Role of epibiotic diatoms isolated from the barnacle shell in the cyprid metamorphosis of Balanus amphitrite.

Barnacle shell (BSh)-associated bacteria, their culture supernatants (CS), and biofilm exopolymers (BE) are known to induce cyprid metamorphosis of Balanus amphitrite. Besides bacteria, the BSh also harbors diatoms. However, the roles of their CS and BE on cyprid metamorphosis were not known, and the same was evaluated using two epibiotic diatoms, Achnanthes longipes and Melosira nummuloides, isolated from the BSh. The CS of M. nummuloides, a waterborne cue, promoted cyprid metamorphosis only when isolated in the presence of BSh, whereas that of A. longipes inhibited the same. The high-performance liquid chromatography (HPLC) of CS of both the diatoms indicated the dominance of arabinose, an inhibitory sugar. However, thiols were additionally present in the CS of M. nummuloides as indicated by fourier-transform infrared spectroscopy (FTIR) and are probably responsible for their promotory effect. The BE, a surface-bound cue, of both the diatoms facilitated metamorphosis only when isolated in the presence of BSh and were rich in N-acetyl-D-glucosamine (NAG). Thus, the interaction of NAG with the shell proteins probably provides a set of cues that facilitate cyprid metamorphosis of B. amphitrite. [ABSTRACT FROM AUTHOR]