Supercooling Point Frequency Distributions in Collembola Are Affected by Moulting

1. Many arthropods depress the freezing point of their body fluids (supercool) to avoid freezing at subzero temperatures. This is normally a seasonal response and is achieved by the production of specific biomolecules including cryoprotectants, a cessation in feeding, and the removal or masking of ice-nucleating material from their bodies. 2. In springtails, the mid-gut is shed during moulting which results in the complete evacuation of the gut and a concomitant reduction in the supercooling point (SCP). We determined whether this non-adaptive explanation could account for the variability observed in the SCP of summer-acclimatized springtails. 3. Moult preparation resulted in a highly significant reduction in the SCP. Feeding after moulting restored the SCP to previous high levels. 4. Significant differences in SCP between springtails sampled from vegetation and the soil surface, on different days, and at different sites on the same day were also documented, demonstrating that not all variation in SCP is environmentally induced. 5. Investigations of the responses of the SCP to environmental variation in springtails and other arthropods should take into account the effects of moulting before solely adaptive conclusions are drawn.