Temperature acclimation in overwintering nymphs of a cockroach, Periplaneta japonica: walking on ice

Nymphs of the Yamato cockroach, Periplaneta japonica, showed a seasonal change in the ability to move at low temperature. Laboratory-reared nymphs buried in ice for 15 min-3 h took about 600 s to get up at 25 degrees C after being placed with their dorsal surface on the floor of a Petri dish. The mean time to get up at 25 degrees C (recovering time) after 15 or 60-min burial in ice was relatively long in early autumn, decreased rapidly in autumn, reached a minimal level in winter (<100 s) and increased in spring. Temperature was responsible for this seasonal change in physiology, and neither photoperiod nor diapause status was important. Recovering time depended on the acclimation temperature and its duration. For a 10-day exposure in a range of 0-25 degrees C, the lower the temperature the shorter the recovering. Longer periods of acclimation at these temperatures tended to shorten recovering time. The acquisition of the ability to move on ice is a seasonal phenomenon unique to P. japonica. No comparable response was found in three other cockroaches including two sub-tropical species (Periplaneta americana and Opisthoplatia orientalis) and a temperate species (Blattela nipponica).