title: Novel photoreception system in sponges? Unique transmission properties of the stalk spicules from the hexactinellid Hyalonemasieboldi.
abstract: Sponges (phylum Porifera) of the classes Hexactinellida and Demospongiae possess a skeleton composed of siliceous spicules, which are synthesized enzymatically. The longest spicules are found among the Hexactinellida, with the stalk spicules (length: 30 cm; diameter: 300 microm) of Hyalonema sieboldi as prominent examples. These spicules are constructed around a central axial filament, which is formed by approximately 40 siliceous layers. The stratified spicules function as optical glass fibers with unique properties. If free-spaced coupled with a white light source (WLS), the entire fiber is illuminated. Special features of the light transmission: (i) only wavelengths between 615 and 1310 nm can pass through the fibers and (ii) light below wavelengths of 615 nm and above 1310 nm is completely cut-off. The transmission efficiency is around 60% (measured at 1080-1100 nm [length of the fiber: 5 cm]). The spicules acts as sharp high- and low-pass filters, suggesting that these silica-based fibers might be involved in a photoreception system. This assumption is supported by the finding that sponges are provided with a bioluminescent system. It is hypothesized that the spicules/siliceous fibers might be involved in a photoreception system in these animals.
authors.affiliation: Institut für Physiologische Chemie, Abteilung Angewandte Molekularbiologie, Universität, Duesbergweg 6, D-55099 Mainz, Germany. wmueller@uni-mainz.de
authors.forename: Werner E G
authors.initials: WE
authors.lastname: Müller
authors.forename: Klaus
authors.initials: K
authors.lastname: Wendt
authors.forename: Christopher
authors.initials: C
authors.lastname: Geppert
authors.forename: Matthias
authors.initials: M
authors.lastname: Wiens
authors.forename: Andreas
authors.initials: A
authors.lastname: Reiber
authors.forename: Heinz C
authors.initials: HC
authors.lastname: Schröder
mesh_terms: D000818:Animals; D005336:Fiber Optic Technology; D008027:Light; D017956:Photoreceptor Cells, Invertebrate / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure*; D011161:Porifera / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure*; D012542:Scattering, Radiation