Ectotherms with a calcareous exoskeleton follow the temperature-size rule-evidence from field survey

Abstract

The temperature-size rule, an increase in body size of ectotherms at lower developmental temperatures and vice versa, prevails across taxa. Most studies in this context have focused on either terrestrial or freshwater species, and little is known about marine organisms with calcareous exoskeletons, in which a slower calcium carbonate precipitation may constrain somatic growth at lower temperatures. Further, as the vast majority of data stems from laboratory experiments, little is known about the applicability of the temperature-size rule under field conditions. If applicable, individuals that grow in warmer seasons should metamorphose at a smaller size than those that grow in cooler seasons. Based on this premise, we monitored size at metamorphosis in 2 natural populations of the intertidal gastropod with determinate growth, Monetaria annulus, for 46 mo in Okinawa. Metamorphosis in summer resulted in significantly smaller sizes compared to other seasons. There was a negative relationship between (summer) temperature and size at metamorphosis across populations. These findings suggest that higher temperatures induce a smaller metamorphic size in this species under natural conditions. © Inter-Research 2009.