Lead elimination and size effects on accumulation by two freshwater gastropods

Freshwater gastropods,Physa integra andCampeloma decisum, inhabiting a small reservoir with elevated levels of lead displayed widely differing soft tissue lead concentrations. Analysis of environmental factors did not fully explain these differences. Several physiological characteristics of the two gastropods were examined. The influence of snail size on concentrations of naturally-accrued lead was examined as was the rate of lead elimination from the two species. Lead concentrations inP. integra were independent of animal size, while those ofC. decisum were described by the curvilinear model:μg Pb/g dry wt=2.29(g dry wt)^?0.25. Naturally-accrued lead inP. integra was eliminated rapidly during the first four days of clearance but slowly thereafter; a portion of the lead is apparently bound strongly. In contrast, no significant change in lead concentration of gravid or nongravidC. decisum occurred during a three to four week period in which the animals were maintained in a lead-free environment.     

海湾扇贝体内重金属镉的富集和消除规律的研究

研究日照海湾扇贝(Argopecten irradiams)分别在Cd2+的浓度为0.001、0.0025、0.005、0.01 mg/L及一个对照共5组海水中培养时,镉在其体内的积累和排出规律。结果表明海湾扇贝对镉具有较强的富集能力,随着时间的延长,Cd2+浓度的增加,富集量也增加,而且内脏的富集能力远高于肌肉。停药后镉的代谢情况是:随着镉的浓度升高,代谢速度基本上是呈上升趋势的,但是代谢相同时间后,镉的残留量是呈上升趋势的。     

Interference of magnesium on zinc adsorption by pond sediment and on zinc accumulation in a freshwater teleost, Labeo rohita (Hamilton)

Two experiments were conducted to evaluate the interference of magnesium on zinc adsorption in freshwater fish pond sediment and zinc accumulation in the freshwater teleost Labeo rohita (Hamilton). The study demonstrated that increasing the concentration of magnesium as magnesium sulfate from 100 to 400 mg kg(-1) decreased the adsorption of zinc in sediment. The maximum adsorption was found at a concentration of 100 mg kg(-1) of Mg(2+) and the minimum with 400 mg kg(-1) of Mg(2+). This study also demonstrated that the exposure of fish to 0.25 mg L(-1) of zinc as zinc sulfate with different concentrations of magnesium (100, 200, 300, and 400 mg L(-1)) for 14 d resulted in the minimum accumulation of zinc in L. rohita (2.97 mg kg(-1) dry weight) at 200 mg L(-1) of Mg(2+), while the maximum accumulation (8.47 mg kg(-1) dry weight) occurred with no magnesium treatment.     

Differences between freshwater and seawater killifish (Oryzias latipes) in the accumulation and elimination of pentachlorophenol

Freshwater and seawater acclimated (FWA and SWA) killifish (Oryzias latipes) were exposed to pentachlorophenol (PCP) for 3–10 days. Uptake and clearance rates of FWA and SWA killifish were determined. The estimated bioaccumulation factors (BCF) of PCP for FWA and SWA killifish were 1680 and 370, respectively. The smaller uptake rate and faster clearance rate resulted in the lower BCF for SWA killifish. Fresh- and seawater killifish excreted the PCP metabolites, the glucuronide and sulfate conjugates of PCP; the major metabolite of freshwater killifish was PCP sulfate; for seawater acclimated fish, it was PCP glucuronide. The greater excretion of PCP glucuronide by seawater killifish may be responsible for the rapid elimination of PCP. PCP accumulation in killifish decreased with higher pH levels in both freshwater and seawater environments, but these differences were less than the effect of salinity. The results indicate that salinity can affect the accumulation and elimination of environmental pollutants in killifish.     

Cadmium kinetics in freshwater clams. I. The pattern of cadmium accumulation inAnodonta cygnea

Freshwater clams (Anodonta cygnea) were exposed to cadmium under laboratory conditions. Time courses of Cd accumulation were determined for whole animal and the separate organs. At 5 g/L, Cd accumulation proceeded mainly linearly. At 25 g/L, the accumulation pattern was biphasic for whole animals and most of the organs: during the first four weeks Cd concentrations increased linearly, remaining at a constant level for the next two weeks. Thereafter, metal concentrations increased strongly until, after 10 weeks, a saturation level was reached. It is argued that the biphasic course of accumulation is not caused by an advancing selection through mortality or by the gradually decreasing mean animal weight, nor by the typical laboratory conditions of absence of food and substratum. The partition of total Cd among the organs gradually changed over the first eight weeks, remaining constant from that time. The ultimate order of Cd concentrations was: gills > labial palps > mantle-edge > mantle, kidney, whole animal > midgut gland > guts/gonads complex > foot. A possible relation between the time course of Cd accumulation and behavioral responses is presented.     

The accumulation and elimination of diflubenzuron by fish.

In summary, diflubenzuron is accumulated from water into fish tissues at levels up to 80 fold within 24 hr when fish are exposed to concentrations of 10 ppb. Within the concentration range of 1-10 ppb, the amount accumulated in a 24 hr exposure is proportional to concentration. After 24 to 48 hr exposure fish degrade and eliminate diflubenzuron and the excretory products are neither the parent compound nor p-chlorophenylurea. The amount of diflubenzuron remaining in fish tissues with time is dependent on the reduction of residue concentration in water; however, the potential for degradation and elimination is very great.     

Selenium accumulation and elimination in mallards

Selenium accumulation and loss were measured in adult mallards (Anas platyrhynchos) fed selenomethionine during two experiments. In Experiment 1, both sexes were fed a diet containing 10 ppm selenium for 6 weeks, followed by 6 weeks on untreated feed. Selenium accumulation in liver and muscle of females was described by C=A(1–e^–bt). Concentrations of selenium were predicted to reach 95% of equilibrium faster in liver (7.8 days) than in muscle (81 days). The loss of selenium from liver and muscle of females was described by the exponential loss rate equation: C=Ae^–bt, with half-times of 18.7 and 30.1 days, respectively. Males reached similar levels of selenium in liver and breast muscle as females and declined to similar levels once selenium treatment ended. In Experiment 2, females were fed increasing levels of selenium until some died. Survivors were switched to an untreated diet and selenium was measured in blood, liver, and breast muscle over 64 days. The same equation as in Experiment 1, C=Ae^–bt, was used to describe the loss of selenium from blood and muscle. Halftimes were 9.8 and 23.9 days, respectively. For liver, the equation was used. Selenium initially decreased in liver by one-half in 3.3 days, with subsequent half-times of 3.9, 6.0, and 45.1 days.