BIOTIC Species Information for Ensis ensis
Click here to view the MarLIN Key Information Review for Ensis ensis
Researched byJacqueline Hill Data supplied byMarLIN
Refereed byThis information is not refereed.
Taxonomy
Scientific nameEnsis ensis Common nameA razor shell
MCS CodeW1999 Recent Synonyms

PhylumMollusca Subphylum
Superclass ClassPelecypoda
Subclass OrderVeneroida
Suborder FamilyPharidae
GenusEnsis Speciesensis
Subspecies   

Additional Information
Taxonomy References
General Biology
Growth formBivalved
Feeding methodActive suspension feeder
Mobility/MovementBurrower
Environmental positionInfaunal
Typical food typesSuspended organic detritus HabitBurrow dwelling
Bioturbator FlexibilityNone (< 10 degrees)
FragilityFragile SizeMedium(11-20 cm)
HeightInsufficient information Growth Rate2-4 cm/year
Adult dispersal potential10-100m DependencyIndependent
SociabilityGregarious
Toxic/Poisonous?No
General Biology Additional InformationTypical abundance
Abundance of Ensis sp. varies from high to low density. In favourable conditions - such as the lee of rocks, rocks and islands for Ensis arcuatus on the western coast, individuals are found in high densities in 'beds' which interchange individuals with the surrounding areas where they occur in a more dispersed pattern (Fahy et al. in press).

Size ranges
Size range given for Ensis ensis. Ensis siliqua males and females up to 20 cm and Ensis arcuatus males and females up to 15 cm.

Growth rates
Growth in the first winter is 2-4 cm. The three species have similar growth patterns but with different asymptotic lengths. In Ensis siliqua males grow faster than females. Growth rates are higher in the summer, when the food supply is abundant, than in the winter when the temperature and food supply are both reduced. Ensis ensis also show a neap-spring lunar growth pattern with smaller growth bands during spring tides when animals are emersed for longer (Henderson & Richardson, 1994). The growth rate given is the maximum rate in the first year or two of life. Thereafter growth falls to 2-3 cm/year (Robinson & Richardson, 1998).

Biology References
Distribution and Habitat
Distribution in Britain & IrelandCommon on all British coasts.
Global distributionFrom Norway to the Atlantic coast of Spain. Ensis ensis and Ensis siliqua found in some parts of the Mediterranean.
Biogeographic rangeNot researched Depth rangeto a depth of 60m
MigratorySee additional information   
Distribution Additional Information
  • Habitat
    Ensis spp. Occur virtually everywhere inshore but favourable conditions, such as the lee of reefs, rocks and islands make for high densities known as 'beds' which interchange individuals with the surrounding areas where they occur in a more dispersed pattern. Ensis ensis beds do occur at extreme low water of spring tides but the species is much more common in depths of about 10m (Holme, 1954). Single specimens have been collected from depths of 60m in the Plymouth area. Ensis arcuatus lives in coarser sediment than either Ensis ensis or Ensis siliqua.
  • Migration
    Henderson & Richardson (1994) observed a distribution of razor clam size classes on a shore in north Wales which may indicate that there is a gradual down-shore migration of juveniles into the adult population. They suggest that juveniles become established further up the shore because the low water mark is exposed to the strongest tidal currents.
  • Wave exposure
    In moderate wave exposure Ensis ensis may be replaced by the larger Ensis siliqua (Holme, 1954).

Substratum preferencesFine clean sand
Coarse clean sand
Physiographic preferencesOpen coast
Offshore seabed
Strait / sound
Enclosed coast / Embayment
Biological zoneLower Eulittoral
Sublittoral Fringe
Upper Infralittoral
Lower Infralittoral
Upper Circalittoral
Lower Circalittoral
Wave exposureSheltered
Very Sheltered
Extremely Sheltered
Ultra Sheltered
Tidal stream strength/Water flowModerately Strong (1-3 kn)
Weak (<1 kn)
SalinityFull (30-40 psu)
Habitat Preferences Additional InformationHabitat
Ensis spp. occur virtually everywhere inshore but favourable conditions, such as the lee of reefs, rocks and islands make for high densities known as 'beds' which interchange individuals with the surrounding areas where they occur in a more dispersed pattern. Ensis ensis beds do occur at extreme low water of spring tides but the species is much more common in depths of about 10 m (Holme, 1954). Single specimens have been collected from depths of 60 m in the Plymouth area. Ensis arcuatus lives in coarser sediment than either Ensis ensis or Ensis siliqua.

Migration
Henderson & Richardson (1994) observed a distribution of razor clam size classes on a shore in north Wales which may indicate that there is a gradual down-shore migration of juveniles into the adult population. They suggest that juveniles become established further up the shore because the low water mark is exposed to the strongest tidal currents.

Wave exposure
In moderate wave exposure Ensis ensis may be replaced by the larger Ensis siliqua (Holme, 1954).
Distribution References
Reproduction/Life History
Reproductive typeGonochoristic
Developmental mechanismPlanktotrophic
Reproductive SeasonSummer Reproductive LocationInsufficient information
Reproductive frequencyAnnual episodic Regeneration potential No
Life span11-20 years Age at reproductive maturity3-5 years
Generation timeInsufficient information FecundityInsufficient information
Egg/propagule sizeInsufficient information Fertilization typeInsufficient information
Larvae/Juveniles
Larval/Juvenile dispersal potentialInsufficient information Larval settlement periodInsufficient information
Duration of larval stage1-2 months   
Reproduction Preferences Additional InformationLife span
The life span of Ensis ensis is likely to be in excess of 10 years. The other two British species Ensis siliqua and Ensis arcuatus are also very long-lived, with a life-span up to 18 years (E. Fahy pers. comm.).

Reproduction
Razor shells in Britain do not appear to breed before they are three years old (Henderson & Richardson, 1994). Breeding occurs during the summer but larval settlement is not successful every year, and recruitment of juveniles is irregular (Hayward et al., 1996). Breeding probably occurs during spring and the veliger larvae has a pelagic life of about a month (Fish & Fish, 1996). Studies on razor shells from North Wales showed that individuals of Ensis ensis were mature in July but were spent in August, indicating that spawning had occurred by the middle of the summer (Henderson & Richardson, 1994).
Reproduction References
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