100 Phaeodactylum tricornutum 三角褐指藻 Phylum: Heterokontophyta 门：不等鞭毛門 Class: Bacillariophyceae incertae sedis 纲：硅藻未定綱 Order: Bacillariophyceae ordo incertae sedis 目：硅藻未定目 Family: Phaeodactylaceae 科：褐指藻科 Morphology Phaeodactylum tricornutum which is the only species in Family Phaeodactylaceae is an atypical diatom. Unlike other diatoms, P. tricornutum can display different morphotypes (oval, fusiform and triradiate) and changes morphology in different environmental conditions. P. tricornutum could gorw in the absence of silicon. Oval cells possess only one roughly semilunate silicified valve and the other is absent. Fusiform cells display poorly silicified frustules which are slightly wider in the center and gradually narrow towards both ends. The center of the triradiate cell is thick, and the branches possess roughly rounded ends. The cell walls of triradiate form are thin with most cells lacking or weakly silicified. 形態 三角褐指藻是褐指藻科唯一的一個物種，是一種非典型的硅藻。和其他硅藻不同， 三角褐指藻可以呈現出卵形、梭形和三叉形三種不同的形態。這三種形態在不同環 境下可以轉變。三角褐指藻可以在沒有硅的條件下生長。卵形細胞細胞壁僅具一個 近半月形的硅質殼面，另一個殼面缺失。梭形細胞細胞壁硅質化較弱，中央略寬， 向兩端逐漸收窄。三叉形細胞中央較厚，臂的末端較圓。細胞壁較薄，多數沒有硅 質或硅質化較弱。 Ecology and distribution Phaeodactylum tricornutum is a frequently observed intertidal benthic species. Cells could also be planktonic.
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