First evidence of chitin as a component of the skeletal fibers of marine sponges. Part I. Verongidae (demospongia: Porifera)

Abstract

The Porifera (sponges) are often regarded as the oldest, extant metazoan phylum, also bearing the ancestral stage for most features occurring in higher animals. The absence of chitin in sponges, except for the wall of peculiar resistance bodies produced by a highly derived fresh-water group, is puzzling, since it points out chitin to be an autapomorphy for a particular sponge family rather than the ancestral condition within the metazoan lineage. By investigating the internal proteinaceous (spongin) skeleton of two demosponges (Aplysina sp. and Verongula gigantea) using a wide array of techniques (Fourier transform infrared (FTIR), Raman, X-ray, Calcofluor White Staining, Immunolabeling, and chitinase test), we show that chitin is a component of the outermost layer (cuticle) of the skeletal fibers of these demosponges. FTIR and Raman spectra, as well as X-ray difractograms consistently revealed that sponge chitin is much closer to the alpha-chitin known from other animals than to beta-chitin. These findings support the view that the occurrence of a chitin-producing system is the ancestral condition in Metazoa, and that the alpha-chitin is the primitive form in animals.

Renewable chitin from marine sponge as a thermostable biological template for hydrothermal synthesis of hematite nanospheres using principles of extreme biomimetics

“…As a preliminary procedure for identifying the intactness of chitin structures in these composites we used a specific chitin stain Calcofluor White (CFW), the fluorescent brightener [26,27,[39][40][41][42][43][44][45][46]. CFW binds to the glucan chains and linear β-(1,4)-glucosidically linked units of N-acetyl-D-glucosamine.…”

First report on chitinous holdfast in sponges (Porifera)

“…Initially, we used insertion of selected L. baicalensis specimens into 2.5 M NaOH at 378C to examine the chemical stability of the sponge skeletons to alkali treatment, because it is a well known fact that spongin can be easily dissolved in solutions that are up to 5 per cent alkali even at room temperature [21]. This stands in contrast to chitin, which is resistant to similar alkali treatment at temperatures of up to 508C [12,13,23,27]. The light microscopy image (figure 2b) of L. baicalensis holdfast after 12 h incubation in alkaline solution shows the presence of residual siliceous spicules as well as brownish pigmented organic matter with some mineral microparticles (figure 2c) that are resistant to the treatment.…”

Biological materials: Structure and mechanical properties

“…Silicon is the most common of the elements on the surface of the earth after oxygen and the ocean floors are covered with amorphous silica sediment, most of which results form living organisms. Ehrlich and coworkers [97,98] indicate that chitin is a component of the skeletal fibers of marine sponges, which have intricate elaborate structures. …”