title: Hemocytes participate in calcium carbonate crystal formation, transportation and shell regeneration in the pearl oyster Pinctada fucata.
abstract: In this study, light microscope, scanning and transmission electron microscope, hematoxylin-eosin and fluorescent staining, and mass spectrometry methods were employed to observe the calcium carbonate (CaCO3) crystal formation, hemocyte release and transportation, and hemocyte distribution at the shell regeneration area and to analyse the proteome of hemocytes in the pearl oyster, Pinctada fucata. The results indicated that intracellular CaCO3 crystals were observed in circulating hemocytes in P. fucata, implying that there was a suitable microenvironment for crystal formation in the hemocytes. This conclusion was further supported by the proteome analysis, in which various biomineralization-related proteins were detected. The crystal-bearing hemocytes, mainly granulocytes, may be released to extrapallial fluid (EPF) by the secretory cavities distributed on the outer surface of the mantle centre. These granulocytes in the EPF and between the regenerated shells were abundant and free. In the regenerated prismatic layer, the granulocytes were fused into each column and fragmented with the duration of shell maturation, suggesting the direct involvement of hemocytes in shell regeneration. Overall, this study provided evidence that hemocytes participated in CaCO3 crystal formation, transportation and shell regeneration in the pearl oyster. These results are helpful to further understand the exact mechanism of hemocyte-mediated biomineralization in shelled molluscs.
authors.affiliation: Institute of Marine Biotechnology, Collaborative Innovation Center of Deep Sea Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Shiguo
authors.initials: S
authors.lastname: Li
authors.affiliation: Institute of Marine Biotechnology, Collaborative Innovation Center of Deep Sea Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Yangjia
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Institute of Marine Biotechnology, Collaborative Innovation Center of Deep Sea Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China; Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Chuang
authors.initials: C
authors.lastname: Liu
authors.affiliation: Institute of Marine Biotechnology, Collaborative Innovation Center of Deep Sea Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Jingliang
authors.initials: J
authors.lastname: Huang
authors.affiliation: Institute of Marine Biotechnology, Collaborative Innovation Center of Deep Sea Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Guilan
authors.initials: G
authors.lastname: Zheng
authors.affiliation: Institute of Marine Biotechnology, Collaborative Innovation Center of Deep Sea Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China. Electronic address: lpxie@tsinghua.edu.cn.
authors.forename: Liping
authors.initials: L
authors.lastname: Xie
authors.affiliation: Institute of Marine Biotechnology, Collaborative Innovation Center of Deep Sea Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China. Electronic address: rqzhang@tsinghua.edu.cn.
authors.forename: Rongqing
authors.initials: R
authors.lastname: Zhang
mesh_terms: D060105:Animal Shells / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D002119:Calcium Carbonate / Q000378:metabolism*; D006098:Granulocytes / Q000378:metabolism; D006434:Hemocytes / Q000378:metabolism* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D049911:Pinctada / Q000378:metabolism*
chemical_list: D002119:Calcium Carbonate
keywords: Biomineralization; CaCO(3) crystal; Hemocyte; Pinctada fucata; Shell regeneration