Rhythmic body movements, cyclic gas exchange and heart activity were studied at low temperature (mostly at 5°C) in bumblebee Bombus terrestris foragers. Simultaneous measurements by means of an electrolytic respirometer combined with an optical system by infrared radiation, revealed a co-ordination between discontinuous gas exchange cycles and body rhythmic movements. No distinct correlation was found between intermittent heart activity and body movements. The carbon dioxide bursts were actively ventilated by abdominal vigorous pumping movements. These bursts followed each other with intervals of 25-30 minutes.
The periods of heart activity regularly alternated with heart pauses. The frequency of the heartbeat was similar to that of the weak abdominal pulsations (0.2-0.25 Hz) which were imperceptible with the naked eye. All bumblebees displayed abdominal pulsations which were independent of vigorous pumping movements. In bumblebee B. terrestris foragers haemolymph oscillation was assumed at 5°C, as is known in the honeybee and some other Bombus species.
Rhythms in abdominal pumping, heartbeats and discontinuous gas exchange cycles (DGCs) of CFV subtype (closed, flutter and ventilation periods) in adults of pine weevil Hylobius abietis were simultaneously recorded using an electrolytic microrespirometer and an infrared (IR) cardiograph or IR actograph (IRA). The cyclic release of carbon dioxide was associated with active ventilation (V phase) provided by vigorous abdominal pumping movements due to contractions of tonic longitudinal and transversal abdominal muscles, which are visible to the naked eye. On the IRA-recordings, the abdominal pumping signals are superimposed on the heartbeat spikes. The relative amplitude of the abdominal pumping signals on these recordings is more than 10 times greater than that of the heart beats. Visual observations showed that the subelytral cavity appeared to be closed during the release of carbon dioxide and open at other times. The flutter (F) of the CFV cycle is characterised by active miniature inspirations or ventilations before the V period. The miniature ventilation movements were imperceptible to the naked eye, but were recorded on the respirometer-actigraph as clear spikes. In addition, movements of the tip of the abdomen, of between 10-20 mm were seen under a stereomicroscope at a magnification of 40×. Some cycles were categorized as (C)FV cycles, when the C period disappears into the end of the V period. Abdominal pumping and miniature inspirations were clearly synchronized with the CFV cycles. Abdominal pumping movements, miniature inspirations or ventilations and heartbeats in adult H. abietis were distinguishable when recordings of the electrolytic microrespirometer-actograph and IRA were made in parallel. These three events were recognized by their different amplitudes and frequencies. It is presumed that abdominal pumping and miniature inspirations in adult H. abietis are obligatory rhythmic movements of different function and origin.
Adults of Colorado potato beetle Leptinotarsa decemlineata are very active at room temperature, and their almost continuous struggling in the respirometer prevents the measurements of the patterns of gas exchange, body movements and heartbeat. The tonic immobility of beetles was evoked by light flashes and by shaking as external stimuli. The immediate reaction to these stimuli was the reflexive closing of the spiracles and the cessation of CO2 release for some minutes, which was followed by a large burst of this gas. The state of the evoked tonic immobility did not influence heartbeat and abdominal pulsations, but the periodically -occurring abdominal-thoracic pumping movements stopped for 2-5 minutes. During the periods of pumping ventilation the metabolic rate was increased about two times.The state of tonic immobility evoked by light flashes lasted 2-6 minutes, but when shaking was applied as a stimulus complete immobility was about two times longer.