BIOTIC

BIOTIC Species Information for 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?

General Biology 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 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 type

Gonochoristic

Developmental mechanism

Ovoviviparous

Reproductive Season

See additional information

Reproductive Location

As adult

Reproductive frequency

Annual episodic

Regeneration potential

Life span

1-2 years

Age at reproductive maturity

Generation time

<1 year

Fecundity

Egg/propagule size

Fertilization type

Internal

Larvae/Juveniles
Larval/Juvenile dispersal potential	100-1000m	Larval settlement period	Not relevant
Duration of larval stage

Reproduction Preferences 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,