Amphiura filiformis

Researched By	Lizzie Tyler	Data Supplied By	University of Sheffield
Refereed by	This information is not refereed.
Taxonomy
Scientific name	Amphiura filiformis	Common name	A brittlestar
MCS Code	ZB154	Recent Synonyms	None
Phylum	Echinodermata	Subphylum	Asterozoa
Superclass		Class	Ophiuroidea
Subclass		Order	Ophiurida
Suborder		Family	Amphiuridae
Genus	Amphiura	Species	filiformis
Subspecies
Additional Information	No text entered
Taxonomy References	Howson & Picton, 1997, Hayward & Ryland, 1995b, Hayward et al., 1996, Mortensen, 1927
General Biology
Growth form	Radial, Stellate	Feeding method	Passive suspension feeder, Active suspension feeder, Surface deposit feeder, Sub-surface deposit feeder
Mobility/Movement	Crawler, Burrower	Environmental position	Infaunal
Typical food types	Plankton and detritus.	Habit	Free living
Bioturbator		Flexibility	High (>45 degrees)
Fragility	Fragile	Size	Medium(11-20 cm)
Height	Insufficient information	Growth Rate	0.20-1.67% body weight per day
Adult dispersal potential	1km-10km	Dependency	Independent
Sociability	Gregarious
Toxic/Poisonous?	No
Additional Information	Typical abundance: High density populations (i.e. higher than an arbitrary figure of 150/m²) of Amphiura filiformis are common in the north east Atlantic Ocean and occur in sediments having silt/clay levels of about 10 to 20%. For example, in Galway Bay, Ireland, populations studied over an 8 year period had a maximum of 904 individuals per m² (O'Connor et al., 1983). Low density populations also occur along the north west European coastline. Size: Sizes at maturity given are from a population of Amphiura filiformis studied in Galway Bay, Ireland (O'Connor et al., 1983). Sköld et al. (2001) reported similar sizes. The disc diameter of Amphiura filiformis shows annual increases and decreases associated with sexual maturity. Maximum size is attained in August, just prior to gamete release and is followed by a decrease in mean size (O'Connor et al., 1983). Growth rate: Muus (1981) reported that newly settled recruits have a disc diameter of 0.3 mm and that they take 2 years to reach a size of 1.3 mm. However, Sköld et al. (2001) suggested that after 2 years, a disk size of ca 4 mm (concomitant with adult size and hence sexual maturity) could be attained. Josefson (1995) estimates the main part of disc growth occurs within the first 5 to 7 years of life. Sköld et al. (2001) studied post-larval recruits in the Gullmarsfjord and reported an asymptotic sigmoidal growth pattern for Amphiura filiformis (when growth data for adults and juveniles were combined). Specific growth rates of the post-larval settlers was 0.42% per day (disk diameter) and 1.76% per day (mean arm length) Sköld et al. (2001). Somatic and germinal growth rates may be enhanced by, for example, nutrient enrichment (Sköld & Gunnarsson, 1996) or temperature (see sensitivity section). Feeding method: Amphiura filiformis feed on suspended material in flowing water, but will change to deposit feeding in stagnant water or areas of very low water flow (Ockelmann & Muus, 1978). Suspension feeding capability is attained after about one year, at which point juveniles experienced exponential growth rates ( Sköld et al., 2001).
Biology References	Loo et al., 1996, Muus, 1981, O'Connor et al., 1983, Ockelmann & Muus, 1978, Josefson, 1995, Sköld et al., 2001, Hayward & Ryland, 1990, Julie Bremner, unpub data
Distribution and Habitat
Distribution in Britain & Ireland	Most British and Irish coasts although records have not been found for the south east of England.
Global distribution	Western Norway to the Mediterranean.
Biogeographic range	Not researched	Depth range	5 - 1200 m
Migratory	Non-migratory / Resident
Distribution Additional Information	Possible density dependent migration where migration occurs on or in the sediment. Burrowing through the sediment takes longer but the risk of predation is decreased.
Substratum preferences	Muddy sand, Sandy mud	Physiographic preferences	Offshore seabed, Sealoch, Enclosed coast / Embayment
Biological zone	Sublittoral Fringe, Upper Infralittoral, Lower Infralittoral, Upper Circalittoral, Lower Circalittoral	Wave exposure	Sheltered, Very Sheltered, Extremely Sheltered
Tidal stream strength/Water flow	Moderately Strong (1-3 kn), Weak (<1 kn), Very Weak (negligible)	Salinity	Full (30-40 psu)
Habitat Additional Information
AMBI Group (Borja et al., 2000)	II
Distribution References	Hayward & Ryland, 1995b, Hayward et al., 1996, Hayward & Ryland, 1990, Julie Bremner, unpub data, Gerdes, 1977, Mortensen, 1927
Reproduction/Life History
Reproductive type	Gonochoristic	Developmental mechanism	Planktotrophic
Reproductive Season	Summer	Reproductive Location	As adult
Reproductive frequency	Annual protracted	Regeneration potential	No
Life span	11-20 years	Age at reproductive maturity	3-5 years
Generation time	Insufficient information	Fecundity	50000
Egg/propagule size		Fertilization type	External
Larvae/Juveniles Larval/Juvenile dispersal potential >10km Larval settlement period See additional information Duration of larval stage 1-6 months
Additional Information	Life span Muus (1981) estimates the life span of the species to be 25 years based on oral width (which does not change with gonadial growth) to determine the stability of population structure, with recruitment taking place at the 0.3mm size levels. In very long term studies of Amphiura filiformis populations in Galway Bay O'Connor et al. (1983) indicate a life span of some 20 years is possible. Sköld et al. (1994) also estimated a similar life span for the species in the Skagerrak, west Sweden. However, early suggestions for the life span of Amphiura filiformis had been estimated at between 2 and 6 years (Buchanan, 1964; O'Conner & McGrath, 1980; Ocklemann & Muus, 1978). These early estimates of the life span of ophiuroids were based on several factors which have been found to give a possible margin for error (Muus, 1981). Firstly, disc diameter had traditionally been used as the basis for population structure determination. However, this introduces a margin of error because gonadial growth causes disc diameter to increase during the breeding season and decrease after spawning. Secondly, most estimates were based on recruitment of individuals at a disc size of around 1mm so that sieving on a 1mm mesh did not retain the earliest settlers which were smaller. Fecundity A total of 50,000 oocytes per ripe female is reported by O'Connor (pers. comm. in Duineveld et al., 1987). Gametes Time of first and last gametes recorded is from Galway Bay, Ireland (Bowmer, 1982). A discrete, relatively short annual breeding period (Jun-Sep) was observed with peak activity in August. In the same area O'Conner & McGrath (1980) observed that all large animals spawned during August/September in two consecutive years. Buchanan (1964) reported that Amphiura filiformis breeds in July in Britain. In the Ligurian Sea in the Mediterranean the spawning period is much longer, lasting from March to November (Pedrotti, 1993). Recruitment Descriptions of the life history of Amphiura filiformis vary greatly in the literature. In most of these studies, the basis for determining the size of recruits, and therefore periods of recruitment, growth rates and lifespan, has been the mesh size used during sampling operations. The most commonly used mesh size, 1mm, has therefore not sampled the earliest settlers. For example, in a study of Amphiura filiformis populations in Galway Bay over a period of 2 years O'Conner & McGrath (1980) were not able to identify discrete periods of recruitment. However, other studies suggest autumn recruitment (Buchanan, 1964) and spring and autumn (Glémarec, 1979). Using a 265µm mesh size Muus (1981) identified a peak settlement period in the autumn with a maximum of 6800 recruits per m². Sköld et al. (2001) reported settling densities of 7,100 - 7,400 per m² in October in the Gullmarsfjord. Muus (1981) shows the mortality of these settlers to be extremely high with less than 5% contributing to the adult population in any given year. In Galway Bay populations, small individuals make up ca. 5% of the population in any given month, which also suggests the actual level of input into the adult population is extremely low (O'Connor et al., 1983). Dispersal potential After cold winter related mass mortality of Amphiura filiformis in the German Bight, Gerdes (1977) calculated that dispersal to a location 10km away was within the reach of the larvae. However, dispersal is largely determined by water movements and currents. The species is thought to have a long pelagic life. Sköld et al. (1994) estimated the time lag between full gonads and settlement to be 88 days. This duration is comparable to the time period when pelagic larvae have been recorded in the plankton from July to November in one study and August to December in another (Sköld et al., 1994).
Reproduction References	O'Connor & McGrath, 1980, Bowmer, 1982, Pedrotti, 1993, Muus, 1981, Gerdes, 1977, Glémarec, 1979, O'Connor et al., 1983, Ockelmann & Muus, 1978, Buchanan, 1964, Sköld, 1994, Duineveld et al., 1987, Sköld et al., 2001, Eckert, 2003, Julie Bremner, unpub data