有关媒介昆虫几个问题的探讨

世界上昆虫种类繁多,但能成为疾病传播媒介者仅其中少数.例如,我国已记载的蚊类有360余种,其中传播疟疾的重要蚊种仅4种,传播登革热的媒介蚊种仅2种[1];我国已记载的恙螨有430余种,其中传播恙虫病的重要媒介恙螨仅2种[2].     

Toxicity and bioaccumulation of biosolids-borne triclosan in terrestrial organisms

Triclosan (TCS) is a common constituent of personal care products and is frequently present in biosolids. Application of biosolids to land transfers significant amounts of TCS to soils. Because TCS is an antimicrobial and is toxic to some aquatic organisms, concern has arisen that TCS may adversely affect soil organisms. The objective of the present study was to investigate the toxicity and bioaccumulation potential of biosolids-borne TCS in terrestrial micro- and macro-organisms (earthworms). Studies were conducted in two biosolids-amended soils (sand, silty clay loam), following U.S. Environmental Protection Agency (U.S. EPA) guidelines. At the concentrations tested herein, microbial toxicity tests suggested no adverse effects of TCS on microbial respiration, ammonification, and nitrification. The no observed effect concentration for TCS for microbial processes was 10?mg/kg soil. Earthworm subchronic toxicity tests showed that biosolids-borne TCS was not toxic to earthworms at the concentrations tested herein. The estimated TCS earthworm lethal concentration (LC50) was greater than 1?mg/kg soil. Greater TCS accumulation was observed in earthworms incubated in a silty clay loam soil (bioaccumulation factor [BAF]?=?12?±?3.1) than in a sand (BAF?=?6.5?±?0.84). Field-collected earthworms had a significantly smaller BAF value (4.3?±?0.7) than our laboratory values (6.5-12.0). The BAF values varied significantly with exposure conditions (e.g., soil characteristics, laboratory vs field conditions); however, a value of 10 represents a reasonable first approximation for risk assessment purposes.     

Bioaccumulation and trophic transfer of polychlorinated biphenyls by aquatic and terrestrial insects to tree swallows (Tachycineta bicolor)

Insectivorous passerines often bioaccumulate polychlorinated biphenyls (PCBs) via trophic transfer processes. Tree swallows (Tachycineta bicolor) frequently are used for estimating PCB bioaccumulation, yet the focus on specific trophic links between contaminated sediment and bird has been limited. Bioaccumulation of PCBs from sediment to tree swallows was examined with focus on trophic pathways by simultaneously examining PCBs in emergent aquatic and terrestrial insects and gut contents of nestlings. Total PCB concentrations increased from sediment (123.65 +/- 15.93 microg/kg) to tree swallow nestlings (2,827.76 +/- 505.67 microg/kg), with emergent aquatic insects, terrestrial insects, and gut content samples having intermediate concentrations. Biota-sediment accumulation factors (BSAFs) varied among congeners for tree swallow nestlings and for male and female Chironomus spp. For nestlings, the highest BSAF was for the mono-ortho-substituted congener 118. Nestling biomagnification values were similar for gut contents and female Chironomus spp., suggesting this diet item may be the main contributor to the overall PCB transfer to nestlings. However, gut content samples were highly variable and, on a PCB congener pattern basis, may have been influenced by other taxa, such as terrestrial insects. Considering dietary plasticity of many insectivorous birds, the present study suggests that a variety of potential food items should be considered when examining PCB accumulation in insectivorous passerines.     

Toxicity of the herbicide glyphosate and several of its formulations to fish and aquatic invertebrates

Studies were initiated to determine the acute toxicity of technical grade glyphosate (MON0573), the isopropylamine salt of glyphosate (MON0139), the formulated herbicide Roundup^® (MON02139), and the Roundup^® surfactant (MON0818) to four aquatic invertebrates and four fishes: daphnids (Daphnia magna), scuds (Gammarus pseudolimnaeus), midge larvae (Chironomous plumosus), mayfly nymphs (Ephemerella walkeri), Rainbow trout (Salmo gairdneri), fathead minnows (Pimephales promelas), channel catfish (Ictalurus punctatus), and bluegills (Lepomis macrochirus). Acute toxicities for Roundup ranged from 2.3 mg/L (96-h LC50, fathead minnow) to 43 mg/L (48-h EC50, mature scuds). Toxicities of the surfactant were similar to those of the Roundup formulation. Technical glyphosate was considerably less toxic than Roundup or the surfactant; for midge larvae, the 48-h EC50 was 55 mg/L and for rainbow trout, the 96-h LC50 was 140 mg/L. Roundup was more toxic to rainbow trout and bluegills at the higher test temperatures, and at pH 7.5 than at pH 6.5. Toxicity did not increase at pH 8.5 or 9.5. Eyed eggs were the least sensitive life stage, but toxicity increased markedly as the fish entered the sac fry and early swim-up stages. No changes in fecundity or gonadosomatic index were observed in adult rainbow trout treated with the isopropylamine salt or Roundup up to 2.0 mg/L. The aging of Roundup test solutions for seven days did not reduce toxicity to midge larvae, rainbow trout or bluegills. In avoidance studies, rainbow trout did not avoid concentrations of the isopropylamine salt up to 10.0 mg/L; mayfly nymphs avoided 10.0 mg/L of Roundup, but not 1.0 mg/L. In a simulated field application, midge larvae avoided 2.0 mg/L of Roundup. Application of Roundup, at recommended rates, along ditchbank areas of irrigation canals should not adversely affect resident populations of fish or invertebrates. However, spring applications in lentic situations, where dissolved oxygen levels are low or temperatures are elevated, could be hazardous to young-of-the-year-fishes.     

Differences in fatty acid composition between aquatic and terrestrial insects used as food in human nutrition

Edible insects may be a source of long-chain polyunsaturated fatty acids (LC-PUFA). The aim of this article is to test for differences in aquatic and terrestrial insects used in human nutrition. We implemented linear models and discovered that differences in the proportion of LC-PUFA between aquatic and terrestrial insects do exist, with terrestrial insects being significantly richer in particular omega-6 fatty acids. In conclusion, any kind of insect may provide valuable sources of LC-PUFA. Because terrestrial insects are more abundant and easier to collect, they can be considered a better source of LC-PUFA than aquatic ones.     

Toxicity of Aroclor® 1254 and its physiological activity in several estuarine organisms

The occurrence of high concentrations of a PCB (Aroclor 1254) in the Pensacola estuary prompted field and laboratory studies by the Gulf Breeze Environmental Research Laboratory (EPA). Monitoring of the estuary indicates the chemical is present in all components-particularly in sediments and fishes. Residues appear to be diminishing in sediments. Toxicity tests show estuarine species sensitive at ppb concentrations in water, with a ciliate protozoan (Tetrahymena pyriformis W), shrimps (Penaeus duorarum, P. aztecus, andPalaemonetes pugio), and a fish (Fundulus similis), affected at or near 1.0 ppb. Tissue concentrations of Aroclor 1254 similar to those found in natural populations of shrimps from the contaminated estuary were successfully duplicated in laboratory experiments. Shrimps also concentrated the PCB from very low concentrations (0.04 ppb) in the water. Three estuarine species demonstrated pathologic changes at tissue and cellular level after chronic exposure to the chemical. Oysters (Crassostrea virginica) developed abnormal infiltration of leukocytes in the connective tissue, spot (Leiostomus xanthurus) developed fatty changes in their livers, and shrimp (Penaeus duorarum) developed crystalloids in hepatopancreatic nuclei.® In this paper, Aroclor and PCB are used interchangeably for Aroclor 1254. Aroclor^® is a registered trademark of the Monsanto Company, St. Louis, Mo. Reference to commercial products does not constitute endorsement by the Environmental Protection Agency.     

灭多威对家蝇的毒力及其对动物的毒性

灭多威对４个不同品系家蝇均有较好的毒杀效果，ＬＤ５０分别为０．０８９５、０．２０１２、０．２３５１和０．１７６８μｇ／♀。对抗溴氰菊酯家蝇无明显的交互抗性。灭多威对家蝇的毒力均大于残杀威、仲丁威、异丙威和甲萘威，该药剂的纯品、工业原药及制剂，对动物的急性经口毒性属高毒类，经皮毒性为低毒性，畜积毒性作用Ｋ＞５．３。灭多威的安全系数为２６８．２。Ａｍｅｓ测试阴性。其中间体灭多威肟是低毒。     

Toxicity of water-soluble fractions of biodiesel fuels derived from castor oil, palm oil, and waste cooking oil

Concerns over the sustained availability of fossil fuels and their impact on global warming and pollution have led to the search for fuels from renewable sources to address worldwide rising energy demands. Biodiesel is emerging as one of the possible solutions for the transport sector. It shows comparable engine performance to that of conventional diesel fuel, while reducing greenhouse gas emissions. However, the toxicity of products and effluents from the biodiesel industry has not yet been sufficiently investigated. Brazil has a very high potential as a biodiesel producer, in view of its climatic conditions and vast areas for cropland, with consequent environmental risks because of possible accidental biodiesel spillages into water bodies and runoff to coastal areas. This research determined the toxicity to two marine organisms of the water-soluble fractions (WSF) of three different biodiesel fuels obtained by methanol transesterification of castor oil (CO), palm oil (PO), and waste cooking oil (WCO). Microalgae and sea urchins were used as the test organisms, respectively, for culture-growth-inhibition and early-life-stage-toxicity tests. The toxicity levels of the analyzed biodiesel WSF showed the highest toxicity for the CO, followed by WCO and the PO. Methanol was the most prominent contaminant; concentrations increased over time in WSF samples stored up to 120 d.     

Toxicity versus accumulation for barley plants exposed to copper in the presence of metal buffers: progress towards development of a terrestrial biotic ligand model

Development of a terrestrial biotic ligand model (TBLM) for higher plants requires a root-Cu accumulation value that corresponds to the 50% inhibitory concentration (IC50). However, it is not yet known which of the two previously reported Cu-binding ligands on the root is associated with Cu toxicity. The aim of the present study was therefore to investigate the relationship between Cu binding to each ligand group and toxicity, so that the key toxicological site could be identified. To obtain accumulation and toxicity data that were not biased by limited Cu supply to the root, 2-d-old barley seedlings were exposed for 48 h to a range of free Cu ion activities (i.e., {Cu(2+)}) in simple exposure media buffered by nitrilotriacetic acid (NTA) or ethylenediaminetetraacetic acid (EDTA). Comparison of the amount of predicted root-bound Cu (calculated with the aqueous geochemical program PHREEQC) with root elongation data showed that toxicity likely resulted from Cu binding to low-affinity ligands, as the high-affinity ligands were approximately 99% saturated when a reduction in root elongation was first observed. For plants exposed to both NTA- and the EDTA-buffered {Cu(2+)} solutions, the root-Cu accumulation value corresponding to the IC50 was approximately 80 microg/g root dry weight, which is similar to the value obtained from previous work with wheat. The linear relationship between the amount of Cu bound to the low-affinity ligands and the percent root growth inhibition suggests that this relationship will be a robust predictor of Cu toxicity when incorporated into the TBLM, and applied to varied exposure scenarios. For the simple solutions used here, the TBLM-predicted and measured IC50 values were statistically indistinguishable.