There are worms and there are worms. There are worms that look like ribbons, peanuts and spoons; worms that play innkeeper, swim like arrows and throw their beaks at prey; worms with bristles that burn, that kill with fire, worms of scales and everything mice; worms with anchors, worms with jaws, worms with tufts that give you reason for pause; worms adrift, worms afoot, worms in the gaps between grains on a slope; worms too thin to be flattened, too rude to be threatened, worms with no hairs or vices to hide; worms with crowns of wheat, beards of palps and mops of noodly appendages; worms that creep in burrows, steal from urchins and fish with nets of sticky slime. There are worms that sit in tubes, assembled from mud, sand or lime, from which they ambush victims, rake in fine food or build reefs on intertidal boulders and the blades of seagrass. And there are worms that are not worms: clams that tunnel through the hulls of wooden ships, irresistible forces from an entirely different kingdom, and the drake lords of smoking rings.
Many of these worms are too small, too shy and too well sequestered in rubble, reefs and rolls of sand bound by a thin organic film, to be a bother to beachcombers, save those with the means and mind to fill a bucket with writhing segments or the muscle to flip a rock and find a league of shadows on the dark side of the mound. The ones that never get away are poor flagships of a taxon that spans multiple phyla and suffers from typological blinkers, which confine their kind to plain, vermiform bodies shorn of baroque embellishments. As a result, sabellids are wont to have their feathers dusted and fans ruffled by visitors who take them to be sea anemones or corals, only to have these guesses shot down in short order by heads that turn tail, bolting down tubes of parchment glued to tidal bluffs.
Several fanworms occur on local shores, where they add a burst of colour and circles of resolution to pools dominated by lower crusts. At Pulau Semakau, almost every basin on the flat between the reef and seagrass meadow is home to one or more sabellids with bands of brown and white, which tower over beds of zoanthids and sponges until a shadow reduces them to dull grey digits. The same plumes line the natural formations of Pulau Sekudu, the artificial seawalls of Tanah Merah and the rocky fringes of the southern islands, feeding in the company of orange countymen and risking the stabs of sneaky ectoparasites. Another species favours sandier bottoms, where its pale spirals, rippling with near-invisible pinnules, rise in gatherings that sink before a spotlight. Also found on fine sediments is a worm with shortish radioles, which are often left untucked at low tide, and bright swirls of yellow and inky blue.
Darker, rather more delicate, whorls, superficially similar to sabellids but arising from worms of a different order, or phylum to be exact, can sometimes be seen in clusters on soft shores, particularly in the perimeter of peacock anemones. These colonies also live in hollow tubes, but construct their shelters with chitin and strengthen the walls with sand or calcareous fragments. The creatures within are a world apart from modified polychaetes – instead of an anus, the distal end of the worm is a closed bulb that serves as an anchor. This ampulla also holds the gonads and guts, with the latter looping back to spew waste via an hole at the head. Located nearby, the mouth is surrounded by ciliated tentacles that funnel edible particles to the oral aperture and may take the form of a simple circlet, a curious horseshoe or a pair of tight spirals. This suspension feeding system, called a lophophore, and a bauplan with a poor exit strategy should shit happen, unites these creatures, called phoronids, with lamp shells, lace animals and entoprocts.
With little more than a dozen species, Phoronida is a clade that has found no room to grow in seas dominated by more exuberant branches of the tree of life. Still, these unsegmented filter-feeders have managed to survive holocausts that killed off the trilobites, rudists, ammonoids, graptolites, conodonts and other once-prevalent marine groups. Today, phoronids maintain a worldwide, though largely temperate, distribution, with the Pacific coast of North American serving as a stronghold; half of all extant species dwell in this region, which also hosts the greatest densities of one species, Phoronopsis harmeri (=viridis) – this worm is reported to form aggregations covering up to an acre on nearshore flats, which turn green when the animals emerge from their tubes to feed.
The only local member of the phylum, Phoronis australis, is closely associated with cerianthids, whose leathery vessels provide a foothold for up to 30 individuals. The cnidarian may enjoy a mite of structural reinforcement from its tenants, while serving as an unwitting shield for the worms as well as tiny copepods that cling to the lophophores. Occasionally, a predator may land a nip, but the worms can regenerate lost mouthparts as well as augment their numbers by budding or splitting into two. Once anchored, the animals grow, feed and shed their gametes into the water column, partaking of an exercise in fertility that lasts for but a year before their time runs out and life loses its sting.