Ishida M, Kawano F, Umeda N, Hirazawa N
Marine Biological Technology Center, Nippon Suisan Kaisha, Ltd, Saeki, Oita 876-1204, Japan.
Parasitology. 2007 Nov;134(Pt 12):1823-30. doi: 10.1017/S0031182007003149. Epub 2007 Jun 29.
Neobenedenia girellae, a capsalid monogenean, is a significant pathogen due to both its ability to cause high mortality in fishes and its low host specificity. Established control methods have both advantages and disadvantages. Biological control measures with no unfavourable effects on the environment should be incorporated into the control strategy. The response of N. girellae oncomiracidia to brightness and black-and-white contrast was investigated to search for an alternative approach of disease prevention or control. Japanese flounder, Paralichthys olivaceus (Paralichthyidae), were exposed to oncomiracidia in an aquarium divided into areas of different brightness ( approximately 1.3, 41.3 and 138.0 lux). The number of parasites on the fish group reared in 138.0 lux was significantly higher than on those reared in the lower brightness levels. Thus, the fish tended to be more vulnerable to infection by N. girellae under brighter conditions. Challenge trials using host fish mucus and whole live fish were established to detect the response by oncomiracidia to black-and-white contrast on a white versus a black background. Markedly more N. girellae oncomiracidia attached to black-painted areas and dark-coloured fish (normal spotted halibut, Verasper variegatus (Pleuronectidae) compared with white-painted areas and light-coloured fish (mal-coloured V. variegatus) on a white-coloured background. On a black-coloured background, more N. girellae oncomiracidia tended to attach to white-painted areas and light-coloured fish. Thus, black-and-white contrast is considered important for host finding by N. girellae oncomiracidia. The simplicity of the positive phototactic behaviour and the response to black-and-white contrast may lead to the development of a simple, practical and inexpensive method to control N. girellae outbreaks.
吉氏新贝尼登虫（Neobenedenia girellae）是一种锚首科单殖吸虫，因其能够导致鱼类高死亡率且宿主特异性低，而成为一种重要的病原体。已有的控制方法都各有优缺点。应将对环境无不利影响的生物控制措施纳入控制策略中。为寻找疾病预防或控制的替代方法，研究了吉氏新贝尼登虫的幼虫对亮度和黑白对比度的反应。将牙鲆（Paralichthys olivaceus，牙鲆科）置于一个分为不同亮度区域（约1.3、41.3和138.0勒克斯）的水族箱中，使其接触幼虫。饲养在138.0勒克斯环境中的鱼群身上的寄生虫数量显著高于饲养在较低亮度环境中的鱼群。因此，在较明亮的条件下，鱼更容易受到吉氏新贝尼登虫的感染。开展了使用宿主鱼黏液和整条活鱼的攻毒试验，以检测幼虫对白色与黑色背景上黑白对比度的反应。在白色背景上，附着在黑色涂漆区域和深色鱼（正常斑纹庸鲽，Verasper variegatus，鲽科）上的吉氏新贝尼登虫幼虫明显多于附着在白色涂漆区域和浅色鱼（变色庸鲽）上的幼虫。在黑色背景上，更多的吉氏新贝尼登虫幼虫倾向于附着在白色涂漆区域和浅色鱼上。因此，黑白对比度被认为对吉氏新贝尼登虫幼虫寻找宿主很重要。正向趋光行为的简单性以及对黑白对比度的反应可能会促成一种简单、实用且廉价的控制吉氏新贝尼登虫暴发的方法的开发。
