The heart ratio (heart weight/body weight x 100) increased markedly during the metamorphosis of Petromyzon marinus, Lampetra fluviatilis and Lampetra planeri, apparently through an increase in the number and density of myocardial fibres. For each life cycle stage, the logarithmic relationship between heart and body weights was close to one. The heart ratio was significantly higher in preserved (11% formalin) than in freshly killed material. Using the fact that adult Lampetra fluviatilis will attach themselves for long periods to the inside of a tube, apparatus were desig.ied to measure oxygen consumption and the ventilatory and cardiac frequencies during periods of inactivity and activity. Activity was low during the light phase of the photoperiod but, together with standard oxygen consumption and the rate of cardiac and ventilatory pumping, it increased during darkness in all but sexually nature animals. In sexually immature lampreys, the standard rate of oxygen consumption at 5, 9.5 and 16°C was 15.8, 39.7 and 89.4 mug/g/h, with the logarithmic relationship between oxygen consumption and body weight at 9.5 and 16°C being slightly less than one. Oxygen consumption, ventilatory frequency and heart rate increased markedly during the later stages of the spawning run, with significant differences being recorded between sexually mature males and females. In immature animals, the Q10 was greatest for oxygen consumption and least for heart rate. At 9.5°C, the oxygen consumption, ventilatory frequency and, to a lesser extent, heart rate increased between 100 and 20% of full oxygen saturation Below 20% lampreys became active, the ventilatory frequency reaching a maximum at 12.5% Although animals survived for 96 hours in death occurred within 5 - 8 hours at 7.5%. Absolute synchrony of the heart with a particular phase of the respiratory cycle was only rarely observed. The heart beat ventilatory cycle ratio although varying with temperature, remained relatively constant throughout the spawning run.
|Date of Award||1974|