. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. vn. FIGURE 2. Serial sections of buds from stage 4 to stage 8 (left), and ventral views of living buds from stage 2 to stage 8 (right). Roman numerals show developmental stages. Arrow with solid shaft, anteroposter- ior axis; arrows with broken shaft, long axis. (A) Stage 4, from dorsal to ventral. (B) Stage 5, from dorsal to ventral. (C) Stage 6, from right dorsal to left ventral. (D) Stage 7, from right to left. (E) Stage 8, from dorsal to ventral, ac, atrial chamber; ae, atrial epithelium; af, atrial fold; as, atrial stal
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. vn. FIGURE 2. Serial sections of buds from stage 4 to stage 8 (left), and ventral views of living buds from stage 2 to stage 8 (right). Roman numerals show developmental stages. Arrow with solid shaft, anteroposter- ior axis; arrows with broken shaft, long axis. (A) Stage 4, from dorsal to ventral. (B) Stage 5, from dorsal to ventral. (C) Stage 6, from right dorsal to left ventral. (D) Stage 7, from right to left. (E) Stage 8, from dorsal to ventral, ac, atrial chamber; ae, atrial epithelium; af, atrial fold; as, atrial stalk; be, branchial chamber; bp, bud primordium; c, concavity; dg, dorsal ganglion; dt, digestive tract; e, epidermis; enp, endostylar placode; g, gonad; gr, gut rudiment; nc, neural complex; ncp, neural complex placode; p, pericardium; pp, posterior projection; tv, 2, test vessel 1, 2. Bars = mm. somewhat to the left of the long axis. The mid-ventral line of Symplegma zooids curves leftward (toward the stomach) near the posterior end, thus showing bilateral asymmetry ( Fig. 3A). The origin of this asymmetry could be traced back to stage 4. During this stage, the bud expands bilaterally and the long axis becomes unclear. Stage 5 Stage 5 begins with the appearance of the neural complex placode (Figs. ID, 2B). This primordium, formed as a thickened disc of cells at the center of the dorsal wall ventral view. Placode of neural complex appears on dorsal side. Concavities (arrows) have not yet devel- oped. Bud is connected with the common vascular system only through tv2. (E) Stage 6, ventral view. Atrial folds begin to invaginate. Note that right anterior region of atrial epithelium (asterisk), presumptive domain of budding zone, has already thickened. (F) Stage 7, dorsal view. Gut rudiment appears, ae, atrial epithelium; af, atrial folds; b, bud; cvs, common vascular system; e, epidermis; g, gonad; gr, gut rudiment; int, intestine; iv, inner vesicle of bud; nc, neural comple
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
