The intertidal collembolan Anurida maritima can endure periods of twice-daily submergence by seawater. The air-breathing terrestrial apterygote insect has developed specific adaptations to prevent respiratory failure during hypoxic stress. When submerged, the animal is initially enclosed by an air-bubble. This bubble lasts three times longer than the small amount of stored oxygen would allow. The air bubble acts not only as an oxygen store but also as a compressible gas gill. This was demonstrated by an O2-needle electrode technique which allowed recordings of pO2 changes in the watery medium close to the animal. Oxygen uptake in A. maritima follows an aerial mode of respiration during the first three hours of submergence. Oxygen consumption rate at decreasing ambient O2 partial pressures showed oxyregulating behaviour during severe hypoxia., Dietmar Zinkler, Raimund Rüssbeck, Marc Biefang, Horst Baumgärtl, and Lit
Myrmica rubra is a northern, temperate Palaearctic ant species with a geographical range that extends from the Atlantic coast of Europe to central Asia. In Europe, its range covers > 25° of latitude where it lives under a variety of climates that vary from extreme oceanic in the west, to continental in the east. Colonies nest in the soil and their life cycles are known to be highly dependent on ambient temperature and soil moisture. We hypothesised that the brood-rearing behaviour of populations might be focally adapted to climate and that we might detect differences when the ants were reared under \"common-garden\" conditions. Brood-rearing behaviour was compared for 38 colonies of M. rubra drawn from 13 populations representing a range of 6 latitudes: all 6 were represented in eastern Europe and 2 in western Europe. A sample of ants from each colony was used to estimate respiration rate, body mass and fat content at the start of the experiment in spring (immediately post hibernation) and at the end of the experiment (mid summer). Respiration had a linear relationship with latitude, with northern populations having greater respiration rate in spring compared to southern populations. It is suggested that this is an adaptation to different seasonality over the species' range that results in the \"more active\" northern workers rearing fewer brood to maturity more quickly than southern workers. Fat content, a measure of worker \"quality\", had a parabolic relationship with latitude with mid latitude colonies having the fattest workers. Fatter workers appeared to rear heavier brood. This probably represented a functional response to environment with populations living at \"edge of range\" sites being physiologically more stressed and performing brood-rearing tasks less well than centre of range populations. We believe that this is the first demonstration of a consistent, intra-specific trend for Variation in the social physiology of an ant species over its geographic range., Graham W. Elmes, Judith C. Wardlaw, Mogens G. Nielsen, Vladilen E. Kipyatko, Elena B. Lopatina, Alexander G. Radchenko, Boyd Barr, and Lit