DEVELOPMENT OF SPATIAL-ORGANIZATION IN PALLEAL BUDS OF THE COMPOUND ASCIDIAN, SYMPLEGMA-REPTANS
DEVELOPMENT OF SPATIAL-ORGANIZATION IN PALLEAL BUDS OF THE COMPOUND ASCIDIAN, SYMPLEGMA-REPTANS
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DOI：
10.2307/1541621
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发表时间：
1986-12-01
影响因子：
1.6
通讯作者：
NAKAUCHI, M
中科院分区：
文献类型：
--
作者：
KAWAMURA, K;NAKAUCHI, M
通过对活体动物的连续观察和固定标本连续切片的重建，揭示了复海鞘Symplegma reptans的生殖芽的15个发育阶段及其时间表。芽原基（第1期）出现在其亲本芽（第9期）心房上皮的右前区。约两天后（18 ℃），它外翻形成一个沿着表皮的囊泡（第3阶段）。C）。第4阶段的特征是形成一个测试血管，通过该血管芽接受活跃的血流。在这个阶段，身体轴线和双侧不对称首次变得明显。神经复合体、咽、肠和内柱的雏形直接由芽的内囊泡形成。在3.5日龄的芽（第5期）中，神经复合体基板是观察到的第一个器官雏形。它变成一个管囊，其前半部分的腔表面上有纤毛（阶段9，8天）;纤毛导管因此形成。在6天的芽（第8阶段）中，组织学上可以在神经复合体下方观察到大细胞团。细胞体很快排列在细胞团的周围，从而形成背神经节。心包、性腺和幽门管的雏形分别在第7、8和11期（12日龄）首先出现为间充质细胞的小聚集体。在第11阶段，肌肉前体出现在与表皮相关的间充质空间中。它们在第12阶段分化为括约肌和纵体肌肉组织，此时，气门也穿透了咽壁。从芽发育约两周后，游动体开始进食，从而达到功能成熟。
The continuous observation of living animals and the reconstruction of serial sections of fixed specimens have revealed 15 developmental stages and their timetable in palleal buds of the compound ascidian, Symplegma reptans. The bud primordium (stage 1) appeared on the right anterior region of the atrial epithelium of its parental bud (stage 9). It evaginated to form a vesicle along with the epidermis (stage 3) about two days later (at 18.degree. C). Stage 4 was characterized by the formation of a test vessel through which the bud received active bloodflow. Body axes and bilateral asymmetry first became visible at this stage. Rudiments of the neural complex, pharynx, gut, and endostyle were formed directly from the inner vesicle of the bud. The neural complex placode was the first organ rudiment observed, in 3.5-day-old buds (stage 5). It changed into a tube sac whose anterior half had cilia on the luminal surface (stage 9, eight days old); the ciliated duct thus formed. In 6-day buds (stage 8), a large cell mass could be observed histologically beneath the neural complex. The cell bodies were soon arranged at the periphery of the cell mass, thus forming the dorsal ganglion. Rudiments of the pericardium, gonad, and pyloric duct appeared first as small aggregates of mesenchymal cells at stages 7, 8, and 11 (12 days old), respectively. Muscle precursors appeared in the mesenchymal space in association with the epidermis at stage 11. They differentiated into the musculus sphincter and longitudinal body musculature during stage 12, at which time, too, the stigmata perforated the pharyngeal wall. Zooids began to feed and thus attained functional maturity after about two weeks of development from buds.