Pairing strategy after today’s failure: unpaired termites synchronize mate search using photic cycles

Abstract

Animals must search for other individuals under spatially and temporally fluctuating environments. During mate searches, search timing is critical to increase encounter rate and internal oscillating clocks often play important roles in synchronization. On the other hands, some species living in areas with no or reduced periodicity do not show endogenous circadian rhythm, where little is known about how they determine search timing. Termites usually live within logs and underground with little light fluctuations, but also come out of their nests during mating flight season. After swarming, termites run on the ground to search for mates. If they fail to find mates on the flight day, they need to continue searching until a day to succeed. Here we found that unpaired termites show daily search–rest cycles and restrict searching activity to a certain period of the day by responding to photic cycles. The search–rest cycles were diel rhythmic and synchronized with light–dark cycles. Termites also showed periodic (period length ≈ 18 h) search–rest patterns under constant darkness. These results indicate that the diel rhythm is caused by the internal oscillating clocks which are entrained to the photic cycles. The search activity in light–dark cycles was observed only at a specific time during the light period, which matches approximately the time of swarming flight. Our results suggest that termites adaptively regulate their daily searching activity, if they fail to encounter mates at the flight day.