title: LiCl inhibits the establishment of left-right asymmetry in larvae of the direct-developing echinoid Peronella japonica.
abstract: The effect of LiCl on the establishment of left-right (LR) asymmetry in larvae of the direct-developing echinoid Peronella japonica was investigated with special attention to the location of the amniotic opening and ciliary band pattern. The larvae of echinoids are LR symmetric, but shortly before metamorphosis the larval LR symmetry is lost as a result of the formation of an amniotic cavity (vestibule), part of the adult rudiment, on the left side of the body. P. japonica has been considered to be the only exception among the echinoids, because the amniotic cavity forms at the midline of the larval body. In the present study we discovered the following two different LR asymmetric traits in larvae of P. japonica: the opening of the amniotic cavity initially forms at the midline of the larval body but shifts to the left dorsal side, and a looped ciliary band that initially forms with LR symmetry becomes LR asymmetric as a result of the formation of a bulge on left dorsal side. The establishment of LR asymmetry in both the location of the amniotic opening and the change in the shape of the ciliary band was influenced by exposing embryos to LiCl. Quantitative analysis of the shift in amniotic opening showed that exposure of embryos to LiCl causes repression of leftward shifting of the amniotic opening in earlier stage larvae, and leftward or rightward shifting in later stage larvae. These findings suggest that LiCl is an effective means of impairing the establishment of LR asymmetry in sea urchin embryos.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan. chisatok@andrew.cmu.edu
authors.forename: Chisato
authors.initials: C
authors.lastname: Kitazawa
authors.forename: Kaori Kajihara
authors.initials: KK
authors.lastname: Takai
authors.forename: Yoko
authors.initials: Y
authors.lastname: Nakajima
authors.forename: Hirosuke
authors.initials: H
authors.lastname: Fujisawa
authors.forename: Shonan
authors.initials: S
authors.lastname: Amemiya
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000187:drug effects*; D001837:Body Weights and Measures; D007814:Larva / Q000254:growth & development / Q000648:ultrastructure; D018021:Lithium Chloride / Q000494:pharmacology*; D008855:Microscopy, Electron, Scanning; D012617:Sea Urchins / Q000254:growth & development*
chemical_list: D018021:Lithium Chloride