Fringehead cirri: for sensing or blending in?

Moss fringehead (Neoclinus bryope) is a cryptobenthic blenny – a fish that lives on the seafloor and usually hides itself in crevices with only its head protruding. Divers often find them in holes along the rocky shores of southern Japan. As implied by their name, fringehead blennies have fringes on their head called “cirri”. Cirri in fish are normally thought to play a role in chemical and tactile sensing, but their function has never been investigated or tested in fringehead blennies. One possibility is that they act as camouflage. The cirri in moss fringeheads seem to mimic turf algae that grow off rocky shores. Among 11 species of fringehead blenny in the genus Neoclinus, all have different cirri structures and colors, depending on the habitat where they are found. The cirri may therefore help these fish to blend in with the turf algae, making them more elusive and protecting them from predation. This hypothesis is waiting to be explored in both functional and evolutionary contexts.