Effects of shell shape, size, and sculpture in burrowing and anchoring abilities in the freshwater musselPotamilus alatus(Unionidae)

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Because of the sedentary lifestyle of freshwater mussels, studies examining their movement capabilities are scarce. However, the ability to burrow into the substrate and the ability to remain stationary are likely crucial components of their behavioural repertoire. The performance of these different tasks is likely to be affected by the presence of the shell ornamentation characteristic of many mussel species. Previous studies have suggested that shell ornamentation results in a trade-off between burrowing ability and remaining stationary when an extrinsic force attempts to dislodge it from the substrate once buried. We examined the effect of morphology and shell ornamentation on burrowing performance and anchoring ability by artificially creating shell ornamentation on a relatively smooth-shelled species (Potamilus alatus). Burrowing behaviours and performance and the force required to dislodge mussels (anchoring ability) were quantified with and without ornamentation. Interestingly, we found that the artificial shell ornamentation had no significant effect on burrowing behaviours and performance or dislodgement force. Burrowing and dislodgement, however, were both highly influenced by shell size and shape. All of the available information suggests that shell size, shape, and sculpture influence burrowing and anchoring in complex ways that needs further examination. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111, 136–144.