Do larger cephalopods live longer? Effects of temperature and phylogeny on interspecific comparisons of age and size at maturity
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The relationship between size and age at maturity in cephalopods is unresolved. The most recent interspecific comparison of size and age of cephalopods contradicts two previous studies by concluding that larger species do not live longer. This paper addresses the confounding effects of temperature and phylogeny while answering the question, “Do larger cephalopods live longer?”. To test this hypothesis, life-history data from 18 species of cephalopods, from five orders, with sizes at maturity spanning five orders of magnitude, were obtained from the literature. Without temperature consideration and with Nautilus spp. included in the sample, regression analysis suggests (r 2 = 0.376, p = 0.007) that larger cephalopods take longer to reach maturity. Once temperature was controlled by using physiological time (degree-days), the coleoid cephalopods moved closer to the best fit line and the genus Nautilus became an outlier. When Nautilus was removed and time measured in degree-days, the relationship was very strong (r 2 = 0.785, p < 0.001). We conclude that coleoid cephalopods achieve larger size by delaying maturity and that temperature, as well as phylogeny, must be considered when making interspecific comparisons.
KeywordsRegression Analysis Confounding Effect Large Species Interspecific Comparison Physiological Time
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