BIOTIC

BIOTIC Species Information for Mya arenaria

Researched by

Lizzie Tyler

Data supplied by

University of Sheffield

Refereed by

This information is not refereed.

Reproduction/Life History

Reproductive type

Gonochoristic

Developmental mechanism

Planktotrophic

Reproductive Season

See additional information

Reproductive Location

Water column

Reproductive frequency

Annual protracted

Regeneration potential

Life span

11-20 years

Age at reproductive maturity

3-5 years

Generation time

3-5 years

Fecundity

100000- 5000000

Egg/propagule size

66 µm diameter

Fertilization type

External

Larvae/Juveniles
Larval/Juvenile dispersal potential	>10km	Larval settlement period	Insufficient information
Duration of larval stage	11-30 days

Reproduction Preferences Additional Information

A life span of 10-12 years was considered normal, although a maximum of 28 years was recorded in the Bay of Fundy (Strasser, 1999). Commito (1982) suggested that Mya sp. delayed reproduction until its fourth year, preferring rapid growth to reach a depth refuge. Strasser (1999) reported that first reproduction usually occurred at a size of about 20 -50 mm, which corresponds to an age of about 1-4 years depending on growth conditions.
Spawning: Spawning occurs once or twice annually, usually starting in spring and can occur between March and November depending on locality. In European waters larvae are usually found in May and June but sometimes as late as October. Annual spawning was reported in the Wadden Sea, on the west coast of Sweden, the east coast of Denmark and the Black Sea whereas biannual spawning was reported in Oslofjord and the south coast of England (Warwick & Price, 1976; Strasser, 1999; and see Brousseau,1987 and Clay, 1966 for reviews).
Both temperature and food availability affect gametogenesis and spawning. Critical spawning temperatures of 10-12 °C were suggested by Nelson (1928) however, peak spawning occurs in Massachusetts at 4-6 °C (Brousseau, 1978a). Peaks of larvae have been observed at 20°C and second spawnings once temperature had dropped below 25 °C (Newell & Hidu, 1986). Optimum larval growth has been reported between 17 -23 °C in the laboratory (Stickney, 1964) and slow growth between 12-15 °C (Loonsanoff & Davis, 1963). Strasser (1999) suggested that further study was required.
Fecundity: Males usually spawn first, releasing a pheromone which stimulates females to spawn (Newell & Hidu, 1986). Fecundity varies with location and size e.g. 120,000 eggs from a 60 mm clam, 3 million from a 63 mm clam and 1-5 million eggs in an individual have been reported (Strasser, 1999).
Fertilization: fertilization is external. Eggs are 66µm in diameter and can be carried many miles by the current (Newell & Hidu, 1986).
Larval stages: larval life lasts about 2-3 weeks, but can be extended, in the laboratory to up to 35 days in unfavourable conditions, most not metamorphosing until 200µm in length (Loosanoff & Davis, 1963; Strasser, 1999).
Recruitment: recruitment in bivalve molluscs is influenced by larval and post-settlement mortality. Mya arenaria demonstrates high fecundity, increasing with female size, with long life and hence high reproductive potential. The high potential population increase is offset by high larval and juvenile mortality. Juvenile mortality reduces rapidly with age (Brousseau, 1978b; Strasser, 1999). Larval mortality results from predation during its pelagic stages, predation from suspension feeding macrofauna (including conspecific adults) during settlement and deposition in unsuitable habitats. Mortality of the juveniles of marine benthic invertebrates can exceed 30% in the first day, and several studies report 90% mortality (Gosselin & Qian, 1997). Larval supply and settlement is often dependant on currents and timing of the phytoplankton bloom and may be sporadic in bivalves (see Cerastoderma edule reproduction) and differs consistently between sites. Recruitment is affected by adult population density, settlement intensity (in some but not all cases), post-settlement and juvenile predation, active and passive transport, and bedload transport or sediment erosion (Olafsson et al., 1994). For example:

in New Hampshire densities of spat ranged from 21 -8,200 /m² from 1975-1980 depending on the year (Newel & Hidu, 1986);
adults (up to 25 mm and occasionally 40 mm) and large numbers of juveniles were subject to bedload sediment transport (up to 790 individuals /m /day in sheltered sites and 2,600 individuals /m /day in exposed) in Nova Scotia;
in the above population bedload transport in exposed conditions accounted for 10 fold increase in clam density in September followed by a significant decrease by November and complete removal of newly settled spat (Emerson & Grant, 1991);
Brousseau (1978b) estimated that 0.1% of egg production survived to successful settlement;
Newell & Hidu (1986) suggested that <1% of settled spat must mature and reproduce in order to sustain the population;
high larval and juvenile mortality decreases with age and size levelling off towards age of first reproduction, with estimates of 88% mortality at 2-4.9 mm falling to <10% at >30 mm, and is highest in summer when predators are most abundant (Brousseau, 1978b; Strasser, 1999);
high densities of settling spat on a shallow exposed shore in southern Sweden in summer were swept away by storms in autumn and early winter (Olafsson et al.,1994);
predation was blamed for a reduction in newly settled spat from 6000/m² to zero in the subtidal in Virginia (Lucy, 1976 cited by Newell & Hidu, 1986);
Strasser et al., (1999) noted that sites of high adult densities do not deter settling spat or prevent successful recruitment, but the presence of Arenicola marina may prevent development to adulthood due to bioturbation.

Reproduction References

Newell & Hidu, 1986, Strasser, 1999, Brousseau & Baglivo, 1987, Brousseau, 1979, Stickney, 1964, Clay, 1966, Brousseau, 1987, Warwick & Price, 1975, Brousseau, 1978(a), Loosanoff et al., 1966, Loosanoff & Davis, 1963, Lutz et al., 1982, Emerson & Grant, 1991, Gosselin & Qian, 1997, Brousseau, 1978(b), Kühl, 1981, Anonymous, 1996, Strasser et al., 1999, Hawkins, 1994, Dow & Wallace, 1961, Nelson, 1928, Olafsson et al., 1994., Commito, 1982, Eckert, 2003, Brousseau, 1978(b), Strasser, 1999,