Short description of Corella eumyota, Orange-tipped sea squirt

A non-colonial sea squirt up to eight cm length in GB. Lays flat, with exhalant siphon slightly to the right. Siphons often have orange tinge. Tunic is translucent, smooth. Gut forms smooth curve around hind end.

Impact summary: Corella eumyota, Orange-tipped sea squirt

Individually small, but may form dense clumps by settlement of larvae onto older individuals.  Clumps could clog pipes or render submerged gear (e.g. in aquaculture) cumbersome. Potential competitor for food and space with cultured bivalves.

Habitat summary: Corella eumyota, Orange-tipped sea squirt

Mainly marinas and harbours, but capable of colonising natural habitats, e.g. shores in Plymouth Sound and the Yealm Estuary, Devon. Also occurs sub-tidally in native range, and likely to do so here.

Overview table

Environment	Marine
Species status	Non-Native
Native range	Australasia, Southern Africa, Southern South America
Functional type	Filter-feeder
Status in England	Non-Native
Status in Scotland	Non-Native
Status in Wales	Non-Native
Location of first record	Brighton Marina, Gosport Marina and Weymouth Harbour
Date of first record	2004

Origin

Southern hemisphere, but exact origin unknown (present on all continents in southern hemisphere).

First Record

Discovered in September 2004 in Brighton Marina, Gosport Marina and Weymouth Harbour.

Pathway and Method

Suspected introduction to northern hemisphere with importation of commercial bivalves; long-distance transport on hulls also possible. Subsequent apparently rapid spread along European Atlantic coasts, probably aided by leisure craft.

Species Status

Well established in GB, also recorded in northern France, northern Spain (Atlantic coast; 2003) and Portugal (south to Oeiras near Lisbon). Not known elsewhere in northern hemisphere; very probably introduced in parts of current southern hemisphere range.

Dispersal Mechanisms

Natural dispersal apparently very limited; sessile as adult, non-feeding swimming larvae brooded and released when ready to settle. Occasional rafting of adults on weed etc. possible.  Spread along coast in Europe probably substantially assisted by leisure craft (hull fouling), with populations in a high proportion of marinas within current introduced range.

Reproduction

Reproduction peaks in summer (studied in sout-west England).  Broods embryos and hatched larvae; larvae ready to settle upon release. Hermaphroditic and capable of self-fertilization, but can also take up sperm shed by neighbours for cross-fertilization.

Known Predators/Herbivores

None known.

Resistant Stages

None

Habitat Occupied in GB

Marinas and harbours (e.g. sides and undersides of pontoon floats). Has also colonised natural shores, as documented for Plymouth Sound and the nearby Yealm estuary, where occurs in sheltered muddy and rocky habitats, often under boulder or cobble-sized rocks where these remain in puddles of standing water at low tide. In southern hemisphere, the species also occurs in natural subtidal habitats (where may form ‘meadows’), but this has not yet been documented in GB.

Established from Oban around the south coast of England to Lowestoft. Also known as an introduced species in a few marinas around the coast of Ireland, and in northern France (discovered 2002, first record in northern hemisphere; Lambert 2004), northern Spain and Portugal (south to Oeiras near Lisbon). Not known elsewhere in northern hemisphere.  Very probably introduced in parts of current southern hemisphere range, which encompasses all continents including Antarctica.

Environmental Impact

Corella eumyota populations might have a negative effect on the abundance and habitat occupancy of other shallow-water suspension feeding sessile invertebrates.  However, it is not clear whether this would cause the local extinction of any species.

Health and Social Impact

None known.

Economic Impact

The species’ potential abundance, coupled with the formation of dense clumps, means it could become a significant fouler of mussel and oyster culture gear, potentially competing for food with target species or smothering them, and rendering underwater gear and lines extremely cumbersome.  Clumps might also have the potential to block intake pipes etc.

Identification

Lambert CL, Lambert IM, Lambert G (1995) Brooding strategies in solitary ascidians: Corella species from north and south temperate waters. Can. J. Zool. 73, 1666-1671.

Marine Aliens II consortium (2010). Identification guide for selected marine non-native species. 2nd Edition Available from: www.marlin.ac.uk/marine_aliens/latest_news.php

Biology, ecology, spread, vectors

Arenas, F., Bishop, J. D. D., Carlton, J. T., Dyrynda, P. J., Farnham, W. F., Gonzalez, D. J., Jacobs, M. W., Lambert, C., Lambert , G., Nielsen, S. E., Pederson, J. A., Porter, J. S., Ward, S. & Wood, C. A. (2006) Alien species and other notable records from a rapid assessment survey of marinas on the south coast of England. Journal of the Marine Biological Association of the United Kingdom, 86, 1329-1337,       doi:10.1017/S0025315406014354

Collin, S. B., Oakley, J. A., Sewell, J. & Bishop, J. D. D. (2010) Widespread occurrence of the non-indigenous ascidian Corella eumyota Traustedt, 1882 on the shores of Plymouth Sound and Estuaries Special Area of Conservation, UK. Aquatic Invasions, 5, 175-179, doi:10.3391/ai.2010.5.2.07

Dupont, L., Viard, F., David, P. & Bishop, J. D. D. (2007) Combined effects of bottlenecks and selfing in populations of Corella eumyota (Tunicata), a recent introduction to the English Channel. Diversity and Distributions, 13, 808–817, doi:10.1111/j.1472-4642.2007.00405.x

El Nagar, A., Huys, R. & Bishop, J. D. D. (2010) Widespread occurrence of the Southern Hemisphere ascidian Corella eumyota Traustedt, 1882 on the Atlantic coast of Iberia. Aquatic Invasions, 5, 169-173, doi:10.3391/ai.2010.5.2.06

Lambert CL, Lambert IM, Lambert G (1995) Brooding strategies in solitary ascidians: Corella species from north and south temperate waters. Can. J. Zool. 73, 1666-1671.

Minchin D (2007) Rapid coastal survey for targeted alien species associated with floating pontoons in Ireland. Aquatic Invasions, 2, 63-70, doi:10.3391/ai.2007.2.1.8

Varela MM, de Matos-Pita SS, Ramil F, Ramos-Espla AA (2008) New report of the Antarctic ascidian Corella eumyota (Tunicata: Ascidiacea) on the Galician coast (north-west Spain). Marine Biodiversity Records 1: e59 doi:10.1017/S1755267207006574

Management and impact

Collin, S. B., Oakley, J. A., Sewell, J. & Bishop, J. D. D. (2010) Widespread occurrence of the non-indigenous ascidian Corella eumyota Traustedt, 1882 on the shores of Plymouth Sound and Estuaries Special Area of Conservation, UK. Aquatic Invasions, 5, 175-179, doi:10.3391/ai.2010.5.2.07

General

Lambert G (2004) The south temperate and Antarctic ascidian Corella eumyota reported in two harbours in northwestern France. Journal of the Marine Biological Association of the United Kingdom, 84, 239-241, doi:10.1017/S0025315404009105h

Minchin D (2007) Rapid coastal survey for targeted alien species associated with floating pontoons in Ireland. Aquatic Invasions, 2, 63-70, doi:10.3391/ai.2007.2.1.8

Varela MM, de Matos-Pita SS, Ramil F, Ramos-Espla AA (2008) New report of the Antarctic ascidian Corella eumyota (Tunicata: Ascidiacea) on the Galician coast (north-west Spain). Marine Biodiversity Records 1: e59 doi:10.1017/S1755267207006574

https://www.cabi.org/isc/datasheet/113454