Effects of injured conspecifics and predators on byssogenesis, attachment strength and movement in the blue mussel, Mytilus edulis

Mussels respond to threats from predators by increasing anti-predator traits, which include a suite of inducible defenses. Blue mussels (Mytilus edulis) can modify the strength, number and attachment site of byssal threads in response to water borne cues from predators and injured conspecifics. We quantified byssal thread production, attachment strength and movement in blue mussels of two size classes in response to effluent from the American lobster Homarus americanus, the rock crab Cancer irroratus, the sea star Asterias rubens, and injured conspecific mussels. In a factorial laboratory experiment effluent from the predatory crab, C. irroratus, resulted in higher numbers of functional byssal threads compared only to exposure to injured conspecific mussels, and not to any other treatment group. Large mussels produced stronger byssal attachments than small mussels. Over 24 h, small mussels formed and released more byssus bundles than large mussels, an indication of increased movement. Small mussels started producing byssal threads sooner than large mussels. Mussels exposed to effluent from injured conspecific mussels began producing byssal threads earlier, compared to the control and not to any other treatment group. Our results show that byssogenesis was influenced by predator type and mussel size, whereas attachment strength and movement depended on mussel size. This study highlights the ability of two size classes of blue mussels to selectively alter byssal thread production and movement in the presence of injured conspecifics and potential predators. (C) 2013 Elsevier B.V. All rights reserved.