Physiological & Molecular Mechanisms of Stress Tolerance in a Polar Insect

 

Polar terrestrial environments are often described as deserts, where water availability is recognized as one of the most important limits on the distribution of terrestrial organisms. In addition, prolonged low winter temperatures threaten survival, and summer temperatures demonstrate extensive diel variations producing potentially rapid transitions from freezing to desiccating conditions, combined with the associated problems of freeze-thaw events. Global warming has further impacted the extreme thermal and hydric conditions experienced by Antarctic terrestrial plant and arthropod communities, especially as a result of glacial retreat along the Antarctic Peninsula. Within this context our project focuses on thermal and hydric adaptations in the terrestrial midge, Belgica antarctica, the largest and most southerly holometabolous insect living in this challenging and changing environment.

Overwintering midge larvae encased in the frozen substrate must endure desert-like conditions for more than 300 days since free water is biologically unavailable as ice. During the summer, depending on the vagaries of precipitation, wind, temperature and insolation, larvae may be immersed in melt water or the detrital outwash from penguin rookeries and seal wallows, in addition to saltwater splash. Alternatively, the larvae may be subjected to extended periods of desiccation as their microhabitats dry out. Due to their small size, relative immobility and the patchiness of suitable microhabitats, larvae may thus be subjected to stresses that include desiccation, hypo- or hyperosmotic conditions, high salinity exposure, and anoxia for extended periods. Research efforts will focus on physiological and molecular mechanisms of stress tolerance operating in these midges. Our project has a significant outreach component as the field team will communicate research progress with elementary and secondary school classes from Palmer Station by website (The Antarctic Connection) and through the publication of hands-on, inquiry-based articles to stimulate interest in an Antarctic biology and scientific research. This research is conducted in collaboration with the laboratory of Dr. David L. Denlinger, Department of Entomology, Ohio State University.