while the blood glucose level was elevated up to 72 hr, after which it was decreased. The probable explanations of phosphamidon-induced changes are discussed.     

Toxic effects of Streptomyces griseus spores and exudate on gill pathology of freshwater fish

Many unexplained fish-kills in British waters are considered microbial in origin and a large proportion of field sites contains elevated concentrations of filamentous actinobacteria. The present study has shown that a strain of Streptomyces griseus, isolated from field sites, elicits pathological changes to the gills of fish under laboratory conditions which mirror those found in situ. These changes include hyperplasia leading to fusion of the secondary lamellae and loss of microridging on the filamental epithelium of the primary lamellae. Juveniles of up to six fish species were exposed to spore suspensions or exudate of S. griseus in the range of 1 x 10(2)-1 x 10(6)spores ml(-1) for up to 96 h. The exudate was more potent than the spores and there was a positive correlation between exudate concentration and the rate and extent of fish gill pathology with bream and rainbow trout being more sensitive than carp, tench and roach. The results are discussed in the context of recognising and managing potential fish mortalities caused by microbial toxins.