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- Title
Terrestrial Insects with Tracheae Breath by Actively Regulating Ventilatory Movements: Physiological Similarities to Humans.
- Authors
Sláma, Karel; Santiago-Blay, Jorge A.
- Abstract
Ventilatory movements were recorded in four species of lepidopteran pupae, as large as 11.5g (Pseudosphinx tetrio) and as small as 0.0015g (Phyllonorycter strigulatella). The ventilatory movements and ventilatory extracardiac pulsations in haemocoelic pressure were monitored by several electronic methods (strain-gauge recording of abdominal movements, recording of pulsations in haemocoelic pressure, thermographic recording of heartbeat, microrespirographic recording of O2 consumption and CO2 output, and nanoanemometric recording of inspirations and expirations through individual spiracles). It appears that all investigated insect pupae, whether large or small, carefully avoided breathing based on gaseous diffusion. Instead, the pupae actively ventilated their tracheal systems, exchanging respiratory gases and preventing respiratory water loss. Further, it was found that larvae and pupae of Cossus cossus, which were used circa 100 years ago as experimental evidence for creating the well-known "Krogh's diffusion theory of insect respiration", exhibited beautiful concerts of previously overlooked ventilatory abdominal movements and ventilatory extracardiac pulsations. These results conflict with the indicated diffusion theory, which claimed that these insects did not need to exhibit ventilatory movements at all. Unfortunately, the diffusion theory has persisted until the present due to the lack of exact experimental data. The evidence that we now provide by means of advanced electronic methods shows a widespread occurrence of ventilatory movements. Even immobile insect pupae with low respiratory metabolism exhibit distinctive ventilatory movements. The movements are quite inconspicuous, occurring in the range of micrometers or nanometers, which obviously were imperceptible to earlier investigators. These results confirm our previous findings of human-like insect breathing, based on convective inhalation and exhalation of air driven by the respectively decreased or increased haemocoelic pressure. The results further confirm the control of insect respiration by an autonomic (brain independent), neuroendocrine system known as the coelopulse system, which consists of the nervous centre located in the mesothoracic ganglion of the ventral nerve cord, the neuromotoric spiracular nerves and the intersegmental or dorsoventral abdominal muscles. The system functions as the abdominal pressure pump. The high-resolution nanoanemometric recordings revealed original data on the movement of air across insect spiracles. The results can be summarized as follows: 1. Spiracular valves open and close in short flutters lasting usually 50 to 250 msec; 2. Active opening of the valves is faster and shorter than their more or less passive closure; 3. Each spiracle can be used for inspirations as well as for expirations of air, depending on its synchronization with the increasing or decreasing phase of the haemocoelic pressure; 4. The contralateral spiracles on each segment can flutter in synchrony or independently, or flutter in synchrony with spiracles on other segments; 5. A spiracles on the same body segment can be used for inspiration, while the contralateral one can be simultaneously used for expiration; 6. Multiple spiracles on different body segments can flutter in concert with other groups of spiracles; 7. A diapausing pupa of Manduca sexta can use only one master spiracle for several hours (usually the left thoracic one), which could open in flutters of 250 msec, once in 3 min.; 8. Some spiracles can open the valves in synchrony with the rising phase of haemocoelic pressure (expiration), while others open at the decreasing pressure phase (passive suction inspiration), which results in a unidirectional ventilation of the whole tracheal system; 9. During extracardiac pulsation in haemocoelic pressure, spiracular valves are programmed to open and close in synchrony with the pulse frequency (previously known as the fluttering spiracles); 10. Coordination of spiracular valve fluttering with the rising or falling haemocoelic pressure is integrated by the coelopulse neuroendocrine system. In summary, these facts seem to provide sufficient experimental evidence to show that insect respiration is controlled by actively regulated ventilation, not by passive diffusion of gas through the spiracles. Curiously enough, we found that the anatomical structure and physiological functions of the insect coelopulse system appear to display similarities with that of the autonomic, parasympathetic neuroendocrine system of the human body. The striking similarity between the two, phylogenetically distant respiratory systems is described and the possibility that insects and humans could evolve respiratory systems based on identical principles is emphasized.
- Subjects
INSECTS; RESPIRATION; PUPAE; ARTHROPODA; VITAL signs
- Publication
Life: The Excitement of Biology, 2017, Vol 5, Issue 1, p4
- ISSN
2325-081X
- Publication type
Article
- DOI
10.9784/LEB5(1)Slama.01