Fig. 1: Byssal system of a B. virescens ark clam.

a The exterior of the ark clam and (b) the giant plaque. c Opened ark clam showing its full body. d Transverse cross-section of the Barbatia foot tissue stained with Masson’s trichrome (right) is an a coloured illustration (left). Stainings performed 3 times on different tissues blocks. e Byssus-soft-tissue interface of the byssal system. gp, giant plaque pad; fg, foot groove; mf, muscle fibres; tg, thread gland; mg, matrix gland; bf, byssal filament; ct, collagenous tissue. (Scalebars: 1 cm for A and C, 0.5 cm for B, 1 mm for D, and 50 mm for E).