title: Metabolic rate and hypoxia tolerance are affected by group interactions and sex in the fruit fly (Drosophila melanogaster): new data and a literature survey.
abstract: Population density and associated behavioral adjustments are potentially important in regulating physiological performance in many animals. Inr-selected species like the fruit fly (Drosophila), where population density rapidly shifts in unpredictable and unstable environments, density-dependent physiological adjustments may aid survival of individuals living in a social environment. Yet, how population density (and associated social behaviors) affects physiological functions like metabolism is poorly understood in insects. Additionally, insects often show marked sexual dimorphism (larger females). Thus, in this study onD. melanogaster, we characterized the effects of fly density and sex on both mass-specific routine oxygen consumption (V̇O2) and hypoxia tolerance (PCrit). Females had significantly lower routineV̇O2(∼4 µl O2mg-1h-1) than males (∼6 µl O2mg-1h-1) at an average fly density of 28 flies·respirometer chamber-1However,V̇O2was inversely related to fly density in males, withV̇O2ranging from 4 to 11 µl O2mg-1h-1at a density of 10 and 40 flies·chamber-1, respectively (r2=0.58,P<0.001). Female flies showed a similar but less pronounced effect, with aV̇O2of 4 and 7 µl O2mg-1h-1at a density of 10 and 40 flies·chamber-1, respectively (r2=0.43,P<0.001). PCrit(∼5.5 to 7.5 kPa) varied significantly with density in male (r2=0.50,P<0.01) but not female (r2=0.02,P>0.5) flies, with higher fly densities having a lower PCritAn extensive survey of the literature on metabolism in fruit flies indicates that not all studies control for, or even report on, fly density and gender, both of which may affect metabolic measurements.
authors.affiliation: Developmental Integrative Biology Group, Department of Biological Sciences, University of North Texas, Denton, TX 76203, USA burggren@unt.edu.
authors.forename: Warren
authors.identifier: http://orcid.org/0000-0001-8023-420X
authors.initials: W
authors.lastname: Burggren
authors.affiliation: Developmental Integrative Biology Group, Department of Biological Sciences, University of North Texas, Denton, TX 76203, USA.
authors.forename: BriAnna M
authors.initials: BM
authors.lastname: Souder
authors.affiliation: Department of Clinical Investigation, Tripler Army Medical Center, Honolulu, HI 96859, USA.
authors.forename: Dao H
authors.initials: DH
authors.lastname: Ho
keywords: Drosophila; Oxygen consumption; Respirometry techniques; Sex; Social interaction