The setae of the gill-cleaning mechanism in the soldier crab Mictyris guinotae Davie, Shih and Chan, 2010 (Decapoda: Brachyura: Mictyridae)

The setae involved in gill-cleaning in the soldier crab Mictyris guinotae were examined using a light microscope and an environmental scanning electron microscope. The setae of the epipods of the first and third maxillipeds are classified into three types: 1) anchor setae, 2) digitate-scale-setule setae, and 3) denticulate setae. The second maxillipeds lack epipods, and this absence can be explained in relation to the presence of the cup-shaped basal part of the third maxilliped epipod. The presence of anchor setae in M. guinotae may support the hypothesis that anchor setae are a brachyuran synapomorphy. The full anchor form may result from a fusing of the denticules on denticulate setae. The presence of digitate-scale-setule setae in M. guinotae may confirm that digitate-scale-setule setae are the ancestral character.