Figure 6.

Two opposing approaches to constructing tough elongated structures, visualized by mapping X-ray opacity in micro-CT reconstructions. (a) The claw on a walking leg of the terrestrial isopod Porcellio is mineralized in its inner layers (red, green), while the surface and the tip of the claw are purely organic (blue). (b) The dactylus and its spikes in the mantis shrimp Squilla are much more heavily mineralized than the rest of its raptorial appendage. Both structures rely on calcium phosphate; it is in its flexible amorphous form in the claw of Porcellio, while Squilla also incorporates the hard and stiff apatite. Both approaches to making protruding structures durable can be found in various exposed skeletal elements in other crustacean groups, such as decapods. Images were obtained from ethanol-fixed specimens using a NeoScan N80 micro-CT device and processed using Dragonfly software (Object Research Systems). The leg of Porcellio was air-dried before imaging.