Oxygen Uptake and Local Po2 Profiles in Submerged Larvae of Phaeoxantha klugii (Coleoptera: Cicindelidae), as Well as Their Metabolic Rate in Air

• Published in: Physiological and biochemical zoology 2004-05, Vol.77 (3), p.378-389
• Main Authors: Zerm, M., Zinkler, D., Adis, J.
• Format: Article
• Language: English
• Subjects: Animals; Body Constitution; Brazil; Carbon Dioxide - metabolism; Coleoptera - physiology; Fresh Water; Larva - physiology; Oxygen Consumption - physiology; Partial Pressure; Regression Analysis
• ISSN: 1522-2152; 1537-5293
• DOI: 10.1086/383504

We studied whether oxygen uptake from the surrounding water might enhance survival in submerged third instar larvae of Phaeoxantha klugii, a tiger beetle from the central Amazonian floodplains. Local oxygen partial pressures (Po2) were measured with microcoaxial needle electrodes close to larvae submerged in initially air-saturated still water. The Po2 profiles showed that the larvae exploit oxygen from the aquatic medium. Metabolism in the air of more or less resting larvae was determined by measuring the rate of CO2 production (sV̇co2) with an infrared gas analyzer at 29°C. The sV̇co2 was around 1.8 μL g−1 min−1, equivalent to an oxygen consumption rate (sV̇o2) of 1.8-2.6 μL g−1 min−1. Oxygen consumption (V̇o2) of individually submerged larvae measured in closed respiration chambers at 19-10.3 kPa Po2 (initially air saturated, 29°C) ranged between 0.05 and 0.2 μL min−1 and was not correlated with body mass. The sV̇o2 ranged between 0.1 and 0.4 μL min−1, that is, 4%-22% of the metabolic rate measured in air. Mean V̇o2 decreased with declining Po2; however, some individuals showed contrary patterns. V̇o2 was additionally measured in dormant larvae, in larvae submerged for 1-2 d in open water or for 30-49 d within sediment, as well as in larvae exposed to anoxia before the measurements. The range of V̇o2 was similar in all groups, indicating that the larvae exploit oxygen from the water whenever available. Similar V̇o2 across the whole range of body mass investigated (0.31-0.76 g) suggests that oxygen uptake occurs by spiracular uptake. Assuming that larvae survive for some time at rates comparable to depressed metabolic rates reported for other insect species, it can be concluded that oxygen uptake from water can sustain aerobic metabolism even under quite severe hypoxia. It might therefore play an important role for survival during inundation periods.