First report on chitinous holdfast in sponges (Porifera)

• Published in: Proceedings of the Royal Society. B, Biological sciences Vol. 280; no. 1762; p. 20130339
• Main Authors: Ehrlich, Hermann, Kaluzhnaya, Oksana V., Tsurkan, Mikhail V., Ereskovsky, Alexander, Tabachnick, Konstantin R., Ilan, Micha, Stelling, Allison, Galli, Roberta, Petrova, Olga V., Nekipelov, Serguei V., Sivkov, Victor N., Vyalikh, Denis, Born, René, Behm, Thomas, Ehrlich, Andre, Chernogor, Lubov I., Belikov, Sergei, Janussen, Dorte, Bazhenov, Vasilii V., Wörheide, Gert
• Format: Journal Article
• Language: English
• Published: England The Royal Society 07.07.2013; Royal Society, The
• Subjects: Acetylglucosamine - metabolism; Amino Acid Sequence; Animal biology; Animals; Benzenesulfonates - metabolism; Chitin; Chitin - chemistry; Chitin - metabolism; Chitin Synthase - chemistry; Chitin Synthase - genetics; Chitin Synthase - metabolism; Contrast Media - metabolism; Endemic Sponges; Holdfast; Invertebrate Zoology; Lakes; Life Sciences; Marine; Molecular Sequence Data; Phylogeny; Polymerase Chain Reaction; Porifera; Porifera - anatomy & histology; Porifera - chemistry; Porifera - genetics; Russia; Sequence Alignment; Spectrometry, Mass, Electrospray Ionization; Spectrum Analysis, Raman; X-Ray Absorption Spectroscopy; holdfast; Porifera; chitin; endemic sponges; Keywords; biochemistry; structural biology; evolution; Subject Areas
• ISSN: 0962-8452; 1471-2954; 1471-2945; 1471-2954
• DOI: 10.1098/rspb.2013.0339

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.