264 Alexandrium tamarense 塔瑪亞歷山大藻 Phylum: Dinoflagellata 门：甲藻門 Class: Dinophyceae 纲：甲藻綱 Order: Gonyaulacales 目：裸甲藻目 Family: Pyrocystaceae 科：梨甲藻科 Morphology The cell occurs solitarily or in pairs, and less commonly in fours. Cells are solitary or occur in pairs, or occasionally form short chains. Theca is thin and smooth. Cells are roughly spherical or hexagonal with nearly equal length and width. The epicone and hypocone are nearly equal in size. The epicone is broadly conical while the hypocone is trapezoidal and slightly concave posteriorly. The left side of hypocone is often longer than the right. The cingulum with narrow lists is median, deeply excavated, descending, and displaced about one time cingular widths. The sulcus with prominent sulcal lists is deeply excavated and widens posteriorly. 形態 細胞單獨生活或成對存在，也可以形成四個細胞的短鏈。甲板較薄，平滑。細胞近 球形或六邊形，長度和寬度相當或稍長於寬度。上殼和下殼大小相當。上殼呈較寬 的錐形，下殼為梯形，底部略凹陷。下殼左側常長於右側。橫溝具窄翼，位於細胞 中間，凹陷較深，下行位移寬度和橫溝寬度相當。縱溝較深，向底部逐漸變寬。 Ecology and distribution Alexandrium tamarense is a widely distributed planktonic species in coastal and estuarine waters. It is a well-known species with capability to form blooms and produce paralytic shellfish poison (PSP). In Hong Kong coastal waters, Alexandrium tamarense formed one bloom together with Noctiluca scintillans in 1991 and 1993, respectively.
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