Interrelationship between red-tide flagellates and zooplankton

1.通过对日本近海15种赤潮鞭毛虫的摄食率、死亡率和产卵率的测定，研究了近岸海洋桡足类Pseudodiaptomus marinus和Acartia omorii与15种赤潮鞭毛虫之间的摄食相互作用。在鞭毛虫中，一种长裸甲藻和4种藻类植物--黄氏裸藻、赤潮异弯藻、滨海查通氏菌和日本纤毛藻几乎完全被桡足类排斥。研究发现，抑制桡足类摄食的威慑性化合物存在于细胞内。这些化合物是短暂的，在20ﾟC下12小时内失活。桡足类的化学排斥是单特异性赤潮形成的重要因素。利用摄像系统观察了中华哲水蚤摄食赤潮鞭毛虫的行为。该物种倾向于摄食被前两种桡足类拒绝的鞭毛虫，这表明拒绝的程度因食草动物物种而异。对野外采集的尺足类幼虫的肠道内容物进行了详细的检测，结果表明它们摄食了多种浮游植物。然而，人们注意到，某些浮游植物群不被一些桡足类摄食，这表明自然界中存在摄食排斥现象。

1. Feeding interactions between inshore marine copepods Pseudodiaptomus marinus and Acartia omorii, and 15 red-tide flagellates from Japanese coastal waters were studied by examining egestion rate, mortality and egg production rate of the copepods offered a suspension of each phytoplankton species. Among flagellates, a dinoflagellate Gymnodinium nagasakiense, and four raphidophytes Olisthodiscus luteus, Heterosigma akashiwo, Chattonella marina and Fibrocapsa japonica were almost entirely rejected by the copepods. It was found that the deterrent chemical compounds which inhibit feeding of copepods were intracellularly present. These compounds were ephemeral, being deactivated within 12 h at 20ﾟC. Chemically-mediated rejection by copepods is an important factor in the development of monospecific red tides.2. Behavior of a copepod Calanus sinicus feeding on red-tide flagellates was examined using a video system. This species tended to ingest the flagellates which were rejected by the former two copepods, indicating the degree of rejection varies with grazer species.3. Gut content of field-collected calanoid copepods was examined in detail, and showed a variety of phytoplankters were ingested by them. However, it was noted certain phytoplankton groups were not ingested by some copepods, indicating feeding rejection occurs in nature.