Mechanical Diversity of Connective Tissue of the Body Wall of Sea Anemones

Abstract

Techniques for analysing polymer mechanics were used to describe quantitatively the time-dependent mechanical properties of the body-wall connective tissue (mesogloea) and to indicate macromolecular mechanisms responsible for the mechanical behaviour of two species of sea anemones, Metridium senile and Anthopleura xanthogrammica. 1. The mesogloea of M. senile is more extensible and less resilient than that of A. xanthogrammica when stressed for periods comparable to the duration of flow forces the anemones encounter and the postural changes they perform.2. Polarized light microscopy and SEM reveal that the reinforcing collagen fibres in the mesogloea are aligned parallel with the major stress axes in the body wall.3. Mechanical tests and observations of composition and microstructure indicate that the mesogloea of A. xanthogrammica is less extensible than that of M. senile because molecular entanglements (due to more closely packed parallel collagen fibres and to a higher concentration of polymers in the interfibrillar matrix) retard the extension of A. xanthogrammica mesogloea. This study illustrates how structural features on the macromolecular and microscopic levels of organization of an organism can equip that organism for the particular mechanical activities it performs and the environmental forces it encounters.