title: First report on chitinous holdfast in sponges (Porifera).
abstract: A holdfast is a root- or basal plate-like structure of principal importance that anchors aquatic sessile organisms, including sponges, to hard substrates. There is to date little information about the nature and origin of sponges' holdfasts in both marine and freshwater environments. This work, to our knowledge, demonstrates for the first time that chitin is an important structural component within holdfasts of the endemic freshwater demosponge Lubomirskia baicalensis. Using a variety of techniques (near-edge X-ray absorption fine structure, Raman, electrospray ionization mas spectrometry, Morgan-Elson assay and Calcofluor White staining), we show that chitin from the sponge holdfast is much closer to α-chitin than to β-chitin. Most of the three-dimensional fibrous skeleton of this sponge consists of spicule-containing proteinaceous spongin. Intriguingly, the chitinous holdfast is not spongin-based, and is ontogenetically the oldest part of the sponge body. Sequencing revealed the presence of four previously undescribed genes encoding chitin synthases in the L. baicalensis sponge. This discovery of chitin within freshwater sponge holdfasts highlights the novel and specific functions of this biopolymer within these ancient sessile invertebrates.
authors.affiliation: Institute of Experimental Physics, TU Bergakademie Freiberg, 09599 Freiberg, Germany. hermann.ehrlich@physik.tu-freiberg.de
authors.forename: Hermann
authors.initials: H
authors.lastname: Ehrlich
authors.forename: Oksana V
authors.initials: OV
authors.lastname: Kaluzhnaya
authors.forename: Mikhail V
authors.initials: MV
authors.lastname: Tsurkan
authors.forename: Alexander
authors.initials: A
authors.lastname: Ereskovsky
authors.forename: Konstantin R
authors.initials: KR
authors.lastname: Tabachnick
authors.forename: Micha
authors.initials: M
authors.lastname: Ilan
authors.forename: Allison
authors.initials: A
authors.lastname: Stelling
authors.forename: Roberta
authors.initials: R
authors.lastname: Galli
authors.forename: Olga V
authors.initials: OV
authors.lastname: Petrova
authors.forename: Serguei V
authors.initials: SV
authors.lastname: Nekipelov
authors.forename: Victor N
authors.initials: VN
authors.lastname: Sivkov
authors.forename: Denis
authors.initials: D
authors.lastname: Vyalikh
authors.forename: René
authors.initials: R
authors.lastname: Born
authors.forename: Thomas
authors.initials: T
authors.lastname: Behm
authors.forename: Andre
authors.initials: A
authors.lastname: Ehrlich
authors.forename: Lubov I
authors.initials: LI
authors.lastname: Chernogor
authors.forename: Sergei
authors.initials: S
authors.lastname: Belikov
authors.forename: Dorte
authors.initials: D
authors.lastname: Janussen
authors.forename: Vasilii V
authors.initials: VV
authors.lastname: Bazhenov
authors.forename: Gert
authors.initials: G
authors.lastname: Wörheide
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001557:Benzenesulfonates / Q000378:metabolism; D002686:Chitin / Q000737:chemistry* / Q000378:metabolism; D002687:Chitin Synthase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D003287:Contrast Media / Q000378:metabolism; D060106:Lakes; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D011161:Porifera / Q000033:anatomy & histology / Q000737:chemistry* / Q000235:genetics*; D012426:Russia; D016415:Sequence Alignment; D021241:Spectrometry, Mass, Electrospray Ionization; D013059:Spectrum Analysis, Raman; D056928:X-Ray Absorption Spectroscopy
chemical_list: D001557:Benzenesulfonates; D003287:Contrast Media; D002686:Chitin; C007061:C.I. Fluorescent Brightening Agent 28; D002687:Chitin Synthase; D000117:Acetylglucosamine
keywords: Porifera; chitin; endemic sponges; holdfast