Responses to rapid temperature change in the Pacific lamprey (Lampetra tridentata)

Abstract

Some aspects of the thermal biology of the Pacific lamprey (Lampetra tridentata) were studied by making rapid changes in the ambient water temperature (Ta). Calorimetric studies were conducted to determine the rate of ensuing changes in mean body temperature [Formula: see text] and various deep body temperatures. Cardiovascular–respiratory alterations were evaluated in an experimental flow-through apparatus in which Ta could be rapidly shifted while changes in ventilation frequency (fV) and heart rate (fH) were recorded. Immediately following a step increase in Ta, the change in [Formula: see text] of a 0.21-kg lamprey was 33% complete in 33 s and 67% complete in 127 s. Deep dorsal muscle temperature changed much more slowly, being 33% complete in 87 s and 67% complete in 225 s. During rapid shifts in Ta, fV and fH changed at a significantly greater rate than would be predicted taking into account the change in [Formula: see text] and the resultant Q10 effects on metabolism. This effect persisted when the [Formula: see text] of the water was held at 600 Torr (1 Torr = 133.322 Pa). A possible interpretation of the results is that lampreys, like other water-breathing vertebrates, sense alterations in peripheral temperature and utilize this information to alter the output of the ventilatory and cardiovascular systems in a way that anticipates some of the metabolic effects of temperature.