Comparative studies on the role of antiplectic metachronism in the generation of water currents by crustacea and ctenophora

Barlow, David Ian (1986) Comparative studies on the role of antiplectic metachronism in the generation of water currents by crustacea and ctenophora. University of Southampton, Doctoral Thesis.

Abstract

The nauplii of Artemia salina swim by means of a single pair of rowing appendages (the second antennae). Two similar sized copepod nauplii, Eucyclops agilis and Cyclops strenuus abyssorum, use all three pairs of naupliar appendages for locomotion. In contrast, adult Artemia and Pleurobrachia pileus possess many appendages that exhibit antiplectic metachronal coordination. This study examines the idea that the coordination shown by these organisms confers propulsive advantages other than the reduction of interference between adjacent structures. Cine-photography was used to record the limb movements and flow patterns around asymmetrically beating appendages. A computer program was developed to aid visualisation of the oscillating flows around the appendages. The role of water currents in swimming and feeding was determined from the flow patterns and estimates made of the energy cost. A. salina, E. agilis, and C. strenuus nauplii showed swimming speeds of 2,5, 10, and 35 mm s^-1 respectively. The corresponding limb beat frequencies were 10, 60 and 100Hz and the maximum measured power outputs 9.7x10^-12, 1.3x10^-10 and 4.8x10^-10 watts. Artemia nauplii were estimated to use less than 0.1% of their energy budget for continuous locomotion, whilst copepod nauplii can expend up to 10% in intermittent bursts. Thrust is controlled by adjusting the frontal area of the setae at the tip of each limb. Artemia uses both the second antennae and the mandibles to collect food. The limbs of adult Artemia beat within a narrow frequency range (2.5-4.OHz), whilst the comb plates of Pleurobrachia beat over a wider range (2 to 20Hz). The estimated maximum continuous mechanical power outputs of both organisms were 1x10^-7 watts. This represented 3% of the total energy consumption of Artemia. Observations indicate that pressure changes between antiplectically coordinated structures may contribute to the acceleration of the water and thereby increase the efficiency of the individual propulsive units. Water is ejected from the interlimb spaces of Artemia by compression at speeds exceeding the maximum setal tip speed. Flow speeds did not exceed the comb plate tip speed in Pleurobrachia. Artemia utilises the suction produced during filling of the interlimb spaces to drive the water through a filter to extract food particles before ejecting it into the propulsive stream. This was not the case in Pleurobrachia. It was concluded that antiplectic metachronal coordination of limb systems may be adapted for low energy propulsion but, unlike rowing propulsion, it may not be suitable for high energy locomotion such as escape or predatory behaviour.

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