Star ascidian (Botryllus schlosseri)

Distribution data supplied by the Ocean Biodiversity Information System (OBIS). To interrogate UK data visit the NBN Atlas.Map Help

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 Ireland

Global 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. 200m

Identifying 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

LevelScientific nameCommon name
PhylumChordata
ClassAscidiacea
OrderStolidobranchia
FamilyStyelidae
GenusBotryllus
Authority(Pallas, 1766)
Recent Synonyms

Biology

ParameterData
Typical abundance
Male size range1-20cm
Male size at maturity
Female size rangeMedium(11-20 cm)
Female size at maturity
Growth formCushion
Growth rateData deficient
Body flexibility
Mobility
Characteristic feeding methodActive suspension feeder, Non-feeding
Diet/food source
Typically feeds onSuspended particulates.
Sociability
Environmental positionEpifaunal
DependencyIndependent.
SupportsNone
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

ParameterData
Physiographic preferencesOpen coast, Offshore seabed, Strait or Sound, Sea loch or Sea lough, Ria or Voe, Estuary, Enclosed coast or Embayment
Biological zone preferencesLower eulittoral, Lower infralittoral, Sublittoral fringe, Upper circalittoral, Upper infralittoral
Substratum / habitat preferencesBedrock, Cobbles, Large to very large boulders, Small boulders
Tidal strength preferencesModerately 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 preferencesExposed, Moderately exposed, Sheltered, Very exposed, Very sheltered
Salinity preferencesFull (30-40 psu), Variable (18-40 psu)
Depth rangeIntertidal to ca. 200m
Other preferencesNo text entered
Migration PatternNon-migratory or 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

ParameterData
Reproductive typePermanent (synchronous) hermaphrodite
Reproductive frequency No information
Fecundity (number of eggs)2-10
Generation time<1 year
Age at maturityc. 50 days
SeasonInsufficient information
Life span<1 year

Larval characteristics

ParameterData
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 reviewHow is sensitivity assessed?

Physical pressures

Use / to open/close text displayed

 IntoleranceRecoverabilitySensitivityEvidence / Confidence
Substratum loss [Show more]

Substratum loss

Benchmark. All of the substratum occupied by the species or biotope under consideration is removed. A single event is assumed for sensitivity assessment. Once the activity or event has stopped (or between regular events) suitable substratum remains or is deposited. Species or community recovery assumes that the substratum within the habitat preferences of the original species or community is present. Further details

Evidence

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 High
Smothering [Show more]

Smothering

Benchmark. All of the population of a species or an area of a biotope is smothered by sediment to a depth of 5 cm above the substratum for one month. Impermeable materials, such as concrete, oil, or tar, are likely to have a greater effect. Further details.

Evidence

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 Low
Increase in suspended sediment [Show more]

Increase in suspended sediment

Benchmark. An arbitrary short-term, acute change in background suspended sediment concentration e.g., a change of 100 mg/l for one month. The resultant light attenuation effects are addressed under turbidity, and the effects of rapid settling out of suspended sediment are addressed under smothering. Further details

Evidence

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.
High High Moderate Moderate
Decrease in suspended sediment [Show more]

Decrease in suspended sediment

Benchmark. An arbitrary short-term, acute change in background suspended sediment concentration e.g., a change of 100 mg/l for one month. The resultant light attenuation effects are addressed under turbidity, and the effects of rapid settling out of suspended sediment are addressed under smothering. Further details

Evidence

No information
Desiccation [Show more]

Desiccation

  1. A normally subtidal, demersal or pelagic species including intertidal migratory or under-boulder species is continuously exposed to air and sunshine for one hour.
  2. A normally intertidal species or community is exposed to a change in desiccation equivalent to a change in position of one vertical biological zone on the shore, e.g., from upper eulittoral to the mid eulittoral or from sublittoral fringe to lower eulittoral for a period of one year. Further details.

Evidence

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
Increase in emergence regime [Show more]

Increase in emergence regime

Benchmark. A one hour change in the time covered or not covered by the sea for a period of one year. Further details

Evidence

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.
Intermediate High Low Moderate
Decrease in emergence regime [Show more]

Decrease in emergence regime

Benchmark. A one hour change in the time covered or not covered by the sea for a period of one year. Further details

Evidence

No information
Increase in water flow rate [Show more]

Increase in water flow rate

A change of two categories in water flow rate (view glossary) for 1 year, for example, from moderately strong (1-3 knots) to very weak (negligible). Further details

Evidence

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.
Intermediate High Low Low
Decrease in water flow rate [Show more]

Decrease in water flow rate

A change of two categories in water flow rate (view glossary) for 1 year, for example, from moderately strong (1-3 knots) to very weak (negligible). Further details

Evidence

No information
Increase in temperature [Show more]

Increase in temperature

  1. A short-term, acute change in temperature; e.g., a 5°C change in the temperature range for three consecutive days. This definition includes ‘short-term’ thermal discharges.
  2. A long-term, chronic change in temperature; e.g. a 2°C change in the temperature range for a year. This definition includes ‘long term’ thermal discharges.

For intertidal species or communities, the range of temperatures includes the air temperature regime for that species or community. Further details

Evidence

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.
Low Very high Very Low Moderate
Decrease in temperature [Show more]

Decrease in temperature

  1. A short-term, acute change in temperature; e.g., a 5°C change in the temperature range for three consecutive days. This definition includes ‘short-term’ thermal discharges.
  2. A long-term, chronic change in temperature; e.g. a 2°C change in the temperature range for a year. This definition includes ‘long term’ thermal discharges.

For intertidal species or communities, the range of temperatures includes the air temperature regime for that species or community. Further details

Evidence

No information
Increase in turbidity [Show more]

Increase in turbidity

  1. A short-term, acute change; e.g., two categories of the water clarity scale (see glossary) for one month, such as from medium to extreme turbidity.
  2. A long-term, chronic change; e.g., one category of the water clarity scale (see glossary) for one year, such as from low to medium turbidity. Further details

Evidence

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.
Low Immediate Not sensitive Low
Decrease in turbidity [Show more]

Decrease in turbidity

  1. A short-term, acute change; e.g., two categories of the water clarity scale (see glossary) for one month, such as from medium to extreme turbidity.
  2. A long-term, chronic change; e.g., one category of the water clarity scale (see glossary) for one year, such as from low to medium turbidity. Further details

Evidence

No information
Increase in wave exposure [Show more]

Increase in wave exposure

A change of two ranks on the wave exposure scale (view glossary) e.g., from Exposed to Extremely exposed for a period of one year. Further details

Evidence

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.
Intermediate Moderate Moderate Low
Decrease in wave exposure [Show more]

Decrease in wave exposure

A change of two ranks on the wave exposure scale (view glossary) e.g., from Exposed to Extremely exposed for a period of one year. Further details

Evidence

No information
Noise [Show more]

Noise

  1. Underwater noise levels e.g., the regular passing of a 30-metre trawler at 100 metres or a working cutter-suction transfer dredge at 100 metres for one month during important feeding or breeding periods.
  2. Atmospheric noise levels e.g., the regular passing of a Boeing 737 passenger jet 300 metres overhead for one month during important feeding or breeding periods. Further details

Evidence

Botryllus schlosseri has no organs for detecting noise.
Tolerant Not relevant Not sensitive High
Visual presence [Show more]

Visual presence

Benchmark. The continuous presence for one month of moving objects not naturally found in the marine environment (e.g., boats, machinery, and humans) within the visual envelope of the species or community under consideration. Further details

Evidence

Botryllus schlosseri has no organs for visual perception.
Tolerant Not relevant Not sensitive Moderate
Abrasion & physical disturbance [Show more]

Abrasion & physical disturbance

Benchmark. Force equivalent to a standard scallop dredge landing on or being dragged across the organism. A single event is assumed for assessment. This factor includes mechanical interference, crushing, physical blows against, or rubbing and erosion of the organism or habitat of interest. Where trampling is relevant, the evidence and trampling intensity will be reported in the rationale. Further details.

Evidence

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.
Intermediate High Low Low
Displacement [Show more]

Displacement

Benchmark. Removal of the organism from the substratum and displacement from its original position onto a suitable substratum. A single event is assumed for assessment. Further details

Evidence

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.
High Moderate Moderate Low

Chemical pressures

Use [show more] / [show less] to open/close text displayed

 IntoleranceRecoverabilitySensitivityEvidence / Confidence
Synthetic compound contamination [Show more]

Synthetic compound contamination

Sensitivity is assessed against the available evidence for the effects of contaminants on the species (or closely related species at low confidence) or community of interest. For example:

  • evidence of mass mortality of a population of the species or community of interest (either short or long term) in response to a contaminant will be ranked as high sensitivity;
  • evidence of reduced abundance, or extent of a population of the species or community of interest (either short or long term) in response to a contaminant will be ranked as intermediate sensitivity;
  • evidence of sub-lethal effects or reduced reproductive potential of a population of the species or community of interest will be assessed as low sensitivity.

The evidence used is stated in the rationale. Where the assessment can be based on a known activity then this is stated. The tolerance to contaminants of species of interest will be included in the rationale when available; together with relevant supporting material. Further details.

Evidence

Recolonization following cessation of exposure to a damaging non-persistent chemical is likely to be rapid.
No information Not relevant No information Not relevant
Heavy metal contamination [Show more]

Heavy metal contamination

Evidence

Recolonization following cessation of exposure to a damaging non-persistent chemical is likely to be rapid.
No information Not relevant No information Not relevant
Hydrocarbon contamination [Show more]

Hydrocarbon contamination

Evidence

Recolonization following cessation of exposure to a damaging non-persistent hydrocarbon is likely to be rapid.
No information Not relevant No information Not relevant
Radionuclide contamination [Show more]

Radionuclide contamination

Evidence

No recorded adverse effects of radionuclides on Botryllus schlosseri or similar species have been found.
No information Not relevant No information Not relevant
Changes in nutrient levels [Show more]

Changes in nutrient levels

Evidence

No recorded adverse effects of nutrients on Botryllus schlosseri or similar species were found.
Low High Low Very low
Increase in salinity [Show more]

Increase in salinity

  1. A short-term, acute change; e.g., a change of two categories from the MNCR salinity scale for one week (view glossary) such as from full to reduced.
  2. A long-term, chronic change; e.g., a change of one category from the MNCR salinity scale for one year (view glossary) such as from reduced to low. Further details.

Evidence

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.
Intermediate High Low Moderate
Decrease in salinity [Show more]

Decrease in salinity

  1. A short-term, acute change; e.g., a change of two categories from the MNCR salinity scale for one week (view glossary) such as from full to reduced.
  2. A long-term, chronic change; e.g., a change of one category from the MNCR salinity scale for one year (view glossary) such as from reduced to low. Further details.

Evidence

No information
Changes in oxygenation [Show more]

Changes in oxygenation

Benchmark.  Exposure to a dissolved oxygen concentration of 2 mg/l for one week. Further details.

Evidence

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.
Intermediate High Low Very low

Biological pressures

Use [show more] / [show less] to open/close text displayed

 IntoleranceRecoverabilitySensitivityEvidence / Confidence
Introduction of microbial pathogens/parasites [Show more]

Introduction of microbial pathogens/parasites

Benchmark. Sensitivity can only be assessed relative to a known, named disease, likely to cause partial loss of a species population or community. Further details.

Evidence

No information was found concerning pathogens or parasites in Botryllus schlosseri.
No information High No information Very low
Introduction of non-native species [Show more]

Introduction of non-native species

Sensitivity assessed against the likely effect of the introduction of alien or non-native species in Britain or Ireland. Further details.

Evidence

Some non-native species (Sargassum muticum) provide additional substrata for colonization.
Tolerant* Not relevant Not sensitive* Low
Extraction of this species [Show more]

Extraction of this species

Benchmark. Extraction removes 50% of the species or community from the area under consideration. Sensitivity will be assessed as 'intermediate'. The habitat remains intact or recovers rapidly. Any effects of the extraction process on the habitat itself are addressed under other factors, e.g. displacement, abrasion and physical disturbance, and substratum loss. Further details.

Evidence

This species is not targeted for extraction.
Not relevant Not relevant Not relevant High
Extraction of other species [Show more]

Extraction of other species

Benchmark. A species that is a required host or prey for the species under consideration (and assuming that no alternative host exists) or a keystone species in a biotope is removed. Any effects of the extraction process on the habitat itself are addressed under other factors, e.g. displacement, abrasion and physical disturbance, and substratum loss. Further details.

Evidence

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.
High Moderate Moderate Low

Additional information

No text entered

Importance review

Policy/legislation

- no data -

Status

Non-native

ParameterData
Native-
Origin-
Date ArrivedNot relevant

Importance information

-none-

Bibliography

  1. Berrill, N.J., 1950. The Tunicata with an account of the British species. London: Ray Society.

  2. 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.

  3. 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.

  4. 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.]

  5. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. Fenwick, 2018. Aphotomarine. Occurrence dataset http://www.aphotomarine.com/index.html Accessed via NBNAtlas.org on 2018-10-01

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Merseyside BioBank., 2018. Merseyside BioBank (unverified). Occurrence dataset: https://doi.org/10.15468/iou2ld accessed via GBIF.org on 2018-10-01.

  17. National Trust, 2017. National Trust Species Records. Occurrence dataset: https://doi.org/10.15468/opc6g1 accessed via GBIF.org on 2018-10-01.

  18. NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.

  19. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2024-05-18

  20. 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.

  21. 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.

  22. 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:

Hiscock, K. 2008. Botryllus schlosseri Star ascidian. In Tyler-Walters H. and Hiscock K. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 18-05-2024]. Available from: https://www.marlin.ac.uk/species/detail/1340

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Last Updated: 08/05/2008