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.

Light alters activity but does not disturb tandem coordination of termite mating pairs

“…The activity pattern of C. formosanus was not as clear as that of R. speratus , possibly because night is often under dim light rather than complete darkness (O'Carroll & Warrant, 2017), and C. formosanus may adapt to dim light environments rather than complete darkness. These results indicate that mate searching behaviour can be affected by the surrounding light environments (Mizumoto et al, 2017; Nutting, 1969). Such decreased mating activity in abnormal light environments is also observed in other insects, such as fruit moths (Li et al, 2019) and olive flies (Kokkari et al, 2017).…”

“…However, we kept colonies under dark conditions for ~1 month before the experiments. In this condition, previous studies showed that alates of Reticulitermes termites show circadian rhythm by taking swarming as a starting point (Mizumoto et al, 2017). Individuals within the colony do not show endogenous activity rhythm (Fuchikawa et al, 2012).…”

“…Second, termites may also use vision as a cue to initiate swarming and form mating pairs, which they are known to perform at a specific time of the day (Nutting, 1969). In this case, the unusual light intensity would result in lower rates of mating pair formation (Mizumoto et al, 2017), without necessarily affecting the coordination of mating pairs. In this study, we tested these hypotheses by examining the effect of light conditions on the movement patterns of alate imagoes in two species of subterranean termites, Coptotermes formosanus (Shiraki) and Reticulitermes speratus (Kolbe).…”

“…Second, termites may also use vision as a cue to initiate swarming and form mating pairs, which they are known to perform at a specific time of the day (Nutting, 1969). In this case, the unusual light intensity would result in lower rates of mating pair formation (Mizumoto et al, 2017), without necessarily affecting the coordination of mating pairs.…”

Wasted efforts impair random search efficiency and reduce choosiness in mate-pairing termites

“…After randomization, we projected the trajectories of a female and a male and calculated if and when they encountered. When mate search of termites extended to multiple days, they synchronized their search efforts with the following swarming events (Mizumoto et al, 2017b). Given that most termites do not extend mate search for multiple days due to pairing or predation (Mizumoto et al, 2016), we expect that mating encounters of extended mate searchers are usually with new mate searchers (day 0 individuals).…”