Matveev V F, Martinez C C, Frutos S M
Centro de Ecologia Aplicada del Litoral, 3400, Corrientes, Argentina.
Oecologia. 1989 Jun;79(4):489-495. doi: 10.1007/BF00378666.
In a small lake in northern Argentina pelagic water mite Piona sp. had the maximum of population density in January following with a five-day delay after the peak of zooplankton dominant - Daphnia laevis. The mite density was highly predicted by the previous variations of Daphnia density during 4 months of observation (December-March). Daphnia density was a negative delayed function of the predator density but only in December-January when Piona was abundant. During that period Daphnia death rate, d was also correlated with the mite density (r =0.80, P<0.005). In laboratory experiments water mites killed 1-7 Daphnia · predator · hour in a broad range of prey density. Another zooplankton component, Diaphanosoma birgei, was consumed at the same rates. The mite hardly consumed any copepods. In the pelagium during 24 hours the mite was more associated with Daphnia, than with Diaphanosoma, probably, because of the coincidence in photoreactions with Daphnia. Piona contribution to the death rates of its prey estimated by using the data on functional and numerical responses as well as by means of Edmondson-Paloheimo model, could reach 53% for Daphnia and 40% for Diaphanosoma. A computer experiment on the reconstruction of prey dynamics after subtraction of predator influence showed that the mite could have caused a depression in Daphnia numbers observed in the lake, but the declines in Diaphanosoma population were caused by other factors. After the "removal" of mite pressure model Daphnia population increased its average density 10-fold. Experiments on Piona feeding revealed a strong effect of interference among predators. This was eliminated by putting one mite per experimental vessel, which led to a 20-fold increase in predation rate. The effect explains the low feeding rates of Piona obtained by the previous authors who ignored the possibility of interference.
在阿根廷北部的一个小湖中，浮游水螨Piona sp.的种群密度在1月达到最大值，比浮游动物优势种——光滑水蚤的密度峰值晚了5天。在4个月的观察期（12月至3月）内，水螨密度与此前光滑水蚤密度的变化高度相关。光滑水蚤密度是捕食者密度的负延迟函数，但仅在12月至1月Piona数量丰富时如此。在此期间，光滑水蚤的死亡率d也与水螨密度相关（r = 0.80，P<0.005）。在实验室实验中，在广泛的猎物密度范围内，水螨每小时杀死1 - 7只光滑水蚤·捕食者。另一种浮游动物成分——布氏透明溞的被捕食速率相同。水螨几乎不捕食任何桡足类动物。在24小时的水层中，水螨与光滑水蚤的关联度高于与布氏透明溞的关联度，这可能是因为其光反应与光滑水蚤一致。利用功能反应和数量反应数据以及埃德蒙森 - 帕洛海莫模型估算，Piona对其猎物死亡率的贡献，对于光滑水蚤可达53%，对于布氏透明溞可达40%。一项减去捕食者影响后重建猎物动态的计算机实验表明，水螨可能导致了湖中观察到的光滑水蚤数量下降，但布氏透明溞种群数量的下降是由其他因素造成的。在“去除”水螨压力模型后，光滑水蚤种群的平均密度增加了10倍。对Piona摄食的实验揭示了捕食者之间强烈的干扰效应。将每只实验容器放置一只水螨可消除这种干扰，这导致捕食率提高了20倍。这种效应解释了之前忽视干扰可能性的作者所得到的Piona较低摄食率。
