BIOTIC Species Information for Arctica islandica
Researched byLizzie Tyler Data supplied byUniversity of Sheffield
Refereed byThis information is not refereed.
Reproduction/Life History
Reproductive typeGonochoristic
 Developmental mechanismPlanktotrophic
Reproductive SeasonJune to October Reproductive LocationWater column
Reproductive frequencyAnnual episodic Regeneration potential No
Life span100+ years Age at reproductive maturity11-20 years
Generation time11-20 years Fecundity
Egg/propagule size85 µm diameter Fertilization typeExternal
Larvae/Juveniles
Larval/Juvenile dispersal potentialInsufficient information Larval settlement periodInsufficient information
Duration of larval stage   
Reproduction Preferences Additional Information
Sexual maturity
Sexual maturity is reached in Arctica islandica at a later age than has been reported for other bivalves. The age at sexual maturity in Arctica islandica was reported to vary between 5 and 11 years and may be dependent upon growth rate and locality (Thorarinsdóttir, 1999) . The mean age of sexual maturity in Nova Scotia was estimated to be 13.1 years for males and 12.5 years for females (Rowell et al. 1990; cited in Cargnelli et al., 1999a). However, Thompson et al. (1980b) reported immature individuals ranging in age from 4 -14 yr., at shell lengths ranging from 2.4 - 4.7 cm. It was suggested that immature Arctica islandica physiologically mimic the reproductive cycle of adults without providing gametes but very little research has been done on annual cycles of reproduction in juveniles (Thompson et al., 1980b).

Gametogenic cycle
Thorarinsdóttir (2000) examined the gametogenic cycle of Arctica islandica from Iceland and suggests that there are five phases in Arctica islandica's gametogenic cycle (Thorarinsdóttir, 2000).
  1. Early Active Phase. In females, oogonia appear and are embedded in the alveolar walls, often before the gonads are completely empty of ripe eggs. The shape of the oocytes may be square, triangular, cylindrical or hemispherical. In males, darkly stained spermatogonia are seen in the thickened alveolar walls but no spermatozoa are present.
  2. Late Active Phase. In females, oocytes are larger and most are free from the membrane of the follicles. In males, secondary spermatocytes are numerous and the surrounding cytoplasm is irregular in shape and sperm appear in the lumina.
  3. Ripe Phase. Follicles are extended and the gonads are full and ripe. In the female gonads the follicle contains almost exclusively free large ripe eggs. In males spermatozoa occupy the largest portion of the follicular spaces, while cells of early stages of spermatogenesis are few and confined to the area near the follicular walls. The sperm then form dense masses in the alveoli.
  4. Partially Spent Phase. Gametes are discharged. In females, few large ripe oocytes are free in the lumina of some follicles but others are void of ripe oocytes. Oogonia and early oocytes may appear in the contracted and thickened walls. In males, substantially less spermatozoa are contained within the centre of the follicles. Most gonads are completely void of sperm.
  5. Spent Phase. The follicles contain few undercharged eggs or sperm. Sometimes oocytes and primary spermatogonia begin to develop before the old ones are fully discharged (Thorarinsdóttir, 2000).
    6. Investigations on Arctica islandica have shown that the timing and duration of events in the gametic cycle can be highly variable between years, which may reflect both environmental and endogenous factors (Thorarinsdóttir, 2000).

    SpawningSpawning is protracted. Loosanoff (1953) reported spawning off Rhode Island between late June or early July when water temperatures reach 13.3 °C, although not all individuals reach ripeness at the same time. The majority of individuals completed spawning by early October. The optimum salinity range for the existence and reproduction of Arctica islandica is between 31.0 - 32.8 ppt (Loosanoff, 1953). However, the spawning period varies with location, for example another study reported spawning between May to November off Rhode Island, while spawning was reported to occur between September and November, and sometimes persisting into January off New Jersey, and between July to September off Nova Scotia (see Cargnelli et al., 1999a). Comparable data for northwest European populations is scarce. Attempts to ripen specimens of Arctica islandica out of season in the laboratory have had no or very limited success (Loosanoff, 1953; Landers, 1976). The average size of a fertilized egg is 75-95 µm (Loosanoff, 1953; Lutz et al., 1982).

    Larval Settling Time
    The settlement of larvae may occur over several months and is believed to occur throughout the adult distribution ranges.

    Recruitment
    The recruitment of this bivalve is considered as very sporadic (Thorarinsdóttir, 1999). Age frequency distributions from a population in Iceland showed recruitment increased at approximately 20 year intervals. A population of the Atlantic coast of the United States did not show any sign of recruitment over a 10 year period (Thorarinsdóttir, 1999).
    Longevity
    Arctica islandica is exceptionally long lived. Growth is relatively fast during the juvenile stage and then slows down (Cargnelli et al., 1999a). Counts of internal growth lines suggested ages of 200 years for individuals living on the U.S. Atlantic coast (Ropes, 1985)
Reproduction References Loosanoff, 1953, Rees & Dare, 1993, Thorarinsdóttir, 2000, Cargnelli et al., 1999a, Thompson et al., 1980b, Thompson et al., 1980a, Thorarinsdóttir, 1999, Landers, 1976, Ropes, 1985, Eckert, 2003, Julie Bremner, unpub data, Rees & Dare, 1993, Kilada, 2007,
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