Janua brasiliensis

Phylum: Annelida
Class: Polychaeta
Order: Sabellida (spirorbid)
Species name: Janua brasiliensis (Grube 1872)
Synonyms: Neodexiospira brasiliensis, Dexiospira brasiliensis
Common name: A tubeworm
 
Date of introduction and origin
Janua brasiliensis is suggested to have been introduced into Portsmouth Harbour, the Solent, in 1974 (Knight-Jones et al. 1975), possibly from Brazil (Zibrowius & Thorp 1989). This species is widespread in tropical areas, including Brazil.
 
Method of introduction
One possible method of transport was on ships' hulls (Zibrowius & Thorp 1989) from the Round the World Yacht Race - the previous stop of the race was Brazil. Another possible method of introduction was as epiphytes on Sargassum muticum (Critchley et al. 1990).
 
Reasons for success
Unknown.
 
Rate of spread and methods involved
No spread has been recorded in British waters. While marginal dispersal is unlikely through the brief, motile, larval stage (Knight-Jones & Knight-Jones 1980), remote dispersal could be expected by adults attached to drifting Sargassum muticum. Spread is also conceivable as a fouling organism on ships' hulls, however, its isolated location in Britain suggests this has not occurred in British waters.
 
Distribution
This species, although widespread in tropical areas, has a very limited distribution in Europe; in the UK it is limited to Portsmouth Harbour; and elsewhere in Europe it is reported from the Oosterschelde, The Netherlands (Critchley & Thorp 1985), and St. Helier, Jersey (C.H. Thorp pers. comm.).
 
Factors likely to influence spread and distribution
This species' epiphytic association with the invasive brown alga Sargassum muticum provides it with a convenient vehicle for dispersal. Sargassum muticum is noted for its habit of casting off lateral branches in late summer and early autumn which, buoyed up with air bladders, are free to drift in surface currents over long distances. Such drifting plants could transport an 'innoculum' of attached Janua brasiliensis. Elsewhere in Europe, in both the Goes Canal (Eastern Scheldt) and Havre des Pas (Jersey), records of Janua brasiliensis are from sites where Sargassum muticum had already been recorded (Critchley, Farnham & Morrell 1983). Janua brasiliensis reaches maturity within a single season and, additionally, has a reduced brooding period for its embryos in higher temperatures (Gray 1978). It would appear that while the means are available for J. brasiliensis to be as widely distributed as its Sargassum host, its limited occurrence within temperate waters may be determined by the availability of waters of suitable temperature. Elevated water temperatures in enclosed or semi-enclosed systems, such as Portsmouth Harbour, are likely to be a significant factor contributing to its success. In Portsmouth Harbour Janua brasiliensis exhibits a marked settlement preference for S. muticum in contrast to the submerged pontoon surfaces. It is notable that elsewhere in Europe, J. brasiliensis has become more successful on native host plants, in the form of Zostera at Goes (Critchley & Thorp 1985), and Fucus serratus at Havre des Pas (C.H. Thorp pers. comm.).
 
Effects on the environment
In the Goes Canal the density of the settlement of J. brasiliensis on the eel grass Zostera was great enough to have weighed down leaves such that lay on the canal sediment. This considerably impaired the eel grass' photosynthetic efficiency (Critchley & Thorp 1985).
 
Effects on commercial interests
It is a fouling organism but has negligible effect in British waters.
 
Control methods used and effectiveness
Not applicable to such a small animal.
 
Beneficial effects
None known.
 
Comments
All three records of J. brasiliensis from European waters have come about as a consequence of monitoring the spread of S. muticum, in the case of the Goes record in particular. It is possible that there are other sites with isolated populations on Channel coasts, both French and English, which have not been visited by competent 'spirorbidologists'. Such sites would be situated in the vicinity of warmed water, coastal power plants etc.
 
References
Critchley, A.T., Farnham, W.F., & Morrell, S.L. 1983. A chronology of European sites of attachment for the invasive brown alga, Sargassum muticum, 1973-81. Journal of the Marine Biological Association of the United Kingdom,63: 799-811.
 
Critchley, A.T., Farnham, W.F., Yoshida, T., & Norton, T.A. 1990. A bibliography of the invasive alga Sargassum muticum (Yendo) Fensholt (Fucales; Sargassaceae). Botanica Marina, 33: 551-562.
 
Critchley, A.T., & Thorp, C.H. 1985. Janua (Dexiospira)brasiliensis (Grube) (Polychaeta: Spirorbidae): a new record from the south-west Netherlands. Zoologische Bijdragen, 31: 1-8. (Delta Institute Communication, No. 304.)
 
Gray, P.W.G. 1978. An investigation of the fauna associated with Sargassum muticum. Ph.D. Thesis, Council for National Academic Awards, Portsmouth Polytechnic.
 
Knight-Jones, P., & Knight-Jones, E.W. 1980. Pacific spirorbids in the east Atlantic. Journal of the Marine Biological Association of the United Kingdom, 60: 461-464.
 
Knight-Jones, P., Knight-Jones, E.W., Thorp, C.H., & Gray, P.W.G. 1975. Immigrant spirorbids (Polychaeta: Sedentaria) on the Japanese Sargassum at Portsmouth, England. Zoologica Scripta 4(4): 145-149.
 
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.