 However, that is exceptional; most adult females are parasitic and have morphological adaptations for attacking the gills of host species of fishes.Though their antennules retain their sensory function, the main second antennae of the adult females are adapted to clinging to the gill filaments of host fishes.In many "Ergasilus" species it is not clear that mature females are able to release their grip once attached, but when forcibly detached from the host's gills they swim without difficulty.