溴氰虫酰胺对白背飞虱室内敏感种群的亚致死效应

为探究溴氰虫酰胺对白背飞虱的亚致死效应,采用稻茎浸渍法,分别以LC10和LC25浓度的溴氰虫酰胺胁迫白背飞虱3龄若虫,观察受胁迫后试虫发育历期、产卵量和雌虫寿命的变化情况,并组建了其F1代种群的特定时间生命表。结果表明:经LC10和LC25浓度溴氰虫酰胺胁迫后,F0代白背飞虱单雌产卵量与对照相比差异显著,分别减少了40.41%和41.36%;F1代雌虫比例（Fr）及孵化率（Ha）与对照相比差异不显著,但其繁殖力（Fd）比对照组分别降低了14.41%和16.31%,预测的后代数量（N）及种群增长趋势指数（I）也均低于对照组。经溴氰虫酰胺LC10和LC25浓度处理后,白背飞虱的相对适合度分别为0.78和0.64。根据研究结果推测,在田间施用溴氰虫酰胺防治水稻害虫时,不仅对当代白背飞虱有致死效应,对其后代种群的增长也有一定的抑制作用。     

唑虫酰胺对小菜蛾的亚致死效应研究

为了解唑虫酰胺对小菜蛾实验种群的亚致死效应,为小菜蛾的综合防治提供理论依据,采用浸叶法确定了唑虫酰胺对小菜蛾3龄幼虫的亚致死剂量（ LC30和LC50）,研究其对小菜蛾的生长发育、繁殖及其体内解毒酶的影响。结果表明,经唑虫酰胺亚致死浓度（ LC30和LC50）处理后,小菜蛾幼虫体质量与蛹质量减轻,幼虫历期和蛹期明显延长,成虫寿命缩短,羽化率、单雌产卵量与卵孵化率亦均低于对照,小菜蛾3龄期幼虫体内的酯酶、谷胱甘肽-s-转移酶和多功能氧化酶活性均显著低于对照。亚致死浓度的唑虫酰胺对小菜蛾的种群增长有一定的抑制作用,对小菜蛾体内的酯酶、谷胱甘肽-s-转移酶和多功能氧化酶均有明显的抑制作用。这一结果可为唑虫酰胺的科学应用以及制定小菜蛾综合防治策略提供理论依据。     

Predator–prey size relationship in siphon cropping between the juvenile stone flounder Platichthys bicoloratus and the bivalve Nuttallia olivacea

ABSTRACT:   The purpose of the present paper was to examine the size relationship between the juvenile stone flounder Platichthys bicoloratus and the bivalve Nuttallia olivacea , the siphon of which is important prey for the juvenile flounder. Juvenile stone flounder feed mainly on tips of the inhalant siphon of the bivalve. The maximum width of siphon tips in the stomach contents of age-0 fish could not reach that of age-1 fish, although the siphons in age-0 fish became larger as they grew. This size discrepancy indicated a limitation in the size of bivalves available to juveniles. The proportion of total cropping frequency for the siphon of the bivalve by juveniles was estimated according to the bivalve size class. Most bivalves that had cropped siphon tips ranged from 5 to 30 mm in shell length. The total cropping frequency per bivalve was particularly intense on bivalves of 10–25 mm shell length in spite of their small proportion of 24.9% of the total. This frequency intensity indicated that the size of bivalves with cropped siphons by juvenile stone flounder might depend on the ability of juveniles rather than the size composition of the bivalves.     

溴氰虫酰胺对斜纹夜蛾生长发育及繁殖的亚致死效应

【目的】研究溴氰虫酰胺对斜纹夜蛾Spodoptera litura Fabricius亲代和F1代生长发育和繁殖的影响.【方法】采用浸叶法,确定溴氰虫酰胺对斜纹夜蛾3龄幼虫的的亚致死剂量LC20和LC40,分别用该剂量处理斜纹夜蛾3龄幼虫,观察其对斜纹夜蛾亲代和F1代的亚致死效应.【结果和结论】经溴氰虫酰胺LC20剂量0.04 mg·L-1和LC40剂量0.07 mg·L-1处理斜纹夜蛾3龄初期幼虫72 h,与对照相比,幼虫从3龄到6龄的发育历期分别延长了2.39和4.32 d,化蛹率(分别为78.67%和60.33%)和羽化率(分别为72.12%和61.28%)均显著降低,处理组雌、雄蛹质量均增加.LC40处理组的单雌产卵量(1 356.67粒)和卵孵化率(59.26%)显著低于对照,而LC20处理组的单雌产卵量和孵化率则与对照组差异不显著.药剂处理对蛹历期、成虫历期以及雌性比均没有显著影响.溴氰虫酰胺处理也同样延长了斜纹夜蛾F1代幼虫的发育历期,降低了化蛹率,但对F1代羽化率和单雌产卵量影响不大.研究结果可以为斜纹夜蛾的综合防治以及溴氰虫酰胺的合理使用提供理论依据.     

Effect of ammonia on the electrolyte status of an Indian major carp Catla catla

Ammonia is present in the aquatic environment due to agricultural runoff, sewage effluents and decomposition of biological waste. High level of ammonium in the aquatic environment or in aquaculture farms is a serious problem for aquatic organisms. In the present investigation, the sublethal effects of total ammonia nitrogen (TAN) at 9.98 mg L^?1 on plasma electrolytes (Na⁺, K⁺ and Cl^?) level of Indian major carp Catla catla fingerlings was studied for a period of 35 days under semistatic conditions. Exposure of fish to sublethal concentration of TAN at 9.98 mg L^?1 caused changes in the levels of plasma electrolytes (Na⁺, K⁺ and Cl^?) compared with control fish. No mortality was observed in any group during the treatment period. The present study reveals that the levels of plasma sodium and potassium (except on 7th day) electrolytes were significantly (P < 0.05) decreased throughout the study period. However, the decrease in plasma chloride level was found to be not significant when compared with control group. The present study concludes that the measurements of plasma electrolytes levels can be used as potential biomarkers for monitoring nitrogenous chemicals in aquatic environment.     

Reduced viability of Colorado potato beetle, Leptinotarsa decemlineata, eggs exposed to novaluron

BACKGROUND: Novaluron is a benzoylphenyl urea chitin synthesis inhibitor that combines good activity against larval stages of the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), with low mammalian toxicity. Previous studies suggest that it has deleterious sublethal effects on adults. RESULTS: Continuous exposure of adult Colorado potato beetles to novaluron-treated foliage as both ovipositional and feeding substrate did not affect their survivorship or the number of eggs produced, but viable larvae hatched only from the eggs that were laid on the first day of the experiment. Viability was restored after adult beetles spent 48-96 hours on untreated leaves. In a separate experiment, direct exposure to novaluron of eggs laid by unexposed beetles also reduced the number of larvae hatching. CONCLUSIONS: Results confirm a negative effect of novaluron on the number of progeny produced by the Colorado potato beetle. Direct toxicity did not explain all of the reduction in egg hatch observed, suggesting that novaluron probably acted on reproductive adults as well as on eggs after they were deposited.