Settling cyprid larvae are highly responsive to the presence of conspecifics, and they preferentially settle on or near to adults and even to scars of adults that previously lived there. Lab studies on Balanus in Wales show that a protein-chemical called “arthropodin” is the stimulating factor. Notice in the photo that not only does the large adult Balanus glandula have conspecific spat settled on its shell plates, but also several generations of another barnacle Chthamalus dalli are present as well.
NOTE (lit. “belonging to arthropods” G.) The name was coined in the late 1950’s by its discoverer, D.J. Crisp, for a quinone-tanned protein substance found in arthropods and a few other marine organisms. Quinone-tanned proteins are structurally hard and are found in vertebrates in nails and hair