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Antarctic fish of the suborder Notothenioidei have evolved several unique adaptations to deal with subzero temperatures. However, these adaptations may come with physiological trade-offs, such as an increased susceptibility to oxidative damage. As such, the expected environmental perturbations brought on by global climate change have the potential to significantly increase the level of oxidative stress and cellular damage in these endemic fish. Previous single stressor studies of the notothenioids have shown they possess the capacity to acclimate to increased temperatures, but the cellularlevel effects remain largely unknown. Additionally, there is little information on the ability of Antarctic fish to respond to ecologically relevant environmental changes where multiple variables change concomitantly. We have examined the potential synergistic effects that increased temperature and Ṗ CO2 have on the level of protein damage in Trematomus bernacchii, Pagothenia borchgrevinki and Trematomus newnesi, and combined these measurements with changes in total enzymatic activity of catalase (CAT) and superoxide dismutase (SOD) in order to gauge tissue-specific changes in antioxidant capacity. Our findings indicate that total SOD and CAT activity levels displayed only small changes across treatments and tissues. Short-term acclimation to decreased seawater pH and increased temperature resulted in significant increases in oxidative damage. Surprisingly, despite no significant change in antioxidant capacity, cellular damage returned to near-basal levels, and significantly decreased in T. bernacchii, after long-term acclimation. Overall, these data suggest that notothenioid fish currently maintain the antioxidant capacity necessary to offset predicted future ocean conditions, but it remains unclear whether this capacity comes with physiological trade-offs.

Bioluminescence of the marine worm Chaetopterus variopedatus was first investigated several decades ago mainly using tissue extract. Light production of the worm, however, originates from a secreted mucus only. Here, we report the optical and physicochemical properties of the luminous mucus. We show that the produced light occurs as a long glow in the blue range (455 nm), which is an unusual color for a shallow benthic invertebrate. We also show that the light originates from a photoprotein whose light production is independent of molecular oxygen yet somewhat related to the physicochemical (rheological) characteristics of the mucus itself. Indeed, the mucus seems to polymerize and become more viscous on exposure to H2O2, which in turn seems to inhibit the light production. Ferrous iron was not associated with any strong stimulatory effect. This is in contrast to past studies on worm tissues showing that the light production is strongly stimulated by H2O2 and ferrous iron. Overall, our results highlight the fact that working on the luminous mucus only (vs. worm tissues) provides the ability to study its chemical properties possibly involved in the fine control of light production-as well as its rheological properties-and identify the possible interactions between these two properties.

Organisms inhabiting the sub-zero waters surrounding Antarctica display remarkably narrow tolerances for environmental change. This study assessed three closely related fish exposed to simultaneous changes in oceanic conditions to ascertain the impact additive stress has on their capacity to acclimate and whether or not these fish employ similar metabolic responses.

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