BURROW MORPHOLOGY OF THE ECHIURAN WORM MAXMUELLEIA-LANKESTERI (ECHIURA, BONELLIIDAE), AND A BRIEF REVIEW OF BURROW STRUCTURE AND RELATED ECOLOGY OF THE ECHIURA

The burrow morphology of the echiuran worm Maxmuelleria lankesteri (Herdman) was investigated in situ using a resin casting technique. Work was carried out in Lochs Sween and Creran on the west coast of Scotland in predominantly fine mud sediments. Burrow casts typically had only 1 opening, although there is evidence to suggest that a second opening may exist. In 58% of burrows, the opening, which was small and funnel-shaped, was associated with a surface mound reaching up to 20 cm in height. The tunnel below the burrow opening, the 'neck', was narrow and circular in transverse section with a smooth wall, possibly due to the action of the mucus-laden proboscis which emerges during feeding. The maximum burrow depth recorded was 80 cm and tunnel orientation became more horizontal with increasing depth. In some larger burrows, the tunnel began to orientate upwards towards its end. Below the neck, the tunnel was much wider but had a sub-circular transverse section. The burrows had distinct striations on the walls of lower tunnels, possibly caused by movements of the animal within. In some cases, a community of symbiotic organisms had developed, including polychaetes and 2 species of bivalve, Mysella bidentata (Montagu) and Saxicavella jeffresii Winckworth. Evidence of burrow modification by the crustacean Jaxea nocturna Nardo was noted and gobies, including Gobius niger Linnaeus, were also responsible for some alterations to the upper burrow around the opening. Evidence suggested that burrows were permanent structures which changed little in position.