The biology and functional morphology of Arctica islandica (Bivalvia: Arcticidae) – A gerontophilic living fossil

Abstract

The North Atlantic bivalve Arctica islandica is a fishery resource and as such there is considerable information about it related to growth, physiology and reproduction. In contrast, however, its form, functional morphology and lifestyle have received scant attention. This study describes the anatomy of A. islandica and provides information to match fossil and rRNA evidence that it is a living fossil probably associated with a Cretaceous heterodont mactrid group adapted to deposit feeding. Arctica islandica lives in buried motionless repose feeding on the carbon-rich seabed surface micro-layer of northern boreal continental shelves. This study concludes that the indolent lifestyle exhibited by A. islandica, along with tissue antioxidant levels sustained into gerontocy, predisposes it to negligible senescence. As a consequence, and as has been demonstrated elsewhere, A. islandica can live for centuries – the current longevity record being 405 years obtained through an analysis of shell growth rings. Its value, therefore, as a ‘tree of the sea’, or archival proxy for marine environmental change in the boreal North Atlantic, is not just an appropriate simile with terrestrial tree rings, but an example and reflection of a conservative morphology and simple lifestyle fostering longevity.

Keywords:

• Anatomy
• Arctica
• biology
• living fossil
• long-living

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgements

I am grateful to the former director, Torliev Brattegard, of the Espeland Marine Biological Station of the University of Bergen, for providing boat and laboratory facilities during a research visit to Norway in August 1980. I am also grateful to C.A. Richardson, School of Ocean Sciences, Bangor University, UK, for subsequently providing additional specimens of Arctica islandica.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark