Journal of Comparative Physiology A

, Volume 163, Issue 2, pp 227–235 | Cite as

Rest in the scorpion — a sleep-like state?

  • Irene Tobler
  • Jaqueline Stalder


Forest-dwelling scorpions (Heterometrus, Pandinus) were continuously observed by time-lapse video recording and their behavior and body position were analyzed. Activity recorded on the tapes was scored into three states: (1) activity, (2) alert immobility, and (3) relaxed immobility. Arousal thresholds were determined by mechanical stimulation. Responsiveness was highest during activity and alert immobility, and significantly lower during relaxed immobility. Heart rate was continuously measured by chronically implanted electrodes and related to the behavioral state. Heart rate was highest during activity, intermediate in alert immobility, and lowest during relaxed immobility. Activity bouts were associated with sudden increases in heart rate. ‘Settling down’, however, was associated with a progressive decline in heart rate.

The presence of rest regulation was investigated by 12 h rest deprivation by mechanical stimulation. During recovery, after initial activation, alert immobility and relaxed immobility were decreased.

It can be concluded that rest in the scorpion is not a homogeneous state. The subdivision into alert and relaxed immobility on the basis of body posture revealed differences in arousal threshold and heart rate between the two states. The compensation of rest after rest deprivation indicates the presence of regulatory mechanisms comparable with those present in mammals and several nonmammalian vertebrate species, thus providing evidence for a ‘sleep-like’ state in scorpions.



sleep deprivation




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Copyright information

© Springer-Verlag 1988

Authors and Affiliations

  • Irene Tobler
    • 1
  • Jaqueline Stalder
    • 1
  1. 1.Pharmakologisches InstitutUniversität ZürichZürich

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