BIOTIC Species Information for Psammechinus miliaris
Researched byLizzie Tyler Data supplied byUniversity of Sheffield
Refereed byThis information is not refereed.
Reproduction/Life History
Reproductive typeGonochoristic
Developmental mechanismPlanktotrophic
Reproductive SeasonJune to August in UK Reproductive LocationWater column
Reproductive frequencyAnnual protracted Regeneration potential No
Life span6-10 years Age at reproductive maturity1 year
Generation time1 year Fecundity2500000
Egg/propagule size Fertilization typeExternal
Larval/Juvenile dispersal potential>10km Larval settlement periodInsufficient information
Duration of larval stage1-2 months   
Reproduction Preferences Additional InformationLongevity
Gage (1991) tried to use skeletal growth bands to estimate the age of urchins but this approach proved to be difficult to use in older specimens due to the proximity of growth lines during slow growth in older individuals. Bull, (1939) estimated longevity to be up to 6 years, Jensen, (1969) up to 8 years and Alain, (1978) up to 10 or 12 years.
Elmhirst (1922; cited in Gage, 1991) noted that maturity was reached in the first year after settlement. In contrast, Jensen (1969) found 75 % of one year old urchins to have immature gonads in their first summer. However, Kelly (2001) noted that one year old Psammechinus miliaris produced viable gametes and were able to breed in the laboratory.
Spawning (see additional images)
Individuals have been recorded as having ripe gonads from as early as February to as late as November (Orton, 1923; Sukarno et al., 1979; Mortensen, 1927). Actual breeding occurs in spring and early summer (Mortensen, 1927; Sukarno et al., 1979; Kelly, 2000). Psammechinus miliaris is a broadcast spawner (Massin, 1999(b)). The spawning period has been reported to be June to August in the Clyde Sea area (Elmhirst, 1922); June to October near Bergen, Norway (Runnström, 1925; cited in Lindahl & Runnström, 1929); June to October and May to October in West Norway and Denmark (Jensen, 1969); and July and August on the west coast of Scotland (Comely, 1979). Psammechinus miliaris from two typical habitats (littoral and sublittoral) on the west coast of Scotland had a defined annual cycle of gametogenesis with a single spawning period (Kelly, 2000) and gonad indices that peaked in June and July.
Estimates of fecundity suggest that females produce between 80,000 and 2,500,000 eggs in a single spawning event (Dr Maeve Kelly, unpublished observations). Breeding probably occurs over a couple of months (Kelly, 2000) but whether individuals breed for this entire period or whether this duration is for a whole population is uncertain. Orton (1923) suggests there is no evidence for collective spawning.
Reproduction References Gage, 1991, Orton, 1923, Allain, 1978, Sukarno et al., 1979, Mortensen, 1927, Jensen, 1969, Massin, 1999(b), Bull, 1939, MacBride, 1903, Boolootian, 1966, Kelly & Cook, 2001, Kelly, 2001, Kelly, 2000, Lindahl & Runnström, 1929, Comely, 1979, Kelly et al., 2000, Hinegardner, 1969, Leighton, 1995, Elmhirst, 1922, Cook et al., 2000, Pantazis, 2000, Julie Bremner, unpub data,
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