. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. VIVIPARITY IN CRYPTASTER1NA 87 $ L - . -.#:#. Figure 4. Light and transmission electron microscopy of Cryptasterina hystera. (A-C) Lipid reserves (L) are shunted basally below the nucleus (Nu) of the cells in the gastrula epithelium (Ep) before secretion into the blastocoel (Be). The lipid is released by an exocrine mechanism, often taking a portion of the cell membrane (arrow). (D) Brachiolaria with lipid droplets (L) filling the blastocoel. A. adhesive disc; B. brachia; St. stomach. Scales: A = /im; B = jum; C = 0.
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. VIVIPARITY IN CRYPTASTER1NA 87 $ L - . -.#:#. Figure 4. Light and transmission electron microscopy of Cryptasterina hystera. (A-C) Lipid reserves (L) are shunted basally below the nucleus (Nu) of the cells in the gastrula epithelium (Ep) before secretion into the blastocoel (Be). The lipid is released by an exocrine mechanism, often taking a portion of the cell membrane (arrow). (D) Brachiolaria with lipid droplets (L) filling the blastocoel. A. adhesive disc; B. brachia; St. stomach. Scales: A = /im; B = jum; C = /urn; D = 85 jiim. cucumbers incubate their offspring in the coelom and juve- niles emerge from the adult body (Reviews: Vaney, 1925: McEuen. 1986: O'Loughlin, 1994). Although live birth is rare in echinoderms, it appears that the potential for making the switch to this mode of propagation is more common in some taxa than others. The Holothuroidea contains the highest number of viviparous species (O'Loughlin. 1994). Aside from the aberrant Xyloplax meditsiformis. all vivipa- rous asteroids are in the Asterinidae (Table 1). As is characteristic of viviparous asterinids, the gonads of Cryptasterina hystera were ovotestes (Komatsu et 1990: Byrne. 1996). This condition is also reported in viviparous holothuroids (Miller, 1985; Frick et al, 1996). Despite their intragonadal location, the sperm of C. hvstera had a well- developed tail, were fully motile, and could fertilize eggs in vitro. Their ultrastructure was the asteroid "echinosperm- type" (sensu Jamieson, 1985) with a round head and em- bedded acrosome. It is likely that these sperm would be functional if released into the sea. For outcrossing to occur in C. hystera and other viviparous echinoderms, sperm. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the o
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
