109 Coscinodiscus 圓篩藻 Phylum: Heterokontophyta 门：不等鞭毛門 Class: Coscinodiscophyceae 纲：中心硅藻綱 Order: Coscinodiscales 目：圓篩藻目 Family: Coscinodiscaceae 科：圓篩藻科 Morphology Coscinodiscus species are generally solitary. The length of pervalvar axis varies, and cells are discoid or cylindrical with different heights. Some species are wedge-shaped in girdle view. Valves of most species are circular, while some species possess elliptical, kidneylike or irregular valves. Valves are flat, convex or concave with hexagonal areolae on the surface and a ring of rimoportula on the margin. Diameters range from 30 to more than 500 μm. Some species possess several large and long areolae arranged in a rose like manner in the center, known as the central rosette. Some species possess central hyaline area on the valve. Chloroplasts are small and numerous, generally. According to AlgaeBase, there are 219 species in total, which are identified mainly based on general morphology, size, areolae size and arrangements. 形態 本屬物種基本單獨生活。貫殼軸長短不一，細胞呈盤狀，或高度不一的圓柱形。有 些物種殼環面觀呈楔形。細胞殼面大多為圓形，個別為橢圓形，腎形或者不規則的 形狀。殼面扁平、隆起或者下凹，具六角形篩室，邊緣有一圈唇形突。直徑從30 微米到500微米以上。部分物種殼面正中心的篩室特別較大較長，似玫瑰狀排列， 稱為中央玫瑰區。部分物種中央具無紋區。色素體小而多。AlgaeBase 記錄本屬219 個物種。不同物種的鑒定主要依據外形、粒徑、篩室大小及排列方式。 Ecology and distribution Coscinodiscus species are planktonic and cosmopolitan globally. They could be found
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