title: Evidence of compositional and ultrastructural shifts during the development of calcareous tubes in the biofouling tubeworm, Hydroides elegans.
abstract: The serpulid tubeworm, Hydroides elegans, is an ecologically and economically important species whose biology has been fairly well studied, especially in the context of larval development and settlement on man-made objects (biofouling). Nevertheless, ontogenetic changes associated with calcareous tube composition and structures have not yet been studied. Here, the ultrastructure and composition of the calcareous tubes built by H. elegans was examined in the three early calcifying juvenile stages and in the adult using XRD, FTIR, ICP-OES, SEM and Raman spectroscopy. Ontogenetic shifts in carbonate mineralogy were observed, for example, juvenile tubes contained more amorphous calcium carbonate and were predominantly aragonitic whereas adult tubes were bimineralic with considerably more calcite. The mineral composition gradually shifted during the tube development as shown by a decrease in Sr/Ca and an increase of Mg/Ca ratios with the tubeworm's age. The inner tube layer contained calcite, whereas the outer layer contained aragonite. Similarly, the tube complexity in terms of ultrastructure was associated with development. The sequential appearance of unoriented ultrastructures followed by oriented ultrastructures may reflect the evolutionary history of serpulid tube biominerals. As aragonitic structures are more susceptible to dissolution under ocean acidification (OA) conditions but are more difficult to be removed by anti-fouling treatments, the early developmental stages of the tubeworms may be vulnerable to OA but act as the important target for biofouling control.
authors.affiliation: The Swire Institute of Marine Science and School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region.
authors.forename: Vera Bin San
authors.initials: VB
authors.lastname: Chan
authors.affiliation: Department of Geology, University of Tartu, Ravila 14A, 50411 Tartu, Estonia.
authors.forename: Olev
authors.initials: O
authors.lastname: Vinn
authors.affiliation: The Swire Institute of Marine Science and School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region.
authors.forename: Chaoyi
authors.initials: C
authors.lastname: Li
authors.affiliation: Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region.
authors.forename: Xingwen
authors.initials: X
authors.lastname: Lu
authors.affiliation: PennState Astrobiology Research Center, University Park, PA 16802, USA; University of Wisconsin Astrobiology Research Consortium, Madison, WI 53706, USA.
authors.forename: Anatoliy B
authors.initials: AB
authors.lastname: Kudryavtsev
authors.affiliation: Department of Earth, Planetary and Space Sciences, Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA; PennState Astrobiology Research Center, University Park, PA 16802, USA; University of Wisconsin Astrobiology Research Consortium, Madison, WI 53706, USA.
authors.forename: J William
authors.initials: JW
authors.lastname: Schopf
authors.affiliation: Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region.
authors.forename: Kaimin
authors.initials: K
authors.lastname: Shih
authors.affiliation: Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region.
authors.forename: Tong
authors.initials: T
authors.lastname: Zhang
authors.affiliation: The Swire Institute of Marine Science and School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region. Electronic address: rajan@hku.hk.
authors.forename: Vengatesen
authors.initials: V
authors.lastname: Thiyagarajan
mesh_terms: D000818:Animals; D057219:Biofouling; D002118:Calcium / Q000032:analysis; D002119:Calcium Carbonate / Q000032:analysis; D004625:Embryo, Nonmammalian; D005260:Female; D008274:Magnesium / Q000032:analysis; D008297:Male; D008675:Metamorphosis, Biological; D008855:Microscopy, Electron, Scanning; D011077:Polychaeta / Q000196:embryology / Q000254:growth & development / Q000502:physiology* / Q000648:ultrastructure*; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D014961:X-Ray Diffraction
chemical_list: D002119:Calcium Carbonate; D008274:Magnesium; D002118:Calcium
keywords: Biofouling; Biomineralization; Calcification; Hydroides elegans; Serpulid; Tube ultrastructure