Greenland sharks: old and cold
A remarkable creature lives beneath the ice floes of the Arctic. Greenland sharks swim excruciatingly slowly, have been known to eat polar bears and live for an implausibly long time. Peter is bringing their mysteries to the surface.
Peter Bushnell
Greenland Sharks
The general aim of this project is to deploy satellite tags on Greenland sharks and collect tissue samples for the purpose of age determination in order to better understand the species’ movements and the age structure of its population(s).
Fishing pressure and a lack of basic knowledge of the species’ natural history are threats to the future of the Greenland shark Somniosus microcephalus – thought by some to be the longest-lived vertebrate on earth. Effective conservation and management of any fish species requires a thorough understanding of growth rates, age at first reproduction, fecundity, distribution, population structure, etc.
Depth and location alter the amount of radioactive carbon incorporated into bodily tissues, which in turn impacts the accuracy of age estimates based on radiocarbon dating. Our two proposed projects are therefore directly related to one and other in that the water masses occupied by an animal and determinations of its age are linked. This research will address both these issues by deploying pop-up satellite archival tags (PSATs) on sharks in eastern and western Greenland, and by collecting tissue samples for radiocarbon analysis. In other research, we have already successfully deployed PSATs on Greenland sharks in north-western Greenland and had them remain attached for the full programmed period of 3.5 months. PSATs deployed in both areas will be programmed to release after one to three and nine to 12 months to provide insights into the water masses the sharks move through. These data will be important for our ageing studies, which comprise the second portion of the study. Eye lenses will be collected from sharks of various sizes for age determination using radiocarbon dating. Several fishermen and fisheries biologists are willing to assist us and supplement our efforts.
The general aim of this project is the deployment of satellite tags and collection of tissues from Greenland sharks for age determination in order to better understand their movements and the age structure of their population(s). Detailed objectives are to:
- Deploy long-lines in north-eastern Greenland to catch (and release) Greenland sharks.
- Record total length, girth, weight, gender, date and location of capture sharks, and release them after tagging with dart tags from the Greenland Fisheries Department.
- Deploy eight PSATs on sharks caught by long-line that are set to release at intervals from one to 12 months.
- Collect vertebrae and eye lenses from any dead or terminally injured sharks for ageing studies.
- Determine age of shark tissue samples by bomb radiocarbon analysis (in collaboration with AMS 14C Dating Center, University of Aarhus, Denmark).
Results:
We now (2024) have exciting news to announce: they have now sequenced this iconic species’ genome. They published their first results on bioRxiv and made the genome sequence accessible. The data suggest that this animal’s toolbox for repairing its own DNA may explain its extreme longevity – and that of other animals. More than that: The team’s work to decode the animal’s genetic makeup will shed new light on general mechanisms enabling longevity.
1: https://www.nytimes.com/2024/09/22/science/greenland-sharks-genetics.html
2: https://www.leibniz-fli.de/news-events/details/international-team-of-scientists-decodes-the-genome-of-the-greenland-shark
3: http://www.mbl.ku.dk/JFSteffensen/OldAndCold/