Shown here are examples of three different kinds of sedentary marine worms that may be found in the waters around Canadian coasts. They resemble each other superficially, having stout bodies whose "front" (anterior) end can be extended.
1. Peanut Worms (worms in the phylum Sipunculida)
There are varied estimates for the number of species of peanut worms, ranging from 144 to 350. One species is illustrated here (1). These worms can vary in size from 2 mm (1/8 in.) up to 50 cm (19.5 in.) long. Peanut worms burrow into sand and mud, or live in rocky crevices or empty snail shells. Tentacles at the end of their body pick up minute plants and detritus (dead organic matter), which they ingest. These worms have a world-wide distribution, mostly in the intertidal zone, but they can extend to the lowest depths of the ocean.
2. Priapulid Worms
There are about 19 known species of priapulid worms. One species is illustrated here (2). The size of these worms can range from less than 1 mm (with the introvert protruded) up to almost 40 cm (16 in.; with the introvert inverted). Large priapulid worms burrow into sand and mud, leaving only their mouth at the surface. Most prey on slow-moving, soft-bodied animals, while some are deposit-feeders. Larger species are found only in cold waters, either at great depths in tropical regions or in shallower waters near the poles. Nearly all smaller species live between grains of sediment in shallow tropical waters.
3. Spoon Worms (worms in the phylum Echiura)
There are about 150 described species of spoon worms. One species is illustrated here (3). These worms can range in size from a few millimetres up to 30 cm (12 in.), although some species can extend their spoon-shaped proboscis to 50 cm (19.5 cm) in length. Spoon worms burrow into sand and mud, in which each may build a "U"-shaped tube. The proboscis collects its food—micro-organisms and detritus—in its sticky secretions. These worms have a world-wide, distribution, usually near shore, but they have also been collected from the floor of oceans at great depths.