Eurydice pulchra

Researched By	Lizzie Tyler	Data Supplied By	University of Sheffield
Refereed by	This information is not refereed.
Taxonomy
Scientific name	Eurydice pulchra	Common name	Speckled selouse
MCS Code	S854	Recent Synonyms	None
Phylum	Crustacea	Subphylum
Superclass		Class	Eumalacostraca
Subclass	Peracarida	Order	Isopoda
Suborder	Flabellifera	Family	Cirolanidae
Genus	Eurydice	Species	pulchra
Subspecies
Additional Information	British 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 form	Articulate	Feeding method	Predator, Scavenger
Mobility/Movement	Swimmer, Burrower	Environmental position	Infaunal
Typical food types	Other infaunal invertebrates associated with sandy shores and dead organic material.	Habit	Free living
Bioturbator		Flexibility	High (>45 degrees)
Fragility	Intermediate	Size	Very small(<1cm)
Height	Insufficient information	Growth Rate	0.3 mm/month
Adult dispersal potential	1km-10km	Dependency	Independent
Sociability	Gregarious
Toxic/Poisonous?	No
Additional Information	Feeding 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 & Ireland	Widespread on open coast and estuarine sandy beaches, with reduced abundance in south-east England.
Global distribution	Eurydice pulchra is found from Norway and the outer Baltic to the Atlantic coast of Morocco, but not in the Mediterranean (Soika, 1955).
Biogeographic range	Not researched	Depth range
Migratory	Diel
Distribution Additional Information	Population 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 preferences	Coarse clean sand, Fine clean sand	Physiographic preferences	Estuary, Open coast, Strait / sound, Enclosed coast / Embayment
Biological zone	Upper Eulittoral, Mid Eulittoral, Lower Eulittoral, Sublittoral Fringe	Wave exposure	Exposed, Moderately Exposed
Tidal stream strength/Water flow		Salinity	Full (30-40 psu)
Habitat Additional Information
AMBI Group (Borja et al., 2000)	I
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 type	Gonochoristic	Developmental mechanism	Ovoviviparous
Reproductive Season	See additional information	Reproductive Location	As adult
Reproductive frequency	Annual episodic	Regeneration potential	No
Life span	1-2 years	Age at reproductive maturity
Generation time	<1 year	Fecundity	32
Egg/propagule size		Fertilization type	Internal
Larvae/Juveniles Larval/Juvenile dispersal potential 100-1000m Larval settlement period Not relevant Duration of larval stage
Additional Information	Fecundity 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