Coordination of the movements of the appendages in the Tasmanian mountain shrimpAnaspides tasmaniae(Crustacea; Malacostraca; Syncarida)

Abstract

The syncaridAnaspideshas changed very little in structure since the Palaeozoic and is considered to represent a very early branch from the main line of crustacean evolution. An examination of locomotory co-ordination inAnaspidesis made on the assumption that a primitive functional condition will be found where a primitive structural condition exists. The animal uses its thoracic endopodites and its abdominal appendages for locomotion and its thoracic exopodites for respiration. The locomotory appendages are coordinated in a linear sequence, with the exception of the large thoracic appendage at the junction of the abdomen and the thorax. Ipsilateral coupling is weak and gliding coordination is common. The respiratory appendages show considerable independence from the locomotory appendages even though the thoracic exopodites and endo-podites share common basal segments. The exception to this is that, where there is ongoing activity in the respiratory appendages while the animal is stationary, the rhythm of the respiratory appendages determines the rhythm of the locomotory appendages at the commencement of movement. The implications of these findings for an understanding of locomotory oscillator function are discussed.