Gas exchange characteristics, metabolic rate and water loss of the Heelwalker, Karoophasma biedouwensis (Mantophasmatodea: Austrophasmatidae)

Respiratory water loss during metabolic gas exchange is an unavoidable cost of living for terrestrial insects. It has been suggested to depend on several factors, such as the mode of gas exchange (convective vs. diffusive), species habitat (aridity), body size and measurement conditions (temperature). We measured this cost in terms of respiratory water loss relative to metabolic rate (respiratory water cost of gas exchange; RWL/V˙CO2) for adults of two insect species, the speckled cockroach (Nauphoeta cinerea) and the darkling beetle (Zophobas morio), which are similar in their mode of gas exchange (dominantly convective), habitat (mesic), body size and measurement conditions, by measuring gas exchange patterns using flow-through respirometry. The speckled cockroaches showed both continuous and discontinuous gas exchange patterns, which had significantly a different metabolic rate and respiratory water loss but the same respiratory water cost of gas exchange. The darkling beetles showed continuous gas exchange pattern only, and their metabolic rate, respiratory water loss and respiratory cost of gas exchange were equivalent to those cockroaches using continuous gas exchange. This outcome from our study highlights that the respiratory water cost of gas exchange is similar between species, regardless of gas exchange pattern used, when the confounding factors affecting this cost are controlled. However, the total evaporative water cost of gas exchange is much higher than the respiratory cost because cuticular water loss contributes considerably more to the overall evaporative water loss than respiratory water. We suggest that the total water cost of gas exchange is likely to be a more useful index of environmental adaptation (e.g., aridity) than just the respiratory water cost.

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Repeatability of standard metabolic rate and gas exchange characteristics in a highly variable cockroach, Perisphaeria sp.

Journal of Experimental Biology ◽

10.1242/jeb.00700 ◽

2003 ◽

Vol 206 (24) ◽

pp. 4565-4574 ◽

Cited By ~ 61

Author(s):

E. Marais

Keyword(s):

Gas Exchange ◽

Metabolic Rate ◽

Standard Metabolic Rate ◽

Gas Exchange Characteristics

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Metabolic rate and respiratory gas-exchange patterns in tenebrionid beetles from the Negev Highlands, Israel

Journal of Experimental Biology ◽

10.1242/jeb.205.6.791 ◽

2002 ◽

Vol 205 (6) ◽

pp. 791-798 ◽

Cited By ~ 4

Author(s):

Frances D. Duncan ◽

Boris Krasnov ◽

Megan McMaster

Keyword(s):

Gas Exchange ◽

Metabolic Rate ◽

Water Loss ◽

Activity Patterns ◽

High Water ◽

Standard Metabolic Rate ◽

Active Species ◽

Habitat Associations ◽

Diel Activity ◽

Water Vapour Pressure

SUMMARY This study correlates the pattern of external gas exchange with the diel activity of nine species of tenebrionid beetle from the Negev Desert, Israel. The study species are active throughout the summer months when daytime temperatures are high and no rain falls. There were no differences in standard metabolic rate, determined by flow-through respirometry, among the nine species. All the nocturnally active beetles exhibited a form of continuous respiration, whereas the two diurnally active and one crepuscular species exhibited a cyclic form of respiration referred to as the discontinuous gas-exchange cycle (DGC). The DGCs recorded have a long flutter period consisting of miniature ventilations, and 29–48 % of the total CO2 output occurred during this period. In this study, the flutter period played an important role in the modulation of metabolic rate, in contrast to other studies in which the burst period has been shown to be important. We suggest that the long flutter period is important in reducing respiratory water loss in arid-dwelling arthropods. This study lends support to the hypothesis that discontinuous gas exchange is important in reducing respiratory water loss from beetles that need to minimise dessication because of the high water vapour pressure gradient they experience. If the use of underground burrows were responsible for the evolution of discontinuous gas exchange, then we would expect all nine tenebrionid species to use DGCs since both the nocturnally and diurnally active species bury in the sand during periods of inactivity. We conclude that the activity patterns of the beetles are more important than their habitat associations in designating the type of respiration used.

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Temperature- and body mass-related variation in cyclic gas exchange characteristics and metabolic rate of seven weevil species: Broader implications

Journal of Insect Physiology ◽

10.1016/j.jinsphys.2005.03.007 ◽

2005 ◽

Vol 51 (7) ◽

pp. 789-801 ◽

Cited By ~ 14

Author(s):

C.J. Klok ◽

S.L. Chown

Keyword(s):

Gas Exchange ◽

Metabolic Rate ◽

Body Mass ◽

Related Variation ◽

Weevil Species ◽

Gas Exchange Characteristics

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Intra-individual variation allows an explicit test of the hygric hypothesis for discontinuous gas exchange in insects

Biology Letters ◽

10.1098/rsbl.2009.0803 ◽

2009 ◽

Vol 6 (2) ◽

pp. 274-277 ◽

Cited By ~ 27

Author(s):

Caroline M. Williams ◽

Shannon L. Pelini ◽

Jessica J. Hellmann ◽

Brent J. Sinclair

Keyword(s):

Carbon Dioxide ◽

Gas Exchange ◽

Metabolic Rate ◽

Water Loss ◽

Individual Variation ◽

Loss Reduction ◽

Total Water ◽

Explicit Test ◽

Carbon Dioxide Release ◽

Flow Through

The hygric hypothesis postulates that insect discontinuous gas exchange cycles (DGCs) are an adaptation that reduces respiratory water loss (RWL), but evidence is lacking for reduction of water loss by insects expressing DGCs under normal ecological conditions. Larvae of Erynnis propertius (Lepidoptera: Hesperiidae) naturally switch between DGCs and continuous gas exchange (CGE), allowing flow-through respirometry comparisons of water loss between the two modes. Water loss was lower during DGCs than CGE, both between individuals using different patterns and within individuals using both patterns. The hygric cost of gas exchange (water loss associated with carbon dioxide release) and the contribution of respiratory to total water loss were lower during DGCs. Metabolic rate did not differ between DGCs and CGE. Thus, DGCs reduce RWL in E. propertius , which is consistent with the suggestion that water loss reduction could account for the evolutionary origin and/or maintenance of DGCs in insects.

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Heterothermy, torpor, respiratory gas exchange, water balance and the effect of feeding in Gould's long-eared bat Nyctophilus gouldi.

Journal of Experimental Biology ◽

10.1242/jeb.197.1.309 ◽

1994 ◽

Vol 197 (1) ◽

pp. 309-335

Author(s):

S Morris ◽

A L Curtin ◽

M B Thompson

Keyword(s):

Body Temperature ◽

Gas Exchange ◽

Nutritional Status ◽

Metabolic Rate ◽

Water Loss ◽

Respiratory Exchange Ratio ◽

Thermal Conductance ◽

Evaporative Water ◽

Effects Of Temperature ◽

Effect Of Feeding

The effects of temperature and nutritional status on the metabolic rate of Nyctophilus gouldi were examined. Bats fed marked meals first defecated approximately 1.34 h after feeding and were calculated to have a mean retention time of 5.38 +/- 0.57 h but to be truly post-absorptive after 9 h. Over the temperature range 1-35 degrees C, the metabolic rate (Vo2) and body temperature (Tb) of fasted bats were extremely labile. Below 30 degrees C, the bats all entered torpor and between 10 and 15 degrees C showed a mean 84% reduction over the maximal Vo2. Body temperature was also minimal over this range (Tb = 12.5 degrees C, Ta = 10-15 degrees C). Both total and dry thermal conductance increased in a curvilinear manner with temperature, total conductance from 3.38 +/- 0.65 J g-1 h-1 degree C-1 at 1 degree C to 24.25 +/- 1.99 J g-1 h-1 degree C-1 at 35 degrees C (mean +/- S.E.M.), while the rate of evaporative water loss increased with Ta by a maximum of 10-fold from 0.21 mg g-1 h-1 at 5 degrees C to 2.69 mg g-1h-1 at 35 degrees C. Between 10 and 25 degrees C, intermittent respiration characterised by episodic bouts of breathing/gas exchange and periods of apnoea with no measurable Vo2 occurred. Although the duration of apnoea decreased when temperature was increased, the volume of oxygen taken up in each episode did not change. Mean respiratory exchange ratio (RER) was low (0.64-0.77) in post-absorptive bats, typical of fat utilisation, but during torpor ranged from near 0 to near 2, indicating discontinuous and disproportional gas exchange. Feeding produced a condition of relatively sustained homeothermy and high RER in the bats which persisted for 9 h, after which the N. gouldi became torpid. Immediately after feeding, the Vo2 of the bats increased fivefold above the post-absorptive level, while the Vco2 increased by more than eightfold. Similarly, body temperature also increased, declining to torpid values after 9. The RER in immediately post-feeding bats was near 1.0 but subsequently declined to near 0.7, indicating a switch from carbohydrate to fat utilisation. Therefore, the N. gouldi were heterothermic, exhibited a highly labile metabolic rate, and rates of heat and water loss, and Tb which were influenced both by ambient temperature and by nutritional status.

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