EXPERIMENTAL-EVIDENCE FOR AGGREGATION OF SALMON LOUSE COPEPODIDS (LEPEOPHTHEIRUS-SALMONIS) IN STEP SALINITY GRADIENTS
EXPERIMENTAL-EVIDENCE FOR AGGREGATION OF SALMON LOUSE COPEPODIDS (LEPEOPHTHEIRUS-SALMONIS) IN STEP SALINITY GRADIENTS
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DOI：
10.1017/s002531540003825x
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发表时间：
1995-11-01
影响因子：
1.2
通讯作者：
HEUCH, PA
中科院分区：
文献类型：
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作者：
HEUCH, PA
桡足类Lepeophtheirus salmonis Kroyer（桡足目：Caligida），鲑鱼虱，是鲑科寄生虫。研究了感染阶段桡足动物在盐度梯度中的垂直分布，在l-m有机玻璃柱中，盐度梯度逐级增加15‰（30.4‰以上为15.4‰），5‰（30.4‰以上为25.4‰）和2‰（30.4‰以上为28.4‰）。还记录到桡足类呈线性梯度分布，盐度从0厘米深度的15.4‰增加到87.5厘米深度的30.4‰。均匀的30.4份/千的盐度柱作为对照。在这些实验中，动物们在1小时的光照下聚集在水柱的顶部，在4小时的黑暗中向下扩散。在含盐量随深度增加而增加千分之十五的石柱中，桡足类不顾光照条件，聚集在断裂带下面。在5‰和2‰S的阶跃盐度梯度下，两种光照条件下，与对照相比，阶跃区动物数量显著增加。在线性梯度中，当受到Ih的光照时，大量的桡足类动物在大约20‰的盐度下积累。在黑暗中，没有明显的聚集。在所有线性梯度实验中，桡足类的盐度为15-17.2‰。这些结果表明，海洋中的鲑鱼虱桡足类聚集在阶梯盐度梯度附近。在某种程度上，鲑鱼虱的宿主利用化学信息来寻找猎物，它们会在密度梯度强的地方花更长的时间，在那里可以找到水生气味的痕迹，而不是在任何同样大的深度间隔，弱分层。因此，桡足类对阶梯式盐度梯度的反应可能会增加宿主-寄生虫相遇的频率。
The copepod Lepeophtheirus salmonis Kroyer (Copepoda: Caligida), the salmon louse, is a parasite of salmonids. The vertical distribution of the infective stage, the copepodid, was studied in salinity gradients with one step increase of 15 parts per thousand (15.4 parts per thousand on top of 30.4 parts per thousand), 5 parts per thousand (25.4 parts per thousand on top of 30.4 parts per thousand) and 2 parts per thousand (28.4 parts per thousand on top of 30.4 parts per thousand) in l-m perspex columns. Copepodid distribution in a linear gradient, where the salinity increased from 15.4 parts per thousand at 0 cm depth to 30.4 parts per thousand at 87.5 cm, was also recorded. Homogeneous 30.4 parts per thousand salinity columns served as the control. In these, the animals gathered in the top section of the water column in response to 1 h of light from above, and spread downwards in response to 4 h of darkness. In columns with a 15 parts per thousand step increase in salinity with depth, copepodids aggregated just underneath the discontinuity irrespective of light conditions. In step salinity gradients of 5 parts per thousand and 2 parts per thousand S, under both light regimes, animals were significantly more numerous in the step sections compared with the control. In the linear gradient, significant numbers of copepodids accumulated at approximately 20 parts per thousand salinity when subjected to Ih of light. In the dark, there were no significant aggregations. Copepodids were found in 15-17.2 parts per thousand salinity in all linear gradient experiments.These results suggest that salmon louse copepodids in the sea aggregate in the vicinity of step salinity gradients. To the extent that salmon louse hosts use chemical information to find prey, they will spend a larger fraction of time inside strong density gradients, where aquatic odour trails are found, than at any equally large depth interval with weak stratification. Consequently, copepodid reactions to step salinity gradients may increase the frequency of host-parasite encounters.