. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. flfcrf ii^^^^^^^%; ^. Figure 4. Juvenile Phyllacanthus parvispinus. Three views of 141- h juveniles, a. Xylene-cleared whole mount, ahoral view. Note "web- bing" between spines, b. Polarized light view of the same specimen. Secretion of the five apical plates (AP) has begun; three are visible in this phase of polarized light. Spines (S) are all of the juvenile type. c. Six-^m eosin and Harris hematoxylin cross section. A single podium (TF) is visible, as are three spines. The section is oriented oral surface down.
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. flfcrf ii^^^^^^^%; ^. Figure 4. Juvenile Phyllacanthus parvispinus. Three views of 141- h juveniles, a. Xylene-cleared whole mount, ahoral view. Note "web- bing" between spines, b. Polarized light view of the same specimen. Secretion of the five apical plates (AP) has begun; three are visible in this phase of polarized light. Spines (S) are all of the juvenile type. c. Six-^m eosin and Harris hematoxylin cross section. A single podium (TF) is visible, as are three spines. The section is oriented oral surface down. Scale bars: a, b = 200 ^m; c = 150 ^m. The larval ectoderm of planktotrophic euechinoids is largely lost during metamorphosis, the adult ectoderm deriving primarily from vestibular ectoderm (Cameron and Hinegardner, 1978). In contrast, the larval ectoderm of the cidaroid Eucidaris t honor si is retained through metamorphosis (Emlet, 1988). Indirect evidence sug- gests that a similar situation exists in P. pan'ispinns. The ectoderm is topologically in the same position in late lar- vae and juveniles, because no inversion of a vestibule takes place. Larval ectoderm retracts onto the aboral surface of the juvenile as metamorphosis proceeds (Figs. 4a, c). Differentiation of mesenchyme cells The differentiation of skeletogenic mesenchyme cells and the pattern of skeletogenesis is highly modified in lecithotrophic echinoids (Raff, 1987; Parks et 1988). The protein mspl30 provides a specific probe for these cells. This protein is produced only by primary mesen- chyme cells in euechinoid embryos (Anstrom el al., 1987; Wray and McClay, 1989) and by skeletogenic cells in adults (Parks et 1988). In planktotrophic larvae of the cidaroid Eucidaris tribuloides, there are 16 spicule- forming cells, homologous to euechinoid primary mes- enchyme cells, that express msp!30 (Wray and McClay, 1988). In E. tribuloides, msp!30 expression begins after spicule-forming cell ingression is comp
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
