Modelling crushing crab predation on bivalve prey using finite element analysis

ABSTRACT

Amongst the many adaptive features of a bivalve shell, valve shape has been hypothesised to increase structural stability and to aid in withstanding crushing predation. Using Finite Element Analysis we modelled the crushing attack of a crab on a hard clam, soft clam, and blue mussel, assessing the effect of shell shape, size and thickness on their structural performance. Nanoindentation tests provide data on material properties. The hard clam is best suited to distribute applied loads evenly over a thick shell. Blue mussel shells work well when they are thin, and an increase in size is structurally disadvantageous. The soft clam accumulates the highest stresses; change in none of the tested variables improves its performance. The material properties and life habits of these taxa complement the structural responses of their shell shapes to crushing predation. Soft clams are poorly adapted to withstand crushing attacks, avoiding predators by living deeply burrowed in the substrate. Hard clams live shallower in the sediment, relying more on their thick valves to withstand attacks; these organisms are well adapted to disperse loads over a brittle shell. Epifaunal blue mussels absorb more energy than more brittle shells serving the organism well when small and thin.

KEYWORDS:

• functional morphology
• bivalves
• predation
• crab claw
• FEA analysis
• Nanoindentation analysis

Acknowledgments

We would like to thank RDK Thomas and a second reviewer for their constructive edits and comments that have greatly improved the manuscript. St. Lawrence University partially funded this project through an undergraduate research grant.

Disclosure statement

No potential conflict of interest was reported by the authors.