Santos Romana, Haesaerts Delphine, Jangoux Michel, Flammang Patrick
Académie Universitaire Wallonie-Bruxelles, Université de Mons-Hainaut, Laboratoire de Biologie marine, 6 Avenue du champ de Mars, 7000 Mons, Belgium.
J Exp Biol. 2005 Jun;208(Pt 12):2277-88. doi: 10.1242/jeb.01641.
Echinoderms possess mutable collagenous tissues (MCTs), which are capable of undergoing rapid changes in their passive mechanical properties mediated by secretions from a specific cell type, the juxtaligamental cell. In this study, the possible presence of MCTs in the tube feet of the echinoid Paracentrotus lividus and the asteroid Marthasterias glacialis was investigated by measuring their extensibility, tensile strength, stiffness and toughness after different treatments known to influence the physiological state of MCTs. Calcium removal reversibly induced a significant plasticization of the tube feet of both species. When exposed to cell-disrupting solutions, the tube foot stem of sea urchins and sea stars showed a significant increase in strength, stiffness and toughness in the absence of calcium. This response, combined with the ultrastructural observation of juxtaligamental-like cells in the connective tissue, confirms that an MCT is present in both echinoid and asteroid tube feet. It was observed, however, that the tube foot stems of P. lividus and M. glacialis are affected differently by exposure to cell-disrupting solutions in the presence of calcium, indicating that their MCTs could be functionally different. In their soft state, MCTs could assist the muscles in tube foot protraction, bending and retraction; in their stiff state, they could play a role in the energy-sparing maintenance of position; for example, during strong attachment to the substratum to resist hydrodynamically generated loads.
棘皮动物拥有可变胶原组织（MCTs），这种组织能够在一种特定细胞类型——韧带旁细胞分泌的介导下，使其被动力学特性发生快速变化。在本研究中，通过测量在已知会影响MCTs生理状态的不同处理后，海胆Paracentrotus lividus和海星Marthasterias glacialis管足的伸展性、拉伸强度、硬度和韧性，来研究这两种棘皮动物管足中MCTs的可能存在情况。去除钙可逆地诱导了这两个物种管足的显著增塑。当暴露于破坏细胞的溶液中时，海胆和海星的管足柄在无钙情况下强度、硬度和韧性显著增加。这种反应，结合结缔组织中类韧带样细胞的超微结构观察，证实了海胆和海星的管足中都存在MCT。然而，观察到在有钙存在的情况下，暴露于破坏细胞的溶液中时，Paracentrotus lividus和Marthasterias glacialis的管足柄受到的影响不同，这表明它们的MCT在功能上可能存在差异。在其柔软状态下，MCT可协助肌肉进行管足伸展、弯曲和收缩；在其僵硬状态下，它们可在节省能量的位置维持中发挥作用；例如，在牢固附着于基质以抵抗流体动力产生的负荷时。
