title: Mechanical mutability in connective tissue of starfish body wall.
abstract: Stiffness changes in response to mechanical and chemical stimulation were studied in muscle-free dermal samples from the body wall of the starfish Linckia laevigata. The ultrastructural study showed that the dermis was packed with collagen fibrils between which only a small number of cells were observed. Muscles were found only in the walls of coelomic extensions leading to papulae. Stress-strain tests were performed on isolated dermis containing no muscles. The tangent modulus was 27.5 MPa at 0.04% strain rate in the stress-strain tests. It was increased to 40.7 MPa by mechanical stimulation, which also increased the tensile strength and breaking-strain energy density. Dynamic mechanical tests showed that the increase in stiffness in response to mechanical stimulation was transient. Acetylcholine (10(-6)-10(-3) mol l(-1)) and artificial seawater with an elevated potassium concentration (KASW) stiffened the dermis. Mechanical stimulation caused a 12% mass loss. KASW also caused mass loss, which was inhibited by anesthesia. These results clearly showed that the stiffness changes in the starfish dermis were based on a non-muscular mechanism that was similar to that of other echinoderm connective tissues with mechanical mutability.
authors.affiliation: Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo, Japan. tmotokaw@bio.titech.ac.jp
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Motokawa
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D001696:Biomechanical Phenomena; D003238:Connective Tissue / Q000502:physiology / Q000648:ultrastructure; D020405:Dermis / Q000502:physiology / Q000648:ultrastructure; D007564:Japan; D008854:Microscopy, Electron; D011188:Potassium / Q000378:metabolism; D013215:Starfish / Q000502:physiology* / Q000648:ultrastructure; D013718:Tensile Strength
chemical_list: D000109:Acetylcholine; D011188:Potassium