239 Chapter 3. Dinoflagellates 第三章 甲藻 Most dinoflagellates are motile and solitary, with some species capable of forming chains. They typically have a large nucleus and two flagella, ranging in size from 5 to 2000 μm. Dinoflagellates exhibit morphological diversity, with most species being spherical or elliptical in shape and showing a clear distinction between dorsal and ventral views. These organisms are classified into two main groups based on their cell surface structure: athecate dinoflagellates and thecate dinoflagellates, the latter possessing cellulose plates that form a protective armor known as theca or lorica. Morphologically, dinoflagellates are further categorized into desmokont and dinokont groups. Desmokont dinoflagellate cells are bilaterally symmetrical, with two flagella emerging anteriorly, while dinokont dinoflagellate cells feature surface grooves. The cell is divided by a transverse groove called the cingulum into an epicone and a hypocone, with a longitudinal groove known as the sulcus connecting to the cingulum and located in the hypotheca. The flagella responsible for forward propulsion and movement control are situated within these grooves: the transverse flagellum in the cingulum and the longitudinal flagellum in the sulcus. 甲藻大多為遊動的單細胞生物，也有部分物種可以成鏈。 甲藻細胞核較大，具有 兩條鞭毛，粒徑介於5微米到2毫米之間。 甲藻的形態多樣，多數呈球形、橢圓形， 有背腹之分。 基於細胞壁的結構，甲藻可以分為兩類：無甲板類甲藻和具有纖維 素甲板構成的盔甲（鞘）的有甲板類甲藻。 基於形態，甲藻也可以分為兩類：縱 裂甲藻和橫裂甲藻。 縱列甲藻細胞兩側對稱，兩根鞭毛從細胞前端伸出。 橫裂甲 藻細胞表面具溝狀結構。 一條橫向的溝貫穿整個細胞，將細胞分為上殼和下殼兩 部分。 一條縱向的溝（縱溝）與橫溝相連，位於下殼。 兩根提供前進和轉向動力 的鞭毛位於溝內，橫鞭毛位於橫溝內，縱鞭毛位於縱溝內。 Currently nearly 3000 dinoflagellate species have been recorded. Differentiation between different species is mainly based on: 1, position and morphology of cingulum and sulcus; 2, shape, number, and arrangement of plates; 3, presence/absence, size, shape, and
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