title: Mechanical adaptability of sea cucumber Cuvierian tubules involves a mutable collagenous tissue.
abstract: Despite their soft body and slow motion, sea cucumbers present a low predation rate, reflecting the presence of efficient defence systems. For instance, members of the family Holothuriidae rely on Cuvierian tubules for their defence. These tubules are normally stored in the posterior coelomic cavity of the animal, but when the sea cucumber is threatened by a potential predator, they are expelled through the cloacal aperture, elongate, become sticky and entangle and immobilise the predator in a matter of seconds. The mechanical properties (extensibility, tensile strength, stiffness and toughness) of quiescent (i.e. in the body cavity) and elongated (i.e. after expulsion) Cuvierian tubules were investigated in the speciesHolothuria forskaliusing traction tests. Important mechanical differences were measured between the two types of tubules, reflecting adaptability to their operating mode: to ease elongation, quiescent tubules present a low resistance to extension, while elongated tubules present a high toughness to resist tractions generated by the predator. We demonstrate that a mutable collagenous tissue (MCT) is involved in the functioning of these organs: (1) some mechanical properties of Cuvierian tubules are modified by incubation in a cell-disrupting solution; (2) the connective tissue layer encloses juxtaligamental-like cells, a cell type present in all MCTs; and (3) tensilin, a MCT stiffening protein, was localised inside these cells. Cuvierian tubules thus appear to enclose a new type of MCT which shows irreversible stiffening.
authors.affiliation: University of Mons, Research Institute for Biosciences, Biology of Marine Organisms and Biomimetics, Mons 7000, Belgium.
authors.forename: Mélanie
authors.initials: M
authors.lastname: Demeuldre
authors.affiliation: University of Mons, Research Institute for Biosciences, Biology of Marine Organisms and Biomimetics, Mons 7000, Belgium.|University of Mons, Research Institute for Biosciences, Laboratory of Cell Biology, Mons 7000, Belgium.
authors.forename: Elise
authors.initials: E
authors.lastname: Hennebert
authors.affiliation: University of Mons, Research Institute for Biosciences, Biology of Marine Organisms and Biomimetics, Mons 7000, Belgium.
authors.forename: Marie
authors.initials: M
authors.lastname: Bonneel
authors.affiliation: University of Innsbruck, Institute of Zoology and Center for Molecular Biosciences, Innsbruck 6020, Austria.
authors.forename: Birgit
authors.initials: B
authors.lastname: Lengerer
authors.affiliation: University of Mons, Research Institute for Biosciences, Biology of Marine Organisms and Biomimetics, Mons 7000, Belgium.
authors.forename: Séverine
authors.initials: S
authors.lastname: Van Dyck
authors.affiliation: University of Mons, Research Institute for Biosciences, Laboratory of Proteomics and Microbiology, Mons 7000, Belgium.
authors.forename: Ruddy
authors.initials: R
authors.lastname: Wattiez
authors.affiliation: University of Innsbruck, Institute of Zoology and Center for Molecular Biosciences, Innsbruck 6020, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Ladurner
authors.affiliation: University of Mons, Research Institute for Biosciences, Biology of Marine Organisms and Biomimetics, Mons 7000, Belgium patrick.flammang@umons.ac.be.
authors.forename: Patrick
authors.identifier: 0000-0001-9938-1154
authors.initials: P
authors.lastname: Flammang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001696:Biomechanical Phenomena; D002352:Carrier Proteins; D003094:Collagen / Q000187:drug effects / Q000502:physiology*; D003238:Connective Tissue / Q000737:chemistry* / Q000648:ultrastructure; D047332:Holothuria / Q000502:physiology*; D017830:Octoxynol; D013718:Tensile Strength / Q000502:physiology
chemical_list: D002352:Carrier Proteins; D017830:Octoxynol; D003094:Collagen
keywords: Connective tissue; Defence system; Echinodermata; Holothuria forskali; Holothuroidea; Mechanical properties; Tensilin; Ultrastructure