The dactyl plunger of Alpheus sp. was found to be a layered
composite, with mineral-rich outer and inner layers and a chitin-rich
middle layer of high porosity. The chitin-rich middle layer is itself
composed of several porous chitin laminae. Modelling heat conduction
through the plunger cross-section revealed that the chitin-rich layer is
able to insulate heat and retard its progress through the material.
Heat accumulates in the plunger after a series of successive snaps and
as such, its thermally resistant design can be considered most useful
under the conditions of successive snapping. The plunger has a
concurrent mechanical damage-tolerant design with biogenic mineral
layers, viscous (chitin–mineral) interfaces, energy-dissipating porous
chitin, and sidewalls composed of ordered, layered aragonite. The
snapping shrimp plunger has a design that may protect it and internal
soft tissues from thermomechanical damage during plunger–socket
compression prior to cavitation bubble release.