作 者：
张家炜;郝瑞娟;王庆恒;杨创业;杜晓东;陈振国
摘 要：
为探究光裸星虫(Sipunculus nudus)发育形态学特征,利用光镜和扫描电镜技术观察了光裸星虫胚胎和幼体发育的结构变化。结果表明:(1)光裸星虫胚胎及幼体发育经历卵裂、囊胚、原肠胚、担轮幼虫、海球幼体、匍匐幼体等主要阶段,卵裂、囊胚、原肠胚和担轮幼虫均在卵膜内发育;海球幼体出膜时,卵膜脱落,不发育为表皮。(2)水温为30~31.5℃条件下,卵子受精30 min后开始卵裂,2 h后形成原肠胚,4 h后发育为担轮幼虫,24 h后出膜成为海球幼体,8~9 d后附着变态为匍匐幼体。(3)光裸星虫为典型的螺旋式完全卵裂。担轮幼虫可做旋转式游动,胚体表面密布纤毛,其中,体前端具有一束较长的顶纤毛;纤毛通过卵膜孔中央伸出体外,分为普通纤毛和勺状纤毛两种类型。胚体形成眼点、肾管等器官。(4)海球幼体游动迅速,摄食浮游植物。口前纤毛环较短,头部具有眼点和神经节;口后纤毛环较长,纤毛类型也分为普通纤毛和勺状纤毛两种;随发育进行,体壁肌肉束不断增强,形成方格状纹理;胃部逐渐前移,肠道不断延长,发生螺旋,在躯干部前段形成肛门。(5)匍匐幼体在底质表面爬行,吞食砂砾;体表具有角质层,体壁肌肉发达;身体前端形成片状突起,将发育成触手;吻部具有规则排列的乳突;身体末端中央外凸形成球形尾器;收吻肌、腹神经索、固肠肌等器官或组织明显。研究结果可为光裸星虫生殖调控与人工繁育研究提供理论参考。
译 名：
Microscopic and ultrastructural observations of embryonic and larval development in Sipunculus nudus
作 者：
ZHANG Jiawei;HAO Ruijuan;WANG Qingheng;YANG Chuangye;DU Xiaodong;CHEN Zhenguo;Fisheries College, Guangdong Ocean University;Zhanjiang Green Bay Aquatic Science and Technology Co, Ltd.;
单 位：
ZHANG Jiawei%HAO Ruijuan%WANG Qingheng%YANG Chuangye%DU Xiaodong%CHEN Zhenguo%Fisheries College, Guangdong Ocean University%Zhanjiang Green Bay Aquatic Science and Technology Co, Ltd.
关键词：
Sipunculus nudus;;embryo;;larva;;development;;morphology
摘 要：
To explore the morphological characteristics of Sipunculus nudus, the morphological changes in the embryos and larvae were observed using scanning electron and optical microscope. The results obtained were as follows.(1) The embryonic and larval development of S. nudus included six stages: cleavage, blastula, gastrula, trochophore, pelagospheric larva, and creeping larva. The cleavage, blastula, gastrula, and trochophore stages occurred within the egg envelope. The egg envelope was discarded when the pelagospheric larva was out of the membrane and did not develop into epidermis.(2) At a water temperature of 30℃–31.5℃, the oosperm began to cleave 30 min after fertilization and the gastrula was formed after 2 h. After 4 h, it developed into trochophore. After 24 h, the larva was out of the envelope and developed to a pelagospheric larva. After 8–9 d, the pelagospheric larva developed into creeping larva.(3) Sipunculus nudus exhibited a typical helical complete cleavage. The trochophore larva could swim by rotating. The surface of the embryo body was covered with cilia, and the front of the body had a bundle of long cilia called apical cilia. The cilia which protruded from the body through the center of the egg envelope can be divided into two types—normal and spoon-shaped cilia. The embryo body formed eyespot, nephridioduct, and other organs.(4) The pelagospheric larva swam rapidly and captured phytoplankton. The anterior ciliary ring was short, and the eyespot and ganglion were on the head. The postoral ciliary ring was long; the cilia were also divided into two kinds(normal and scoop-shaped cilia). With development, the muscle bundles of the body wall continued to become strong and formed the square lattice texture. The stomach gradually moved forward to the head, intestine extended and spiraled, and anus was formed in the anterior end of the body.(5) The creeping larva crawled on the surface of the sediment and devoured gravel. The body surface developed a stratum corneum, and the body wall muscle became strong. Flaky protuberances were formed in the anterior part of the body, which developed into tentacles. The introvert had regularly arranged mastoid; it was convex to the central zone of the body, forming a spherical tail. The retractor muscle, ventral nerve cord, fixing muscles organ, and other tissues were obvious. The study provides morphological details of embryonic and larval development in S. nudus. Furthermore, it provides a theoretical reference for the procreation regulation and artificial breeding of S. nudus.
