Surviving in a frozen desert: environmental stress physiology of terrestrial Antarctic arthropods

Abstract

Abiotic stress is one of the primary constraints limiting the range and success of arthropods, and nowhere is this more apparent than Antarctica. Antarctic arthropods have evolved a suite of adaptations to cope with extremes in temperature and water availability. Here, we review the current state of knowledge regarding the environmental physiology of terrestrial arthropods in Antarctica. To survive low temperatures, mites and Collembola are freeze-intolerant and rely on deep supercooling, in some cases supercooling below -30°C. Also, some of these microarthropods are capable of cryoprotective dehydration to extend their supercooling capacity and reduce the risk of freezing. In contrast, the two best-studied Antarctic insects, the midges Belgica antarctica and Eretmoptera murphyi, are freezetolerant year-round and rely on both seasonal and rapid coldhardening to cope with decreases in temperature. A common theme among Antarctic arthropods is extreme tolerance of dehydration; some accomplish this by cuticular mechanisms to minimize water loss across their cuticle, while a majority have highly permeable cuticles but tolerate upwards of 50-70% loss of body water. Molecular studies of Antarctic arthropod stress physiology are still in their infancy, but several recent studies are beginning to shed light on the underlying mechanisms that govern extreme stress tolerance. Some common themes that are emerging include the importance of cuticular and cytoskeletal rearrangements, heat shock proteins, metabolic restructuring and cell recycling pathways as key mediators of cold and water stress in the Antarctic. KEY WORDS: Antarctica, Cold tolerance, Dehydration, Environmental stress, Physiology IntroductionEnvironmental stress, in the form of both biotic and abiotic stress, is one of the primary constraints governing the abundance and distribution of terrestrial arthropods. While insects on all continents encounter some form of environmental stress, perhaps nowhere are the environmental onslaughts more challenging than the continent of Antarctica. Even in maritime Antarctica, where proximity to the sea limits temperature extremes, winter lows exceed -40°C and subzero temperatures can be experienced any time of year . Furthermore, water is frozen and biologically unavailable for much of the year, thus water availability is perhaps the biggest challenge confronting terrestrial arthropods in Antarctica (Kennedy, 1993). Whereas arthropods are the predominant terrestrial life form on Earth, only a handful of species have successfully established in Antarctica, and most of these are restricted to maritime regions (Convey, 1996a; Convey, 2013 In this review, we summarize the limits and mechanisms of environmental stress tolerance in Antarctic arthropods. In particular, we focus on the biochemical and molecular underpinnings of the stress response in Antarctic arthropods. As non-model (not to mention difficult to access) species, molecular studies of Antarctic arthropods have been limited in scope. However, recent advances i...

Compact genome of the Antarctic midge is likely an adaptation to an extreme environment

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Insect capa neuropeptides impact desiccation and cold tolerance

“…Both cold and desiccation stress result in decreased hemolymph volume and increased hemolymph osmolarity (4), so it is reasonable to expect mechanistic overlap between these stresses. Indeed, similar molecular mechanisms, including calcium signaling pathways, appear to modulate cold and desiccation responses (5,6). Several studies have shown that freezetolerant insects can improve their cold tolerance in response to a mild desiccation stress (7)(8)(9), and artificial selection for desiccation tolerance in Drosophila melanogaster impacts the ability to recover from chill coma (10).…”

Cold adaptive potential of chironomids overwintering in a glacial stream

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