Limnodrilus monothecus

Annelids-Oligochaetes

Limnodrilus monothecus is a marine oligochaete, described from Bahia de San Quintin, Mexico. Marine oligochaetes resemble terresteiail earthworms, but are usually less than 60-70 mm long. However, this worm is found from Delaware to Venezuela, and is presumed native to the northwest Atlantic. The type specimen had ~46 segments, and was 9.5 mm long. Oligochaetes lack parapodia, and have relatively short setae. They are hermaphroditic, with a few anterior segments modified to form a reproductive section, called the clitellum. At sexual maturity, they have a few modified segments forming a reproductive section, called a clitellum. The worms copulate, and lay fertilized eggs in cocoons. The type specimens were found in sandy silt. On the Pacific coast, it has been found in Bahia San Quintin, Mexico, San Francisco Bay, and from Friday Harbor, Washington to Haida Gwai, British Columbia. It may have been introduced to the West Coast with solid ballast, ballast water, or Eastern Oysters. The photo is of the fresh-brackish oligochaete L. hoiffmeisteri.