Surface structures of Pugettia quadridens and P. intermedia (Majidae, Decapoda)

Surface structures of Pugettia quadridens and P. intermedia were examined by scanning electron microscopy. Both crabs attach pieces of sea algae to six hooked setae sites on the carapace. In addition to the hooked setae, the crabs develop plate setae, which cover the entire surface except the tips of the chelae. The plate setae of P. quadridens were flat and played no role in decoration, whereas those of P. intermedia were variously modified in shape. For example, the setae on the abdominal carapace surface were flat, whereas those on the walking legs and the dorsal carapace were conical and in some cases considerably elongated. These modified plate setae served as attachment sites for algae and other small materials on the carapace and walking legs, blurring the outline of P. intermedia.