Barnacles are notorious marine foulants that adhere to submerged surfaces with surprising tenacity. The adhesion process is complex, involving multiple physiological processes and timed secretions. Previous biochemical analyses of barnacle cement have primarily focused on the bulk cement. However, barnacle cement contains a series of concentric circles that are commonly observed in optical, epifluorescent, and confocal microscopy, suggesting the composition of the adhesive may vary on a microscopic scale. To explore the heterogeneity of barnacle cement, the adhesive plaques of multiple barnacles were examined with several high spatial resolution techniques, including optical, epifluorescent, confocal, and infrared (IR) absorption microscopy, as well as X-ray photoelectron spectroscopy and atomic force microscopy. Using IR absorption microscopy, a technique sensitive to local changes in chemical composition, we have observed a non-uniform distribution of multiple chemical species in radial patterns that coincide with visible and autofluorescent features in the barnacle cement. The IR spectra also show significant chemical changes near secretory structures at the adhesive interface. We found substantial shifts in the Amide I band, suggesting that the secondary structure of proteins is not constant throughout the cement. Specific vibrations corresponding to phenolic compounds and polysaccharides were also found in variable intensities. Analysis of these data reveals distinct chemical differences that vary both radially and perpendicular to the substrate, providing insight to the construction of the barnacle adhesive interface.

Biochemical variations in the tree ring-like growth patterns of barnacle adhesive interfaces

245th National Meeting (2013)

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