By Susan Milius
Inside their hearts, crocodiles have toothlike gear cogs. Researchers now have figured out what makes those teeth clench.
Unlike more standard heart valves, which swing open or closed as blood pressure changes, the cogs interlock to reroute blood in response to changing hormone levels, say Craig E. Franklin of the University of Queensland in Australia and Michael Axelsson of the University of Göteborg in Sweden. “To our knowledge, this is the first report of an actively controlled intra-cardiac valve in a vertebrate,” they claim in the Aug. 24 Nature.