Growth in the limpet Nacella concinna from contrasting sites in Antarctica

Annual shell growth was determined by mark and recapture in the limpet Nacella concinna (Strebel 1908) at two contrasting sites in Antarctica. At Signy Island, 60degreesS, growth was moderately fast, comparable with some limpets in more temperate areas. The fluorescent calcium marker calcein was used to validate the results from the mark/recapture study, and fine-scale growth increments showed that shell growth was seasonal. Further south at Rothera Point, 67degreesS, mean annual growth over a 3-year period was significantly slower than at Signy, and in 1 year was the slowest yet reported for a limpet. Comparison with an earlier mark/ recapture study at Arthur Harbour, Palmer Station (64degreesS) revealed a cline of decreasing growth performance with increasing latitude along the Antarctic Peninsula. It is not clear whether the slower annual growth rate at higher latitude was caused by physiological constraints, a reduced length of growing season, or a combination of both. Limpets show a global cline in growth performance, which decreases towards higher latitudes.