The inhospitable Antarctic Peninsula hosts only one native insect, and scientists from Japan have just identified an unprecedented combination of adaptations that allow it to thrive in the extreme cold.
The Antarctic midge is a tiny, flightless insect that lives most of its two-year life as a larva, the grub-like stage that follows the egg stage. (Complete metamorphosis in insects includes egg, larva, pupa, and adult stages).
How these larvae overwinter in Antarctica could have implications for cryopreservation technology but, perhaps more pressingly, better understanding of the species’ response to climate change. Previous researchers have suggested that the Antarctic midge be developed as a model organism for survival in extreme and fluctuating temperatures.
The Japanese research team led by Shin Goto of Osaka Metropolitan University studied the unique midge after developing a specialised rearing method, which took them six years to establish.
The team then tracked the growth and physiology of the midge larvae through their natural lifecycle. In a first for science, they documented two distinct forms of dormancy used as seasonal survival adaptations.
In general, dormancy is a state of inactivity, suspended development and reduced metabolism, but insect scientists distinguish between two types: quiescence and diapause.
In the first winter, the Antarctic midge larvae adapted via quiescence, a form of dormancy triggered by external conditions, such as cold temperatures. This means all the midge larvae go dormant at the same time. Quiescence ends when the temperature rises.
In contrast, in the second winter, the larvae adapted via diapause, a form of dormancy triggered by reaching a developmental milestone. For the Antarctic midge, this is the final larval stage, right before pupating.
Unlike the quiescent phase, some larvae will reach this milestone and go dormant before others. This is critical for reproductive success because it ensures the entire population reaches maturity simultaneously.
Adult Antarctic midges live only for a few days, so this timing is crucial and represents a strong evolutionary selection pressure.
Goto and colleagues suspect that comparable selection pressures have produced similar adaptations in other insects around the world.
“Although seasonal adaptation strategies involving overwintering multiple times using both quiescence and diapause have not been reported in other organisms, we believe that insects inhabiting harsh environments such as the Arctic and high altitudes might be employing similar strategies,” concludes Goto.
The research is published in the journal, Scientific Reports.
