Perna perna (L.), the edible brown mussel, is very widely distributed in the tropical and subtropical regions and is commonly found in rocky shores. Apart from being a candidate for commercial cultivation, P. perna is...
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Perna perna (L.), the edible brown mussel, is very widely distributed in the tropical and subtropical regions and is commonly found in rocky shores. Apart from being a candidate for commercial cultivation, P. perna is also a common pest organism in cooling water systems of coastal power stations. Therefore, a lethal and sublethal response of this mussel to commonly used antifouling biocides is of considerable interest to the industry. Mortality pattern (LT50 and LT100) and physiological activities (oxygen consumption, filtration rate, foot activity index, and byssus thread production) of different size groups (9-34 mm shell lengths) of P. perna were studied in the laboratory under different residual chlorine concentrations (0.25, 0.50, 0.75, and 1.00 mg/L for sublethal responses and 1, 2, 3, and 5 mg/L for mortality). Results showed that exposure time for 100% mortality of mussels significantly decreased with increasing residual chlorine concentration. For example, mussels of 9 mm size group exposed to 1 mg/L chlorine residual took 384 h (16 days) to reach 100% mortality, whereas those exposed to 5 mg/L chlorine took 84 h (4 days). The effect of mussel size on mortality was significant between I mg/L and 5 mg/L residual chlorine, with larger mussels showing greater resistance than smaller ones. For example, at 2 mg/L residual chlorine, 9 mm and 34 mm size group mussels took 228 h (10 days) and 304 h (13 days), respectively, to achieve 100% mortality. All size groups of P. perna showed progressive reduction in physiological activities, when chlorine residuals were gradually increased from 0 to I mg/L. Reduction in physiological activities was strongly correlated with the residual level. A comparison of present data with data available for other common fouling organisms suggests that P. perna is relatively less tolerant to chlorine than Perna viridis (L.) and Brachidontes striatulus (Hanley), which also cause fouling problems in tropical coastal waters.
Chlorine is one of the most abundant elements on the surface of the earth. Until recently, it was widely believed that all chlorinated organic compounds were xenobiotic, that chlorine does not participate in biologica...
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Chlorine is one of the most abundant elements on the surface of the earth. Until recently, it was widely believed that all chlorinated organic compounds were xenobiotic, that chlorine does not participate in biological processes and that it is present in the environment only as chloride. However, over the years, research has revealed that chlorine takes part in a complex biogeochemical cycle, that it is one of the major elements of soil organic matter and that the amount of naturally formed organic chlorine present in the environment can be counted in tons per km(2). Interestingly enough, some of the pieces of the chlorine puzzle have actually been known for decades, but the information has been scattered among a number of different disciplines with little or no exchange of information. The lack of communication appears to be due to the fact that the points of departure in the various fields have not corresponded;a number of paradoxes are actually revealed when the known pieces of the chlorine puzzle are fit together. It appears as if a number of generally agreed statements or tacit understandings have guided perceptions, and that these have obstructed the understanding of the chlorine-cycle as a whole. The present review enlightens four paradoxes that spring up when some persistent tacit understandings are viewed in the light of recent work as well as earlier findings in other areas. The paradoxes illuminated in this paper are that it is generally agreed that: (1) chlorinated organic compounds are xenobiotic even though more than 1,000 naturally produced chlorinated compounds have been identified;(2) only a few, rather specialised, organisms are able to convert chloride to organic chlorine even though it appears as if the ability among organisms to transform chloride to organic chlorine is more the rule than the exception;, (3) all chlorinated organic compounds are persistent and toxic even though the vast majority of naturally produced organic chlorine is neither
The three fungicides, captan, captofol and folpet and a structurally related compound, thalidomide, were investigated for possible mutagenic activity by the dominant lethal mutagenicity study in mice and by the host-m...
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The three fungicides, captan, captofol and folpet and a structurally related compound, thalidomide, were investigated for possible mutagenic activity by the dominant lethal mutagenicity study in mice and by the host-mediated assay in rats using a histidine auxotroph of Salmonella typhimurium . Male mice were treated with a single ip injection of captan (3 or 6 mg/kg), captofol (1·5 or 3·0 mg/kg), folpet (5 or 10 mg/kg) or thalidomide (50 or 1000 mg/kg). The results of weekly matings with untreated virgin females disclosed no increase in early embryonic death among conceptuses obtained from females mated with the treated males. Groups of male rats were treated by oral intubation for 14 days with one of the three fungicides at levels of 125 or 250 mg/kg/day or with thalidomide at 500 or 1000 mg/kg/day. Indicator micro-organisms recovered from the peritoneal cavity of the treated male rats after a 3-hy residence showed no increase in numbers of revertants. Thus captan, captofol, folpet and thalidomide were not mutagenic in either of these test systems.
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