Absence of typical diel vertical migration in Daphnia:: varying role of water clarity, food, and dissolved oxygen in Lake Eymir, Turkey
Absence of typical diel vertical migration in Daphnia:: varying role of water clarity, food, and dissolved oxygen in Lake Eymir, Turkey
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DOI：
10.1007/s10750-004-2789-7
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发表时间：
2005-03-15
期刊：
影响因子：
2.6
通讯作者：
Beklioglu, M
中科院分区：
文献类型：
--
作者：
Muluk, CB;Beklioglu, M
Diel垂直迁移（DVM）是一种复杂的、动态的捕食行为，因为迁移生物对光照强度的反应起主要作用，但受其他因素的影响。在相对较浅但热分层的Eyrnir湖，水蚤在白天和夜晚都利用了低阴离子提供的垂直避难所。对鱼类捕食的总体脆弱性的差异决定了不同种群类别的平均居住深度（MRDs）的差异，如最显眼和最脆弱的成虫卵居住在最深的深度，而幼虫则停留在温跃层附近。在春末，记录到低阴离子内的剧烈位移，可能是由于低阴离子对鱼类来说光线充足，氧气相对充足，对大型水蚤来说相当不安全。因此，大型水蚤白天的避难所接近底部，而在夜间，它们向上移动，以受益于温暖的水温以及存在鱼类捕食的食物供应，但仍然处于温跃层以下。在夏季，低运动的振幅不明显，后来变为渐动，位移可能是由于在温跃层下发现的接近缺氧的情况。这可能阻止了鱼类，从而为水蚤提供了一个更安全的避难所，在下面的温跃层中，后来变成了上面的温跃层。低氧可用性被认为是夏季的近似因素。温跃层上下丰富的食物和温暖的水条件也解释了夏季DVM的缺失。因此，本研究表明水蚤的DVM是一种适应环境条件变化的可塑性适应。
Diel vertical migration (DVM) is a complex and dynamic behaviour against predation because the reaction of migrating organisms to light intensity plays a primary role, but is modified by other factors. In the relatively shallow but thermally stratified Lake Eyrnir, Daphnia pulex de Geers utilized vertical refugia afforded by the hypolimnion during both day and night. Differences in general vulnerability to fish predation determined the differences in their mean residence depths (MRDs) of different population categories such as most conspicuous and vulnerable individuals of adult with eggs inhabited the deepest depth, whereas juveniles stayed close the thermocline. In late spring, profoundly high amplitude of displacement within the hypolimnion, probably due to the hypolimnion being well-lit and relatively well-oxygenated for the fish and rather unsafe for the large-sized daphnids, was recorded. Therefore, the large-sized daphnids daytime refuge was close to the bottom whereas at night they moved upward to benefit from warmer water temperature along with food availability in the presence of fish predation but still remained below the thermocline. In summer, the insignificant amplitude of the hypolimnetic, which later became epilimnetic, displacements were probably due to the near-anoxic condition found below the thermocline. This might have deterred the fish, thus providing a safer refuge for daphnids in the below thermocline, which afterwards became the above thermocline. Low oxygen availability was regarded as the summer proximate factor. The abundant food and warmer water conditions found in the below/above thermocline also accounted for absence of DVM in summer. Consequently, this study suggests that DVM by Daphnia is an adaptation that is plastic to changing environmental conditions.