Effects of predator-induced visual and olfactory cues on 0+ perch (Perca fluviatilis L.) foraging behaviour

Abstract –  Foraging juvenile fish with relatively high food demands are usually vulnerable to various aquatic and avian predators. To compromise between foraging and antipredator activity, they need exact and reliable information about current predation risk. Among direct predator-induced cues, visual and olfactory signals are considered to be most important. Food intake rates and prey-size selectivity of laboratory-reared, naive young-of-the-year (YOY) perch, Perca fluviatilis , were studied in experiments with Daphnia magna of two size classes: 2.8 and 1.3 mm as prey and northern pike, Esox lucius , as predator. Neither total intake rate nor prey-size selectivity was modified by predator kairomones alone (water from an aquarium with a pike was pumped into the test aquaria) under daylight conditions. Visual presentation of pike reduced total food intake by perch. This effect was significantly more pronounced (synergistic) when visual and olfactory cues were presented simultaneously to foraging perch. Moreover, the combination of cues caused a significant shift in prey-size selection, expressed as a reduced proportion of large prey in the diet. Our observations demonstrate that predator-induced olfactory cues alone are less important modifiers of the feeding behaviour of naive YOY perch than visual cues under daylight conditions. However, pike odour acts as a modulatory stimulus enhancing the effects of visual cues, which trigger an innate response in perch.     

利它素对中华通草蛉不同龄期幼虫捕食行为的影响

本文测定了棉蚜及棉花嫩梢不同溶剂提取液对中华通草蛉捕食行为的影响。结果表明，棉花受害嫩梢及未受害嫩梢提取液对中华通草蛉幼虫捕食行为无明显影响；棉蚜虫体浆液、棉蚜水提液，均含有很强的利它素活性物质，而棉蚜无水乙醇提取液利它素活性物质含量甚微，中华通草蛉各龄幼虫对棉蚜水提液均表现有明显的滞留和调转行为。     

Sea lamprey avoid areas scented with conspecific tissue extract in Michigan streams

Three in‐stream experiments were conducted to determine whether sea lamprey, Petromyzon marinus L., tissue extract (alarm cue) and 2‐phenylethylamine hydrochloride (PEA HCl, a putative predator cue) influenced the distribution of migrating adult sea lamprey. Experiments evaluated sea lamprey movement when an odour was applied to (1) a tributary of a larger stream; and (2) half of a stream channel. Fewer sea lamprey entered the tributary and side of the river scented with sea lamprey tissue extract compared to the control treatment. Sea lamprey did not avoid the tributary and side of the river scented with PEA HCl. A final laboratory experiment found no difference in the avoidance response of sea lamprey to PEA HCl mixed with river water vs PEA HCl mixed with water from Lake Huron. As such, the lack of sea lamprey response to PEA HCl in the stream was unlikely to have been caused by the presence of the river water. Rather, the difference between laboratory and field results may be attributed to the complexity of the physical environment.     

Differential response of male and female Diabrotica speciosa (Coleoptera: Chrysomelidae) to bitter cucurbit-based toxic baits in relation to the treated area size

Cucurbitacin-rich extracts are phagostimulants for both male and female Luperini, but field trials reveal that males are far more attracted to them than females. The sex ratio and number of beetles killed by an application of cucurbitacin-based toxic baits was assessed at two different scales: small areas of 100 m², and a larger area of 10,000 m². The small area bait applications killed mostly males (95.2%), but the 1-ha treated plot showed a lower sexual bias (57% male). An earlier study indicated point sources (sticky traps) attracted only males. Results indicate that the distance attraction to bitter cucurbit extracts is almost exclusive to males, but the wide dispersal of a toxic bait based on them should promote encounter and control of both sexes within the treated area. No significant non-target effects were observed.     

四种赤眼蜂对米蛾利他素的嗅觉反应

在实验室条件下用四臂嗅觉仪分别测定了卷蛾分索赤眼蜂Trichogrammatoidea bactrae、拟澳洲赤眼蜂Trichogramma confusum、微突赤眼蜂T.raoi、舟蛾赤眼蜂T.closlerae对来源于米蛾Corcyra cephalomica卵、米蛾卵浸提液、米蛾腹部鳞片浸提液的利他素的嗅觉反应．结果表明，这4种赤眼蜂对米蛾利他素有明显的趋向反应，表现为600s内，赤眼蜂在处理区的滞留时间比对照区的滞留时间明显延长，二者之间差异显著．     

拟澳洲赤眼蜂对小菜蛾腹部鳞片和卵表十三种饱和烷烃的接触反应

为了解小菜蛾利他素对拟澳洲赤眼蜂搜索行为及寄生率的影响,在室内条件下测定了拟澳洲赤眼蜂对小菜蛾卵表和腹部鳞片13种饱和烷烃单一成分的接触反应。结果表明,在正十六烷处理卵卡上,拟澳洲赤眼蜂的活动指数(PAI)最大,为79.67;其次为正三十六烷,PAI为67.50;正二十二烷PAI最低,仅为3.00。拟澳洲赤眼蜂对正三十六烷处理卵卡的寄生总数最高,为183.17;其次为正十六烷,寄生总数为153.00;正二十二烷处理卵卡的寄生总数最低,仅为0.67。拟澳洲赤眼蜂最大寄生率在20%以上的有正十六烷、正十七烷、正二十五烷、正二十七烷、正二十八烷和正三十六烷处理;最大寄生率在5%以下的为正二十二烷处理。     

The Potential of Semiochemicals for Control of Phorodon humuli (Homoptera: Aphididae)

Field experiments employing yellow water-traps with vials releasing methyl salicylate, butyl isothiocyanate, 4-pentenyl isothiocyanate and diethyltoluamide were conducted during the spring migration of Phorodon humuli (Schrank), with the aim of identifying substances which might be used in the field to deter landing on hop plants. Methyl salicylate and the two isothiocyanates reduced trap catches of P. humuli. During the spring of 1994 a slow-release formulation of methyl salicylate and a β-acid-rich hop resin sprayed on to hop plants did not reduce aphid infestations significantly. In autumn cis,cis-nepetalactol, the main component of P. ‘humuli’s sex pheromone, prepared by various synthetic routes, increased trap catches of males and gynoparae equally. Catches of males in pheromone traps situated in a hop garden decreased with increasing trap height. Catches of males in traps charged with increasing doses of the cis,cis-nepetalactol peaked at 1 mg and then plateaued, whereas catches of gynoparae peaked similarly at 1 mg and then decreased. The effects of kairomones from an extract of the primary host, sex pheromone and a visual cue from yellow compared with clear water-traps were additive. The prospects for developing a semiochemicals-based control strategy against P. humuli, using some or all of the above elements, are discussed.