. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 6. A larvae of Asthenosoma ijimai. a. Light micrograph of live specimen shows five primary podia just beginning to form on left side of larva. Scale bar, mm. b. Frontal section with continued hydrocoelic (and podial) development. The hydrocoel (H) is almost completely separated from the archenteron (A). Same scale as a. c. Detail of hydrocoel (H) with parts of two podial extensions from a different section of the same larva as b. Scale bar. 100 ^m. showed the hydrocoelic compartments with thickened epitheli
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 6. A larvae of Asthenosoma ijimai. a. Light micrograph of live specimen shows five primary podia just beginning to form on left side of larva. Scale bar, mm. b. Frontal section with continued hydrocoelic (and podial) development. The hydrocoel (H) is almost completely separated from the archenteron (A). Same scale as a. c. Detail of hydrocoel (H) with parts of two podial extensions from a different section of the same larva as b. Scale bar. 100 ^m. showed the hydrocoelic compartments with thickened epithelia beneath the podial swelling of the ectoderm (Fig. 6c). Serial sections revealed that the connection between the hydrocoel and archenteron was greatly reduced in one larva (Fig. 6b) and completely severed in a second larva examined. All coelomic and archenteric cavities contained stained materials that appeared to be yolky cytoplasm and some cells (Fig. 6b, c). By 101 h post fertilization, primary podia elongated to mm length (Fig. 7b, c, d). Sections of the juvenile oral surface showed folds of ectodermal tissue lying between the five primary podia (Fig. 7c, d). These folds were evi- dently epineural folds that were growing over the juvenile oral surface to form the epineural sinus (von Ubisch, 1913; Hyman, 1955; Emlet, 1988). SEM observations of the external surface of the developing juvenile oral region confirm that these epineural folds were spreading toward the oral center (Fig. 7f-h). Coincident with the lengthening of the primary podia and development of the epineural folds, the oral surface sank to become indented in the surface of the developing larva. This indentation was notable in live specimens viewed from the side at 101 h (Fig. 7b), as well as in sec- tioned material (Fig. 7c) and in specimens fixed for SEM (Fig. 7f). Though the developing juvenile oral surface was never deeply enclosed as occurs within the amniotic in- vagination (or vestibule) of the euech
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
