In the sea, annelids do their utmost to shatter the traditional search image of worms as long, plain tubes of slimy segments capable of little more interesting than grubbing through soil or getting a grip on passing veins. In the sea, worms have had much more time and room to expand into nearly every habitat, from deep sea vents to the fallen bodies of baleen whales. Others cling to the arms of crinoids, ride the tube-feet of sea stars or prowl the guts of sea urchins. Several families are active hunters and the largest of these are the bane of intertidal explorers, for they pop up from cracks in the rubble with little warning and seldom stay long enough to permit a record of their presence.
Many other families of polychaetes have given up adult motility for the comfort of holes and hollow tubes. In these taxa, the parapodia that allow free-living relatives to crawl or swim are reduced to minute grips and the limitations of a sedentary existence overcome by heads with extendible appendages. Pectinarids construct slender cones of sand and gulp their way through the sediment, while their relatives in the families Ampharetidae and Terebellidae have recognisably wormy bodies topped by a medusae of tentacles that scour the surroundings for edible deposits. What results is the unnerving sight of pasta-like tendrils that emerge from a gap in the grains and stream over the silt with noodly grace. Only when their owner is dislodged can one discern a body that seldom suffers light and feels out of place with nowhere to go but down.
Sabellida is an unranked taxon of polychaetes that have fixed their feeding tentacles into crowns with distinct forms. These are the feather dusters, peacocks, fans and christmas trees of reefs and intertidal rubble, the segmented rivals of polyps for particles of protein in the water column. Serpulids and spirorbids build calcerous coils on the surface of rocks and shells, while the sabellids dwell in soft, thin columns embedded in mud or sand. A brownish-red worm specked with white is the most prominent, though almost certainly not the most common, representative of the group locally. Others have pale orange or white plumes that beam in black light and withdraw when struck by a shadow. Some smaller specimens, such as this pale-crowned thing by a shrimp hole at Pulau Semakau, exhibit shades that offer little contrast between their radioles and the rest of the scene. It's likely that many, many more lurk on the flat, sifting the tide for plankton and scanning the sea for an excuse to swing into inaction when things come to a head.
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