BIOTIC Species Information for Cerastoderma edule
|Researched by||Lizzie Tyler||Data supplied by||University of Sheffield|
|Refereed by||This information is not refereed.|
|Reproductive Season||Spawn over summer||Reproductive Location||Water column|
|Reproductive frequency||Annual protracted||Regeneration potential||No|
|Life span||6-10 years||Age at reproductive maturity||1-2 years|
|Generation time||1-2 years||Fecundity|
|Egg/propagule size||75 µm diameter||Fertilization type||External|
|Reproduction Preferences Additional Information||Longevity and sexual maturity
Cerastoderma edule may live for up to 9 years or more in some habitats but 2 -4 years is normal. The sex ratio was reported to be 40% males to 60% females (Fretter & Graham, 1964). Adults first mature and spawn in their second summer, at about 18 months old and 15-20 mm in length, however, large cockles (>15 mm) may mature in their first year suggesting that size and maturity are linked (Orton, 1926; Hancock & Franklin, 1972; Seed & Brown, 1977).
Gametogenesis is initiated in winter (October to March) but increases rapidly in spring (February -April) (Newell & Bayne, 1980) and the majority of the population are ripe by mid-summer (Seed & Brown, 1977). Most adults spawn in a short peak period over summer with remaining adults spawning over a protracted period, resulting in a short (ca. 3 month) period of peak settlement followed by generally declining numbers of recruits (Hancock, 1967; Seed & Brown, 1977). Spawning generally occurs between March - August in the UK followed by peak spatfall between May and September, however the exact dates vary between sites in the UK and Europe (Seed & Brown, 1977; Newell & Bayne, 1980). Boyden (1971) suggested that warming of water in spring to 13 °C or above was required to induce spawning, however Ducrotoy et al. (1991) suggested that a sudden temperature rise (rather than an absolute level) was probably required to initiate spawning. An occasional late peak in settlement may occur e.g. on the Llanrhidian Sands, Hancock (1967) reported an additional settlement peak in August -September after the main peak in May -July.
Fertilization is external. Males may release about 15 million sperm/sec and females were reported to release about 1900 eggs/sec. Gamete viability is short and André & Lindegarth (1995) found that fertilization was reduced to 50% in 2 hours and that no fertilization was observed after 4 -8 hrs. André & Lindegarth (1995) noted that fertilization efficiency was dependant on sperm concentration so that at high water flow rates fertilisation was only likely between close individuals. However, this may be compensated for by high population densities and synchronous spawning of a large proportion of the population. Eggs (50-60µm) develop into a trochophore stage within the egg membrane and then into a typical bivalve veliger at ca. 80µm, the D -larvae (so called due to the D -shaped shell) after about 3 -4 days the foot develops and the veliger metamorphoses into a juvenile cockle (pediveliger) at ca. 270µm after about 3 -5 weeks (Lebour, 1938; Creek, 1960). The juveniles reach ca. 600-700µm after about 3 weeks, and by 3 months are ca. 0.75-1.5 mm long (Creek, 1960).
Settlement and subsequent recruitment has a significant impact on the dynamics of Cerastoderma edule populations, in many but not all circumstances (Olaffsson et al., 1994). Settlement and recruitment is sporadic and varies with geographic location, year, season, reproductive condition of the adults and climatic variation. Factors reported to affect recruitment follow.
|Reproduction References||Fretter & Graham, 1964, Seed & Brown, 1977, Hancock & Franklin, 1972, Jones & Baxter, 1987a, Richardson et al., 1980, Orton, 1926, Newell & Bayne, 1980, Montaudouin & Bachelet, 1996, Ducrotoy et al. , 1991, Jensen, 1993, Lebour, 1938, Creek, 1960, Sanchez-Salazar et al. 1987, Olafsson et al., 1994., André et al. , 1993, Guillou & Tartu, 1994, Möller & Rosenberg, 1983, Hummel & Bogaaards, 1989, Kingston, 1974, Rygg, 1970, Ansell et al., 1981, Eckert, 2003, Julie Bremner, unpub data,|