Simultaneous freeze tolerance and avoidance in individual fungus gnats, Exechia nugatoria

Abstract

Freeze tolerance and freeze avoidance are typically described as mutually exclusive strategies for overwintering in animals. Here we show an insect species that combines both strategies. Individual fungus gnats, collected in Fairbanks, Alaska, display two freezing events when experimentally cooled and different rates of survival after each event (mean +/- SEM: -31.5 +/- 0.2 degrees C, 70% survival and -50.7 +/- 0.4 degrees C, 0% survival). To determine which body compartments froze at each event, we dissected the abdomen from the head/thorax and cooled each part separately. There was a significant difference between temperature levels of abdominal freezing (-30.1 +/- 1.1 degrees C) and head/thorax freezing (-48.7 +/- 1.3 degrees C). We suggest that freezing is initially restricted to one body compartment by regional dehydration in the head/thorax that prevents inoculative freezing between the freeze-tolerant abdomen (71.0 +/- 0.8% water) and the supercooled, freeze-sensitive head/thorax (46.6 +/- 0.8% water).

An invitation to measure insect cold tolerance: Methods, approaches, and workflow

“…Infrared thermography is another approach to detecting and measuring SCPs without physical contact. This approach has been used successfully to detect SCPs (Palmer et al, 2004), to analyze the ice formation process (Sformo et al, 2009), and to separate freezing of insects from ice formation in their substrate (Koštál et al, 2012). It is now possible to purchase infrared cameras that interface with a smartphone, so the availability of this technology may increase rapidly.…”

Supercooling and Freezing Tolerant Animals

“…There must be further lethal events at lower temperatures after ice formation has been completed. Given the high proportion of ice that is formed initially it seems unlikely that this is due to further compartments freezing; as has been observed in an Alaskan fungus gnat (Sformo et al, 2009). …”

Pseudo amino acid composition improves antifreeze protein prediction

“…where ω is the weight factor and τ k the k-th tier correlation factor that reflects the sequence order correlation between all the k-th most contiguous residues as formulated by: (4) where H 1 (R i ), H 2 (R i ) and M(R i ) are respectively the normalized hydrophobicity value, hydrophilicity value and the side chain mass for amino acid residue R i ; while H 1 (R i+k ) H 2 (R i+k ) M(R i+k ) are those for amino acid residue R i+k .…”