A review of the occurrence and ecology of dense populations of Ditrupa arietina (Polychaeta: Serpulidae)

Abstract

Hartley, J.P. 2014. A review of the occurrence and ecology of dense populations of Ditrupa arietina (Polychaeta: Serpulidae). Memoirs of Museum Victoria 71: 85–95. Dense populations of the free-living serpulid Ditrupa arietina were first recorded to the west and north of the Shetland Isles in the 1920s and have since been reported from the Celtic and North Seas, the Armorican shelf, the Mediterranean and the Azores. These dense populations (of many thousands per square metre) numerically dominate the benthic fauna, and the tubes provide sites of attachment for a range of other species. Vacated tubes are also occupied by other animals, and tube fragments can contribute significantly to biogenic carbonate sediments, both Recent and fossil. Dense Ditrupa populations have been the subject of detailed autecological research over the last 15 years, but in spite of the apparent ecological importance of the species, it is not reflected in the European Nature Information System (EUNIS) or other North-east (NE) Atlantic habitat classifications. This paper provides a synthesis of the environmental conditions where high densities of Ditrupa have been found, with new data from seabed samples and photos. Ditrupa appears to occupy different habitats in the NE Atlantic and the Mediterranean, and studies of its morphology and genetics are needed to determine if there is a taxonomic basis to this ecological separation. Although the evidence is sparse, it is concluded that, in the NE Atlantic, dense populations of Ditrupa are found in areas where the seabed is periodically disturbed by internal wave action. European and other habitat classification schemes require revision to reflect the areas of occurrence and benthic effects of internal waves.