BIOTIC Species Information for Eurydice pulchra
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Researched byLizzie Tyler Data supplied byUniversity of Sheffield
Refereed byThis information is not refereed.
Taxonomy
Scientific nameEurydice pulchra Common nameSpeckled selouse
MCS CodeS854 Recent SynonymsNone

PhylumCrustacea Subphylum
Superclass ClassEumalacostraca
SubclassPeracarida OrderIsopoda
SuborderFlabellifera FamilyCirolanidae
GenusEurydice Speciespulchra
Subspecies   

Additional InformationBritish coastal isopods have been described by Naylor (1972, 1990). A second intertidal species of Eurydice, Eurydice affinis Hansen, is also found on British shores. It is distinguished from Eurydice pulchra by an overall paler appearance, with black spots only on its dorsal surface. In Britain it has a more restricted distribution than Eurydice pulchra, from south-west England into North Wales, where it occurs amongst populations of Eurydice pulchra.
Taxonomy References Howson & Picton, 1997, Naylor, 1972, Naylor, 1990, Hayward & Ryland, 1995b, Hayward, 1994, Hayward et al., 1996, Fish & Fish, 1996,
General Biology
Growth formArticulate
Feeding methodPredator
Scavenger
Mobility/MovementSwimmer
Burrower
Environmental positionInfaunal
Typical food typesOther infaunal invertebrates associated with sandy shores and dead organic material. HabitFree living
Bioturbator FlexibilityHigh (>45 degrees)
FragilityIntermediate SizeVery small(<1cm)
HeightInsufficient information Growth Rate0.3 mm/month
Adult dispersal potential1km-10km DependencyIndependent
SociabilityGregarious
Toxic/Poisonous?No
General Biology Additional InformationFeeding
Eurydice pulchra is a highly predatory carnivore, its mouthparts are adapted for tearing and macerating animal tissue (Naylor, 1972).
Endogenous swimming rhythm
Eurydice pulchra has been shown to have an endogenously controlled circatidal rhythm cycle of swimming that is coupled to a circasemilunar pattern of emergence from the substratum (Alheit & Naylor, 1976; Jones & Naylor, 1970).
On the beach, the animals rely on the cue of increasing water agitation caused by the flood tide to swim from the sand, the endogenous component of the rhythm ensuring that they swim for up to 5-6 hours before reburying in the sand in a restricted zone between mean tide level (MTL) and high water neaps (HWN).
Eurydice pulchra swims mostly at night. Animals emerging from the sand, or washed out by turbulence during the day show photonegative behaviour and immediately bury themselves again.
Biology References Naylor, 1972, Hayward, 1994, Fish & Fish, 1996, Fish, 1970, Jones, 1970, Salvat, 1966, Jones & Naylor, 1970, Alheit & Naylor, 1976, Hayward & Ryland, 1990,
Distribution and Habitat
Distribution in Britain & IrelandWidespread on open coast and estuarine sandy beaches, with reduced abundance in south-east England.
Global distributionEurydice pulchra is found from Norway and the outer Baltic to the Atlantic coast of Morocco, but not in the Mediterranean (Soika, 1955).
Biogeographic rangeNot researched Depth range
MigratoryDiel   
Distribution Additional InformationPopulation densities
Eurydice pulchra populations may occur at densities of 1500 per m² or more and, on a South Wales beach studied by Jones (1970b), the population exceeded 4000 per m².
Intertidal distribution
Eurydice pulchra lives on the upper half of the shore, generally being most abundant between mean tide level (MTL) and mean high water of neap tides (MHWN). Eurydice pulchra relies upon the cue of increasing wave action caused by the flood tide (Jones, 1970b) to initiate swimming from the substratum. It swims in search of food, and buries itself in the sand again as the tide ebbs. As the fortnightly spring tides carry water further up the shore, so Eurydice pulchra moves up, and it can be found in the sand right up to the mean high water of spring tides. When the tidal cycles swings again towards neaps, the Eurydice population also moves down shore again, and avoids being stranded above the neap high water mark (Fish, 1970).

Substratum preferencesCoarse clean sand
Fine clean sand
Physiographic preferencesEstuary
Open coast
Strait / sound
Enclosed coast / Embayment
Biological zoneUpper Eulittoral
Mid Eulittoral
Lower Eulittoral
Sublittoral Fringe
Wave exposureExposed
Moderately Exposed
Tidal stream strength/Water flow SalinityFull (30-40 psu)
Habitat Preferences Additional Information
Distribution References Naylor, 1972, Hayward & Ryland, 1995b, Hayward et al., 1996, Fish, 1970, Jones, 1970b, Alheit & Naylor, 1976, Soika, 1955, Jones & Naylor, 1967, Hayward & Ryland, 1990,
Reproduction/Life History
Reproductive typeGonochoristic
Developmental mechanismOvoviviparous
Reproductive SeasonSee additional information Reproductive LocationAs adult
Reproductive frequencyAnnual episodic Regeneration potential No
Life span1-2 years Age at reproductive maturity
Generation time<1 year Fecundity32
Egg/propagule size Fertilization typeInternal
Larvae/Juveniles
Larval/Juvenile dispersal potential100-1000m Larval settlement periodNot relevant
Duration of larval stage   
Reproduction Preferences Additional InformationFecundity
The number of eggs carried by females of Eurydice pulchra was reported to vary in populations from different localities. In a population from the Dovey Estuary, west Wales, Fish (1970) observed the total number of eggs in any one female to vary between 22 to 54. Jones (1970) found that small females, 4.5 mm body length, carried a minimum of 10 eggs, whilst larger females, 7 mm body length, carried up to 40 eggs. In France, Salvat (1966) reported females of 6.0 mm body length to carry at least 45 eggs.
Reproduction
Fish (1970) and Jones (1970) describe the reproductive cycle of two British populations of Eurydice pulchra from an estuarine and open coast location respectively. Some differences concerning the duration of the breeding period, number of eggs carried by females of a particular size were found.
The sexes are separate and pair whilst swimming. Development of the embryo occurs within the internal brood pouch (marsupium) of the female, and the incubation period takes 7-8 weeks. Embryonic development is similar to that for other isopods (Forsman, 1944; Kjennerud, 1950; Naylor, 1955b, cited in Fish, 1970), and four distinct stages are recognised, the last stage being a miniature version of the adult. The minimum recorded length of newly emerged juveniles is 1.7 mm and they are able to swim and feed immediately.
Early broods released during July were reported by Jones (1970), to reach maturity before winter within the same year, breed early during the following spring and consequently provide the first broods of that year, before dying in their second autumn after a total life span of approximately 15 months. Broods released in August and September, initially grew as rapidly as the early spring brood but did not reach maturity and consequently overwintered as juveniles. Over-wintering juveniles matured as late as July and themselves produced the late broods of the following year. In contrast, on the west coast of Wales, sexually immature specimens of Eurydice pulchra overwintered twice and took 20 months to attain sexual maturity, produced only one brood per year and had a life span of about 2 years (Fish, 1970). Furthermore, Salvat (1966) reported a population of Eurydice pulchra from Arcachon, France, to have an annual reproductive cycle with sexual maturity being reached within 8 months. It is suspected (Fish, 1970; Jones, 1970; Salvat, 1966), that these variations in reproductive life cycle are related to the significant temperature differences between localities. The effect of temperature being reflected in the duration of the post-hatching growth stages, which are accelerated at higher temperatures.
Reproduction References Fish, 1970, Jones, 1970, Salvat, 1966,
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