Acartia tonsa

Phylum: Crustacea
Class: Maxillopoda
Order: Calanoida
Species name: Acartia tonsa Dana 1848
Synonyms: None
Common name: None
Date of introduction and origin
Acartia tonsa was first recorded from Southampton Water by between 1916 and 1956 Conover (1957). This copepod was first reported in France by Remy (1927). It was previously known from the western Atlantic and Indo-Pacific coasts although it is not known from where it was introduced.
Method of introduction
It was possibly introduced through transport on ships hulls and/or in ballast waters (Remy 1927).
Reasons for success
Tolerance of low salinities found in estuaries will have contributed to its success.
Rate of spread and methods involved
Not known.
In Britain this species has been found in Southampton Water (Conover 1957), the Tamar estuary, Devon and Cornwall, the Exe estuary in Devon (J.A. Lindley pers. comm.) and the Firth of Forth (Taylor 1987). European populations occur from Normandy to the Gulf of Finland (Brylinski 1981).
Factors likely to influence spread and distribution
Its distribution will be influenced by shipping as it occurs in estuarine sites of less than 33%o salinity, which are also of higher temperatures than off-shore waters and provide the temperatures required for reproduction.
Effects on the environment
Effects on commercial interests
Control methods used and effectiveness
None used.
Beneficial effects
None known.
This species produces diapause eggs (Zilhoux & Gonzalez 1972) which may have helped with transport in ballast waters.
Brylinski, J.M. 1981. Reports on the presence of Acartia tonsa Dana (Copepoda) in the area of Dunkirk and its geographical distribution in Europe. Journal of Plankton Research, 3: 255-261.
Conover, R.J. 1957. Notes on the seasonal distribution of zooplankton in Southampton Water with special reference to the genus Acartia. Annals and Magazine of Natural History, 12th Series, 10: 63-67.
Remy, P. 1927. Note sur un copépode de la saumâtre du canal de Caen à la mer. Annales de Biologie Lacustre, 15: 169-186.
Rose, M. 1933. Copépodes pélagiques. Paris, Paul Lechevalier. (Faune de France, No. 26.)
Taylor, C.J.L. 1987. The zooplankton of the Forth, Scotland. In: The natural environment of the estuary and Firth of Forth, ed. by D.S. McLusky.Proceedings of the Royal Society of Edinburgh, 93B (3/4): 377-388.
Zilhoux, E.J., & Gonzalez, J.G. 1972. Egg dormancy in a neritic calanoid copepod and its implications to overwintering in boreal waters. In: 5th European Marine Biology Symposium, ed. by B. Battaglia, 217 -230, B. Padova, Piccin Editore.
Acknowledgements (contributions from questionnaire)
J.A. Lindley, Plymouth Marine Laboratory.