60-27 Shortened Longevity of the Bivalve Arctica islandica During the mid-Pliocene Warm Period

Session: 2YC and 4YCU Geoscience Student Research Poster Showcase

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Abstract:

Arctic islandica, a bivalve, is the longest lived non colonial animal on the planet today. In Iceland it has a maximum reported lifespan of 507 years and individuals with lifespans more than 200 years are common. In addition to being long-lived, modern A. islandica from Iceland are also slow growing and display some of the lowest von Bertalanffy k values of any bivalve. This extreme longevity and slow growth are perhaps a result of the combination of both cold temperatures and seasonal food availability driven by polar light regimes. Though A. islandica has a stratigraphic record that dates back to at least the Oligocene, the life history strategies of this species in deep time remain unknown. Here, we examined lifespans and growth rates of A. islandica from the Tjörnes beds in northern Iceland during the mid-Pliocene warm period. To examine internal growth increments, specimens were first embedded in an epoxy resin and then cut with a rock saw, polished with a lapidary wheel, and finally imaged using a light microscope. Our results suggest that Arctica islandica was much shorter lived during the Pliocene, with maximum lifespans of only 80 years, but that von Bertalanffy k values (k=0.02) were similar to today’s populations. It is possible that this reduced longevity is a result of higher temperature, and that the similarly low growth rates are a response to persistence of a seasonally available food regime at high latitudes.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8118

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