Amphiura chiajei

Researched By	Lizzie Tyler	Data Supplied By	University of Sheffield
Refereed by	This information is not refereed.
Taxonomy
Scientific name	Amphiura chiajei	Common name	A brittlestar
MCS Code	ZB152	Recent Synonyms	None
Phylum	Echinodermata	Subphylum
Superclass		Class	Ophiuroidea
Subclass		Order	Ophiurida
Suborder		Family	Amphiuridae
Genus	Amphiura	Species	chiajei
Subspecies
Additional Information	Other Amphiura species are similar. Mixed populations of Amphiura chiajei and Amphiura filiformis are common.
Taxonomy References	Mortensen, 1927, Hayward et al., 1996, Picton, 1993, Hayward & Ryland, 1995b
General Biology
Growth form	Stellate, Radial	Feeding method	Surface deposit feeder, Sub-surface deposit feeder
Mobility/Movement	Crawler, Burrower	Environmental position	Infaunal
Typical food types	Organic detritus.	Habit	Free living
Bioturbator		Flexibility	High (>45 degrees)
Fragility	Fragile	Size	Small-medium(3-10cm)
Height	Insufficient information	Growth Rate	0.5 mm/year
Adult dispersal potential	1km-10km	Dependency	Independent
Sociability	Gregarious
Toxic/Poisonous?	No
Additional Information	Feeding method Amphiura chiajei buries in the sediment with its disc at 4-6 cm depth. One or two arms are stretched up above the sediment to collect food at the surface. Food particles are then transported along the arms to its mouth and ingested (Buchanan, 1964). Population densities The species is mostly found in low numbers throughout its range, although a number of high density populations are reported. Survey work by Keegan & Mercer (1986) revealed Amphiura chiajei to be a dominant member of the bottom community in Killary Harbour (a fjord-like inlet on the west coast of Ireland). The highly dense population of about 700 individuals per m², occurred in sediments with a silt/clay content of 80-90% and organic carbon levels of 5-7%. In contrast, Buchanan (1964) reported the mean population density of Amphiura chiajei to be 13 individuals per m² off the Northumbrian coast. Interactions with other species The heart urchin, Brissopsis lyrifera, which typically co-occurs with Amphiura chiajei, can negatively affect the growth of body and gonads of Amphiura chiajei, whilst Amphiura chiajei seemingly has no effect on the growth of Brissopsis lyrifera. Hollertz et al. (1998) suggested that this was attributable to the extensive bioturbation of the sediment caused by Brissopsis lyrifera.
Biology References	Buchanan, 1964, Keegan & Mercer,1986, Hollertz et al., 1998, Aizenberg et al., 2001, Hayward & Ryland, 1990
Distribution and Habitat
Distribution in Britain & Ireland	Recorded off the west, north and east coasts of the British Isles, mostly below 10 m in depth. There is some doubt over records from the south coast.
Global distribution	Distributed from western Norway (Trondhjemfjord), southwards along European coasts to the Mediterranean, the west coast of North Africa, and the Azores.
Biogeographic range	Not researched	Depth range	9 - 1000 m
Migratory	Non-migratory / Resident
Distribution Additional Information
Substratum preferences	Mud, Muddy sand	Physiographic preferences	Open coast, Offshore seabed, Sealoch, Enclosed coast / Embayment
Biological zone	Upper Circalittoral, Lower Circalittoral, Circalittoral Offshore, Bathybenthic (Bathyal)	Wave exposure	Sheltered, Very Sheltered, Extremely Sheltered
Tidal stream strength/Water flow	Weak (<1 kn), Very Weak (negligible)	Salinity	Full (30-40 psu), Variable (18-40 psu)
Habitat Additional Information
AMBI Group (Borja et al., 2000)	II
Distribution References	Mortensen, 1927, Picton, 1993, Crothers, 1966, Bruce et al., 1963, Foster-Smith, 2000, Mortensen, 1927
Reproduction/Life History
Reproductive type	Gonochoristic	Developmental mechanism	Planktotrophic
Reproductive Season	End of summer until middle of autumn	Reproductive Location	As adult
Reproductive frequency	Annual episodic	Regeneration potential	No
Life span	6-10 years	Age at reproductive maturity	3-5 years
Generation time	See additional information	Fecundity
Egg/propagule size		Fertilization type	External
Larvae/Juveniles Larval/Juvenile dispersal potential See additional information Larval settlement period Insufficient information Duration of larval stage
Additional Information	Life span Munday (1992) suggested from his observations in Killary Harbour, Ireland that individuals of Amphiura chiajei attained an age of 10 years, an estimate that was consistent with that reported for populations of Amphiura chiajei living off the Northumbrian coast (Buchanan, 1964). Reproduction In most species of ophiuroids the sexes are separate and fertilization external, leading to the development of a pelagic larva, the ophiopluteus (Fish & Fish, 1996). Individuals reach reproductive maturity after four years and in Amphiura chiajei there is a seasonal cycle in gonad development. A period of rest occurs at the end of autumn followed by growth over winter. Gonads reach maturity towards the end of spring and summer. Spawning occurs over the period from the end of summer until the middle of autumn (Fenaux, 1970). Larval settling time and recruitment In the laboratory, Fenaux (1970) observed a complete larval metamorphosis through to the formation of a young ophiuroid within 8 days at temperature 18-20 °C. Fenaux (1970) suggested that for eggs laid at the end of summer and at the beginning of autumn in which the water temperature exceeds 20°C, the pelagic life is probably shorter. With such a short life in the plankton the dispersal potential is likely to be rather limited in comparison to other echinoderms. Amphiura chiajei is a species with sporadic recruitment, which, in combination with its slow growth rate, later maturity and longevity make it a striking contrast to Amphiura filiformis (see Buchanan, 1964). Cohort dominance A heavy and successful settlement of Amphiura chiajei can dominate an area for over 10 years. Buchanan (1964), sampled Amphiura chiajei off the Northumbrian coast between 1958 and 1965, and found the entire population to consist of large individuals (disc diameter > 7.5 mm). Between 1958 and 1964, there was no evidence of any new recruitment to the population, but at the end of 1965 a heavy and successful recruitment occurred. Prior to this settlement it was apparent that the same single ageing population had been measured for over 8 years. Spawning had occurred but without successful recruitment. This pattern of longevity and of episodic recruitment is consistent with that if the population of Amphiura chiajei in Killary Harbour, west coast of Ireland (Munday & Keegan, 1992). The mortality rate was measured between 1961-1963 and shown to be small.
Reproduction References	Buchanan, 1964, Munday, 1993, Fish & Fish, 1996, Munday & Keegan, 1992, Fenaux, 1970, Eckert, 2003