Slime fanworm (Myxicola infundibulum)
This strange worm is a member of the polychaete group of worms, which are characterized by a segmented body with many segments bearing bristles. Polychaetes are common in the marine environment (see past stories on the feather duster worm and the pile worm).
Unlike its relatives, the slime fanworm is characterized by a fan that has tentacles joined over most of its length. In addition, and most unusual, the body is encased in a thick, transparent gelatinous tube (other species use a leather-like material). The fan is used to filter out plankton on which it feeds.
This 5-inch-long specimen — they can grow up to 8 inches in length — was found under a float where it shared space with several other individuals, forming a fist-size jelly mass. It normally occurs singly buried in mud or sand from the shallow subtidal zone to a depth of 90 feet. It is most abundant in wave-sheltered environments and can tolerate variable salinity levels. It is widely distributed in the Northern Hemisphere, occurring locally from the Bering Sea to California.
The animal possesses a giant nerve that runs the length of its body, allowing it to rapidly retract into its tube when danger threatens. Because of its large size, the nerve has been used by many scientists to study nerve physiology.
David W. Jamison is a Boston Harbor resident and marine biologist.