title: Ecology of ontogenetic body-mass scaling of gill surface area in a freshwater crustacean.
abstract: Several studies have documented ecological effects on intraspecific and interspecific body-size scaling of metabolic rate. However, little is known about how various ecological factors may affect the scaling of respiratory structures supporting oxygen uptake for metabolism. To our knowledge, our study is the first to provide evidence for ecological effects on the scaling of a respiratory structure among conspecific populations of any animal. We compared the body-mass scaling of gill surface area (SA) among eight spring-dwelling populations of the amphipod crustaceanGammarus minusAlthough gill SA scaling was not related to water temperature, conductivity orG. minuspopulation density, it was significantly related to predation regime (and secondarily to pH). Body-mass scaling slopes for gill SA were significantly lower in four populations inhabiting springs with fish predators than for four populations in springs without fish (based on comparing means of the population slopes, or slopes calculated from pooled raw data for each comparison group). As a result, gill SA was proportionately smaller in adult amphipods from springs with versus without fish. This scaling difference paralleled similar differences in the scaling exponents for the rates of growth and resting metabolic rate. We hypothesized that gill SA scaling is shallower in fish-containing versus fishless spring populations ofG. minusbecause of effects of size-selective predation on size-specific growth and activity that in turn affect the scaling of oxygen demand and concomitantly the gill capacity (SA) for oxygen uptake. Although influential theory claims that metabolic scaling is constrained by internal body design, our study builds on previous work to show that the scaling of both metabolism and the respiratory structures supporting it may be ecologically sensitive and evolutionarily malleable.
authors.affiliation: Department of Biology, Juniata College, 1700 Moore Street, Huntingdon, PA 16652, USA glazier@juniata.edu.
authors.forename: Douglas S
authors.identifier: 0000-0001-7164-1823
authors.initials: DS
authors.lastname: Glazier
authors.affiliation: Aqua Pennsylvania, 644 North Water Avenue, Sharon, PA 16146, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Paul
mesh_terms: D033304:Amphipoda / Q000254:growth & development* / Q000378:metabolism; D000818:Animals; D001835:Body Weight; D017753:Ecosystem; D005399:Fishes; D005880:Gills / Q000033:anatomy & histology* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D060985:Natural Springs; D010101:Oxygen Consumption; D011235:Predatory Behavior
keywords: Allometry; Freshwater springs; Gammarus minus; Metabolism; Oxygen uptake; Predation