Squat lobster latitudinal life habitat shifts and metabolic response to combined temperature and oxygen conditions in the Humboldt Current System.

We examined how a species inhabiting a latitudinal gradient, from warm oxygenated surface waters to cold oxygen-limited subsurface waters along the Eastern South Pacific (ESP) shelf, responds to latitudinal temperature shifts at low-oxygen isopleths. We combined temperature-oxygen sections from the World Ocean Database, historical records of pelagic/benthic Grimothea monodon occurrence across latitude, models with these data, and laboratory experiments assessing juveniles' routine and postprandial metabolism under realistic temperature-oxygen conditions. The life habits (pelagic or benthic) of squat lobsters were related to temperature at the 2 mL O2 L-1 oxygen isopleth. At temperatures > 15 °C near the upper oxygen minimum zone isopleth, mostly pelagic individuals were observed, suggesting restricted vertical migration. The physiological performance of juveniles (main migratory stage) was negatively affected by high temperature-hypoxia interaction. Routine metabolic rates decreased by 60% under hypoxia at 21 °C, and postprandial metabolism (as Specific Dynamic Action) was also strongly reduced under those conditions. Grimothea monodon can shift between pelagic and benthic habitats across a range of ESP conditions, maintaining the intergenerational ability to alternate habitats. This plasticity, expressed as vertical expansion or restriction, may help maintain or expand its latitudinal ranges, with natural food webs and fisheries adjusting to its availability as key prey item.