Malacostracans · Isopoda · Cirolanidae

Speckled Sea Louse

Eurydice pulchra

Not Evaluated

It has not yet been assessed against the IUCN criteria. See full glossary

A minute isopod that lives buried in beach sand and which, at every high tide, emerges and swims actively in the water film in search of small animals and debris. As the tide falls it buries itself again. It is a key prey for fish and shorebirds.

Size

up to 0.8 cm

Diet

Carnivore

Feeds mainly on other animals.

Activity

Nocturnal

Active mainly at night.

Social structure

Colony

Lives in large concentrations, often for breeding reasons.

Sighting difficulty

Unknown

OceanCarnivore Nocturnal Colonial Ocean Crustacean

13countries 30parks 33dive sites1same family

Fun facts

It keeps its activity rhythm every 12.4 hours even when isolated in a laboratory without tides: it is one of the classic models for studying the circatidal biological clock.
As well as the tidal clock, it changes colour according to the time of day thanks to an independent circadian rhythm.
It has a tidal clock of its own: an endogenous circatidal rhythm of about 12.4 hours that brings it out of the sand on the flooding tide, keeps it swimming for five or six hours and sends it back into the sand.
That clock settled an old debate. For years it was argued that tidal rhythms were merely a submultiple of the circadian clock; experiments on this species showed that there is a circatidal pacemaker independent of the circadian system.
It swims mainly at night, and if turbulence lifts it out of the sand by day it buries itself at once.
It reaches densities of more than 1,500 individuals per square metre, and on one beach in south Wales more than 4,000 were recorded.