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棕囊藻(Phaeocystis)在全球海域广泛分布,可以引起大规模的有害藻华,导致严重的自然灾害及经济损失.棕囊藻具有复杂的异型生活史,游离的单细胞和囊体两种形态交替出现,但是关于生活史转换调控机制的研究非常有限.本文通过研究不同的浮游动物释放的化学信息对球形棕囊藻生长和囊体形成的影响,力图从摄食防御的角度理解和阐明棕囊藻生活史的转换机制.研究表明,当球形棕囊藻与安氏伪镖水蚤的化学信息接触后,游动单细胞数量减少,囊体数量和直径显著提高;与游仆虫的化学信息接触后,游动单细胞数量增多,但囊体直径和数量显著降低.不同浮游动物释放的化学信息可能诱导球形棕囊藻采取不同的防御策略:较大囊体的形成以阻碍较大粒径桡足类的摄食,而应对较小粒径的纤毛虫,形成较小的囊体即足以抵御摄食.棕囊藻对不同摄食者采取特异性防御策略,有效减少摄食死亡率,有助于形成藻华,从而影响海洋食物链结构和功能.“,”The genus Phaeocystis has been observed to form extensive blooms in the coast water throughout the world, and led to serious natural disasters and economic damage. Phaeocystis has a complex polymorphic life cycle that involves both solitary cells and colony forms. To understand the mechanisms controlling the life cycle of Phaeocystis, we conducted experiments to investigate the responses of growth and colony development to chemical cues released from grazing ciliate and copepod. Exposure to chemical cues derived from copepod Pseudodiaptomus annandalei resulted in the reduced solitary cells abundance, increased colony abundance and colonial diameter significantly. In the presence of chemical cues derived from Eupoltes sp, globosa showed increased solitary cell abundance, decreased colony abundance and size. When confront with chemical cues released by different grazers, different defense strategies can be employed by P. globosa. Larger colony can escape from the grazing by the copepod, and smaller colony can protect colonial cells against ciliate. The induced-defense in Phaeocystis reduced mortality and facilitated the occurrence of bloom, which may significantly affect the structure and function of marine food chain.