Gas exchange and metabolic rate at rest

Following the theoretical analysis by Krogh, and subsequent confirmation thereof by Weis-Fogh (review in Miller 1974), which showed that diffusion could serve the gas exchange requirements of small insects and most large insects at rest, diffusion has regularly been assumed to be the only means by which insects exchange gases at rest. Indeed, this idea continues to permeate modern discussions (West et al. 1997), despite the fact that ventilation, either by abdominal pumping or by movements of...

Gas exchange and metabolic rate during activity

Insects show tremendous scope for the increase of metabolic rates above resting levels. This is due mainly to the energetic demands of flight, which can be responsible for 100-fold increases in metabolic rate. Although many insects, such as ants and honeybees, might never experience levels of metabolism as low as SMRs measured under solitary conditions (sometimes including anaesthesia), and therefore have factorial aerobic scopes more in keeping with those of vertebrates (4-10) (Harrison and...

Molecular Mechanisms Of Insect Amino Acid Absorption

Na K -ATPase are located on apical and basal membranes, respectively. The plasma membrane V-ATPase of M. sexta is well characterized Harvey et al. 1998 . When feeding ceases in preparation for a larval-larval moult, downregulation of the V-ATPase is thought to be achieved by reversible dissociation of the peripheral ATP-hydrolysing complex from the membrane-bound H -translocating complex Sumner et al. 1995 . Expression of V-ATPase genes is also downregulated at this time, under the control of...

Metabolism and gas exchange

The concept that insect respiration depends only on diffusion supplemented in larger species by ventilation is in need of an overhaul the situation is much more complex. Insects, like all living organisms, are far-from-equilibrium, dissipative structures. That is, they actively take up energy and nutrients and in doing so alter both themselves and their surrounding environment. Initially, the changes in both directions might appear insignificant, but on a longer time scale their impact can be...

Metabolic rate variation size

Discontinuous gas exchange in ticks is thought to be one of the ways in which these animals maintain the very low metabolic rates required by their sit-and-wait strategy, which includes long periods of fasting Lighton and Fielden 1995 . Scorpions are also thought to have uncharacteristically low metabolic rates, and this has prompted considerable speculation regarding the benefits of low metabolic rates in both groups Lighton et al. 2001 . In turn, this speculation has raised the question of...

Anaerobic pathways and environmental hypoxia

Insects generally do not have well developed anaerobic metabolic capabilities. Nonetheless, the majority of species show a remarkable ability to recover from either hypoxia or anoxia, and at least some taxa are capable of surviving, being active, and reproducing under conditions of profound hypoxia. While high altitude insects such as those found in the high Himalayas experience prolonged hypoxia and hypobaria, hypoxia or anoxia is also characteristic of several other environments. These...

Metabolic rate variation temperature and water availability

Temperature and water availability are both thought to influence metabolic rate, especially over the longer term, resulting in adaptations that apparently reflect the need either for water conservation or starvation resistance, or the response to low environmental temperatures Chown and Gaston 1999 . The influence of temperature on metabolic rate over short timescales has been called the most overconfirmed fact in insect physiology Keister and Buck 1964 , and acute modifications of metabolic...

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Intake Target Receptors

Stoffolano 1995 has referred to the midgut as the least studied, but largest, endocrine tissue in insects. 2.2.3 Regulation of protein and carbohydrate intake Waldbauer and Friedman 1991 defined self-selection of optimal diets as a continuous regulation of intake involving frequent shifts between foods. The fact that insects perceive nutritional deficiencies, and alter behaviour to correct them, has been clearly illustrated by application of the geometrical approach to protein and carbohydrate...

Responses to osmotic stress

Trehalulose

Larval Diptera inhabiting saline waters exhibit extraordinary osmoregulatory abilities. For example, soldier fly larvae Odontomyia cincta Stratiomyidae maintain haemolymph osmolalities of 232 and 419 mOsmol kg-1 when acclimated to external media of 3 and 5414 mOsmol kg-1, respectively Gainey 1984 . The transition from hypo-osmotic to hyper-osmotic regulation occurs at an isosmotic point of 280 mOsmol kg-1, comparable to that of other aquatic insects. Brine flies Ephydridae are superbly tolerant...

Origin and adaptive value of the DGC

Discontinuous Gas Exchange Insects

Discontinuous gas exchange cycles have long been thought to represent a water-saving adaptation in insects Chapter 4 . The main reasons for this idea are that spiracles are kept closed for a portion of the DGC, thus reducing respiratory water loss to zero, and a largely convective F-period restricts outward movement of water Kestler 1985 Lighton 1996 . If the spiracles are artificially held open, water loss increases considerably Loveridge 1968 , and by calculation it can also be shown that a...