. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 92 I I BALSER ET AL. ,: SA >,-•- ••••« : K #« ^##-** '. Figures 11-14. Transmission electron micrographs of tangenital sections of the hydrocoel region of the axohydrocoel of field-collected synaptid auriculariae. Figure 11. Hydrocoel epithelial cells have elongated nuclei (nu). numerous putative small (500-750 nm in diameter) lysosomes (arrowheads), and larger lysosomes (ly). Scale bar = 1 pm; lu. lumen of hydrocoel. Figure 12. Hydrocoel epithelial cells show extensive basal interdigitation. Basally located mitochond
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 92 I I BALSER ET AL. ,: SA >,-•- ••••« : K #« ^##-** '. Figures 11-14. Transmission electron micrographs of tangenital sections of the hydrocoel region of the axohydrocoel of field-collected synaptid auriculariae. Figure 11. Hydrocoel epithelial cells have elongated nuclei (nu). numerous putative small (500-750 nm in diameter) lysosomes (arrowheads), and larger lysosomes (ly). Scale bar = 1 pm; lu. lumen of hydrocoel. Figure 12. Hydrocoel epithelial cells show extensive basal interdigitation. Basally located mitochondria (mi) are often associated with these dighations. Scale bar = pm; be, blastocoel: lu. lumen; ve, vesicle; arrowhead indicates putative lysosome. Figure 13. Apical adhering junctions (ad) are followed by septate junctions (se). Scale bar = jim; lu, lumen; ve, vesicle; arrowhead indicates putative lysosome. Figure 14. Basal junctions are similar to vertebrate tight junctions. Arrows indicate definitive points of membrane contact. Scale bar = ^m. Ruppert, 1993). Crinoids differ from other echinoderms because the archenteron separates into anterior and pos- terior cavities. The anterior cavity gives rise to the enteric sac and the axohydrocoel. The posterior cavity gives rise to the left and right somatocoels. A connection, which is maintained in the adult, is secondarily established between the somatocoels and the axohydrocoel. In noncrinoid larvae, the left anterior coelom separates from the archenteron and is the primordium of the paired somatocoel, hydrocoel, and axocoel. The somatocoel pri- mordium eventually loses its connection to the anterior coelom, but the axocoel and hydrocoel remain united. The axohydrocoel establishes a duct that opens to the exterior via the dorsal pore. In crinoids, asteroids, ophiu- roids, and echinoids, the undivided axohydrocoel and its union with the exterior are retained through metamor- phosis via the stone canal and
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
