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

Abstract

The syncarid Anaspides has 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 in Anaspides is 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.

Nonreciprocal model swimmer at intermediate Reynolds numbers

“…2(a),(b). Interestingly, in contrast to previous works [24,37,38], the direction of net motion is opposite to the metachronal wave, which travels from tail-to-head or (the negative x), so our model swims in the direction of its tail.…”

Nonreciprocal model swimmer at intermediate Reynolds numbers

“…2(a),(b). Interestingly, in contrast to previous works [24,37,38], the direction of net motion is opposite to the metachronal wave, which travels from tail-to-head or (the negative x), so our model swims in the direction of its tail.…”

Swimming with stiff legs at low Reynolds number

“…A phase lag between successive legs produces the appearance of a metachronal wave, and the model predicts locomotion in the direction of the traveling wave. The direction is consistent with observations of crustaceans swimming by paddling their legs in an ordered sequence from the rear to the front end of the body and not the other way [13][14][15]. While the model may not yet capture all aspects of animal locomotion in quantitative detail, it could be readily extended in the future by incorporating additional effects such as the exact shape or flexibility of the body.…”

Nonreciprocal model swimmer at intermediate Reynolds numbers

“…2(a),(b). Interestingly, in contrast to previous works [24,37,38], the direction of net motion is opposite to the metachronal wave, which travels from tail-to-head or (the negative x), so our model swims in the direction of its tail.…”

Swimming with stiff legs at low Reynolds number

“…A phase lag between successive legs produces the appearance of a metachronal wave, and the model predicts locomotion in the direction of the traveling wave. The direction is consistent with observations of crustaceans swimming by paddling their legs in an ordered sequence from the rear to the front end of the body and not the other way [13][14][15]. While the model may not yet capture all aspects of animal locomotion in quantitative detail, it could be readily extended in the future by incorporating additional effects such as the exact shape or flexibility of the body.…”

Nonreciprocal model swimmer at intermediate Reynolds numbers

“…2(a),(b). Interestingly, in contrast to previous works [24,37,38], the direction of net motion is opposite to the metachronal wave, which travels from tail-to-head or (the negative x), so our model swims in the direction of its tail.…”

Swimming with stiff legs at low Reynolds number

“…A phase lag between successive legs produces the appearance of a metachronal wave, and the model predicts locomotion in the direction of the traveling wave. The direction is consistent with observations of crustaceans swimming by paddling their legs in an ordered sequence from the rear to the front end of the body and not the other way [13][14][15]. While the model may not yet capture all aspects of animal locomotion in quantitative detail, it could be readily extended in the future by incorporating additional effects such as the exact shape or flexibility of the body.…”