The temporary adhesion of echinoderm tube feet

The phylum Echinodermata is remarkable in the sense that most of its species use temporary adhe-sion extensively for attachment to the substratum or food capture. Their adhesive systems are asso-ciated to specialized organs, the podia or tube feet. Tube feet function as duo-gland adhesive sys-tems in which adhesive cells release a proteinaceous secretion, while de-adhesive cells allow de-tachment. In this chapter recent advances in the areas of tube foot morphology and mechanical properties, ultrastructure and composition of the adhesive material, and development of tube foot-inspired structures and materials are covered. Although tube feet are present in every extant echi-noderm species, only those of asteroids and regular echinoids have been studied in detail in terms of adhesion. From an ecological perspective, the strength with which echinoderms can attach to a surface is determined by tube foot adhesive and tensile strength as well as by the number of tube feet involved. Data on echinoderm attachment strengths, usually reported as critical detachment forces, are now available for several sea star and sea urchin species. They can be integrated with the animals’ body size and shape to calculate a safety factor which proved to be useful to predict the flow velocity at which organisms would be dislodged in the field. From a molecular point of view, the recent use of “omic” approaches such as transcriptomics and proteomics on echinoderm tube feet and their adhesive secretions considerably expanded the list of adhesive protein candidates. Their comparison in terms of amino acid or domain composition indicate substantial conservation of some adhesion-related proteins across echinoderm classes. Their glycosylation patterns, howev-er, may differ between species of a same class. Based on this knowledge, bio-inspired adhesives are developed, mostly as formulations of recombinant proteins, and investigated for biomedical appli-cations.