GROWTH RATES AND LIFESPANS OF GLYCYMERIS AMERICANA FROM NORTH CAROLINA, USA DURING THE PLIOCENE AND PLEISTOCENE

Marine bivalves exhibit some of the longest lifespans of non-colonial animals, marine or terrestrial. Like rings on a tree, growth increments preserved in the shell record information about a bivalve’s life history. The study of these accretionary structures, called sclerochronology, can used to determine the lifespans and growth rates of bivalves. Data derived from these increments can help understand the controls on extreme longevity. Several factors are thought to influence lifespan, but two of the most important are nutrient availability (food) and water temperature. Here, we examine the lifespans and growth rates of Glycymeris americana, from the Pleistocene Waccamaw Formation of North Carolina and compare them to Pliocene data from a previous study to evaluate these factors. We found that Pleistocene bivalves lived much longer (max lifespan = 93) than those found in the Pliocene (max lifespan = 51). We also found that the growth rates of Pleistocene G. americana are slower than those of Pliocene. This difference in lifespan and growth rate might be attributed to cooler ocean temperatures found in the Pleistocene, which would have promoted lower metabolic rates. These results are important not only to paleontologists, but also biologists because they document how marine bivalves might respond to changing ocean temperatures.