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The caridean shrimp Lysmata wurdemanni (Gibbes) displays protandric simultaneous hermaphroditism with out-crossing, but not all males become simultaneous hermaphrodites (euhermaphrodites). In this laboratory study, we attempted to determine why some shrimp remain males. In our experiment, we grew L. wurdemanni from postlarvae to adults in several group sizes and observed their reproductive function. We found that all shrimp reared in isolation become euhermaphrodites. When cultured in a group, the proportion of shrimp remaining male decreased with increasing group size. Except for those that mated within a day, inter-molt euhermaphrodite-phase shrimp (with or without embryos) and inter-molt male-phase shrimp fertilized eggs successfully. On the other hand, euhermaphrodite shrimp can only mate as females and have their eggs fertilized during a narrow post-molt window (less than 12 h) in each molt cycle (10 days). The fertilization rate of male-euhermaphrodite pairs was similar to that of euhermaphrodite-euhermaphrodite pairs. There are at least two non-exclusive explanations for the persistence of male shrimp in a group. In certain group compositions, an individual may gain more reproductive fitness as a large male with multiple mating partners than as a small female with low clutch size. Alternatively, the presence of male-phase individuals, with variable molt-cycle duration (5-8 days), may be necessary to ensure mating. This study is the first direct experimental demonstration of social control of sex change in the decapod crustaceans. 相似文献
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羧甲基-β-环糊精对土壤中萘的洗脱去除作用 总被引:5,自引:0,他引:5
研究了不同浓度的羧甲基-β-环糊精溶液对不同组分土壤中萘的洗脱去除作用,同非离子表面活性剂脂肪醇聚氧乙烯醚的洗脱去除作用比较,讨论了其对洗脱效果的影响因素.结果表明:羧甲基-β-环糊精溶液对土壤中的萘有较好的洗脱去除效果,20g·1-1的羧甲基-β-环糊精溶液的洗脱率可达90%以上;洗脱液浓度和土壤质地是影响洗脱去除率的主要因素;适当地增加洗脱液浓度对洗脱去除率有显著提高;与脂肪醇聚氧乙烯醚相比,以羧甲基-β-环糊精溶液作为增溶试剂,对土壤中的弱极性有机污染物进行洗脱处理具有更好的效果 相似文献
395.
通过共存元素对土壤小麦系统Cd、Pb行为影响的调查研究发现:大田条件下共存元素以正对数模式与根系Cd、Pb密切相关,同种元素间相关程度最高;根系Cd、Pb积累主要取决于土壤环境Cd、Pb的含量,共存元素也产生一定的影响,认为要防止重金属通过食物链对人类的危害,就必须降低土壤环境中重金属的总量。 相似文献
396.
钱金平 《城市环境与城市生态》2001,14(3):50-51,53
运用专家调查打分法,以具体的承德兴业造纸项目为例,初步探讨了清滞生产量化评价方法,程序以及清洁生产评价指标的应用。 相似文献
397.
Yunpeng Yu Fanghong Nie Anthony Hay Hongying Lin Yi Ma Xianghong Ju Dongliang Gong Jinjun Chen Ravi Gooneratne 《Environmental monitoring and assessment》2017,189(6):289
Dioxin-like polychlorinated biphenyls (DLPCBs) are ubiquitous persistent pollutants that cause adverse effects in many environmental organisms. DLPCBs in marine sediments can be absorbed by benthic organisms, bioaccumulate, and biomagnify through the food chain and threaten animal and human health. There are no reports of DLPCBs concentrations in the Zhanjiang Gulf seabed. This study was designed to investigate the concentration of DLPCBs in the Zhanjiang coastal sediment and histopathological changes in zebrafish (Diano rerio) embryos exposed to environmentally relevant concentrations of DLPCBs. Of the five sites selected, two sites TS and JSW contained DLPCBs at concentrations of 0.08 and 22.54 ng/g dry sediment, respectively. Two groups of zebrafish embryos were used. One group was exposed to 3.75, 7.5, 15, 30, and 60 mg/ml of DLPCBs extracted from the sediments sampled from the TS site and the second group to 4.375, 8.75, 17.5, 35, and 70 mg/ml of DLPCBs from JSW site from 0.75 h post-fertilization (hpf) to 96 hpf. The zebrafish exposed to 60 and 70 mg/ml of DLPCBs at 96 hpf displayed gross histopathological changes with cardiac lesions including pericardial edema being the most deleterious. Other changes observed were hydropic degeneration of gill filaments and hepatocytes, loss of intestinal folds, and uninflated swim bladder. It appears that only a few sites of the Zhanjiang gulf are contaminated with DLPCBs. This is the first report of histopathological changes in the gills, hepatocytes, intestines, heart, and the swim bladder in zebrafish embryos exposed to DLPCBs from a coastal sediment. Further studies with sampling at different stages of development are required to identify which organ/tissue is most sensitive to DLPCBs. 相似文献
398.
介绍了江苏省重污染天气监测预报预警系统以及大气重污染预警会商流程,将2015年13个地级市的模式预报、人工预报结果分别与实际观测值进行比较。结果表明:人工预报更准确,PM_(2.5)日均值、臭氧日最大8 h平均值、AQI 3个指标人工预报和实况的相关性分别比模式预报高出12.8%、0.3%、11.4%,平均标准误差(MNE)分别低20.7%、3.1%、23.1%。依据国家空气质量预报技术指南评分办法,对各市2015年全年空气质量级别为"良"时进行评分。通过开展07∶00预报更新,使2015年上半年空气质量预报级别得分平均提高了0.9分,全年级别得分平均提高了2.6分;通过改进模式预报参数,使PM_(2.5)日均预报值、臭氧日最大8 h平均预报值、AQI预报值和实际观测值的相关性比上年同期分别提高26.0%、5.0%、33.9%,MNE分别降低3.6%、31.3%、7.6%。 相似文献
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