Arenicolidae Family of Lugworms

One Lugworm of trhe Arenicolidae Family can be found in this website:

Glassell’s Lugworm, Arenicola glasselli. A representative of the Arenicolidae Family of Lugworms.

Phylogeny: Lug Worms in the Arenicolidae Family are segmented worms of the phylum Annelida. They are in the class Polychaeta, which are aquatic worms that have well-developed heads and numerous paddle-shaped paired appendages (parapodia). The Parapodia are covered with numerous chitinous bristles (chaetae). Polychaeta means “many bristles”. They are in the subclass Sedentaria meaning that they spend most of their life in a burrow or tube. They are further classified into the infraclass Solecida meaning they generally don’t have antennae or palps, they have a conical or sack-like proboscis, and they have thin tapering chaetae. The Arenicolidae Family is one of nine families within this infraclass. The Arenicolidae Family contains four genera and twenty-three species. The family name Arenicolidae comes from the Latin words meaning “sand-dweller”. Species in the Arenicolidae Family are also commonly known as Arenicolids.

Morphology: Lug Worms have cylindrical bodies that are divided into two or three segments. The head (prostomium)  is small and lacks eyes and appendages. Their thoracic or posterior segments bear bushy, red-tinged gills. All but one or two anterior segments bear unbranched chaetae. The largest species in the family have a maximum of 80 cm (2 feet 7 inches) in length. Some sources extend that length to 1.0 m (3 feet 3 inches).

Habitat and Distribution: Arenicolids are usually found lying in there U-shaped borrows in sand or mud substrates. Their borrows can reach 40 cm (15.5 inches) under the substrate. They are usually found in fairly sheltered waters such as bays and estuaries. Lug Worms are usually located by the coiled tubes of sand that they excrete. They live in the intertidal zone, and to depths of 30 m (100 feet), though most are found in less than 10 m (33 feet) of water. Lug Worms are found worldwide in polar to tropical seas. Two species from the Arenicolidae Family are found in Mexican waters.

Reproduction: Lugworms are gonochoric (male or female for life). Reproduction is sexual with swarming behavior. Swarming involves females producing a pheromone, which attracts and signals  the males to shed sperm which in turn stimulates females to shed eggs. Gametes are spawned through a rupture in the body wall (metanephridia).  After fertilization, most eggs become planktonic; although some are retained in the worm tubes or burrowed in jelly masses attached to the tubes (egg brooders). The fertilized eggs develop into trocophore larva, which later metamorphose into the juvenile, and then adult, stages.

Ecosystem interactions: Arenicolids may be depositional detritivores or algavores. They are preyed upon by shore birds, crabs and fish. As a defense mechanism, if a predator grabs their tail, they can shed their tail to allow the rest of the body to escape.