Cold-blooded animals, including fish, amphibians, crustaceans, and reptiles, seem to live longer under cooler conditions, suggesting that warming climate could have impacts on the lifespan of creatures whose body temperatures vary with the temperature of their surroundings, report researchers writing in the Proceedings of the National Academy of Sciences (PNAS).
Stephan Munch and Santiago Salinas of Stony Brook University examined lifespan data for 90 species from terrestrial, freshwater, and marine environments, comparing the differences in lifespan across an individual species’ range. They found significant differences. For example, pearl mussels in Spain (latitude: 43°N) have a maximum lifespan of 29 years, while in Russia the species lives nearly 200 years (latitude: 66°N).
Munch and Salinas determined that “ambient temperature is the dominant factor controlling geographic variation of lifespan within species.” They found that the observed relationship between temperature and lifespan was similar to the relationship that predicted by the metabolic theory of ecology (MTE), a model that explains how life history, population dynamics, geographic patterns, and other ecological processes scale with an organism’s body size and temperature. Overall the lifespan in 87 percent of the non-sessile species studied was explained by MTE.
“You can think of an animal as a beaker in which chemical reactions are taking place,” said Salinas. “The same rules that apply to a liquid inside a beaker should apply to animals. Chemists have a relationship for how an increase in temperature will speed up reaction rates, so the MTE borrows that relationship and applies it–with some obvious caveats–to living things.”
The researchers say the findings suggest that climate change could trigger changes in lifespans among cold-blooded species.
“It is interesting to consider how cold-blooded species are likely to react in the face of global warming,” said Salinas. “Because of the exponential relationship between temperature and lifespan, small changes in temperature could result in relatively large changes in lifespan. We could see changes to ecosystem structure and stability if cold-blooded species change their life histories to accommodate warmer temperatures but warm-blooded species do not.”
Research published last week suggests that warmer climate could favor smaller species over larger ones. Meanwhile NOAA announced earlier this month that global ocean temperatures in June reached the highest level since record-keeping began in 1880.
Stephan B. Munch and Santiago Salinas. Latitudinal variation in lifespan within species is explained by the metabolic theory of ecology. PNAS Online Early Edition the week of July 27-31 2009