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研究螠虫动物体壁发生和体节形成，可为阐释其早期发育机制以及体节在螠虫动物进化中的意义提供科学数据。本文以生活于沿海底质U形洞穴中的单环刺螠为材料，研究了单环刺螠幼虫的体壁发生和体节形成过程。研究显示，单环刺螠(Urechis unicinctus)担轮幼虫的体壁由单层上皮组织构成；至体节幼虫时，体壁变为单层上皮组织、结缔组织和纵向分布的肌纤维组成的多层结构，且体壁表面出现明显的分节；蠕虫状幼虫体节消失，体壁单层上皮细胞聚集形成不规则的乳突状结构，上皮中黏液细胞增多、结缔组织和肌纤维增多；至幼螠时，体壁的组织结构与成体基本一致，由复层上皮组织、结缔组织和肌肉组织(外环肌-中纵肌-内环肌)构成；单环刺螠体壁结构的不断分化，体现了其由浮游生活方式向爬行和穴居生活方式转变的适应过程。TUNEL检测发现，在单环刺螠幼虫体节发生过程中未出现明显的细胞凋亡现象。使用细胞增殖标记分子PCNA(Proliferating cell nuclear antigen)检测单环刺螠体节发生区域增殖细胞的分布时发现：在担轮幼虫中期，其后体部首先出现增殖细胞带，并在随后的发育过程中形成体节细胞增厚区；担轮幼虫晚期，其后体部腹面两侧增殖细胞隐约呈分节状分布；之后，这些PCNA阳性细胞的分布区域由腹面向背面延伸并在早期体节幼虫中呈明显的分节状；至体节幼虫体节完全形成时，体节处的PCNA阳性信号消失。单环刺螠幼虫体节形成模式类似于多毛类小头虫的侧增殖带模式。
Abstract：The study on the body wall genesis and the segmentation formation in echiuran worms will provide scientific data for elucidating the early development mechanism and the evolution significance of the larval segmentation. In this study, we characterized the body wall ontogenesis and segment formation of echiuran worm Urechis unicinctus, a marine benthic invertebrate inhabiting U-shaped burrows along the coast. The body wall was only monolayer epithelial cells in the trochophore larva. In the segmentation larva, it became multilayered, composing of monolayer epithelium, connective tissue and longitudinal muscle fibers, and the body wall surface appeared obvious segments. In the worm-like larva, the segments disappeared, and the monolayer epithelial cells gathered to form some mastoid structures. Meanwhile the number of mucous cells in the epithelium, connective tissue and muscle fibers increased. In juveniles, the body wall structure was basically the same as that of the adult, which was consisted of stratified epithelial tissue, connective tissue and muscle tissue, from outside to inside, circular muscle, longitudinal muscle and circular muscle. The differentiation characteristics of the body wall structure reflects the adaptation to the inhabiting mode from plankton to crawling and burrowing mode in U. unicinctus. TUNEL detection showed that no significant cell apoptosis occurred in U. unicinctus larvae during segment formation. The results of fluorescence immunohistochemistry with a monoclonal antibody of PCNA(Proliferating cell nuclear antigen, a cell division marker) showed that the cell proliferation area appeared firstly at the ventral side of the larval hyposphere in mid-trochophore larva, and then formed a thickened area of the proliferative cells. In the late-trochophore larva, the distribution of the proliferative cells exhibited faintly a segmental arrangement on the ventral side, and then the distribution of these PCNA positive cells extended from the ventral to the dorsal side of the larva and presented with obvious segmented mode in the early-segmentation larva. Until the segmentation larva, segments became visible morphologically, and the PCNA positive signal disappeared in this area. We proposed that the formation pattern of the larval segments of U. unicinctus is similar to the lateral proliferative banding pattern observed in polychaete Capitella teleta.
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基本信息:
DOI：10.16441/j.cnki.hdxb.20220174
中图分类号:S917.4
引用信息:
[1]郑巧军,谢跃洋,魏茂凯,等.单环刺螠幼虫的体壁发生和体节形成[J],2023,53(04):25-30.DOI:10.16441/j.cnki.hdxb.20220174.
基金信息:
国家自然科学基金项目(31572601)资助~~