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Some structural aspects by TEM (DCEM and EELS) of the tube wall from Riftia pachyptila
Lechaire, J.-P.; Frebourg, Gh.; Gaill, F. (1997). Some structural aspects by TEM (DCEM and EELS) of the tube wall from Riftia pachyptila, in: Biologie des sources hydrothermales profondes = Biology of deep-sea hydrothermal vents: Journées d'échanges du Programme DORSALES = DORSALES Workshop Roscoff 6-8 octobre 1997. Cahiers de Biologie Marine, 38(2): pp. 132
In: (1997). Biologie des sources hydrothermales profondes = Biology of deep-sea hydrothermal vents: Journées d'échanges du Programme DORSALES = DORSALES Workshop Roscoff 6-8 octobre 1997. Cahiers de Biologie Marine, 38(2)[s.n.][s.l.]. 111-149 pp., more
In: Cahiers de Biologie Marine. Station Biologique de Roscoff: Paris. ISSN 0007-9723, more
Peer reviewed article  

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Keyword
    Marine

Authors  Top 
  • Lechaire, J.-P.
  • Frebourg, Gh.
  • Gaill, F.

Abstract
    Riftia pachyptila are large tubeworms characteristic of deep-sea hydrothermal vents. The tube, acting as a skeleton, protects the animals from the agressive environment (Gaill F., 1993). The tube wall is composed of parallel bundles of chitin microfibrils embedded in a dense matrix. This structure is made of an original chitin-protein complex which is secreted by a highly differerentiated chitin secreting system (Shillito et al., 1995). In order to study the different steps of formation of the tube wall, two different natural states of secretion were compared. The first one was a "clump" located at the base of the tube (Gaill et al, 1997) which corresponded to a freshly secreted chitin-protein gel. The second one was the corresponding mature tube wall. The main results showed that the freshly secreted material had a higher thickness (ranging from 0.7 to 1.5 mm) than that of the mature tube wall (0.2 to 0.4 mm). Successive layers of chitin microfibrils were observed in both cases. The clump microfibril layers are quite isotropic and are included inside a lucent gel (18 to 24 microfibrils per microM super(2)) whereas they are more tightly arranged in the mature tube wall (19 to 38 microfibrils per microM super(2)). The physical properties of the chitin microfibribrils seemed to be also different, these microfibrils being more flexible in the gels. Recent biomechanical data indicate that such 3D fibrillar organization confers unusual biomechanical properties. Microorganisms were observed at the outer side of the tube wall and in the mature portion thickness. These microorganisms were absent from the tube wall inner side and from the clumps of the analysed samples. One or two electron dense particles could be seen inside these cells when studied by Diffraction Contrast in Transmission Electron Microscopy (DCTEM). Electron Energy Loss Spectroscopy (EELS) preliminary results suggest that these dense particles are Iron rich. Some hypothesis are discussed about these granules which appear to be interesting biological markers.

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