Forming a tough shell via an intracellular matrix and cellular junctions in the tail epidermis of Oikopleura dioica (Chordata: Tunicata: Appendicularia)
Forming a tough shell via an intracellular matrix and cellular junctions in the tail epidermis of Oikopleura dioica (Chordata: Tunicata: Appendicularia)
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DOI：
10.1007/s00114-011-0815-y
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发表时间：
2011-08-01
影响因子：
--
通讯作者：
Hirose, Euichi
中科院分区：
文献类型：
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作者：
Nakashima, Keisuke;Nishino, Atsuo;Hirose, Euichi
后尾是脊索动物门的主要突触形态，由脊椎动物亚门、头索动物亚门和脊索动物亚门(尾索动物)组成。在被囊动物中，附肢动物是唯一在成虫身上保留尾巴的类群，成虫的尾巴与以纤维素为基础的房屋结构结合在一起，起着运动和取食的作用。鉴于被毛类的系统发育地位，附肢类成体尾巴可能具有脊索状尾巴的祖先特征。我们对附肢动物Oikopleura dioica尾部表皮的超微结构发育进行了研究。幼虫尾部的表皮被幼虫的包膜包裹，幼虫的包膜是一层薄片，类似于海囊幼虫的外被膜层。成虫尾部的表皮似乎没有类似被膜的纤维性珠被，尾鳍是表皮的简单折叠。除了尾鳍边缘的三角形细胞外，所有的表皮细胞在顶端细胞质中都有一层明显的纤维性基质层，没有包膜。幼虫尾部的表皮没有纤维基质层，表明该层是在幼虫发育和变态过程中产生的。粘附带将成虫尾部的表皮细胞牢牢地结合在一起，排列在细胞边缘的致密微丝构成了细胞膜的机械支撑。细胞内基质、细胞连接和细胞骨架可能使尾部表皮成为坚韧、柔韧的外壳，支持罗非鱼成体尾巴的主动跳动。
A postanal tail is a major synapomorphy of the phylum Chordata, which is composed of three subphyla: Vertebrata, Cephalochordata, and Tunicata (Urochordata). Among tunicates, appendicularians are the only group that retains the tail in the adult, and the adult tail functions in locomotion and feeding in combination with a cellulose-based house structure. Given the phylogenetic position of tunicates, the appendicularian adult tail may possess ancestral features of the chordate tail. We assess the ultrastructural development of the tail epidermis of the appendicularian Oikopleura dioica. The epidermis of the larval tail is enclosed by the larval envelope, which is a thin sheet similar to the outer tunic layer of ascidian larvae. The epidermis of the adult tail seems to bear no tunic-like cellulosic integuments, and the tail fin is a simple folding of the epidermis. Every epidermal cell, except for the triangular cells at the edge of the tail fin, has a conspicuous matrix layer of fibrous content in the apical cytoplasm without enclosing membranes. The epidermis of the larval tail does not have a fibrous matrix layer, suggesting the production of the layer during larval development and metamorphosis. Zonulae adhaerentes firmly bind the epidermal cells of the adult tail to one another, and the dense microfilaments lining the cell borders constitute a mechanical support for the cell membranes. The intracellular matrix, cell junctions, and cytoskeletons probably make the tail epidermis a tough, flexible shell supporting the active beating of the oikopleuran adult tail.