title: A possible mechanism for the formation of annual growth lines in bivalve shells.
abstract: We report a unique shell margin that differed from the usual shell structure of Pinctada fucata. We observed empty organic envelopes in the prismatic layer and the formation of the nacreous layer in the shell margin. All the characteristics of the growing margin indicated that the shell was growing rapidly. To explain this anomaly, we propose the concept of "jumping development". During jumping development, the center of growth in the bivalve shell jumps forward over a short time interval when the position of the mantle changes. Jumping development explains the unusual structure of the anomalous shell and the development of annual growth lines in typical shells. Annual growth lines are the result of a discontinuity in the shell microstructure induced by jumping development.
authors.affiliation: Institute of Marine Biotechnology, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: XiaoJun
authors.initials: X
authors.lastname: Liu
authors.forename: ZhenGuang
authors.initials: Z
authors.lastname: Yan
authors.forename: GuiLan
authors.initials: G
authors.lastname: Zheng
authors.forename: GuiYou
authors.initials: G
authors.lastname: Zhang
authors.forename: HongZhong
authors.initials: H
authors.lastname: Wang
authors.forename: LiPing
authors.initials: L
authors.lastname: Xie
authors.forename: RongQing
authors.initials: R
authors.lastname: Zhang
mesh_terms: D000375:Aging / Q000502:physiology; D000818:Animals; D049911:Pinctada / Q000033:anatomy & histology* / Q000254:growth & development* / Q000648:ultrastructure