Swimming by the water mite Limnochares americana Lundblad (Acari, Parasitengona, Limnocharidae)

Abstract

Locomotory patterns of Limnochares americana were analyzed from visual observations and cinema and still photography. In free swimming it uses only the last two pairs of legs such that the third leg on the left side and the fourth leg on the right side are in phase and the third leg on the right side and fourth leg on the left side are in phase. Legs on opposite sides and successive legs on the same side show a phase difference of 0.5 cycle (180°). Orientation appears to be cued primarily by direction of illumination and water movement. The swimming hairs form collapsible blades that improve the efficiency of each leg in swimming. Manoeuvering and control of roll, pitch, and yaw are accomplished primarily by altering the direction of the power stroke of various legs as the distal segments are rotated at the trochantofemoral joint.