LOCOMOTION IN THE ABALONE HALIOTIS-KAMTSCHATKANA - PEDAL MORPHOLOGY AND COST OF TRANSPORT

Morphological analyses of pedal sole area and pedal waves were conduct ed for a range of speeds and body sizes in the abalone Haliotis kamtsc hatkana. The pedal sole of resting abalone increased in size dispropor tionately with animal volume (slope of log(10)-transformed data, b=0.8 3; expected slope for isometry, b(0)=0.67) and length (b=2.51; b(0)=2. 0). Pedal wave frequency increased linearly with speed, confirming tha t abalone increase speed by increasing the velocity of pedal waves. To tal area of the pedal sole decreased by 2.1% for each shell length per minute increase in speed. Likewise, the area of the foot incorporated into pedal waves increased by 1.8% for each shell length per minute i ncrease in speed. Together, these changes translated into a 50% decrea se in the pedal sole area in contact with the substratum at a maximum escape speed of 15 shell lengths min(-1), relative to the pedal sole a t rest. The amount of mucus secreted by resting animals during adhesio n to the substratum increased isometrically with foot area (slope of l og(10)-transformed data, b=1.08). The amount of mucus secreted during locomotion did not vary with speed, but was less than the amount neede d for adhesion. We suggest that these morphological and physiological changes reduce the energy expenditure during locomotion. Cost of trans port was investigated for a range of speeds and abalone sizes. The rat e of oxygen consumption (V) over dot(O2) (in mu l O-2 g(-1) h(-1)) inc reased linearly with increasing absolute speed nu (in cm min(-1)): (V) over dot(O2)=40.1+0.58 nu-0.15m (r(2)=0.35, P=0.04), where m is body mass (in g). Minimum cost of transport, calculated from the slope of a bsolute speed on (V) over dot(O2), was 20.3 J kg(-1) m(-1). Total cost of transport (COTT) and net cost of transport (COTN) were high at low speeds and decreased as speed increased, to minima of 86.0 J kg(-1) m (-1) and 29.7 J kg(-1) m(-1), respectively, at speeds measured in the respirometer. Log(10)-transformation of both cost of transport and spe ed data yielded linear relationships with the following regression equ ations: log(10)COT(T)=3.35-0.90log(10)nu-0.21log(10)m (r(2)=0.89; P<0. 006) and log(10)COT(N)=2.29-0.69log(10)nu-0.09log(10)m (r(2)=0.48; P<0 .006), respectively.