title: Development ofDentalium following removal of D-quadrant blastomeres at successive cleavage stages.
abstract: Each primary micromere and macromere of the D-quadrant ofDentalium was deleted, through the mesentoblast stage, to investigate the way in which the polar lobe cytoplasm exerts its influence on development.-D and -1D embryos form an apical tuft but no posttrochal structures.-2D embryos form an apical tuft and a reduced posttrochal region without a shell. -3D and -4D are externally similar to control embryos. -1d embryos and -1c embryos have an apical tuft with a reduced number of cilia. Embryos in which both 1c and 1d are deleted lack the apical tuft.-2d embryos lack shell and most other posstrochal structures. -3d and-4d embryos appear externally equivalent to controls.The polar lobe cytoplasm exerts its influence sequentially, and as inIlyanassa the maximal effect is at the third quartet stage.
authors.affiliation: Division of Biological Science, The University of Michigan, 48109, Ann Arbor, Michigan, USA.
authors.forename: James Newton
authors.initials: JN
authors.lastname: Cather
authors.affiliation: Zoological Laboratory, The University of Utrecht, Padualaan 8, Utrecht, The Netherlands.
authors.forename: Nicolaas Hendrikus
authors.initials: NH
authors.lastname: Verdonk
keywords: Dentalium; Development analysis; Embryology experimental; Invertebrate development; Mollusca