. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. FERTILIZATION AND DEVELOPMENTAL BIOLOGY Reference: Bi,>/. Bull 191: 285-2X6. (October, 1996) 285 Modified Spiral Cleavage: The Duet Cleavage Pattern and Early Blastomere Fates in the Acoel Turbellarian Neochildia fusca Barbara C. Borer (Department of Biology. Union College, Schenectady, NY 12308), Jonathan Q. Henry], anil Mark Q. Martindale2 Spiral cleavage, which characterizes the embryos of phyla be- longing to the Spiralia, typically involves the generation of four quartets of micromeres from the four macromeres produc
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. FERTILIZATION AND DEVELOPMENTAL BIOLOGY Reference: Bi,>/. Bull 191: 285-2X6. (October, 1996) 285 Modified Spiral Cleavage: The Duet Cleavage Pattern and Early Blastomere Fates in the Acoel Turbellarian Neochildia fusca Barbara C. Borer (Department of Biology. Union College, Schenectady, NY 12308), Jonathan Q. Henry], anil Mark Q. Martindale2 Spiral cleavage, which characterizes the embryos of phyla be- longing to the Spiralia, typically involves the generation of four quartets of micromeres from the four macromeres produced by the first and second cleavages. The direction of the cleavage planes forming the micromere quartets alternates between dex- iotropic (clockwise) and laeotropic (counterclockwise), with the first quartet usually resulting from a dexiotropic division to ' Department of Cell and Structural Biology. LIniversity of Illinois. Urhana. 1L. 2 Department of Organismal Biology and Anatomy. University of Chicago. Chicago. IL. the eight-cell stage. Cell lineage studies of embryos with quartet spiral cleavage demonstrate that the first three quartets form ectoderm (1). Embryos of the acoel turbellarian Platyhelminthes exhibit a modified form of spiral cleavage in which only two macromeres form before pairs or duets of micromeres are generated begin- ning at the four-cell stage (Fig. la. b). However, the few studies on acoel development are in disagreement as to the direction of the cleavage planes during micromere formation, and there have been no lineage analyses since the 1909 work of Bresslau (2). We have examined the cleavage pattern and fates of the first three micromere duets in the embryo of the acoel Neochildia fnsca. Adult specimens of N. fusca were collected from Sippewisset IslDiie! 2ndD MKTnmerc MKN CD. Duel 2nd Duct Macrnmere Mac rumen: Zygote 2-CellSlage 4-Cell Stage 6-Cell Stage 8-Cell Stage 10-Cell Stage 12-Cell Stage. Please note that these images are extracted from sc
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
