Hydroides ezoensis

Phylum: Annelida
Class: Polychaeta
Order: Sabellida (Serpulidae; serpulid)
Species name: Hydroides ezoensis Okuda 1934
Synonyms: None
Common name: A tubeworm
Date of introduction and origin
Hydroides ezoensis was first recorded in 1976 in Southampton Water and is thought to have been introduced in that year (Thorp, Pyne & West 1987; Zibrowius & Thorp 1989) probably from Japan. It originates in Asia where it is found on the Japanese and east Chinese coasts, and the Russian coast of the Sea of Japan.
Method of introduction
Probably introduced on the hulls of Nissan and Datsun car transporters to Southampton, Hampshire, and possibly also in ballast water (C.H. Thorp pers. comm.).
Reasons for success
Its success in Southampton Water was due to high levels of phytoplankton and hot summers. This would have encouraged this suspension-feeding serpulid to grow rapidly and reproduce. Success is also possibly due to a lack of predators and favourable physical conditions, including long residence time of water in the dock. Southampton Water is dominated by phytoplankton populations which, in summer, may exceed those elsewhere in the Solent by a factor of three or four (Anon 1976; Williams 1980). 1976 witnessed an extraordinarily prolonged and hot summer with sufficient sunshine to maintain high levels of phytoplankton within Southampton Water. High levels of phytoplankton, coupled with elevated temperatures within Southampton Water, would have enabled this suspension-feeding serpulid both to grow rapidly and to reproduce. Crisp (1958) emphasised that Southampton Water, due to its enclosed nature and small tidal range, would exchange water very slowly with that of the Solent. The consequent 'retention' of water within Southampton Water could have contributed to a rapid build-up of the H. ezoensis population through retention of larvae, as Crisp (1958) suggested for the non-native barnacle Elminius modestus.
Rate of spread and methods involved
This species has not spread outside the Solent (Thorp, Pyne & West1987; Zibrowius & Thorp 1989). It was introduced into France with Crassostrea gigas (Gruet, Héral & Robert 1976; Zibrowius 1978) but died out (Thorp, Pyne & West 1987).
It is only found in the Solent area, including the harbours complex of Portsmouth, Langstone and Chichester. Outside of Southampton Water numbers are very small and, apart from a significant population at Cowes, Isle of Wight, comprise mostly single individuals with no aggregation. A dense fouling population on the hull of HMS Cavalier, transferred from Southampton Water to Brighton Marina in 1984, failed to reproduce and rapidly deteriorated (C.H. Thorp pers. comm.). The only other record in Europe was from the Atlantic coast of France (Gruet, Héral & Robert 1976; Zibrowius 1978) where Hydroides ezoensis was introduced with imported oyster spat from Japan. This introduction was very short-lived and apparently did not spread from the point of introduction (Thorp, Pyne & West 1987).
Factors likely to influence spread and distribution
It only survives where there are good planktotrophic waters and its failure to colonise Brighton Marina following transfer on a ship's hull may be due to insufficient food availability (Thorp, Pyne & West 1987). In its native Japanese waters H.ezoensis appears to require temperatures of approximately 20oC to spawn and settle (Miura & Kajihara 1984). However, its distribution suggests that lethal temperatures have little influence over the spread of the species. Thorp (1994) has shown for the serpulid Ficopomatus enigmaticus that even when minimum temperatures are reached, spawning may be delayed in the absence of adequate phytoplankton (Himmelman 1980).
Effects on the environment
It has unknown effects, although perhaps some displacement of 'waterline' green algae Ulva and Enteromorpha occurs (C.H. Thorp pers. comm.). It has not displaced the heavy sea-squirt-dominated fouling community at an immediately lower level.
Effects on commercial interests
It is a severe fouling organism on harbour structures and ships' hulls throughout Southampton Water. While this additional fouling load does not appear to have had any deleterious effect on fixed harbour structures, it has caused flotation problems of buoys and added considerably to fouling of poorly-protected ships.
Control methods used and effectiveness
It can be removed by scraping of buoys and ships' hulls.
Beneficial effects
It probably adds to the diversity and success of indigenous species. Within the bulk of its massive encrustations (30 cm thick (Thorp, Pyne & West 1987)) is a protected habitat for free-living and sessile invertebrates (C.H. Thorp pers. comm.). It provides food: the opercula and branchial crown are eaten by fish predators, and larvae and eggs are produced in very large numbers, food for filter-feeders (C.H. Thorp pers. comm.).
This massive introduction, initiated almost certainly in 1976, passed without comment until specimens were removed from the hull of a fouled tug in 1982. Although enquiries elicited the information that heavy tube-worm fouling had been observed in 1980, and perhaps earlier, it was only the 'accident' of a research student collecting fouling algae that brought the massive encrustations to light.
Anon. 1976. Langstone Harbour study: the effect of sewage effluent on the ecology of the harbour. Unpublished report to Southern Water Authority by Portsmouth Polytechnic.
Crisp, D.J. 1958. The spread of Elminius modestus Darwin in north-east Europe. Journal of the Marine Biological Association of the United Kingdom, 37: 438-520.
Gruet, Y., Héral, M., & Robert, J.M. 1976. Premières observations sur l'introduction de la faune associée au naissan d'huîtres japonaises Crassostrea gigas (Thunberg), importé sur la côte atlantique Française. Cahiers de Biologie Marine, 17: 173-184.
Himmelman, J.H. 1980. Synchronisation of spawning in marine invertebrates by phytoplankton. In: Invertebrate reproduction, ed. by W.H. Clarke Jnr & T.S. Adams. 3-19. Amsterdam, Elsevier (Developments in Endocrinology).
Imajima, M. 1976. Serpulidae (Annelida: Polychaeta) from Japan. I. The genus Hydroides. Bulletin of the National Museum, Tokyo, Series A (Zoology), 2: 229-248.
Miura, T., & Kajihara, T. 1984. An ecological study of the life histories of two Japanese serpulid worms, Hydroides ezoensis and Pomatoleios kraussi. In: Proceedings of the First International Polychaete Conference, Sydney, Australia July 1983, ed. by P.A. Hutchings: 338-354. The Linnaean Society of New South Wales.
Thorp, C.H. 1994. Population variation in Ficopomatus enigmaticus (Fauvel) (Polychaeta: Serpulidae) in a brackish water millpond at Emsworth, West Sussex, UK. Memoires de Museum National d'Histoire Naturelle, 162: 585-591.
Thorp, C.H., Pyne, S., & West, S.A. 1987. Hydroides ezoensis Okuda, a fouling serpulid new to British coastal waters. Journal of Natural History, 21: 863-877.
Williams, P.J. le B. 1980. Phytoplankton in Southampton Water. In: The Solent estuarine system: an assessment of present knowledge. 25-36. Natural Environment Research Council, Publications Series C. No. 22.
Zibrowius, H. 1978. Introduction du polychète Serpulidae japonaise Hydroides ezoensis sur la côte atlantique française et remarques sur la repartition d'autres espèces de Serpulidae. Téthys, 8: 141-150.
Zibrowius, H., & Thorp, C.H. 1989. A review of the alien serpulid and spirorbid polychaetes in the British Isles. Cahiers de Biologie Marine, 30: 271-285.
Acknowledgements (contributions from questionnaire)
Dr C.H. Thorp, University of Portsmouth.