Image of Mytilus Linnaeus 1758

Description:

These living mussels are from Ala Spit, Whidbey Island, WA. The barnacle is Balanus glandula. Photo by Dave Cowles, Sept 2005 Note here the two color phases, brown and black, seen in mussels. The black phase is usually much more common than the brown. Nagarajan et al. (2002) found that black oystercatchers optimized their long-term energy intake by preferentially eating the brown mussels of the related species Mytilus edulis. While shell thickness and tissue content was similar between the color phases, the brown phase had significantly lower moisture content so that the oystercatchers were able to pack more energy-yielding food into their crops by eating the brown phase mussels.