Respiratory and circulatory changes accompanying aquatic treadmill exercise of Carcinus maenas (L.) and Homarus vulgaris (M.E.)
Respirometers were designed which allowed the exercise physiology of Carcinus maenas (L.) and Homarus vulgaris (M.E.) to be examined in an aquatic environment. A treadmill system, incorporated into each respirometer, was used to induce exercise at a known velocity. The rate of oxygen consumption, (VO2), of Carcinus maenas exercised at different velocities was examined. It was found that at each velocity, VO2 reached a steady state. The steady state VO 2 was found to be linearly related to velocity. The VO2 of inactive animals, and the maximal rate of oxygen consumption were both found to be linearly related to animal live weight. The VO2, rate of heart beat (fH) and rate of scaphognathite beat (fScaph) of both C. maenas and H. vulgaris were measured prior to, during and after exercise, at one specific velocity. Various haemolymph gas parameters were also measured. In both species, the VO2, f H and FScaph increased at the onset of exercise until a steady state was achieved. Estimates of the rate of branchial water flow for C. maenas suggest that this parameter also increased as a result of exercise. The rate of blood flow increased as a result of excerise in both species, achieved by an increase in the rate of heart beat and stroke volume of the heart. In vitro oxygen equilibrium curve determinations suggest that at the velocities examined, a Bohr shift plays a minimal role in increasing oxygen delivery to the tissues during exercise of the two species. No significant change in haemolymph carbon dioxide tension or total gas content was found in either species, suggesting that gas exchange across the respiratory surface was not impared during exercise. In C. maenas, whole body and haemolymph L-lactate concentration increased as a result of exercise. No increase in haemolymph L-lactate was observed after exercise in H. vulgaris.