Nakajima Yoko, Humphreys Tom, Kaneko Hiroyuki, Tagawa Kunifumi
Department of Biology, Keio University, Yokohama, Japan.
Zoolog Sci. 2004 Jan;21(1):69-78. doi: 10.2108/0289-0003(2004)21[69:DANOOT]2.0.CO;2.
We report scanning and transmission electron microscopic studies of the early development of the Hawaiian acorn worm, Ptychodera flava. In addition, we provide an immunohistochemical identification of the larval nervous system. Development occurs and is constrained within the stout chorion and fertilization envelope that forms upon the release of the cortical granules in the cytoplasm of the egg. The blastula consists of tall columnar blastomeres encircling a small blastocoel. Typical gastrulation occurs and a definitive tornaria is formed compressed within the fertilization envelope. The young tornaria hatches at 44 hr and begins to expand. The major circumoral ciliary band that crosses the dorsal surface and passes preorally and postorally is well developed. In addition, we find a nascent telotroch, as well as a midventral ciliary band that is already clearly developed. The epithelium of tornaria is a mosaic of monociliated and multiciliated cells. Immunohistochemistry with a novel neural marker, monoclonal antibody 1E11, first detects nerve cells at the gastrula stage. In tornaria, 1E11 staining nerve cells occur throughout the length of the ciliary bands, in the apical organ, in a circle around the mouth, in the esophageal epithelium and in circumpylorus regions. Axon(s) and apical processes extend from the nerve cell bodies and run in tracks along the ciliary bands. Axons extending from the preoral and postoral bands extend into the oral field and form a network. The tornaria nervous system with ciliary bands and an apical organ is rather similar to the echinoderm bipinnaria larvae.
我们报告了对夏威夷柱头虫（Ptychodera flava）早期发育的扫描电子显微镜和透射电子显微镜研究。此外，我们还对幼虫神经系统进行了免疫组织化学鉴定。发育过程在卵细胞质中皮质颗粒释放后形成的坚固卵壳和受精膜内发生并受到限制。囊胚由围绕小囊胚腔的高柱状分裂球组成。典型的原肠胚形成过程发生，在受精膜内形成一个压缩的定型柱头幼虫。幼体柱头幼虫在44小时孵化并开始扩张。穿过背面并在口前和口后通过的主要围口纤毛带发育良好。此外，我们发现了一个新生的端纤毛环，以及一条已经明显发育的腹中线纤毛带。柱头幼虫的上皮是单纤毛细胞和多纤毛细胞的镶嵌体。用一种新型神经标记物单克隆抗体1E11进行免疫组织化学分析，在原肠胚阶段首次检测到神经细胞。在柱头幼虫中，1E11染色的神经细胞出现在纤毛带的全长、顶器、口周围的一圈、食管上皮和幽门周围区域。轴突和顶突从神经细胞体延伸出来，沿着纤毛带形成的轨迹运行。从口前带和口后带延伸出来的轴突延伸到口区并形成一个网络。具有纤毛带和顶器的柱头幼虫神经系统与棘皮动物双羽幼虫相当相似。
