Ultrastructure and mineral composition of serpulid tubes (Polychaeta, Annelida)

Abstract

We have studied the tube ultrastructure of 44 recent species from 36 serpulid genera. Twelve distinct ultrastructures are identified. Serpulids possess very diverse tube ultrastructures, in contrast with the traditional point of view. Most species show single-layered tubes, but 34% of these species have between two and four ultrastructurally different layers. Tubes are mostly bimineralic, and are composed of aragonite and calcite; however, one of the polymorphs is always dominant. All the studied single-layered tubes with a lamello fibrillar tube ultrastructure are exclusively calcitic; prismatic structures, both in regular or irregular orientation, are either calcitic or aragonitic in composition. There is no correlation between tube mineralogy, and ultrastructure, and marine, brackish, and freshwater environments. We find that 47% of the serpulid species studied possess a unique combination of tube structure characters.

Written in stone: history of serpulid polychaetes through time

“…reveals a striking difference in the complexity of tube ultrastructures between the two major clades. The complex oriented structures and the oriented prismatic structures restricted to the clade A (Vinn et al, 2008b;Vinn and Kupriyanova, 2011: fig. 1) seem to be derived from isotropic structures that are considered to be plesiomorphic (Vinn, 2013c).…”

“…Vinn et al (2008b) examined 44 species belonging to 36 genera and showed that 47% of studied species possess a unique combination (ultrastructural types and their arrangement into layers) of tube characters. Most advanced and highly ordered types of structures are difficult to explain from the point of the classic for serpulids "granular secreting" model (Neff, 1971), so a matrix-mediated model of biomineralisation was proposed .…”

“…However, oriented prismatic structures are also known for spirorbins (Ippolitov and Rzhavsky, 2008) nested inside clade B that predominantly has isotropic structures, thus suggesting an evolutionarily independent origin. In both clade A (Vinn and Kupriyanova, 2011) and in spirorbins (Ippolitov and Rzhavsky, 2008) (Jäger, 1993(Jäger, , 2005 Ehlers, 1908, inner tube layer, cross section of irregularly oriented prismatic structure (IOP), B -Pseudovermilia madracicola ten Hove, 1989, cross section of spherulitic irregularly oriented prismatic structure (SIOP) (after Vinn et al, 2008b: fig. 2A), C -Neovermilia falcigera (Roule, 1898), cross section of irregularly oriented platy structure (IOPL), D -Laminatubus alvini ten Hove et Zibrowius, 1986, cross section of homogeneous angular crystal structure (HAC), E -Pomatostegus stellatus (Abildgaard, 1789), cross section of homogeneous rounded crystal structure (HRC) (after Vinn et al, 2008b: fig.…”

“…Bohnné Havas, 1981;Bubel et al, 1983;Bandel, 1986;ten Hove and Zibrowius, 1986;Zibrowius and ten Hove, 1987;Nishi, 1993;Sanfilippo, 1998a, b;Vinn, 2005;2007;2008;Vinn et al, 2008b, d). Vinn et al (2008b) recognised four main groups of tube ultrastructures in serpulids according to orientation of calcium carbonate crystals: 1) isotropic structures (the crystallisation axis lacks a uniform orientation, fig. 3A-E); 2) semi-oriented structures (the crystallisation axis has semiuniform orientation, fig.…”

“…5B, enlarged), J-L: oriented complex structures: J -Hydroides dianthus Verrill, 1873, third layer from outside, longitudinal section of lamello-fibrillar structure (LF) (after Vinn, 2008: fig. 4.5), K -Floriprotis sabiuraensis Uchida, 1978, inner layer, cross section of spherulitic lamello-fibrillar structure (SLF), L -Spirobranchus giganteus (Pallas, 1766), outer layer, longitudinal section of ordered fibrillar structure (OF) (after Vinn et al, 2008b: oriented prismatic structures tend to form dense outer tube layer near the surface of the wall. Unilayered tubes with prismatic structure of the only layer are transparent (Ippolitov and Rzhavsky, 2008;Vinn et al, 2008b) because of parallel orientation of optical axes in crystals.…”