Ciliatocardium ciliatum (Fabricius, 1780)
Hairy cockle (English)
Ciliatocardium ciliatum is a common bivalve of north polar regions, ranging from Greenland to Norway to the Aleutian islands. It lives in loose mixed substrate and filter feeds with a life expectancy of up to 25 years. It is usually sedentary, but when threatened may use it's foot to escape predators.
English: Hairy Cockle, Iceland Cockle; Japanese: Kokeraishikage-gai; Icelandian: Bàruskel; local in Greenland: kirksoarsak (Kafanov, 2001)
In a laboratory test (Legault and Himmelman, 1993), C. ciliatum escaped from predators with an initial ejection of water followed by violent movements of the foot. Response intensity tended to increase with predation risk. This rapid and strong response to contact with predators is considered striking compared to its normal slow movements. C. ciliatum is never buried more than 4cm deep and is sometimes found on the surface, suggesting that it relies on its escape behaviour to limit predation (Legault and Himmelman, 1993).
Typically 40 mm in length up to a maximum of 70 mm, sub-ovate, inflated, with an average of 34-36 triangular shaped ribs along with well marked growth rings, a weakened hinge and a nymph that is at least twenty percent of the shell length (Kafanov, 2001; Tallqvist and Sundet, 2000).
C. ciliatum grows rapidly until an age of 6 years, after which growth rate slows. Water depth can affect the growth of C. ciliatum, with it growing larger in shallower depths (Tallqvist and Sundet, 2000). Subarctic populations grow slower than Arctic populations and the growth has been shown to be related to both temperature and salinity; however, ice coverage and water temperature do not affect C. ciliatum as greatly is in other benthic animals in polar areas (Tallqvist and Sundet, 2000).
The subspecies C. likharevi (Kafanov in Scarlato, 1981) may be confused, but it differs in that it's shell is not oblique and has a shorter nymph (on average no more than 1/5 of the shell length) than C. ciliatum (Kafanov 2001).
Shell medium sized, sub-ovate, inflated, with a maximum length of 65 or 70 mm. The posterior end is less rounded and slightly more produced than the anterior (inequilateral). The left and right valves appear equal in size and shape (equivalve). The sculpture comprises radial ribs that number, on average, 34 to 36 (Kafanov, 2001) with a triangular profile, as well as well defined growth lines, and an interlocking shell margin. Internally, C. ciliatum has a smooth white surface, continuous pallial line and clearly marked adductor muscle scars. The interior margin is crenulated. Hinge of the right valve with two cardinal teeth (the anterior much smaller), two anterior laterals (the dorsal much shorter and smaller) and one posterior lateral. Hinge of the left valve with two cardinals (the anterior slightly more pronounced), one anterior lateral, and one or two posterior lateral teeth. The ligament is external and supported by a nymphal ridge that extends for at least twenty percent of the shell length (Kafanov, 2001).
Ecology and Distribution
C. ciliatum's predators include, but are not limited to: walruses, whales, halibuts, flounders, haddock, wolffishes (Kafanov, 2001). The main predators of the species appear to be whelks and seastars (Legault and Himmelman, 1993)
C. ciliatum is generally a slow and sedentary creature (Legault and Himmelman, 1993), but drifting sea ice may be responsible for transporting it to lower depths (Kafanov, 2001).
C. ciliatum lives in Arctic seas, from Greenland to the North Pacific (south to Korea, Hokkaido, Boso Peninsula, Honshu, Aleutian and Commander Islands and Puget Sound, Washington), and the North Atlantic (south to southern Norway, south Iceland, south Greenland and Cape Cod, Massachusetts) (Kafanov 1980).
According to observations by Kafanov, 2001, C. ciliatum inhabits depths of up to 700m, but mostly between 30 and 150m; in European sub-Arctic areas it frequently inhabits larger depths, which is likely caused by transport activity of sea ice. It lives preferably on silts, sandy silts and sands but often occurs on mixed soils and on pebbles (Kafanov, 2001). It prefers salinity of 33-35% though is tolerable of salinities as low as 24% (Kafanov, 2001). C. ciliatum may be a comon component of bottom communities, with a maximum biomass of 134g/m^2 recorded by Kafanov, 2001.
Life span is of approximately 25 years (Tallqvist and Sundet, 2000).
Suspension Feeder (Tallqvist and Sundet 2000).
C. ciliatum is edible but is rarely consumed. It tastes similar to Spisula sachalinensis (common name Sakhalin surf-clam) (Kafanov 2001).
- Clinocardium ciliatum (Fabricius, 1780) (synonym (objective = homotypic))
- Clinocardium arcticum Sowerby, 1834 (synonym)
- Clinocardium boreale Broderip and Sowerby, 1829 (synonym)
- Clinocardium dawsoni Stimpson, 1862 (synonym)
- Clinocardium hayesii Stimpson, 1863 (synonym)
- Clinocardium pubescens Couthouy, 1838 (synonym)
- Cardium islandicum Gmelin, 1791 (synonym)
- Cardium californiense comoxense Dall, 1900 (synonym)
- Cardium islandicum Bruguière, 1789 (synonym)