Does global warming cause animals to shrink?
A study of copepods found that the growth rates of the tiny marine crustaceans is highly sensitive to temperature, with implications for the entire food chain.
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Their analysis also revealed that while the egg did not respond to warmth, the gap between development rate and growth rate tended to widen begining around the second life stage until adulthood. When the animal reached maturity, its final adult size was smaller as a result, they found.Skip to next paragraph
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As zooplankton, or tiny, floating animals, copepods are a key component of the ocean food web, so if warming in the oceans prompts these animals to shrink, it could have a direct effect on the things they eat and what eats them. The fish that eat them, for example, will have to spend more time searching for more of them to eat. As cold-blooded creatures themselves, the fish could also be affected by the warming waters, creating a compound effect, which could result in even smaller fish.
It's also possible that the fish could switch to other prey, a move that could have its own ripple effects. However, both of these scenarios are hypothetical, Forster said.
The researchers' previous work has shown that size decreases by an average of 2.5 percent for every 1.8 degrees Fahrenheit (1 degree Celsius) of warming for a range of cold-blooded creatures, including insects, crustaceans, fish, amphibians and reptiles. Some species of copepods have shown larger size changes with temperature.
Cold-blooded animals may not be the only ones affected by temperature changes: There is evidence that the temperature size rule also holds for single-celled protists and in plants, according to Forster.
The research was published online Sept. 29 in the journal The American Naturalist.
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