First evidence of chitin as a component of the skeletal fibers of marine sponges. Part I. Verongidae (demospongia: Porifera).
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.
Ehrlich
Hermann
H
Max Bergmann Center of Biomaterials, Institute of Materials Science, Dresden University of Technology, D-01069 Dresden, Germany. hermann.ehrlich@mailbox.tu-dresden.de
Maldonado
Manuel
M
Spindler
Klaus-Dieter
KD
Eckert
Carsten
C
Hanke
Thomas
T
Born
René
R
Goebel
Caren
C
Simon
Paul
P
Heinemann
Sascha
S
Worch
Hartmut
H
D000818:Animals; D002686:Chitin / Q000032:analysis*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D011161:Porifera / Q000737:chemistry* / Q000648:ultrastructure*; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D014961:X-Ray Diffraction
D002686:Chitin