Respiratory physiology and water relations of three species of Pogonomyrmex harvester ants (Hymenoptera: Formicidae)

Abstract

The respiratory physiology and water relations of three harvester ant species (Pogonomyrmex rugosus Emery, P. occidentalis[Cresson] and P. californicus[Buckley]) were examined at three temperatures (15, 25 and 35°C) using a flow‐through respirometry system. As intact ants tended to be active during testing, we performed a parallel set of experiments on individuals rendered motionless by decapitation. Both intact and decapitated ants exhibited discontinuous ventilation. Decapitation caused metabolic rate (V˙CO2) and burst frequency to decrease in all three species. Burst volume either remained constant or increased after removal of the head, though mass‐specific V˙CO2 was unaffected except in P. rugosus. Mass‐specific V˙CO2s of headless harvesters were comparable with published values derived from motionless specimens of other ant species. The mean Q10 for intact ants of all three species was 2.37; for decapitated insects the mean was 2.32. Respiratory water constituted a small (< 5%) fraction of total loss, and we believe that discontinuous ventilation does not act to conserve water in these organisms, although it may serve other functions.

Reversible brain inactivation induces discontinuous gas exchange in cockroaches

“…In comparison, the DGCs displayed by decapitated insects that have been rendered insensible to such disturbances are far more consistent. For example, the standard deviation of DGC frequency in three ant species is 1.7 to 3.8 times lower when they are headless compared with when they are intact, a decrease that is not solely attributable to a significantly lower MR (Quinlan and Lighton, 1999).…”

“…Previous studies have used decapitation, decerebration and anaesthetisation to elicit DGCs in cockroaches (Edwards and Miller, 1986;Matthews and White, 2011b), ants (Duncan and Newton, 2000;Lighton, 1992;Lighton et al, 1993;Quinlan and Lighton, 1999) and moth pupae (Ito, 1954;Levy and Schneiderman, 1966). While it has been acknowledged that decerebration may alter the interactions between respiratory pattern generators, and so alter the behaviour of the DGCs produced by decapitated individuals (Quinlan and Lighton, 1999), the primary cause underlying the emergence of DGCs in decerebrated insects was believed to be their quiescence and low MR, a state that is not significantly different to that exhibited by resting individuals spontaneously displaying DGCs (Lighton et al, 1993;Lighton and Garrigan, 1995;Quinlan and Lighton, 1999).…”

“…While it has been acknowledged that decerebration may alter the interactions between respiratory pattern generators, and so alter the behaviour of the DGCs produced by decapitated individuals (Quinlan and Lighton, 1999), the primary cause underlying the emergence of DGCs in decerebrated insects was believed to be their quiescence and low MR, a state that is not significantly different to that exhibited by resting individuals spontaneously displaying DGCs (Lighton et al, 1993;Lighton and Garrigan, 1995;Quinlan and Lighton, 1999). By reversibly inactivating the insect's brains, we have demonstrated that DGCs can emerge due to a decrease in the activity of the insect's nervous system.…”

Tonic immobility in adult Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae) evoked by mechanical and optical stimuli

“…Decapitation has been demonstrated as a useful means of immobilizing ants for the measurement of the resting gas exchange, while movement is minimal and ventilation (i.e., the DGCs) is much more regular and stereotyped (Lighton, 1992;Quinlan & Lighton, 1999).…”

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

“…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).…”