Title: The Biological bulletin
Identifier: biologicalbullet182mari (find matches)
Year: [1] (s)
Authors: Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-1983
Subjects: Biology; Zoology; Biology; Marine Biology
Publisher: Woods Hole, Mass. : Marine Biological Laboratory
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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Figure 2. Later embryonic stages of Asthenosoma ijiinai. All embryos and sections are oriented with the animal pole up. a. Light micrograph of a live, 25.5-h-old, early gastrula. Same scale as b. b. Section through animal-vegetal axis of flattened gastrula (25.5 h), showing blastocoel filled with yolky cytoplasm. Scale bar, 1 mm. c. Lateral wall of gastrula (25.5 h), shows yolky cytoplasm exocylosing from basal ends of ectodermal cells. Same scale as d. d. Vegetal wall of gastrula (25.5 h), showing exocytosis of cytoplasm and ingression of cells. Scale bar, 200 urn. e. Section of a 25.5-h gastrula shows fluorescently staining nuclei (H33258 fluorescent dye) of ectodermal and probable mesenchyme cells. Same scale as f. f. Section of 35- h gastrula, with fluorescently stained nuclei. Scale bar, 200 Mm. g. Section of 51.5-h embryo, stained with B2C2 antibody, arrow shows first occurrence of expression of MSP-130 glycoprotein associated with blas- tocoelic cells. Scale bar, 50 ^m. h, i. Section of an 88.5-h larva, doubly stained with B2C2 antibody (h) and H33258 fluorescent dye (i) shows not all blastocoelic cells express MSP-130. The concentrated clusters of nuclei in (i) are epithelia of the archenteron (A) and a coelomic compartment (C). Scale bar, 200 ^m. variation in size of the blastomeres in 16-cell embryos, but there was no evidence of micromeres at the vegetal pole. The absence of an unequal, fourth cleavage parallels the cleavage patterns of other echinoid species large yolky eggs and modified development (Williams and Anderson, 1975; Raff, 1987; Parks et til., 1989). Like other echinoderm species with yolky eggs, embryos of Asthenosoma ijimai formed wrinkled blastulae (Ame- miya and Tsuchiya, 1979; Parks et at., 1989). This stage was followed by egression and loss of wrinkles and led to a lobate blastula (Fig. Ib). At this stage, small, cylindrical pits were present on the external surface of the embryo and passed into the ectodermal layer (Fig. Ib, c, d). Serial sections showed that some of these pits terminated blindly within the ectoderm, while others passed through the ec- toderm to another external opening. Several of these pits or passages coincided with large indentations in the em- bryo's surface and, therefore, may have been the remnants of the wrinkled indentations. Parks et at. (1989) reported pits in the yolky embryo of the cidaroid Phyllacanthus pan'ispimts, though they did not see any association of pits with egression tracks, where wrinkles diminished. Further work is necessary to determine whether the pits in the two species arise by similar mechanisms.

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