AN EXPANDING sea otter population is not behind the decline of abalones in the underwater kelp forests off northern California. In fact, otters may have helped the hard-shelled molluscs become so large.
Cold-water abalones can sport shells 30 centimetres long, whereas tropical species reach only 5 to 10 centimetres. David Lindberg at the University of California, Berkeley, and his colleagues studied how the meaty molluscs evolved to be so big, even alongside California sea otters, which break open abalones with rocks.
Lindberg analysed DNA from 29 small and large abalone species from around the world and found that large species…
