Isolation and Characterization of Adhesive Secretion from Cuvierian Tubules of Sea Cucumber Holothuria forskåli (Echinodermata: Holothuroidea)

Linking properties of an orb-weaving spider's capture thread glycoprotein adhesive and flagelliform fiber components to prey retention time

An orb web's adhesive capture spiral is responsible for prey retention. This thread is formed of regularly spaced glue droplets supported by two flagelliform axial lines. Each glue droplet features a glycoprotein adhesive core covered by a hygroscopic aqueous layer, which also covers axial lines between the droplets, making the entire thread responsive to environmental humidity.We characterized the effect of relative humidity (RH) on ability of Argiope aurantia and Argiope trifasciata thread arrays to retain houseflies and characterize the effect of humidity on their droplet properties. Using these data and those of Araneus marmoreus from a previous study, we then develop a regression model that correlated glycoprotein and flagelliform fiber properties with prey retention time. The model selection process included newly determined, humidity-specific Young's modulus and toughness values for the three species' glycoproteins.Argiope aurantia droplets are more hygroscopic than A. trifasciata droplets, causing the glycoprotein within A. aurantia droplets to become oversaturated at RH greater than 55% RH and their extension to decrease, whereas A. trifasciata droplet performance increases to 72% RH. This difference is reflected in species' prey retention times, with that of A. aurantia peaking at 55% RH and that of A. trifasciata at 72% RH.Fly retention time was explained by a regression model of five variables: glue droplet distribution, flagelliform fiber work of extension, glycoprotein volume, glycoprotein thickness, and glycoprotein Young's modulus.The material properties of both glycoprotein and flagelliform fibers appear to be phylogenetically constrained, whereas natural selection can more freely act on the amount of each material invested in a thread and on components of the thread's aqueous layer. Thus, it becomes easier to understand how natural selection can tune the performance of viscous capture threads by directing small changes in these components.

Identification of proteins associated with adhesive prints from Holothuria dofleinii Cuvierian tubules

Cuvierian tubules are expelled as a defence mechanism against predators by various species within the family Holothuridae. When the tubules are expelled, they become sticky almost immediately and ensnare the predator. The mechanism of this rapid adhesion is not clear, but proteins on the surface of the expelled tubules are widely believed to be involved. This study has examined such proteins from Holothuria dofleinii, sourced from adhesive prints left on glass after the removal of adhered tubules. Gel electrophoresis showed that seven strongly staining protein bands were consistently present in all samples, with molecular masses ranging from 89 to 17 kDa. N-terminal sequence data was obtained from two bands, while others seemed blocked. Tandem mass spectrometry-based sequencing of tryptic peptides derived from individual protein bands indicated that the proteins were unlikely to be homopolymers. PCR primers designed using the peptide sequences enabled us to amplify, clone and sequence cDNA segments relating to four gel bands; for each, the predicted translation product contained other peptide sequences observed for that band that had not been used in primer design. Database searches using the peptide and cDNA-encoded sequences suggest that two of the seven proteins are novel and one is a C-type lectin, while-surprisingly-at least three of the other four are closely related to enzymes associated with the pentose phosphate cycle and glycolysis. We discuss precedents in which lectins and metabolic enzymes are involved in attachment and adhesion phenomena.