. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 90 E. J. BALSER ET AL. Figures 5-6. Light micrographs of tangential sections through the larval coeloms of a field-collected aspidochirotid auricularia. Figure 5. Shows axocoel (ax) and hydrocoel (hy). The axocoel consists of a thin-walled cavity and a ciliated axocoelic duct (du), which opens at the dorsal pore (dp) on the left dorsal side of the animal. Scale bar = mm; he, blastocoel; ep, epidermis, lu. lumen of the stomach; me, vesiculated mesenchyme cell. Figure 6. The somatocoels (so) lie lateral to the stomach (st
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 90 E. J. BALSER ET AL. Figures 5-6. Light micrographs of tangential sections through the larval coeloms of a field-collected aspidochirotid auricularia. Figure 5. Shows axocoel (ax) and hydrocoel (hy). The axocoel consists of a thin-walled cavity and a ciliated axocoelic duct (du), which opens at the dorsal pore (dp) on the left dorsal side of the animal. Scale bar = mm; he, blastocoel; ep, epidermis, lu. lumen of the stomach; me, vesiculated mesenchyme cell. Figure 6. The somatocoels (so) lie lateral to the stomach (st) and the upper intestine (in). Scale bar = mm; be, blastocoel; me, vesiculated mesenchyme cell. tions suggestive of transfer tubules (Fig. 8). Somatocoel cells, like those of the other coelomic mesothelia, are monociliated (Fig. 7). The cytoplasm contains coated vesicles, numerous other vesicles, mitochondria, and a large nucleus. The hydrocoel lobe of the axohydrocoel is lined by squamous and cubodial epithelial cells joined by apical adhering junctions followed by septate junctions (Figs. 11, 13). Basally, the lateral membranes are extensively interdigitated and are interconnected by tight junctions (Figs. 12, 14). The cytoplasm is replete with basal mito- chondria, putative lysosomes, and vesicles. The nucleus is basal and is elongated. Apical microvilli were infre- quently observed. The defining feature of the axocoel mesothelium is the presence of podocytes (Figs. 15-19). Podocytes are epi- thelial cells that exhibit basal modifications forming foot processes, or pedicels (Figs. 16, 18, 19). Pedicels rest on the underlying basal lamina and provide breaks, or fen- estrations, in an otherwise continuous epithelium. Pedicels are bridged by the extracellular matrix of the underlying basal lamina (Figs. 18, 19). In addition to the basal lamina, some pedicels are bridged by diaphragms similar to fil- tration-slit membranes found across the pores of the fen- estrated epith
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