Star ascidian (Botryllus schlosseri)
Colony of Botryllus schlosseri on rock.
Photographer: Keith Hiscock Copyright: Dr Keith Hiscock
Botryllus schlosseri and Calliostoma zizyphinum.
Photographer: Keith Hiscock Copyright: Dr Keith Hiscock
Botryllus schlosseri at Skomer Island.
Photographer: Judith Oakley Copyright: Judith Oakley
Botryllus schlosseri on a rocky shore.
Photographer: Judith Oakley Copyright: Judith Oakley
Botryllus schlosseri over Styela clava.
Photographer: Judith Oakley Copyright: Judith Oakley
Botryllus schlosseri under an overhang.
Photographer: Judith Oakley Copyright: Judith Oakley
Botryllus schlosseri.
Photographer: Keith Hiscock Copyright: Dr Keith Hiscock
Botryllus schlosseri.
Photographer: Keith Hiscock Copyright: Dr Keith Hiscock
Botryllus schlosseri. Most likely a transparent colony growing on red algae.
Photographer: Judith Oakley Copyright: Judith Oakley
A blue morph star ascidian.
Photographer: Judith Oakley Copyright: Judith Oakley
Dark coloured Botryllus schlosseri.
Photographer: Judith Oakley Copyright: Judith Oakley
The colonial sea squirt Botryllus schlosseri.
Photographer: Keith Hiscock Copyright: Dr Keith Hiscock
Distribution data supplied by the Ocean Biodiversity Information System (OBIS). To interrogate UK data visit the NBN Atlas.Map Help
| Researched by | Dr Keith Hiscock | Refereed by | This information is not refereed |
| Authority | (Pallas, 1766) | ||
| Other common names | - | Synonyms | - |
Summary
Description
Flat or fleshy colonies with zooids 2-4 mm across arranged in conspicuous star shaped systems, each with a central cloacal opening. Colonies vary greatly in colour including green, violet, brown and yellow.
Recorded distribution in Britain and Ireland
Found all around Britain and IrelandGlobal distribution
Present from the Faeroe Islands and west and south Norway to the Mediterranean including the Adriatic and Black Seas. Also present in the western Atlantic from Maine to New Jersey and in Florida.Habitat
Grows on a variety of stable substrata including algae and artificial substrata. Thrives in sheltered areas including docks. Although mainly found on the lower shore and in shallow depths, Berrill (1950) notes that it has been found at depths of several hundred metres.Depth range
Intertidal to ca. 200mIdentifying features
- Gelatinous often colourful colonies.
- The zooids arranged as 'stars' 2-4 mm across.
Additional information
No text entered
Listed by
- none -
Biology review
Taxonomy
| Phylum | Chordata | Sea squirts, fish, reptiles, birds and mammals |
| Class | Ascidiacea | Sea squirts |
| Order | Stolidobranchia | |
| Family | Styelidae | |
| Genus | Botryllus | |
| Authority | (Pallas, 1766) | |
| Recent Synonyms | ||
Biology
| Typical abundance | |||
| Male size range | 1-20cm | ||
| Male size at maturity | |||
| Female size range | Medium(11-20 cm) | ||
| Female size at maturity | |||
| Growth form | Cushion | ||
| Growth rate | Data deficient | ||
| Body flexibility | |||
| Mobility | |||
| Characteristic feeding method | Active suspension feeder, Non-feeding | ||
| Diet/food source | |||
| Typically feeds on | Suspended particulates. | ||
| Sociability | |||
| Environmental position | Epifaunal | ||
| Dependency | Independent. | ||
| Supports | None | ||
| Is the species harmful? | No information | ||
Biology information
Colonies that encrust algae may completely cover their substratum and appear pendant-like. Provides a source of food for cowries (Trivia spp.).
Habitat preferences
| Physiographic preferences | Open coast, Offshore seabed, Strait / sound, Sea loch / Sea lough, Ria / Voe, Estuary, Enclosed coast / Embayment |
| Biological zone preferences | Lower eulittoral, Lower infralittoral, Sublittoral fringe, Upper circalittoral, Upper infralittoral |
| Substratum / habitat preferences | Bedrock, Cobbles, Large to very large boulders, Small boulders |
| Tidal strength preferences | Moderately Strong 1 to 3 knots (0.5-1.5 m/sec.), Strong 3 to 6 knots (1.5-3 m/sec.), Very Strong > 6 knots (>3 m/sec.), Very Weak (negligible), Weak < 1 knot (<0.5 m/sec.) |
| Wave exposure preferences | Exposed, Moderately exposed, Sheltered, Very exposed, Very sheltered |
| Salinity preferences | Full (30-40 psu), Variable (18-40 psu) |
| Depth range | Intertidal to ca. 200m |
| Other preferences | No text entered |
| Migration Pattern | Non-migratory / resident |
Habitat Information
Populations in the western Atlantic may have arrived on shipping and it is likely that, as a fast-growing fouling organism, Botryllus schlosseri may spread readily to other parts of the world.Life history
Adult characteristics
| Reproductive type | Permanent (synchronous) hermaphrodite | |
| Reproductive frequency | No information | |
| Fecundity (number of eggs) | 2-10 | |
| Generation time | <1 year | |
| Age at maturity | c. 50 days | |
| Season | Insufficient information | |
| Life span | <1 year |
Larval characteristics
| Larval/propagule type | - |
| Larval/juvenile development | Lecithotrophic |
| Duration of larval stage | < 1 day |
| Larval dispersal potential | 1 km -10 km |
| Larval settlement period |
Life history information
Up to eight eggs are produced per zooid. After fertilization and development to a tadpole stage, the tadpole is released and is free swimming for up to 36 hours (Berrill 1950; Berrill, 1975).Sensitivity review
The MarLIN sensitivity assessment approach used below has been superseded by the MarESA (Marine Evidence-based Sensitivity Assessment) approach (see menu). The MarLIN approach was used for assessments from 1999-2010. The MarESA approach reflects the recent conservation imperatives and terminology and is used for sensitivity assessments from 2014 onwards.
Physical pressures
| Intolerance | Recoverability | Sensitivity | Evidence/Confidence | |
| High | High | Moderate | High | |
| Botryllus schlosseri is a sessile species dependant on the continued presence of the substratum to which it is attached. Removal of the substratum would remove the species. However, providing that suitable substratum remains after disturbance, settlement and growth from larvae is high. | ||||
| High | High | Moderate | Low | |
| Botryllus schlosseri occurs in areas where high levels of smothering due to siltation may occur but is generally found where silt is unlikely to settle (down-facing or suspended surfaces) suggesting that it is intolerant of smothering. Smothering may prevent feeding and respiratory flows through the colony and the species may not survive burial. However, providing that suitable substratum is available after the smothering event is over, settlement and growth from larvae is high. | ||||
| High | High | Moderate | Moderate | |
| Botryllus schlosseri occurs in areas where high levels of siltation and smothering may occur but is generally found where silt is unlikely to settle (down-facing or suspended surfaces) suggesting that it is intolerant of siltation. Silt may clog feeding and respiratory flows through the colony. However, providing that suitable substratum is available, settlement and growth from larvae is high. | ||||
| No information | ||||
| Intermediate | High | Low | Moderate | |
| Botryllus schlosseri occurs only in shaded areas on the lower shore in the intertidal where the atmosphere remains damp. Exposure to air and sunshine (for instance if boulders with colonies are overturned) would be likely to destroy colonies. However, providing that suitable substratum is available after a desiccation event, settlement and growth from larvae is high. | ||||
| Intermediate | High | Low | Moderate | |
| Botryllus schlosseri occurs only in shaded areas on the lower shore in the intertidal where the atmosphere remains damp. Increased exposure to air would be likely to destroy colonies. However, providing that suitable substratum is available after a emergence event, settlement and growth from larvae is high. | ||||
| No information | ||||
| Intermediate | High | Low | Low | |
| Water flow rate is important for maintaining colonies free of silt where they occur in sheltered areas. If water flow rate is decreased in such areas, and siltation occurs, colonies are likely to be adversely affected. However, once a high water flow rate is regained, settlement and growth from larvae is high. | ||||
| No information | ||||
| Low | Very high | Very Low | Moderate | |
| Botryllus schlosserioccurs from sub-arctic to warm temperate conditions and most likely tolerates a wide range of temperatures. Recolonization of suitable substrata would be rapid following once temperatures return to normal. | ||||
| No information | ||||
| Low | Immediate | Not sensitive | Low | |
| Botryllus schlosserioccurs in areas where high levels of turbidity occur although, as a passive suspension feeder, it may be susceptible to clogging (see siltation above). Increased turbidity may decrease phytoplankton productivity which may indirectly decrease food availability. Recolonization of suitable substrata would be rapid once turbidity returned to normal. | ||||
| No information | ||||
| Intermediate | Moderate | Moderate | Low | |
| Increase in wave exposure or storm events would remove predominantly the plants on which Botryllus schlosseri grows and therefore incidentally Botryllus schlosseri. Speed of recovery would depend on regrowth rates of the plant substrata. | ||||
| No information | ||||
| Tolerant | Not relevant | Not sensitive | High | |
| Botryllus schlosseri has no organs for detecting noise. | ||||
| Tolerant | Not relevant | Not sensitive | Moderate | |
| Botryllus schlosseri has no organs for visual perception. | ||||
| Intermediate | High | Low | Low | |
| Abrasion from sand is likely to be tolerated and Botryllus schlosseri occurs attached to algae on surf beaches. However, abrasion caused by mobile hard substrata, and anchor or dredge, is likely to remove colonies. Recolonization of suitable substrata would be rapid following cessation of abrasion. | ||||
| High | Moderate | Moderate | Low | |
| Botryllus schlosseri is permanently attached to the substratum and displacement is likely to have the same effect as substratum loss. Speed of recolonization would depend on the presence of suitable substrata. | ||||
Chemical pressures
| Intolerance | Recoverability | Sensitivity | Evidence/Confidence | |
| No information | Not relevant | No information | Not relevant | |
| Recolonization following cessation of exposure to a damaging non-persistent chemical is likely to be rapid. | ||||
| No information | Not relevant | No information | Not relevant | |
| Recolonization following cessation of exposure to a damaging non-persistent chemical is likely to be rapid. | ||||
| No information | Not relevant | No information | Not relevant | |
| Recolonization following cessation of exposure to a damaging non-persistent hydrocarbon is likely to be rapid. | ||||
| No information | Not relevant | No information | Not relevant | |
| No recorded adverse effects of radionuclides on Botryllus schlosseri or similar species have been found. | ||||
| Low | High | Low | Very low | |
| No recorded adverse effects of nutrients on Botryllus schlosseri or similar species were found. | ||||
| Intermediate | High | Low | Moderate | |
| Botryllus schlosseri lives in enclosed waters including docks and in estuaries where salinity is variable. However, its absence from low salinity conditions in upper estuaries and lagoons suggests that colonies will be intolerant of low salinities. Recolonization following cessation of exposure to low salinity is likely to be rapid. | ||||
| No information | ||||
| Intermediate | High | Low | Very low | |
| Botryllus schlosseri lives in habitats where periods of calm conditions may result in short term reduced oxygen levels. However, no studies relevant to de-oxygenation effects have been found. | ||||
Biological pressures
| Intolerance | Recoverability | Sensitivity | Evidence/Confidence | |
| No information | High | No information | Very low | |
| No information was found concerning pathogens or parasites in Botryllus schlosseri. | ||||
| Tolerant* | Not relevant | Not sensitive* | Low | |
| Some non-native species (Sargassum muticum) provide additional substrata for colonization. | ||||
| Not relevant | Not relevant | Not relevant | High | |
| This species is not targeted for extraction. | ||||
| High | Moderate | Moderate | Low | |
| Extraction of algae on which Botryllus schlosseri grows will remove the Botryllus schlosseri. Colonization of new algal substrata will be high once algae have grown. | ||||
Additional information
No text enteredImportance review
Policy/legislation
- no data -
Status
| National (GB) importance | - | Global red list (IUCN) category | - |
Non-native
| Native | - | ||
| Origin | - | Date Arrived | Not relevant |
Importance information
-none-Bibliography
Berrill, N.J., 1950. The Tunicata with an account of the British species. London: Ray Society.
Berrill, N.J., 1975. Chordata: Tunicata. In Reproduction of marine Invertebrates, vol. II, (ed. A.C. Geise & J.S. Pearse), pp. 241-282. New York: Academic Press.
Chadwick-Furman, N.E., & Weissman, I.L., 1995. Life histories and senescence of Botryllus schlosseri (Chordata: Ascidiacea) in Monterey Bay. Biological Bulletin, Marine Biological Laboratory, Woods Hole, 189, 36-41.
Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]
Rumohr, H. & Kujawski, T., 2000. The impact of trawl fishery on the epifauna of the southern North Sea. ICES Journal of Marine Science, 57, 1389-1394.
Datasets
Bristol Regional Environmental Records Centre, 2017. BRERC species records recorded over 15 years ago. Occurrence dataset: https://doi.org/10.15468/h1ln5p accessed via GBIF.org on 2018-09-25.
Centre for Environmental Data and Recording, 2018. IBIS Project Data. Occurrence dataset: https://www.nmni.com/CEDaR/CEDaR-Centre-for-Environmental-Data-and-Recording.aspx accessed via NBNAtlas.org on 2018-09-25.
Centre for Environmental Data and Recording, 2018. Ulster Museum Marine Surveys of Northern Ireland Coastal Waters. Occurrence dataset https://www.nmni.com/CEDaR/CEDaR-Centre-for-Environmental-Data-and-Recording.aspx accessed via NBNAtlas.org on 2018-09-25.
Cofnod – North Wales Environmental Information Service, 2018. Miscellaneous records held on the Cofnod database. Occurrence dataset: https://doi.org/10.15468/hcgqsi accessed via GBIF.org on 2018-09-25.
Dorset Environmental Records Centre, 2018. Ross Coral Mapping Project - NBN South West Pilot Project Case Studies. Occurrence dataset:https://doi.org/10.15468/mnlzxc accessed via GBIF.org on 2018-09-25.
Environmental Records Information Centre North East, 2018. ERIC NE Combined dataset to 2017. Occurrence dataset: http://www.ericnortheast.org.ukl accessed via NBNAtlas.org on 2018-09-38
Fenwick, 2018. Aphotomarine. Occurrence dataset http://www.aphotomarine.com/index.html Accessed via NBNAtlas.org on 2018-10-01
Fife Nature Records Centre, 2018. St Andrews BioBlitz 2014. Occurrence dataset: https://doi.org/10.15468/erweal accessed via GBIF.org on 2018-09-27.
Fife Nature Records Centre, 2018. St Andrews BioBlitz 2015. Occurrence dataset: https://doi.org/10.15468/xtrbvy accessed via GBIF.org on 2018-09-27.
Fife Nature Records Centre, 2018. St Andrews BioBlitz 2016. Occurrence dataset: https://doi.org/10.15468/146yiz accessed via GBIF.org on 2018-09-27.
Kent Wildlife Trust, 2018. Biological survey of the intertidal chalk reefs between Folkestone Warren and Kingsdown, Kent 2009-2011. Occurrence dataset: https://www.kentwildlifetrust.org.uk/ accessed via NBNAtlas.org on 2018-10-01.
Kent Wildlife Trust, 2018. Kent Wildlife Trust Shoresearch Intertidal Survey 2004 onwards. Occurrence dataset: https://www.kentwildlifetrust.org.uk/ accessed via NBNAtlas.org on 2018-10-01.
Manx Biological Recording Partnership, 2017. Isle of Man wildlife records from 01/01/2000 to 13/02/2017. Occurrence dataset: https://doi.org/10.15468/mopwow accessed via GBIF.org on 2018-10-01.
Manx Biological Recording Partnership, 2018. Isle of Man historical wildlife records 1990 to 1994. Occurrence dataset:https://doi.org/10.15468/aru16v accessed via GBIF.org on 2018-10-01.
Manx Biological Recording Partnership, 2018. Isle of Man historical wildlife records 1995 to 1999. Occurrence dataset: https://doi.org/10.15468/lo2tge accessed via GBIF.org on 2018-10-01.
Merseyside BioBank., 2018. Merseyside BioBank (unverified). Occurrence dataset: https://doi.org/10.15468/iou2ld accessed via GBIF.org on 2018-10-01.
National Trust, 2017. National Trust Species Records. Occurrence dataset: https://doi.org/10.15468/opc6g1 accessed via GBIF.org on 2018-10-01.
NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.
OBIS (Ocean Biodiversity Information System), 2023. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2023-04-01
Outer Hebrides Biological Recording, 2018. Invertebrates (except insects), Outer Hebrides. Occurrence dataset: https://doi.org/10.15468/hpavud accessed via GBIF.org on 2018-10-01.
South East Wales Biodiversity Records Centre, 2018. SEWBReC Marine and other Aquatic Invertebrates (South East Wales). Occurrence dataset:https://doi.org/10.15468/zxy1n6 accessed via GBIF.org on 2018-10-02.
Yorkshire Wildlife Trust, 2018. Yorkshire Wildlife Trust Shoresearch. Occurrence dataset: https://doi.org/10.15468/1nw3ch accessed via GBIF.org on 2018-10-02.
Citation
This review can be cited as:
Last Updated: 08/05/2008
