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Common brittlestar (Ophiothrix fragilis)

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

Summary

Description

A large brittlestar whose disk may reach up to 2 cm in diameter. The five arms are long (about five times the disk diameter) and spiny. The upper disk surface has a 5-rayed pattern of spines. This species is very varied in colour, commonly brown or grey but ranging through purple, red, orange, yellow, and white. Colouration may be plain or banded (particularly on the arms). The arms are fragile and often broken.

Recorded distribution in Britain and Ireland

All British and Irish coasts.

Global distribution

Widely distributed in the eastern Atlantic from northern Norway to the Cape of Good Hope.

Habitat

Found from the lower shore to circalittoral offshore habitats on hard substrata including bedrock, boulders and on coarse sediment. Most abundant on tideswept rock and on mixed coarse sediments. In the intertidal the species is found in crevices and under boulders.

Depth range

0-85

Identifying features

  • Large, long-armed brittle star
  • Pentagonal disk up to 2 cm in diameter.
  • Conspicuous radial shields and 5-rayed pattern of small spines on disk.
  • Arm length about 5 times diameter of disk with seven serrated spines on each segment.
  • Keel on naked dorsal arm plates.

Additional information

No text entered

Listed by

- none -

Further information sources

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Biology review

Taxonomy

PhylumEchinodermata
ClassOphiuroidea
OrderAmphilepidida
FamilyOphiotrichidae
GenusOphiothrix
Authority(Abildgaard in O.F. Müller, 1789)
Recent Synonyms

Biology

Typical abundanceHigh density
Male size range2-20mm
Male size at maturity
Female size rangeMedium(11-20 cm)
Female size at maturity
Growth formRadial
Growth rateSee additional information
Body flexibilityLow (10-45 degrees)
Mobility
Characteristic feeding methodPassive suspension feeder
Diet/food source
Typically feeds onPhytoplankton
Sociability
Environmental positionEpibenthic
DependencyIndependent.
SupportsHost

symbiotic sub-cuticular bacteria

Is the species harmful?No

Little evidence of toxicity (McClintock, 1989 cited in Sköld, 1998)

Biology information

  • This species can be found in very high densities of up to 2000 individuals per square metre (Davoult, 1989).
  • The smallest brittle stars found have a disk diameter of 2 mm and two segments per arm.
  • Some gonad development is present in individuals with disks of 3 mm although full sexual maturity is probably achieved at about 10 mm disk diameter (Gage, 1990).
  • Growth rate estimates vary considerably. Growth in juveniles may be between 1.6-3.1 and 3.5-10.3 increase in body disk diameter per day (Davoult et al., 1990) On average the body disk diameter is estimated to increase by 1.1 mm per month. Other growth rate estimates are much slower (Gage, 1990)
  • Optimal feeding can occur at water flow rates below 20 cm per second (Davoult & Gounin, 1995). Water moving at above 25 cm per second causes the arms to be brought down from being extended in the water column (Warner & Woodley, 1975; Hiscock, 1983). Water flow rates refer to water movements at the seabed. Surface flow rates will be considerably higher.
  • Although not an important dietary component, Ophiothrix fragilis may be found in the stomach contents of most common predators (Warner, 1971). Ophiothrix fragilis avoids predation by moving away from sources of mechanical disturbance (Warner, 1971). The escape response of Ophiothrix fragilis is slow in comparison to other brittle stars and it avoids visual predation through sheltering in crevices etc. and cryptic colouration (Sköld, 1998). Predatory starfish such as Asterias rubens and Marthasterias glacialis produce steroid glycoside chemicals that elicit an avoidance response in Ophiothrix fragilis (Mackie, 1970). Although not toxic, Ophiothrix fragilis achieves unpalatability through heavy calcification and possession of glassy spines (Sköld, 1998).
  • Brittle stars, such as Ophiothrix fragilis, have symbiotic subcuticular bacteria. The host-bacteria association can be perturbed by acute stress and changes in bacterial loading may be used as an indicator of sub-lethal stress (Newton & McKenzie, 1995)
  • The strong tidal current, coarse sediment communities from the English Channel are dominated by Ophiothrix fragilis, Urticina felina and Alcyonium digitatum (Migné & Davoult, 1997(c)).

Habitat preferences

Physiographic preferencesOffshore seabed, Open coast, Strait / sound
Biological zone preferencesLower circalittoral, Lower eulittoral, Lower infralittoral, Sublittoral fringe, Upper circalittoral, Upper infralittoral
Substratum / habitat preferencesBedrock, Cobbles, Crevices / fissures, Gravel / shingle, Large to very large boulders, Maerl, Muddy gravel, Other species, Pebbles, Small boulders, Under 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.), Weak < 1 knot (<0.5 m/sec.)
Wave exposure preferencesExposed, Extremely exposed, Moderately exposed, Sheltered, Very exposed, Very sheltered
Salinity preferencesFull (30-40 psu), Low (<18 psu), Reduced (18-30 psu), Variable (18-40 psu)
Depth range0-85
Other preferencesNo text entered
Migration PatternNon-migratory / resident

Habitat Information

  • Ophiothrix fragilis may be found in low densities on Crepidula fornicata (slipper limpet) beds (Bourgoin et al., 1985) or also overlying Modiolus shells (Magorrian et al., 1995)
  • Wolff, (1968) notes the species occurring in normal salinities of 16 psu and even persisting down to 10 psu.

Life history

Adult characteristics

Reproductive typeGonochoristic (dioecious)
Reproductive frequency Annual episodic
Fecundity (number of eggs)No information
Generation timeInsufficient information
Age at maturity6-10 months - see additional information.
SeasonJune - October
Life span5-10 years

Larval characteristics

Larval/propagule type-
Larval/juvenile development Planktotrophic
Duration of larval stage11-30 days
Larval dispersal potential Greater than 10 km
Larval settlement periodAugust to September

Life history information

  • Longevity estimates vary from 9 months (Davoult et al., 1990) to over 10 years (Gage, 1990). Work by Gage (1990) on skeletal growth bands in Ophiothrix fragilis indicate a slow rate of growth and considerable longevity suggesting that individuals with a disk diameter of 13mm are around 10 years old (disk diameters reach 20mm). N.B. This is not yet a validated age determining mechanism.
  • Davoult et al., (1990) consider development to maturity to take 6-10 months depending on the cohort and time of recruitment. Gonads are most developed in May-July (George & Warwick, 1985). Some gonad development is present in individuals with disks of 3 mm although full sexual maturity is probably achieved at about 10 mm disk diameter (Gage, 1990). Development of sexual maturity is dependent on day length and temperature although temperature is not believed to be a trigger for spawning (Davoult, et al., 1990).
  • Gamete release - Davoult et al., (1990) record spawning in the eastern Channel from mid July to mid August. Spawning in the Plymouth area has been recorded from June to the start of September (Davoult et al., 1990) and in October (Marine Biological Association 1957). In Kinsale Harbour on the south coast of Ireland Ball et al. (1995) found that Ophiothrix fragilis had a long breeding season, extending from May to January, with peak activity in summer/autumn, a small percentage of the population can breed throughout most of the year in certain regions. The evidence suggests that each animal spawns only once during a breeding season, although spawning may take place as several bursts over the period based on the presence of a number of different size classes of oocytes within the gonad at any particular time. Further north, in Sweden, spawning is recorded from August and September (Davoult et al., 1990).
  • Recruitment from the planktonic larvae occurs from August to September (Allain, 1974). Davoult et al., (1990) consider there to be multiple recruitments in the eastern Channel, a primary one in September and three secondary ones in February, April and June. Individual cohorts can be followed for 4-6 months after which variable growth rates and overlap in size precludes their separation. These multiple recruitments indicate more than one discrete spawning episode.
  • Larvae appear in the water column about a week after gamete release and fertilisation of the eggs. The larvae metamorphose into juvenile brittlestars whilst still in the plankton. The pelagic phase lasts about 26 days (MacBride, 1907).
  • The larvae may undertake a passive migration in areas such as the English Channel where there are strong water flow rates (Davoult et al., 1990). Here, with water that may move over 4 km per day and a larval duration of 26 days, the larvae can disperse up to 70-100 km. This may preclude auto-recruitment of local populations (Davoult at al., 1990).
  • Mean disk diameter can decrease by up to 20 % during gamete production (Davoult et al., 1990).
  • Although the species is gonochoristic Davoult et al., (1990) record a 1 % incidence of hermaphroditism.
  • Recruitment success is heavily dependent on environmental conditions including temperature and food availability. In years after mild winters Ophiothrix fragilis occurred in extremely high densities in the Oosterschelde estuary in Holland (Smaal, 1994). Populations seem to be stable in the long-term although there may be strong variation from year to year. A multi annual cycle of around 4 years may exist in the eastern English Channel (Davoult et al., 1993). However, Holme (1984) notes long-term changes in Ophiothrix fragilis populations in the western Channel, possibly linked with predator abundance (Luidia ciliaris and Luidia sarsi) and water quality.

    Sensitivity reviewHow is sensitivity assessed?

    Physical pressures

     IntoleranceRecoverabilitySensitivityEvidence/Confidence
    Substratum loss
    		 High High Moderate High
    Ophiothrix fragilis is an epibenthic species so substratum loss would result in mortality. Breeding occurs annually and there may be multiple recruitment phases (Davoult et al., 1990). The larvae of this species can disperse over considerable distances in areas such as the English Channel where there are strong water flow rates (Davoult et al., 1990). With water that may move several kilometres per day due to residual flow (e.g. see Pingree & Maddock, 1977) and a larval duration of 26 days, the larvae can disperse up to 70-100 km and establish populations elsewhere. Adults, although mobile, are not highly active. Some immigration of adults from nearby populations may be possible. Longevity estimates vary from 9 months (Davoult et al., 1990) to over 10 years (Gage, 1990). Reproductive capability may be reached in 6-10 months depending on time of recruitment (Davoult et al., 1990).
    Smothering
    		 High High Moderate Low
    Although Ophiothrix fragilis is an epibenthic crawling species, it has a low level of locomotory activity and lacks muscular development. Smothering by 5 cm of sediment would probably cause death as it is unlikely that the brittle star would be able to burrow out of the covering material. Breeding occurs annually and there may be multiple recruitment phases (Davoult et al., 1990). The larvae of this species can disperse over considerable distances in areas such as the English Channel where there are strong water flow rates (Davoult et al., 1990). With water that may move several kilometres per day due to residual flow (e.g. see Pingree & Maddock, 1977) and a larval duration of 26 days, the larvae can disperse up to 70-100 km and establish populations elsewhere. Adults, although mobile, are not highly active. Some immigration of adults from nearby populations may be possible. Longevity estimates vary from 9 months (Davoult et al., 1990) to over 10 years (Gage, 1990). Reproductive capability may be reached in 6-10 months depending on time of recruitment (Davoult et al., 1990).
    Increase in suspended sediment
    		 Low Very high Very Low Low
    Ophiothrix fragilis is a passive suspension feeder. Increases in siltation of inorganic particles may interfere with the feeding of this species (Aronson, 1992 cited in Hughes, 1998), particularly in non current-swept areas. Respiration rate is low and the species can tolerate considerable loss of body mass during reproductive periods (Davoult et al., 1990) so restricted feeding may be tolerated. Once normal feeding recommences it may take a short time for condition to be regained.
    Decrease in suspended sediment
    		 No information
    Desiccation
    		 Intermediate High Low Low
    Although mainly subtidal, this species may also be found on the lower shore, sheltering under boulders etc. Consequently the brittle star may be tolerant to some degree of desiccation. However, increased desiccation through exposure to air and sunlight may kill part of the intertidal population. Breeding occurs annually and there may be multiple recruitment phases (Davoult et al., 1990). The larvae of this species can disperse over considerable distances in areas such as the English Channel where there are strong water flow rates (Davoult et al., 1990). With water that may move several kilometres per day due to residual flow (e.g. see Pingree & Maddock, 1977) and a larval duration of 26 days, the larvae can disperse up to 70-100 km and establish populations elsewhere. This may preclude auto-recruitment of local populations (Davoult at al., 1990) Adults, although mobile, are not highly active. Some immigration of adults from nearby populations may be possible. Longevity estimates vary from 9 months (Davoult et al., 1990) to over 10 years (Gage, 1990). Reproductive capability may be reached in 6-10 months depending on time of recruitment (Davoult et al., 1990).
    Increase in emergence regime
    		 Not relevant Not relevant Not relevant Low
    Ophiothrix fragilis is a mobile epibenthic crawler and should be able to relocate to a suitable location on the shore should the emergence regime be altered.
    Decrease in emergence regime
    		 No information
    Increase in water flow rate
    		 Low Very high Very Low Moderate
    Ophiothrix fragilis frequently inhabits areas with strong tidal currents e.g. up to 1.5 m/s in the Dover Straits (Hughes, 1998b) (although water flow rate will not be continuously high e.g. during periods of slack water). A certain degree of water movement is important to the feeding mechanism of this species. However, above a certain water speed (25 cm/s) the feeding arms are withdrawn from the water column (Warner & Woodley, 1975; Hiscock, 1983). At water speeds above about 28 cm/s individuals or even small groups may be displaced from the substratum and they have been observed being rolled along the seabed by the current (Warner, 1971). Living in dense aggregations may reduce displacement by strong currents (Warner & Woodley, 1975). Water flow rates refer to water movements at the seabed. Surface flow rates will be considerably higher. Respiration rate is low and the species can tolerate considerable loss of body mass during reproductive periods (Davoult et al., 1990) so restricted feeding may be tolerated. Once normal feeding recommences it may take a short time for condition to be regained. Ophiothrix fragilis also has specific behaviours and abilities to relocate conspecifics following displacement (Broom, 1975).
    Decrease in water flow rate
    		 No information
    Increase in temperature
    		 Intermediate High Low Low
    Changes in temperature can have a considerable effect on Ophiothrix fragilis populations. In years following mild winters Ophiothrix fragilis may recruit in very high numbers (Smaal, 1994). However, the distribution of Ophiothrix fragilis is large, ranging from northern Norway south to the Cape of Good Hope. Consequently this species is exposed to temperatures both above and below those found in the British Isles. In the long term, some populations in the English Channel have remained stable (Davoult et al., 1993). In other areas of the Channel considerable fluctuations have been noted over the last century, believed to be due to variations in water masses present (Holme, 1984). Long term chronic changes in temperature will probably have little effect on the species. Short term acute changes in temperature are noted to cause a reduction in the loading of subcutaneous symbiotic bacteria in echinoderms such as Ophiothrix fragilis. Reductions in these bacteria are probably indicative of levels of stress and may lead to mortality (Newton & McKenzie, 1995). The species is noted to exist in shallow, enclosed waters that regularly drop to 3 °C but is absent from areas where temperatures drop to 0 °C. Breeding occurs annually and there may be multiple recruitment phases (Davoult et al., 1990). The larvae of this species can disperse over considerable distances in areas such as the English Channel where there are strong water flow rates (Davoult et al., 1990). With water that may move several kilometres per day due to residual flow (e.g. see Pingree & Maddock, 1977) and a larval duration of 26 days, the larvae can disperse up to 70-100 km and establish populations elsewhere. This may preclude auto-recruitment of local populations (Davoult at al., 1990). Adults, although mobile, are not highly active. Some immigration of adults from nearby populations may be possible. Longevity estimates vary from 9 months (Davoult et al., 1990) to over 10 years (Gage, 1990). Reproductive capability may be reached in 6-10 months depending on time of recruitment (Davoult et al., 1990).
    Decrease in temperature
    		 No information
    Increase in turbidity
    		 Low Very high Very Low Low
    Ophiothrix fragilis is likely to have poor facility for visual perception and consequently is probably not directly sensitive to changes in turbidity. However, the main food source of this species is phytoplankton which have a requirement for light. Increases in turbidity may limit the amount of phytoplankton available to the brittle stars. Food availability is one of the main factors controlling growth and development (Migné & Davoult, 1997; Davoult et al., 1990). Once normal feeding recommences it may take a short time for condition to be regained.
    Decrease in turbidity
    		 No information
    Increase in wave exposure
    		 Low Very high Very Low Moderate
    The species occurs in a wide range of wave exposures as well as on offshore seabeds where wave action is less important. Increases in wave exposure may cause increases in the incidence of damaged individuals (Ophiothrix fragilis arms are brittle). Strong wave action may cause displacement of brittle stars. Ophiothrix fragilis has specific behaviours and abilities to relocate conspecifics following displacement (Broom, 1975). Brittle stars often have broken arms but are capable of arm and even some disk regeneration (Sköld, 1998).
    Decrease in wave exposure
    		 No information
    Noise
    		 Low Very high Very Low Low
    Ophiothrix fragilis reacts to mechanical disturbance (predator evasion response) (Warner, 1971). Although there are no records of reaction to noise, sound vibrations may trigger this sort of behaviour. There is some evidence of autotomy of arms in response to predator threat (Emson & Wilkie, 1980). Brittle stars are capable of arm and even some disk regeneration (Sköld, 1998).
    Visual presence
    		 Tolerant Not relevant Not sensitive High
    Ophiothrix fragilis is likely to have poor facility for visual perception and consequently is probably not sensitive to visual disturbance. Movement of a hand near to Ophiothrix fragilis elicits no escape response (Skö, 1998).
    Abrasion & physical disturbance
    		 Intermediate High Low Moderate
    Brittlestars have fragile arms that are likely to be damaged by abrasion. Brittlestars can tolerate considerable damage to arms and even the disk without suffering mortality and are capable of arm and even some disk regeneration (Sköld, 1998). Fishermen tend to avoid brittlestar beds since the animals clog their nets (Jones et al., 2000). However, a passing scallop dredge is likely to remove, displace, or damage brittlestars caught in its path. Although several species of brittlestar are reported to increase in abundance in trawled areas, Bradshaw et al. (2002) noted that the relatively sessile Ophiothrix fragilis decreased in the long term in areas subject to scallop dredging. Overall, a proportion of the population is likely to be damaged or removed and an intolerance of intermediate has been recorded.
    Breeding occurs annually and there may be multiple recruitment phases (Davoult et al., 1990). The larvae of this species can disperse over considerable distances in areas such as the English Channel where there are strong water flow rates (Davoult et al., 1990). With water that may move several kilometres per day due to residual flow (e.g. see Pingree & Maddock, 1977) and a larval duration of 26 days, the larvae can disperse up to 70 -100 km and establish populations elsewhere. This may preclude auto-recruitment of local populations (Davoult at al., 1990). Adults, although mobile, are not highly active. Some immigration of adults from nearby populations may be possible. Longevity estimates vary from 9 months (Davoult et al., 1990) to over 10 years (Gage, 1990). Reproductive capability may be reached in 6-10 months depending on time of recruitment (Davoult et al., 1990).
    Displacement
    		 Tolerant Not relevant Not sensitive High
    Although not highly active, Ophiothrix fragilis is a crawling epibenthic species. Following displacement from a brittlestar bed, individuals will crawl back and forth across water currents until a conspecific is found (Broom, 1975). This may preclude auto-recruitment of local populations (Davoult at al., 1990).

    Chemical pressures

     IntoleranceRecoverabilitySensitivityEvidence/Confidence
    Synthetic compound contamination
    		 No information Not relevant No information Not relevant
    Echinoderms tend to be very intolerant of various types of marine pollution (Newton & McKenzie, 1995) but there is no more detailed information than this broad statement. Breeding occurs annually and there may be multiple recruitment phases (Davoult et al., 1990). The larvae of this species can disperse over considerable distances in areas such as the English Channel where there are strong water flow rates (Davoult et al., 1990). With water that may move several kilometres per day due to residual flow (e.g. see Pingree & Maddock, 1977) and a larval duration of 26 days, the larvae can disperse up to 70-100 km and establish populations elsewhere. Adults, although mobile, are not highly active. Some immigration of adults from nearby populations may be possible. Longevity estimates vary from 9 months (Davoult et al., 1990) to over 10 years (Gage, 1990). Reproductive capability may be reached in 6-10 months depending on time of recruitment (Davoult et al., 1990).
    Heavy metal contamination
    		 No information Not relevant No information Not relevant
    Adult echinoderms such as Ophiothrix fragilis are known to be efficient concentrators of heavy metals including those that are biologically active and toxic (Hutchins et al., 1996). There is no information available regarding the effects of this bioaccumulation.
    Hydrocarbon contamination
    		 High High Moderate High
    Echinoderms tend to be very sensitive to various types of marine pollution (Newton & McKenzie, 1995). Adult Ophiothrix fragilis have documented intolerance to hydrocarbons (Newton & McKenzie, 1995). The sub-cuticular bacteria that are symbiotic with Ophiothrix fragilis are reduced in number following exposure to hydrocarbons. Exposure to 30,000 ppm oil reduces the bacterial load by 50 % and brittle stars begin to die (Newton & McKenzie, 1995). However, there are no field observations of mortalities caused by exposure to hydrocarbons. Breeding occurs annually and there may be multiple recruitment phases (Davoult et al., 1990). The larvae of this species can disperse over considerable distances in areas such as the English Channel where there are strong water flow rates (Davoult et al., 1990). With water that may move several kilometres per day due to residual flow (e.g. see Pingree & Maddock, 1977) and a larval duration of 26 days, the larvae can disperse up to 70-100 km and establish populations elsewhere. Adults, although mobile, are not highly active. Some immigration of adults from nearby populations may be possible. Longevity estimates vary from 9 months (Davoult et al., 1990) to over 10 years (Gage, 1990). Reproductive capability may be reached in 6-10 months depending on time of recruitment (Davoult et al., 1990).
    Radionuclide contamination
    		 No information Not relevant No information Not relevant
    Adult echinoderms such as Ophiothrix fragilis are known to be efficient concentrators of radionuclides (Hutchins et al., 1996). There is no information available regarding the effects of this bioaccumulation.
    Changes in nutrient levels
    		 Intermediate High Low Moderate
    Decreases in sub-cuticular bacteria have also been recorded following nutrient limitation. Reductions in these bacteria are probably indicative of levels of stress and may lead to mortality (Newton & McKenzie, 1995). Breeding occurs annually and there may be multiple recruitment phases (Davoult et al., 1990). The larvae of this species can disperse over considerable distances in areas such as the English Channel where there are strong water flow rates (Davoult et al., 1990). With water that may move over several kilometres per day due to residual flow (e.g. see Pingree & Maddock, 1977) and a larval duration of 26 days, the larvae can disperse up to 70-100 km and establish populations elsewhere. This may preclude auto-recruitment of local populations (Davoult at al., 1990). Adults, although mobile, are not highly active. Some immigration of adults from nearby populations may be possible. Longevity estimates vary from 9 months (Davoult et al., 1990) to over 10 years (Gage, 1990). Reproductive capability may be reached in 6-10 months depending on time of recruitment (Davoult et al., 1990).
    Increase in salinity
    		 Low High Low Moderate
    Ophiothrix fragilis is predominantly a marine species. However, in the Dutch Oosterschelde Estuary, Wolff, (1968) notes dense aggregations of the species occurring in normal salinities of 16 psu and even persisting down to 10 psu. Therefore, the species may be tolerant of some change in salinity so intolerance is assessed as low.
    Decrease in salinity
    		 No information
    Changes in oxygenation
    		 High High Moderate Low
    Cole et al. (1999) suggest possible adverse effects on marine species below 4 mg/l and probable adverse effects below 2mg/l. Although the species is known to have a low respiration rate (Migné & Davoult, 1997(b)), particularly during colder winter temperatures extreme hypoxia is known to cause mass mortality (Stachowitsch, 1984). Breeding occurs annually and there may be multiple recruitment phases (Davoult et al., 1990). The larvae of this species can disperse over considerable distances in areas such as the English Channel where there are strong water flow rates (Davoult et al., 1990). With water that may move over several kilometres per day due to residual flow (e.g. see Pingree & Maddock, 1977) and a larval duration of 26 days, the larvae can disperse up to 70-100 km and establish populations elsewhere. This may preclude auto-recruitment of local populations (Davoult at al., 1990). Adults, although mobile, are not highly active. Some immigration of adults from nearby populations may be possible. Longevity estimates vary from 9 months (Davoult et al., 1990) to over 10 years (Gage, 1990). Reproductive capability may be reached in 6-10 months depending on time of recruitment (Davoult et al., 1990).

    Biological pressures

     IntoleranceRecoverabilitySensitivityEvidence/Confidence
    Introduction of microbial pathogens/parasites
    		 Low High Low Low
    The brittle star Ophiothrix fragilis has symbiotic subcuticular bacteria. The host-bacteria association can be perturbed by acute stress and changes in bacterial loading may be used as an indicator of sub-lethal stress (Newton & McKenzie, 1995). The dense aggregations of brittlestars seen in certain habitats probably provide the ideal conditions for the spread of diseases or parasites. Although no such infestations have been recorded for O. fragilis brittlestar beds there are several examples of echinoderm populations, that have been dramatically reduced by sudden outbreaks of epidemic diseases. Therefore, although an intolerance rank of low is reported epidemic disease does have the potential to significantly affect the biotope.
    Introduction of non-native species
    		 Tolerant Not relevant Not sensitive Low
    There are no records of any non-native species that may compete with or predate upon Ophiothrix fragilis and so the species is assessed as not sensitive. However, as several species have become established in British waters there is always the potential for this to occur.
    Extraction of this species
    		 Not relevant Not relevant Not relevant Low
    It is extremely unlikely that this species would be subject to extraction as it has no commercial and limited research value.
    Extraction of other species
    		 Tolerant Not relevant Not sensitive Low
    Ophiothrix fragilis has no known obligate relationships with other species so removal of these species will not have any direct effect. The physical effects caused by removal of other species are addressed in the factors above.

    Additional information

    Importance review

    Policy/legislation

    - no data -

    Status

    Non-native

    Importance information

    • Benthic suspension feeders such as Ophiothrix fragilis can occur in very high densities and can have a dominant role in the main nutrient exchanges in estuarine and coastal ecosystems (Dame 1993 cited in Smaal 1994; Lefebvre & Davoult, 1997).
    • Suspension feeders are important in coastal ecosystems because they can remove large amounts of suspended particulate matter (Davoult & Gounin, 1995).
    • Ophiothrix fragilis may be considered a keystone species in the coastal marine ecosystem of the eastern Channel and a dominant species of gravel communities (Lefebvre & Davoult, 1997).
    • Dense brittle star beds form an area of considerable physical complexity with many crevices and places to shelter. Despite the apparent dominance of Ophiothrix fragilis, up to 78 species have been recorded from a brittle star bed (of which half the biomass was O. fragilis) the most common of which was the bivalve Abra alba (Warner, 1971).
    • Ophiothrix fragilis has been recorded as representing up to 62 % of the biomass in coarse sediment communities (Migné & Davoult, 1997(b)).
    • Precipitation of calcium carbonate in skeletal ossicles is a source of carbon dioxide in sea water (Ware et al., 1992). The Ophiothrix fragilis community in the English Channel could provide 35 % of the phytoplankton carbon requirements (Migné & Davoult, 1997(b)).

    Bibliography

    1. Allain, J-Y., 1974. Écologie des bancs d'Ophiothrix fragilis (Abildgaard) (Echinodermata: Ophiuroidea) dans le Golfe Normanno-Breton. Cahiers de Biologie Marine, 15, 235-273.

    2. Ball, B.J., Costelloe, J., Könnecker, G. & Keegan, B.F., 1995. The rocky subtidal assemblages of Kinsale Harbour (south coast of Ireland). In Proceedings of the 28th European Marine Biology Symposium, Instiitute of Marine Biology of Crete, Iraklio, Crete, 1993. Biology and Ecology of Shallow Coastal Waters (ed. A. Eleftheriou, A.D. Ansell & C.J. Smith), pp.293-302. Fredensborg: Olsen & Olsen.

    3. Bourgoin, A., Guilloum, M. & Morvan, C., 1985. Étude préliminaire de l'épifaune des sédiments meubles de la Rade de Brest (Finistère, France) à l'aide d'une caméra vidéo sous-marine. Annals de l'Institut Océanographique, 61, 39-50.

    4. Broom, D.M., 1975. Aggregation behaviour of the brittle star Ophiothrix fragilis. Journal of the Marine Biological Association of the United Kingdom, 55, 191-197.

    5. Bruce, J.R., Colman, J.S. & Jones, N.S., 1963. Marine fauna of the Isle of Man. Liverpool: Liverpool University Press.

    6. Campbell, A., 1994. Seashores and shallow seas of Britain and Europe. London: Hamlyn.

    7. Davoult, D., & Gounin, F., 1995. Suspension feeding activity of a dense Ophiothrix fragilis (Abildgaard) population at the water-sediment interface: Time coupling of food availability and feeding behaviour of the species. Estuarine, Coastal and Shelf Science, 41, 567-577.

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    Citation

    This review can be cited as:

    Jackson, A. 2008. Ophiothrix fragilis Common brittlestar. 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 03-06-2023]. Available from: https://www.marlin.ac.uk/species/detail/1198

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    Last Updated: 08/05/2008