Re‐examining extreme longevity of the cave crayfish Orconectes australis using new mark–recapture data: a lesson on the limitations of iterative size‐at‐age models

Abstract

Summary1. Centenarian species, defined as those taxa with life spans that frequently exceed 100 years, have long been of interest to ecologists because they represent an extreme end point in a continuum of life history strategies. One frequently reported example of a freshwater centenarian is the obligate cave crayfish Orconectes australis, with a maximum longevity reported to exceed 176 years. As a consequence of its reported longevity, O. australis has been used as a textbook example of life history adaptation to the organic‐carbon limitation that characterises many cave‐stream food webs.2. Despite being widely reported, uncertainties surround the original estimates of longevity for O. australis, which were based on a single study dating from the mid‐1970s. In the present study, we re‐evaluated the growth rate, time‐to‐maturity, female age‐at‐first‐reproduction and longevity of O. australis using a mark–recapture study of more than 5 years based upon more than 3800 free‐ranging individuals from three isolated cave streams in the south‐eastern United States.3. The results of our study indicate that accurate estimates of the longevity of O. australis are ≤22 years, with only a small proportion of individuals (<5%) exceeding this age. Our estimates for female time‐to‐maturity (4–5 years) and age‐at‐first‐reproduction (5–6 years) are also substantially lower than earlier estimates.4. These new data indicate that the age thresholds for life history events of O. australis are comparable to other estimates for a modest assemblage of cave and surface species of crayfish for which credible age estimate exists, suggesting that a cave environment per se is not required for the evolution of extreme longevity in crayfish.