Lugworm

The lugworm is a well-known Polychaete worm. It burrows in sandy beaches and mudflats below the mid-tide level. These worms are common bait for fishermen and prey for long-billed wading birds. It is also called the sandworm, rock worm, and blow lug.

Kingdom: Animalia

Phylum: Annelida

Class: Polychaetae

Order: Sedentaria

Family: Arenicolidae

Genus: Arenicola

Species: Various (see below)

The genus Arenicola contains several marine worms, including the black lugworm (Arenicola defodiens) and the blow lugworm (Arenicola marina). The lugworm is one of the most common species of the 8,000 worms in its class, all called Polychaete worms. Like other Polychaete worms, the lugworm has many body segments, each one separated from the others by ring-like marks on the outside of its body and inside by tissues called septa. On each side is a pair of muscular extensions called parapodia. Each parapodium has a bundle of bristly hair called chaetae made of a material called chitin. Because these worms have many chaetae for each segment, they are called Polychaete worms. Each segment also has tiny hairs called cirri which help sense the worm's surroundings.

The lugworm is four to eight inches (10 to 20 centimeters) long and measures about 1/2 inch (one centimeter) around its body. It has a yellowish, orange, or brownish body. Thirteen pairs of bushy, feathery gills extend from the sides of the lugworm's body midway between head and tail. These collect oxygen so the worm can breathe in the water.

The home of the lugworm is a U-shaped burrow in the ground between the high and low tide levels. They can be 2 feet (60 centimeters) deep. It lives alone and prefers sandy beaches, mudflats, or the dark, muddy sand of sheltered bays and estuaries. These places along the North Atlantic Ocean and Mediterranean Sea are quiet and provide plenty of food.

The burrow of the lugworm has two openings. Mucus which the worm secretes lines the burrow and keeps both holes open and clear. At high tide, water flows into the burrow, past the head, and down toward the tail. The water brings sand and mud into the burrow which the worm filters for food. The water also carries oxygen for the worm's gills. The worm ripples its tail to help circulate water through the burrow to get more food and oxygen. As the water flows out of the opening near the tail, it carries out carbon dioxide and other wastes. Its tail can also regrow to allow it to get away from predators.

When the tide flows out, a little water remains in the burrow, but the oxygen in this water is soon gone. The worm then relies on a substance in its blood called hemoglobin which contains large amounts of oxygen. This keeps the worm alive until the next tide returns about 12 hours later. In this way, the worm can live in the same burrow for several months and receives food and oxygen twice a day.

Predators of the slow-moving lugworm are flatfish and long-billed wading birds, which can probe into the sand and pull out the worms. Two other threats are fishermen, who use the worms for bait, and pollution chemicals and oil spills.

Reproduction for the lugworm is an amazing event that occurs in its burrow. For two weeks in mid-October, males release sperm into the water as females release eggs into the water. Males and females time the release of sperm and eggs according to the tides so the eggs and sperm mix in the water. The larvae stay underwater near the seabed until they are adults. They drift into the shore and burrow into the sand or mud. They reach maturity after 2 to 3 years.

The lugworm's life span is five to six years.

Bibliography

"Lugworm." The Wildlife Trusts, www.wildlifetrusts.org/wildlife-explorer/marine/worms/lugworm. Accessed 1 May 2024.

McNish, James. "Lugworm Poos and the Secrets They Hold." The Natural History Museum, www.nhm.ac.uk/discover/lugworm-poos-and-the-secrets-they-hold.html. Accessed 1 May 2024.