BIOTIC

BIOTIC Species Information for Psammechinus miliaris
All Taxonomy Biology Distribution Reproduction

Researched by	Lizzie Tyler	Data supplied by	University of Sheffield
Refereed by	This information is not refereed.
General Biology
Growth form	Globose	Feeding method	Predator Scavenger
Mobility/Movement	Crawler	Environmental position	Epifaunal
Typical food types	Macroalgae, hydroids, bryozoans, boring sponges, barnacles, mussels, cockles and worms (see Lawrence, 1975).	Habit	Free living
Bioturbator	Not relevant	Flexibility	None (< 10 degrees)
Fragility	Fragile	Size	Small-medium(3-10cm)
Height		Growth Rate	See additional information
Adult dispersal potential	100-1000m	Dependency	Independent
Sociability	Gregarious
Toxic/Poisonous?	No
General Biology Additional Information	Abundance In Scotland Psammechinus miliaris typically occurs in dense, localized populations in sheltered areas of sea lochs on the west coast (Davies, 1989; Holt, 1991). Densities have been recorded of 18 individuals per 100 g dry weight of sea weed (Bedford & Moore, 1985); several /m² in beam trawls in the Wadden Sea (Cranmer, 1985); 34 individuals per m² in a subtidal Laminaria saccharina bed, 182.4 /m² in a shallow bed of Zostera and 28.4 /m² on adjacent mud surfaces (Comely, 1979) and 352 /m² for littoral populations (Kelly, 2000) where individuals in one 0.25 m² quadrat ranged from 3.7 to 24.2 mm horizontal test diameter. Densities of several individuals /m² have been recorded in the German Waddensea (Ursin, 1960). Larsson (1968) found up to 10 individuals /m² in Saltkälle Fjord, Sweden. Size Maximum size varies with location. In some places the maximum diameter reached is small (< 20 mm (Jensen, 1969); around 35 mm (Bedford & Moore, 1985; Gage, 1991; Bull, 1939) although others have recorded diameters up to 57.5 mm (Allain, 1978) or up to 50 mm (Massin, 1999b; Aquascope, 2000a). The minimum diameter at maturity recorded (Brattström, 1941 cited in Jensen, 1969) is 6-7 mm but more usually 8-10 mm. Growth rates Estimates of growth rate vary. Gage, (1991) tried to relate growth bands found in the calcified plates of the test to seasonal differences in skeletal growth rate. This approach can be used reasonably accurately for estimating age of young urchins. However, when growth slows down, the reduced distance between bands make it difficult to distinguish individual markings. Bull, (1939) recorded growth up to 20 mm test diameter in the first year which then slowed considerably. In the second year mean diameters increased from 20 to 26.2 mm and by the sixth year saw growth of only a further 12 mm or so. Jensen, (1969) found that newly settled urchins (in August) grew 2 mm in the first 2 months and had reached 5.8 mm by the following July. Growth was recorded as maximal in spring and early summer by Gage (1991) and Bedford & Moore (1985) but work by Jensen, (1969) showed no growth between May and October. Growth rates of cultivated Psammechinus miliaris are given by Cook et al. (1998). Locomotion Locomotion is mediated by the movable spines attached to the test. The echinoid test is very brittle and easily damaged by impact. The spines which are articulated at the base and controlled by muscles may provide some cushioning to impact but overall the flexibility is negligible. Feeding Psammechinus miliaris has been recorded as feeding on a wide variety of species (see Lawrence, 1975). Loose lying brown macro algae, particularly Laminaria saccharina, is probably the main nutrient source although softer green algae such as Ulva lactuca may be important when small (Cook et al., 1998). The green sea urchin also feeds on epifauna such as hydroids, barnacles, small bivalves, boring sponges (e.g. Cliona), worms (e.g. Polydora) (Hancock, 1957; Lawrence, 1975). Parasites Psammechinus miliaris (as well as other echinoderms) frequently harbours a polychaete, Flabelligera affinis amongst the spines. Use The gonads of Psammechinus miliaris, but more commonly Paracentrotus lividus, are eaten as a delicacy in Mediterranean countries. As wild populations of Psammechinus miliaris typically have small gonads, its potential for aquaculture is being investigated (Kelly et al., 1998).
Biology References	Gage, 1991, Cranmer, 1985, Bedford & Moore, 1985, Cook et al., 1998, Hancock, 1957, Mortensen, 1927, Jensen, 1969, Massin, 1999(b), Aquascope, 2000(a), Bull, 1939, Kelly et al., 1998, Boolootian, 1966, Kelly & Cook, 2001, Kelly, 2000, Lindahl & Runnström, 1929, Comely, 1979, Lawrence, 1975, Davies, 1989, Holt, 1991, Ursin, 1960, Larsson, 1968, Hinegardner, 1969, Hayward & Ryland, 1990, Julie Bremner, unpub data,