Setae for Gill-Cleaning of Six Species of Japanese Sentinel Crabs (Macrophthalmus)

Abstract The setae involved in the gill-cleaning mechanism of six species of Japanese sentinel crabs are described. The setae are classified as belonging to five types: anchor, serrate, simple, digitate-scale-setule, and normal setule setae. The anchor setae are further divided into ten sub types based on the combinations of digitate-scale setule, normal setule, anchor type, and the shape of their tip. Setae on out-growths and tips were compared with those identified in previous studies. As a result, the single row half anchor setae were found only in the subgenus Macrophthalmus and might be used as a special characteristic in the subgenus.