Urmas Tartes

Diversity in gas exchange and muscular activity patterns in insects studied by a respirometer‐actograph

Different events in insect gas exchange and muscular activity are described by a new system of automatic respirometers, a differential electrolytic microrespirometer‐actograph. This is very sensitive to volumetric changes caused by insect respiration and/or body movements. In this system, oxygen generation and its regulation are combined in the same current circuit. According to this principle, the oxygen consumed by the insect is continuously replaced by equal amounts of electrolytically produced oxygen. This simple laboratory‐made apparatus records simultaneously metabolic rate, the cyclicity of external gas exchange, rhythms of muscular ventilating and the pattern of other body movements, including abdominal pulsations not observable with the naked eye. The respirometer‐actograph described here is applicable also to the recording of the respiration of other terrestrial arthropods or other living organisms or tissues.

Abdominal movements, heartbeats and gas exchange in pupae of the Colorado potato beetle, Leptinotarsa decemlineata

The rhythms of abdominal movements, heartbeats and gas exchange in the pupae of Leptiontarsa decemlineata (Say) were recorded simultaneously using an electrolytic respirometer and infrared gas analyser, both combined with contact thermography.

Periodic muscular activity and its possible functions in pupae of Tenebrio molitor

Abstract. During pupal development, Tenebrio molitor L. show regular periods of rhythmic muscular contractions and associated body movements. These periods of activity last 2.5‐5.8 min and are more frequent in newly ecdysed pupae (c. 3h‐1). They become less frequent (c. 1.5 h‐1) when the basal metabolism reaches its lowest level. In the pharate adult stage the clear pattern of muscular activity disappears.

Studies on insect growth regulating (IGR) and toxic effects of Ledum palustre extracts on Tenebrio molitor pupae (Coleoptera, Tenebrionidae) using calorimetric recordings

Abstract Insect growth regulating (IGR) and toxic effects evoked by Ledum palustre extracts on the metamorphosis stages of Tenebrio molitor were studied using differential thermocouple calorimeters. The timing of normal and failed ecdysis as well as the length of interecdysial periods were measured exactly from calorimetric recordings. Respiratory and muscular responses of poisoned insects were also reflected by characteristic patterns on the recordings.

Body movements and their role as triggers of heartbeats in pupae of the Colorado potato beetle Leptinotarsa decemlineata

Rhythmic body movements and their role as triggers of intermittent heartbeats were studied in pupae of Leptinotarsa decemlineata Say. Heartbeats and body movements were recorded simultaneously by means of an optical method (infra‐red cardiography) combined with respirometry. IR‐cardiography allows heartbeats and body movements to be distinguished on the basis of their different rates (40–80 min−1 and 4–8 min−1, respectively) and amplitude.

Calorimetric investigations on physiological stress in Tenebrio molitor (Coleoptera, Tenebrionidae) pupae

Abstract Individual variation in the susceptibility to handling stress (mechanical irritation) in laboratory-reared pupae of yellow mealworm, Tenebrio molitor , was studied by means of simple thermocouple twin set-up calorimeters. The stress condition was characterised by disturbances in normal rhythms of gas exchange and body stereotyped movements well distinguishable from calorimetric recordings. Recovering time from stress, induced by the device, was 10–15 min. In every newly established population, a portion of pupal individuals (13–15%) was highly sensitive to handling and these pupae lost significantly more water than the pupae exhibiting no symptoms of stress.

Cyclic release of carbon dioxide accompanied by abdominal telescoping movements in forager ants of Formica polyctena (Hymenoptera, Formicidae)

Abstract.  Discontinuous gas exchange and abdominal telescoping movements were investigated in intact forager ants of Formica polyctena Förster. For simultaneous recording of discontinuous gas exchange and abdominal movements, an electrolytic differential microrespirometer was combined with an infrared‐optical device using an infrared‐sensor diode commonly applied as a cardiograph in insect studies. The air in the insect chamber was saturated with water vapour, and an ant was contacted with a sliver of wet filter paper. Accordingly, the ants used in the experiments were regarded as being hydrated. The enforced immobility of the ant in the respirometry chamber (0.15 mL volume) induced continuous struggling during the first hours of measurement but, after 3–4 h, the activity periods alternated with quiescent periods when regular cycles of discontinuous gas exchange (8.97 mHz) were displayed. After remaining in the chamber for a day, the ants showed such cycles (8.15 mHz) without any interruption by periods of activity. The cyclic release of carbon dioxide (burst) was accompanied by a bout of telescoping movements of the abdominal segments (rapid contractions and slow relaxations), which were interpreted as active ventilation. The irregular and rare abdominal contractions, recorded during the interburst periods on the first day of measurements, were regarded as a symptom of stress because these disappeared on the second day. In approximately 20% of foragers, the telescoping movements during the interburst periods were characterized by very rapid (0.09 s) protractions and slow retractions of the abdominal segments, obviously acting as inspiration movements. The results do not support the hypothesis that discontinuous gas exchange is an adaptation for conserving water in ants.

Respiration rhythms and heartbeats of diapausing Colorado potato beetles, Leptinotarsa decemlineata, at low temperatures

Discontinuous gas exchange cycles (DGCs), active muscular ventilation, microcycles of repetitive openings, and heartbeats of diapausing adult Colorado potato beetle, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae), were studied at low temperatures (0, 5, and 10 °C) using an electrolytic respirometer combined with an infrared actograph. The DGC of the adult constriction‐flutter‐open type was the main respiration mode in fully quiescent beetles at temperatures from 5 to 10 °C. The CO2 bursts were actively ventilated at temperatures above 5 °C. During the flutter period, a series of microcycles appeared, but no muscular contractions associated with the microcycles were detected. We identified this respiration mode as discontinuous suction ventilation.