FLAMMANG, P.: Tube feet and Cuvierian tubules: two different adhesive systems from echinoderms

The fact that many marine invertebrates produce adhesives that act in the presence of water has raised a growing scientific interest because such bioadhesives may find applications in underwater construction or in the medical and dental fields. In our laboratory, we are studying two different adhesive systems from echinoderms, the tube feet and the Cuvierian tubules. The tube feet, or podia, are the external appendages of the echinoderm water-vascular system and are one of the distinctive characters of the phylum. According to the considered echinoderm taxon, tube feet may be involved in fixation, locomotion, feeding or burrowing, functions that all require the formation of a strong though temporary adhesive bond between the tube foot and a substratum. Cuvierian tubules, on the other hand are restricted to a few species of sea-cucumbers. This very peculiar and specialized defense system is mobilized when the animal is mechanically stimulated, resulting in the discharge of a few white filaments, the tubules. In seawater, the expelled tubules considerably lengthen, instantly become sticky upon contact to any object, and therefore rapidly entangle and immobilize most potential predators. Integration of the results from three approaches – biomechanical (the measurement of adhesion strengths), morphological (the ultrastructural description of the adhesive organs), and biochemical (the molecular characterization of the adhesive secretions)- indicates that tube feet and Cuvierian tubules differ radically in their mode of adhesion, their structure, and the composition of their adhesive secretions. Therefore, they turn out to be complementary biological models for the study of adhesion in the marine environment and both could offer novel features or performance characteristics for applications as underwater adhesives.