Metabolism in mesopelagic and bathypelagic

In reply to the Comment by Childress et al. (2008; Mar Ecol Prog Ser 373:187–191), a rationale is given for the use of N-specific respiration data (instead of live-mass specific respiration data), life stage/sex structured data (instead of species structured data), capture depth (instead of minimum depth of occurrence, MDO) and respirometry design including enzyme assay of electron transfer system (ETS) (instead of citrate synthase [CS] assay), low oxygen seawater from the capture depth of the copepods (instead of oxygen enriched seawater) and density effect in the experiment of Ikeda et al. (2006; Mar Ecol Prog Ser 322:199–211). These results, combined with recent reports on chemical composition and RNA:DNA ratios, continue to support the conclusion of reduced respiration in deeper-living copepods. The gap between the species-based wet-mass specific respirationMDO approach promoted by Childress et al. (2008) and the individual-based N-specific respirationcapture depth approach of Ikeda et al. (2006) is due to the different philosophical outlooks of the 2 research groups. One is based on the highly focused view of animal physiology, the other is based on the broad view of biological oceanography that incorporates all aspects of biology.