Polychaete worms make up one of the largest classes of marine invertebrates with well over 300 species found along the Atlantic shore. The polychaete clam worm species Nereis virens, also known by the scientific name Alitta virens, has 4 to 5 pairs of tentacular cirri (the antenna-like appendages on its head), 1 pair of short blunt palps (sensory appendages near the mouth) and four eyes. It also has two pincer like jaws that are capable of delivering a painful bite if handled. Of the Nereis species found in New England, N. virens is the most common, with a range extending from the Gulf of St. Lawrence to Delaware Bay. 

Neries virens can reach great lengths (the one pictured here was approximately a foot long, but they can get considerably larger – up to 3 feet). Like all polychaetes (a name that literally means “many bristles”) each segment of their body contains a pair of movable parapodia, giving them the appearance of having many pairs of feet. These parapodia vary in appearance among species from inconspicuous tiny bumps to elaborately lobed appendages. As the shape of the parapodia is distinct for each species, they can be used as a useful identifying feature. In addition, they function both as external gills, as well as a means of locomotion.

Clam worms prey on a variety of other organisms, including other clam worms, but also feed on various seaweeds and will feed as a scavenger when necessary. On the flip side, they are also an important link in the food chain for many other creatures, particularly bottom feeding fish, skates and crabs. Clam worms also make up a large percentage of the live sea-bait industry.

Clam worms can be found in a variety of sediment types, from soft mud to muddy sand to sediments containing a large proportion of gravel or small stones, and spend most of their time burrowed under the surface. When burrowing, they form sandy tubes glued together with mucus. N. virens is also tolerant of salinity changes, making it well adapted for estuarine habitats. Although harder to find at the surface at other times of the year, N. virens emerges to breed between late March and June, typically at night. Both the lunar phase and an increase in temperature seem to be involved in initiating spawning activity.