BIOTIC Species Information for Arctica islandica
Researched byLizzie Tyler Data supplied byUniversity of Sheffield
Refereed byThis information is not refereed.
General Biology
Growth formBivalved
Feeding methodPassive suspension feeder
Active suspension feeder
Surface deposit feeder
Sub-surface deposit feeder
Environmental positionInfaunal
Typical food typesPhytoplankton HabitBurrow dwelling
Bioturbator FlexibilityNone (< 10 degrees)
FragilityIntermediate SizeMedium(11-20 cm)
HeightInsufficient information Growth RateAverage 0-1.5 mm / year (Whitsand Bay)
Adult dispersal potential100-1000m DependencyIndependent
General Biology Additional InformationGrowth
The growth rate of Arctica islandica is very slow and highly variable. Internal growth bands visible in cross-sections of the valves and hinge plates of Arctica islandica are deposited annually, possibly in response to the reproductive cycle of Arctica islandica (Thompson et al., 1980a). The presence of these annual growth rings on the shell of Arctica islandica allows individuals to be aged. The following ages have been recorded:
  • in New Jersey, (U.S.A) specimens as old as 53 years (13.6 cm) were recorded (Ropes & Murawski, 1983);
  • in Georges Bank, (U.S.A) specimens as old as 93 years (13 cm) were recorded (Ropes & Murawski, 1983);
  • whereas, a specimen 10.7 cm in length was estimated to be 221 years old in Massachusetts (U.S.A) (Ropes & Murawski, 1983).
It has been suggested that maximum growth occurs between 3 - 7 years of age and that growth slows down after 15 years (Thompson et al., 1980b). Individuals of similar size may vary greatly in age. For example, individuals ranging in age from about 50 - 179 years showed little discernible difference in mean length (Ropes & Murawski, 1983). Growth rates may be reduced at high densities and are also dependent on the temperature. Arctica islandica also exhibits geographical variation in growth rates. For example:
  • in Whitsand Bay, (UK) individuals grew on average 0 -1.5 mm/yr.;
  • whereas off the coast of Long Island, (U.S.A) individuals grew 0.56 mm/yr. in 1970 and 11.7 mm/yr. in 1980; and
  • specimens from New Jersey grew an average of 1 mm in 1.6 years (Kennish et al., 1994; cited in Cargnelli et al., 1999a).
Conditions required for fast growth, large size and longevity in this species are unknown (Ropes & Murawski,1983).

In the southeast North Sea, the average density of adults >10 mm in length was 7 specimens per 100 m². The highest abundances of spat and adults were recorded in the central regions of the North Sea with 21 individuals >10 mm per 100 m² (Witbaard & Bergman, 2003). The northern North Sea (Fladden Grounds) was dominated by juveniles with 28,600 individuals per 100 m² (Witbaard & Bergman, 2003). In Kiel Bay, Baltic Sea, recorded abundances were 50 /m² but, no size was recorded (Rees & Dare, 1993).

Biomass / Production
In major areas of the northwest Atlantic the standing stock was (expressed as wet meat weight) over 119,000 km², an average of 10 g/m², with a maximum (over 19,000 km²) of 16 g/m² (Murawski & Serchuk, 1989; cited in Rees & Dare, 1993). The total live shell weight /flesh weight ratio was not stated but was presumed to be 2:1 or 3:1). In Kiel Bay, the annual production was estimated to be 15 g ash free dry weight (AFDW) / m² and the biomass was estimated to be 44.4 g AFDW /m² (Rees & Dare, 1993).

Arctica islandica like many other bivalves is able to respire aerobically and anaerobically. The change from aerobic to anaerobic respiration in bivalves usually occurs when oxygen levels in the water are reduced. However, Arctica islandica may experience periods of self induced anaerobiosis (Taylor, 1976).

Arctica islandica has only short siphons and siphonal contact with the water cannot be maintained when they burrow several centimetres beneath the sea bed. When this occurs they are able to respire anaerobically. No obvious rhythmic pattern has been detected but these periods of inactivity can last up to 10 days (Taylor, 1976). The heart rate of Arctica islandica after long periods of shell closure usually takes over 20 hours to return to normal (in Mytilus edulis this is accomplished in a few minutes). This behaviour in Arctica islandica is apparently self induced (Oeschger, 1990) since no stimulus that initiates either burrowing or a return to the surface has been identified. It was suggested that this behaviour is a likely response to hypoxic conditions however, previous studies showed that Arctica islandica was readily able to deal with hypoxic conditions. Other suggestions for this self induced burrowing behaviour included saving energy and a reduction in the risk of predation, as Arctica islandica would be less accessible to potential predators such as large starfish. However, more knowledge of their ecology is required (Taylor, 1976).

Biology References Fish & Fish, 1996, Rees & Dare, 1993, Taylor, 1976, Cargnelli et al., 1999a, Ropes & Murawski, 1983, Thompson et al., 1980b, Witbaard & Bergman, 2003, Thompson et al., 1980a, Thorarinsdóttir, 1999, Oeschger, 1990, Lauckner, 1983, Hayward & Ryland, 1990, Julie Bremner, unpub data,
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