Gating of ventilatory activity in the cave‐cricket, Troglophilus cavicola

Abstract

ABSTRACT. The rhythm of ‘abdominal respiratory movements’ (ARMs) in partly tethered cave‐crickets was recorded via correlated hindleg movements associated with abdominal ventilation, and analysed with respect to postural changes (cricket placed horizontally or vertically) under the following stimulus regimes: touch stimuli of constant duration but varying rates were presented to the hind legs independently of the ARM rhythm; touch stimuli with constant delays were triggered by the previous ARM; and light stimuli were presented, preceding the touch stimuli. With constantly spaced touch stimuli, on‐ and off‐effects are visible in the number of ARMs per time unit and this is more pronounced in the horizontal than in the vertical position. Continuous modulations of ARMs patterning (tonic effects) are revealed in free run cycles which are intercalated in rhythmic driving series: at intertouch lengths of 20 s such free run cycling is faster under vertical than under horizontal conditions. With the vertical stance it is delayed by additional light. Even the kind of vertical orientation causes tonic effects. Thus crickets that face downward exhibit a slower ARM rhythm than those facing upward. Under entrainment to constantly delayed touches, two parameters of ARM rhythm (‘basic period’ and ‘consecutive period’) were studied to elucidate the hypothetical cycling of the pacemaker under different stances. Under horizontal conditions the ‘basic periods’ are shortened if the delay of touch does not exceed 0.2 periods of free run cycling. However, in the vertical position, the ‘basic periods’ are prolonged. With delay times exceeding 0.5 periods of free run cycle, the ‘consecutive periods’ are lengthened if the cricket is oriented vertically, but remain unaffected under horizontal conditions. On the basis of these results, a model for resetting and sensory modulation of ARM control is presented.