(de Blainville, 1827)
This species is rather variable in its external appearance, hence many synonyms have been described and six or seven subspecies recognized.
It is a large species, up to 150-200 mm in length, with a cylindrical trunk. The tentacular crown becomes more complex with increasing size; small individuals (10-15 mm long) have about 20 tentacles arranged in pairs in a single circle around the mouth. With growth, further tentacles develop in radial/longitudinal rows. When a body length of about 30 mm is reached, 50-60 tentacles are present whilst in the largest specimens the tentacle count may total over 150. Simple, spine-like hooks are arranged irregularly over the anterior introvert. The skin of the introvert and trunk is finely wrinkled; at both ends of the trunk it is rugose, has prominent papillae and is usually dark in colour (G. vulgaris). The nephridiopores are ventrolateral and just anterior of the anus. The longitudinal muscle layer of the body wall is continuous, not collected into bands.
Internally, four retractor muscles are present, the ventral pair being inserted in the middle third of the trunk and the dorsal pair posterior of the anus (G. vulgaris-internal). The intestine is tightly coiled in a double spiral supported by a spindle muscle attached anteriorly near the anus, but not posteriorly. The rectal caecum is conspicuous. Gut-fixing muscles fasten the oesophagus and anterior coils of the gut-spiral to the body wall in the region between the roots of the dorsal and ventral retractors. The contractile vessel is simple. Two nephridia; these hang freely in coelom.
Frequently, there is a large number of the entoproct Loxosomella phascolosomata attached to the trunk surface, particularly over the posterior region. The bivalve Mysella bidentata often inhabits the burrows of G.vulgaris . It spawns in the period June to September.
Inhabits muddy sand/gravel, from the lower shore to about 2000 m depth.
A widespread species. In the North Atlantic it ranges from Greenland and northern Norway to West Africa and the eastern Mediterranean. Also reported from scattered localities within the Indo-West Pacific region and from the Antarctic.