Sleep patterns in the lizard Ctenosaura pectinata.

Specimens of the lizard Ctenosaura pectinata were chronically implanted for polygraphic recordings. Four different vigilance states were observed throughout the nyctohemeral cycle: Active wakefulness (Aw), quiet wakefulness (Qw), quiet sleep (Qs) and active sleep (As). Each state displayed its own behavioral and electrophysiological characteristics. Aw, Qw, Qs and As occupied 5.9%, 25.7%, 67.7% and 0.6% of the 24-h period, respectively. The frequency and the duration of As episodes showed great interanimal variability and the mean duration was very short (12.9 +/- 9 s, mean +/- standard deviation). Stimuli reaction threshold was highest during sleep. It is concluded that the lizard Ctenosaura pectinata exhibits two sleep phases (Qs and As) that may be assimilated to slow wave sleep (SWS) and paradoxical sleep (PS) of birds and mammals.