Sandmason and honeycomb tubeworms

These worms (Family Sabellariidae) prefer to live in high-energy areas where the current or waves can provide them with abundant food along with sediment for building their tubes. The body shape is quite bizarre, but divers will only see the anterior ends protruding from the tubes. Close inspection may reveal various small structures, including opercula (trap doors) of modified bristles, branchiae (gills), buccal (feeding) tentacles and palps (anterior feeding appendages). These worms are thought to be suspension feeders that use their buccal tentacles to generate feeding currents and trap fine particles in boluses (mucus balls), before transporting them to their mouths. Both the buccal tentacles and grooved palps have the dexterity to capture and manipulate large particles. Depending on the type of particles gathered, the worms eat them, eject them or use them for tube building. In some areas of the world, sandmason and honeycomb tubeworms have built extensive reef systems that have had considerable impact on beach profiles, wave patterns and sediment distribution. Considering that their life span may be three to 10 years, their larvae can swim about in the water column for up to two months and 12,000 to 15,000 mature worms can live per sq metre (10 sq ft), their impact can be very significant! On subtidal reefs the two species pictured can apparently occupy distinct positions: the cemented sandmason tubeworm (AN69) forms the upper part of the reef and the stone-cave sandmason tubeworm (AN70) inhabits the lower portion.