CYTOPLASMIC FILAMENTS AND MORPHOGENESIS - ROLE OF NOTOCHORD IN ASCIDIAN METAMORPHOSIS
CYTOPLASMIC FILAMENTS AND MORPHOGENESIS - ROLE OF NOTOCHORD IN ASCIDIAN METAMORPHOSIS
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DOI：
10.1007/bf00343819
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发表时间：
1969-01-01
期刊：
影响因子：
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通讯作者：
CLONEY, RA
中科院分区：
文献类型：
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作者：
CLONEY, RA
绒毛螺脊索是由鳞状上皮样细胞和被丝状鞘包围的基质物质组成的管状结构。它在幼虫尾部起骨架的作用。在尾巴的吸收过程中，脊索细胞变短、游离并随基质移动，通过脊索鞘前端新形成的裂口进入躯干体腔。当脊索细胞变短时，它们的基底表面产生褶皱。这些褶皱在脊索鞘中突出成互补的褶皱。褶皱的形成与基面质膜下厚层细胞质丝的出现有关。这些细丝大多在缩短轴上定向。提出了一种新的假说来解释该物种的尾巴吸收：脊索细胞是可收缩的，并主动压缩脊索鞘。肌肉细胞、神经索、内胚层链和表皮随着骨骼的丧失而塌陷，并受到脊索的压迫。在尾吸收过程中，脊索的功能被认为类似于复合海鞘、西方海鞘和macdonaldi的收缩表皮的功能。这些海鞘的收缩性表皮细胞所具有的有向丝和顶端突出特征，在绒毛boltenia的表皮中没有发现。
The notochord ofBoltenia villosais a tubular structure composed of squamous epithelioid cells and matrix material surrounded by a filamentous sheath. It acts asa skeleton in the larval tail. During resorption of the tail the notochordal cells shorten, dissociate and move along with the matrix through a newly formed breach in the anterior end of the notochordal sheath into the body cavity of the trunk. As the notochordal cells shorten they develop folds at their basal surfaces. These folds protrude into complementary folds in the notochordal sheath. The development of the folds is associated with the appearance of a thick layer of cytoplasmic filaments just beneath the plasmalemma of the basal surface. Most of these filaments are oriented in the axis of shortening.A new hypothesis is proposed to explain the resorption of the tail in this species: The notochordal cells are contractile and actively compress the notochordal sheath. The muscle cells, nerve cord, endodermal strand and epidermis collapse with the loss of the skeleton and are compressed by the notochord.The function of the notochord during resorption of the tail inBoltenia villosais regarded as analogous to the function of the contractile epidermis in the compound ascidiansAmaroucium constellatum, Distaplia occidentalisandDiplosoma macdonaldi. The oriented filaments and apical protrusions characteristic of the contractile epidermal cells of these ascidians were not found in the epidermis ofBoltenia villosa.