作者: C.A. Byrum
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摘要: Unipolar ingression is a common form of gastrulation in the phylum Cnidaria. Here, this process examined hydrozoan Phialidium. Ultrastructural investigation confirmed that, during process, oral cells elongate, constricting at their apical ends and/or expanding basal as they ingress. Marking studies show that most entodermal originate from area, but few also come lateral, aboral-lateral, and aboral areas. Based on orientation mitotic spindles gastrulation, may enter region by delamination. Cell sorting experiments showed postgastrulation, areas preingression embryo developed lower adhesive capacities than those regions. Differences capacity allow maintenance distinct cell layers. Postgastrulae are shorter, thinner, more streamlined embryos. Total volume decrease, blastocoel disappears, 34.4% mass becomes entoderm. Activities ectodermal layer play an important role gastrulation: become columnar less columnar. Also, oral-lateral regions shift toward midline, causing portions to elongate. A model unipolar proposed.