An encrusting bryozoan (Oshurkovia littoralis)

Oshurkovia littoralis

Photographer: Dr 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	Dr Peter J. Hayward
Researched by Dr Keith Hiscock	Refereed by Dr Peter J. Hayward
Authority	(Hastings, 1944)
Authority (Hastings, 1944)
Other common names	-	Synonyms	Umbonula littoralis
Other common names -	Synonyms Umbonula littoralis

Summary

Description

Colonies form large orange crusts that spread irregularly and are often fringed with green.

Recorded distribution in Britain and Ireland

Present all around the British Isles.

Global distribution

Present from Bergen, Norway south along the western Atlantic coast to at least the Channel Isles and western Brittany. Not present in the Mediterranean.

Habitat

A characteristic species of the sublittoral fringe and underboulder habitats. Occurs on rock and on Laminaria spp. holdfasts and Himanthalia elongata buttons.

Depth range

Intertidal to 6 m

Identifying features

Sheet-like encrusting form orange in colour.
Zooids 0.6 to 0.8 mm x 0.46 x 0.6 mm, oval to hexagonal bordered by raised lines.
Aperture of zooid elliptical.
Frontal wall finely granular with 14-20 large and conspicuous areolae.

Additional information

No text entered

Listed by

- none -

Biology review

Taxonomy

Level	Scientific name	Common name
Phylum	Bryozoa	Sea mats, horn wrack & lace corals
Sea mats, horn wrack & lace corals
Class	Gymnolaemata	Naked throat bryozoans
Naked throat bryozoans
Order	Cheilostomatida

Family	Umbonulidae
Genus	Oshurkovia
Authority	(Hastings, 1944)
Recent Synonyms	Umbonula littoralis

Biology

Parameter	Data
Typical abundance	Moderate density
Male size range
Male size at maturity
Female size range	Very small(<1cm)
Female size at maturity
Growth form	Crustose hard
Growth rate	Data deficient
Body flexibility
Mobility	Sessile, permanent attachment
Characteristic feeding method	Active suspension feeder
Diet/food source
Typically feeds on	Suspended material
Sociability	Colonial
Environmental position	Epifaunal
Dependency	Independent.
Supports	None
Is the species harmful?	No information

Biology information

Oshurkovia (syn. Umbonula) littoralis is a hermaphrodite. The size range given above is for individual zooids.

Habitat preferences

Parameter	Data
Physiographic preferences	Open coast, Strait or Sound, Ria or Voe, Enclosed coast or Embayment
Biological zone preferences	Sublittoral fringe, 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.), Weak < 1 knot (<0.5 m/sec.)
Wave exposure preferences	Exposed, Extremely exposed, Moderately exposed, Sheltered, Very exposed
Salinity preferences	Full (30-40 psu)
Depth range	Intertidal to 6 m
Other preferences	None
Migration Pattern	Non-migratory or resident

Habitat Information

No text entered

Life history

Adult characteristics

Parameter	Data
Reproductive type	Permanent (synchronous) hermaphrodite
Reproductive frequency	Annual protracted
Fecundity (number of eggs)	No information
Generation time	Insufficient information
Age at maturity	Insufficient information
Season	June - November
Life span	Insufficient information

Larval characteristics

Parameter	Data
Larval/propagule type	-
Larval/juvenile development	Lecithotrophic
Duration of larval stage	No information
Larval dispersal potential	No information
Larval settlement period

Life history information

The dispersal phase is probably brief and larvae probably do not travel far.
Embryos were recorded as present in the Plymouth area in June and August (Marine Biological Association, 1957), from October and November on the north-east coast of England (Hastings, 1944) and from September to February in Manx waters (Eggleston, 1969).

Sensitivity reviewHow is sensitivity assessed?

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

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	Intolerance	Recoverability	Sensitivity	Evidence / 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 Removal of substratum will remove the attached species. However, larvae are produced annually and are likely to disperse from nearby unaffected substrata to recolonize.	High	High	Moderate	Moderate
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 Smothering by overgrowth of competing encrusting ascidians may not kill Umbonula sp. (see Turner, 1988). Smothering by silt may however have an adverse effect. Larvae are produced annually and are likely to disperse from nearby unaffected substrata to recolonize.	Intermediate	High	Low	Moderate
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 Umbonula lives in habitats that are generally clear of silt (exposed coasts and downward facing surfaces) but is likely to have at least limited ability to clear silt. Larvae are produced annually and are likely to disperse from nearby unaffected substrata to recolonize.	Intermediate	High	Low	Low
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 A normally subtidal, demersal or pelagic species including intertidal migratory or under-boulder species is continuously exposed to air and sunshine for one hour. 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 Umbonula lives in habitats that are in damp situations where it occurs on the lower shore suggesting that it would not survive desiccating conditions for very long. Larvae are produced annually and are likely to disperse from nearby unaffected substrata to recolonize.	Intermediate	High	Low	Low
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 Umbonula lives in habitats that are in damp situations where it occurs on the lower shore suggesting that it usually requires submerged conditions. Increased amounts of emergence in desiccating situations are likely to lead to mortality. Larvae are produced annually and are likely to disperse from nearby unaffected substrata to recolonize.	Intermediate	High	Low	Low
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 Umbonula thrives in habitats that are in areas of strong water movement and is not generally found in sheltered areas suggesting that a decrease in water flow rates where wave action is also weak would be likely to result in mortality most likely as a secondary effect from siltation but possibly reduction in food source. Larvae are produced annually and are likely to disperse from nearby unaffected substrata to recolonize.	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 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. 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 The British Isles are at the centre of geographical range for Umbonula littoralis suggesting that colonies are likely to tolerate both warmer and colder conditions than those existing in Britain and Ireland. Larvae are produced annually and are likely to disperse from nearby unaffected substrata to recolonize.	Low	High	Low	Low
Decrease in temperature [Show more] Decrease in temperature 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. 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 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. 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 Increased turbidity may reduce phytoplankton production and therefore reduce food availability except where increased turbidity results from a plankton bloom.	Low	High	Low
Decrease in turbidity [Show more] Decrease in turbidity 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. 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 Umbonula thrives in habitats that are in areas of strong water movement and is not generally found in sheltered areas suggesting that a decrease in wave exposure where tidal streams are also weak would be likely to result in mortality most likely as a secondary effect from siltation but possibly reduction in food source. Larvae are produced annually and are likely to disperse from nearby unaffected substrata to recolonize.	Intermediate	High	Low	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 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. 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 Umbonula is unlikely to sense noise but may be sensitive to vibration.	Tolerant	Not relevant	Not sensitive	Moderate
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 Umbonula may sense changes in light (shadowing) but has no visual organs.	Tolerant	Not relevant	Not sensitive	High
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 Umbonula has a hard calcareous skeleton which is likely to be broken through contact with hard surfaces such as cobbles moving around during storms. However, small portions of the colony might survive in irregularities of the substratum and spread after abrasion has ceased. Encrusting bryozoans occupy the zone above bare rock on abraded surfaces where there is a zonation from bare to dense erect growths (authors observations). Larvae are produced annually and are likely to disperse from nearby unaffected substrata to recolonize and so recoverability is recorded as high.	Intermediate	High	Low	Moderate
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 Displacement of colonies off the substratum will result in mortality. Larvae are produced annually and are likely to disperse from nearby unaffected substrata to recolonize.	High	High	Moderate	Low

Chemical pressures

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	Intolerance	Recoverability	Sensitivity	Evidence / 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 Insufficient information.	No information	Not relevant	No information	Not relevant
Heavy metal contamination [Show more] Heavy metal contamination Evidence Insufficient information.	No information	Not relevant	No information	Not relevant
Hydrocarbon contamination [Show more] Hydrocarbon contamination Evidence Ryland & DePutron (1998) observed no detectable damage to underboulder faunas affected by oil pollution in Watwick Bay, Pembrokeshire. These communities most likely included encrusting Bryozoa. However, it seems likely in the case of heavy pollution or pollution by light oils, damage may occur to encrusting bryozoans. Larvae are produced annually and are likely to disperse from nearby unaffected substrata to recolonize.	Intermediate	High	Low	Low
Radionuclide contamination [Show more] Radionuclide contamination Evidence Insufficient information.	No information	Not relevant	No information	Not relevant
Changes in nutrient levels [Show more] Changes in nutrient levels Evidence Insufficient information.	No information	Not relevant	No information	Not relevant
Increase in salinity [Show more] Increase in salinity 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. 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 Umbonula littoralis appears to be restricted in distribution to areas that are continuously in full salinity conditions. It seems likely that variable or low salinity conditions will have an adverse effect. Larvae are produced annually and are likely to disperse from nearby unaffected substrata to recolonize.	High	High	Moderate	Low
Decrease in salinity [Show more] Decrease in salinity 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. 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 Umbonula littoralis probably survives overgrowth by encrusting ascidians as described by Turner (1988) suggesting that it can survive isolation from easily obtained oxygen. Larvae are produced annually and are likely to disperse from nearby unaffected substrata to recolonize.	Low	High	Low

Biological pressures

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	Intolerance	Recoverability	Sensitivity	Evidence / 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 Insufficient information.	No information	Not relevant	No information	Not relevant
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 Insufficient information.	No information	Not relevant	No information	Not relevant
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 Insufficient information.	Not relevant	Not relevant	Not relevant	Not relevant
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 Kelp harvesting is removal of substratum (see above). Larvae are produced annually and are likely to disperse from nearby unaffected substrata to recolonize.	High	High	Moderate	Low

Additional information

Importance review

Policy/legislation

- no data -

Status

National (GB) importance	-	Global red list (IUCN) category	-
National (GB) importance -
Global red list (IUCN) category -

Non-native

Parameter	Data
Native	-
Origin	-
Date Arrived	Not relevant

Importance information

Oshurkovia (syn. Umbonula) littoralis is a characteristic species of the sublittoral fringe and of some biotopes.

Bibliography

Eggleston, D., 1969. Marine fauna of the Isle of Man: revised lists of phylum Entoprocta (=Kamptozoa) and phylum Ectoprocta(=Bryozoa). Report of the Marine Biology Station Port Erin, 81, 57-80.
Eggleston, D., 1972a. Patterns of reproduction in marine Ectoprocta off the Isle of Man. Journal of Natural History, 6, 31-38.
Hastings, A.B., 1944. Notes on Polyzoa (Bryozoa). I. Umbonula littoralis auctt: U. ovicellata, sp.n. and U. littoralis, sp.n.. Annals & Magazine of Natural History, Series 11, Vol. 11, 273-284
Hayward, P.J. & Ryland, J.S. 1979. British ascophoran bryozoans. London: Academic Press.
JNCC (Joint Nature Conservation Committee), 1999. Marine Environment Resource Mapping And Information Database (MERMAID): Marine Nature Conservation Review Survey Database. [on-line] http://www.jncc.gov.uk/mermaid
MBA (Marine Biological Association), 1957. Plymouth Marine Fauna. Plymouth: Marine Biological Association of the United Kingdom.
Picton, B.E. & Costello, M.J., 1998. BioMar biotope viewer: a guide to marine habitats, fauna and flora of Britain and Ireland. [CD-ROM] Environmental Sciences Unit, Trinity College, Dublin.
Turner, S.J., 1988. Ecology of intertidal and sublittoral cryptic epifaunal assemblages. II. Non-lethal overgrowth of encrusting bryozoans by colonial tunicates. Journal of Experimental Marine Biology and Ecology, 115, 113-126.

Datasets

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.
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
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, 2022. Isle of Man historical wildlife records 1990 to 1994. Occurrence dataset:https://doi.org/10.15468/aru16v accessed via GBIF.org on 2024-09-27.
NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.
OBIS (Ocean Biodiversity Information System), 2025. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2025-05-02
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:

Hiscock, K. 2005. Oshurkovia littoralis An encrusting bryozoan. In Tyler-Walters H. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 02-05-2025]. Available from: https://www.marlin.ac.uk/species/detail/1347

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Last Updated: 24/02/2005

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