Hypotheses regarding the discontinuous gas exchange cycle (DGC) of insects

Contreras, Heidy; Heinrich, Erica C.; Bradley, Timothy J.

doi:10.1016/j.cois.2014.08.008

Cited by 23 publications

(31 citation statements)

References 42 publications

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“…The most striking pattern was the high-frequency cycles of continuous CO 2 emission shown by the majority of post-immersion pupae (12 of 18). We use the term 'cycling' to mean something different from the 'cyclic ventilation' described by Bradley, 2009, 2010;Contreras et al, 2014): in their descriptions, cyclic ventilation involves brief but complete closure of the spiracles with regular peaks of emission betweenessentially shortened DGC with very short inter-burst intervals and no fluttering phase. If the spiracles do not close all the way, they call this a 'continuous' respiratory pattern.…”

Section: Patterns Of Respiratory Exchangementioning

confidence: 99%

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Metabolic recovery from drowning by insect pupae

Woods

2016

Journal of Experimental Biology

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Many terrestrial insects live in environments that flood intermittently, and some life stages may spend days underwater without access to oxygen. We tested the hypothesis that terrestrial insects with underground pupae show respiratory adaptations for surviving anoxia and subsequently reestablishing normal patterns of respiration. Pupae of Manduca sexta were experimentally immersed in water for between 0 and 13 days. All pupae survived up to 5 days of immersion regardless of whether the water was aerated or anoxic. By contrast, fifth-instar larvae survived a maximum of 4 h of immersion. There were no effects of immersion during the pupal period on adult size and morphology. After immersion, pupae initially emitted large pulses of CO 2 . After a subsequent trough in CO 2 emission, spiracular activity resumed and average levels of CO 2 emission were then elevated for approximately 1 day in the group immersed for 1 day and for at least 2 days in the 3-and 5-day immersion treatments. Although patterns of CO 2 emission were diverse, most pupae went through a period during which they emitted CO 2 in a cyclic pattern with periods of 0.78-2.2 min. These highfrequency cycles are not predicted by the recent models of Förster and Hetz (2010) and Grieshaber and Terblanche (2015), and we suggest several potential ways to reconcile the models with our observations. During immersion, pupae accumulated lactate, which then declined to low levels over 12-48 h. Pupae in the 3-and 5-day immersion groups still had elevated rates of CO 2 emission after 48 h, suggesting that they continued to spend energy on reestablishing homeostasis even after lactate had returned to low levels. Despite their status as terrestrial insects, pupae of M. sexta can withstand long periods of immersion and anoxia and can reestablish homeostasis subsequently.

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Section: Patterns Of Respiratory Exchangementioning

confidence: 99%

“…However, even their continuous patterns can show regular peaks of emission (see fig. 1 in Contreras et al, 2014). Here we use the term cycling to describe more broadly any rhythmic emission that is not DGC.…”

Section: Patterns Of Respiratory Exchangementioning

confidence: 99%

Metabolic recovery from drowning by insect pupae

Woods

2016

Journal of Experimental Biology

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“…It has been suggested that transitions in insect gas exchange pattern are controlled by changes in metabolic rate (Contreras & Bradley, 2010;Contreras et al, 2014). Cyclic release of CO 2 is commonly associated with lower metabolic rates, and continuous gas exchange with higher ones (Gibbs & Johnson, 2004).…”

Section: Demonstrated That Adultmentioning

confidence: 99%

“…Several competing hypotheses about the origin and function of DGE have been proposed (Chown et al, 2006;Contreras et al, 2014;Matthews & Terblanche, 2015). The oldest of these is the hygric hypothesis which states that DGE is an adaptation to restrict water loss, and this idea has often been supported (Hadley, 1994;Lighton, 1998;Chown, 2002).…”

Section: Introductionmentioning

confidence: 99%

Gas exchange pattern in the two‐spot ladybird beetle, Adalia bipunctata, differs in dry vs. moist air

Jõgar

Kuusik

Metspalu

et al. 2016

Entomologia Exp Applicata

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Gas exchange patterns in the ladybird beetle, Adalia bipunctata (L.) (Coleoptera: Coccinellidae), were investigated using an infrared gaseous analyser (IRGA) and a coulometric O 2 respirometer (manometric-volumetric system). Before testing, the beetles were kept either in dry (dehydrated) or moist (hydrated) conditions for 1 day. Their subsequent gas exchange patterns did not depend on their state of humidity but rather were controlled by the humidity of the insect chamber during gas exchange measurement. If this chamber contained dry air, the beetles exhibited CO 2 release by burst, which we interpreted as cyclic gas exchange (CGE) with inter-burst periods, but if the chamber was switched to contain moist air, then cyclic CO 2 release was soon abandoned and a pattern of continuous gas exchange appeared. Measurements with the coulometric respirometer in moist air showed that continuous gas exchange was often associated with weak abdominal pulsations, which we interpreted as active ventilation. Their metabolic rate was lower during gas exchange cycles than during continuous gas exchange. We revealed that in the ladybird beetle metabolic rate increased in moist air when the gas exchange pattern transitioned from cyclic to continuous.

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“…Several hypotheses have been proposed to explain the adaptive benefit of DGE cycles or their mechanistic origin (reviewed in Kestler, 1985;Lighton, 1988;Chown and Nicolson, 2004;Chown et al, 2006;Contreras et al, 2014;Matthews and Terblanche, 2015). Originally, DGE was considered to be an adaptation to restrict respiratory water loss (Edney, 1977;Hadley, 1994;Lighton, 1988Lighton, , 1996Chown et al, 2002Chown et al, , 2006, although only a small fraction of the overall water loss is thought to be lost through respiration (reviewed in, for example, Quinlan and Lighton, 1999;Quinlan and Hadley, 1993;Chown, 2002).…”

Section: Introductionmentioning

confidence: 99%

The opening-closing rhythms of the subelytral cavity associated with gas exchange patterns in diapausing Colorado potato beetle, Leptinotarsa decemlineata

Kuusik

Jõgar

Metspalu

et al. 2016

Journal of Experimental Biology

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The opening-closing rhythms of the subelytral cavity and associated gas exchange patterns were monitored in diapausing Leptinotarsa decemlineata beetles. Measurements were made by means of a flowthrough CO 2 analyser and a coulometric respirometer. Under the elytra of these beetles there is a more or less tightly enclosed space, the subelytral cavity (SEC). When the cavity was tightly closed, air pressure inside was sub-atmospheric, as a result of oxygen uptake into the tracheae by the beetle. In about half of the beetles, regular opening-closing rhythms of the SEC were observed visually and also recorded; these beetles displayed a discontinuous gas exchange pattern. The SEC opened at the start of the CO 2 burst and was immediately closed. On opening, a rapid passive suction inflow of atmospheric air into the SEC occurred, recorded coulometrically as a sharp upward peak. As the CO 2 burst lasted beyond the closure of the SEC, we suggest that most of the CO 2 was expelled through the mesothoracic spiracles. In the remaining beetles, the SEC was continually semi-open, and cyclic gas exchange was exhibited. The locking mechanisms and structures between the elytra and between the elytra and the body were examined under a stereomicroscope and by means of microphotography. We conclude that at least some of the L. decemlineata diapausing beetles were able to close their subelytral cavity tightly, and that the cavity then served as a water-saving device.

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Hypotheses regarding the discontinuous gas exchange cycle (DGC) of insects

Cited by 23 publications

References 42 publications

Metabolic recovery from drowning by insect pupae

Metabolic recovery from drowning by insect pupae

Gas exchange pattern in the two‐spot ladybird beetle, Adalia bipunctata, differs in dry vs. moist air

The opening-closing rhythms of the subelytral cavity associated with gas exchange patterns in diapausing Colorado potato beetle, Leptinotarsa decemlineata

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