Franceschini M C, de Wysiecki M L, Poi A
Centro de Ecología Aplicada del Litoral-CECOAL (CCT Nordeste-CONICET-UNNE), Ruta 5, km 2.5, 3400, Corrientes, Argentina.
Neotrop Entomol. 2013 Aug;42(4):344-50. doi: 10.1007/s13744-013-0130-8. Epub 2013 Apr 19.
We aimed to evaluate the variation in the age structure of Cornops aquaticum (Bruner) population and its relation to the host plant biomass and the feeding of the different age classes of this grasshopper on the water hyacinth Eichhornia crassipes along 2 years, in a Paraná River floodplain lake (Chaco, Argentina). Individuals of C. aquaticum were captured with a 70-cm diameter sweep and separated in nymphs A (instars I and II), nymphs B (instars III to VI), adult females, and adult males; host plant biomass was sampled using a ring with a 0.30-m(2) diameter. Relative daily feeding of C. aquaticum population was calculated by multiplying the number of individuals captured per minute by the daily consumption by individual obtained in each age classes. We found that the age structure and the relative daily feeding of C. aquaticum varied between seasons and years. The highest values of grasshopper abundance, leaf biomass, and relative daily feeding of C. aquaticum population were observed in summer 2006. Plant biomass was directly correlated with nymph abundance and not correlated with adult abundance. Plant biomass available as refuge (leaves), food (laminas), and oviposition site (petioles) to C. aquaticum represented up to 62% of the total plant biomass. The results obtained in C. aquaticum show the importance of considering total plant biomass and plant biomass available for herbivores separately. Our study highlights the need to find an adequate method to estimate the density of C. aquaticum and other semiaquatic grasshoppers in the Paraná River floodplain involving different seasons, years, and water phases (rising and falling).
我们旨在评估阿根廷巴拉那河河漫滩湖泊（查科地区）中，连续两年内水栖玉米蝗（布鲁纳）种群年龄结构的变化及其与寄主植物生物量的关系，以及该蝗虫不同年龄段对凤眼莲的取食情况。用水栖玉米蝗个体的捕获直径为70厘米的扫网进行捕获，并将其分为若虫A（一龄和二龄）、若虫B（三龄至六龄）、成年雌性和成年雄性；寄主植物生物量采用直径为0.30平方米的环进行采样。水栖玉米蝗种群的相对日取食量通过将每分钟捕获的个体数量乘以每个年龄段个体的日消耗量来计算。我们发现，水栖玉米蝗的年龄结构和相对日取食量在季节和年份之间存在差异。2006年夏季观察到蝗虫丰度、叶片生物量和水栖玉米蝗种群相对日取食量的最高值。植物生物量与若虫丰度直接相关，与成虫丰度无关。可供水栖玉米蝗作为避难所（叶片）、食物（叶片）和产卵场所（叶柄）的植物生物量占植物总生物量的比例高达62%。在水栖玉米蝗中获得的结果表明，分别考虑植物总生物量和可供食草动物利用的植物生物量非常重要。我们的研究强调，需要找到一种合适的方法来估计巴拉那河河漫滩不同季节、年份和水期（涨水期和落水期）中水栖玉米蝗及其他半水生蝗虫的密度。
