Diurnal ventilatory patterns in the garter snake,Thamnophis elegans

Summary

Garter snakes,Thamnophis elegans, were entrained to a 14L (06.30–20.30 h) 10D (20.30–06.30 h) cycle for five weeks at 25 °C. Following entrainment, simultaneous measurements of ventilation and oxygen uptake were made. Pulmonary oxygen uptake ($\dot V_{O_2 }$) exhibited a diurnal rhythm with minimum values of$\dot V_{O_2 }$ occurring during 10D. The diurnal rhythm persisted during continuous darkness (24D) and was considered to be endogenous. Minute ventilation ($\dot VE$) decreased during 10D. The decrease in$\dot VE$ persisted during 24D. Diurnal alterations in$\dot VE$ were attributed to a change in breathing frequency (f). The decrease inf during 10D was postulated to be characteristic of a ‘sleeping’ state. The decrease in$\dot VE$ of the ‘sleeping’ state was of a greater magnitude than that for$\dot V_{O_2 }$. Consequently, a pronounced diurnal rhythm in air convection requirement$(\dot VE/\dot V_{O_2 } )$ resulted. The data suggest that the regulatory mechanisms of the ‘sleeping’ state differ from that of the ‘waking’ state.