285 Prorocentrum gracile 纖細原甲藻 Phylum: Dinoflagellata 门：甲藻門 Class: Dinophyceae 纲：甲藻綱 Order: Prorocentrales 目：原甲藻目 Family: Prorocentraceae 科：原甲藻科 Morphology Cells are solitary, asymmetrically lanceolate, with rounded anterior end and pointed antapex. Cells are slightly convex anteriorly and have 2 apical spines anteriorly. One apical spine is relatively long, robust, and winged, while another is small and almost invisible. The dorsal part is smoothly convex while the ventral part is concave in the opposite position. Cell length is about twice of the width generally. 形態 細胞獨立生活，呈不對稱的披針形，前端圓鈍，後端尖細。頂端輕微下凹，具兩根 頂刺。其中一根頂刺較長，粗壯，具翼，另一根幾乎不可見。背面平緩的隆起，腹 面相對的位置內凹。細胞長度約為寬度的兩倍。 Ecology and distribution Prorocentrum gracile is principally a neritic and estuarine cosmopolitan species widely distributed in cold temperate to tropical waters. It is a bloom forming species, which is remarkably frequently observed in Hong Kong coastal waters. According to Hong Kong Red Tide Database from AFCD (Agriculture, Fisheries and Conservation Department, Hong Kong), Prorocentrum gracile has caused 12 blooms in Hong Kong coastal waters since 1980. 生態與分佈
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