Mussel bound
Invading zebra mussels have colonised at least 2,000 sq km of soft sediment on the beds of the Great Lakes in the US, says a recent report. Till now, it was thought that these mussels could grow only on hard surfaces. Paul Berkman of Ohio State University, USA, says his discovery that the creatures can grow on soft substrates has "stunned' US and Canadian officials fighting these invaders. "The potential expansion is huge,' according to Berkman.