Use of bilateral information to determine the walking direction during orientation to a pheromone source in the silkmoth Bombyx mori

Abstract

Odor source localization is an important animal behavior. Male moths locate mates by tracking sex pheromone emitted by conspecific females. During this type of behavior, males exhibit a combination of upwind surge and zigzagging flight. Similarly, the male walking moth Bombyx mori responds to transient pheromone exposure with a surge in movement, followed by sustained zigzagging walking. The initial surge direction is known to be influenced by the pheromone input pattern. Here, we identified the sensory input patterns that determine the initial walking direction of males. We first quantified the stimulus by measuring electroantennogram values, which were used as a reference for subsequent tests. We used a brief stimulus pulse to examine the relationship between sensory stimulus patterns and the turning direction of initial surge. We found that the difference in input timing and intensity between left and right antennae affected the walking direction, indicating that B. mori integrate bilateral pheromone information during orientation behavior. When we tested pheromone stimulation for longer periods, turning behavior was suppressed, which was induced by stimulus cessation. This study contributes toward understanding efficient strategies for odor-source localization that is utilized by walking insects.

Dynamic use of optic flow during pheromone tracking by the male silkmoth, Bombyx mori

“…turning towards the direction of higher pheromone concentration (Takasaki et al, 2012). The optomotor response observed in our experiments is also involved in directional control during surge; therefore, it was convincing that there was an interaction between visual and surge-related olfactory pathways.…”

“…1A). The surge is elicited shortly after pheromone detection, during which the moth turns towards the direction of the higher pheromone concentration perceived by the left and right antennae (Takasaki et al, 2012). If the moth loses the pheromone cue, it initiates zigzag walking or consecutive turning from side to side.…”

A simple behaviour provides accuracy and flexibility in odour plume tracking—the robotic control of sensory-motor coupling in silkmoths

“…Behavioural and neurophysiological evidence indicates that the surge is a reflex, while zigzagging and looping are pre-programmed behaviours (we therefore do not discriminate looping from zigzagging) (Olberg, 1983;Kanzaki and Mishima, 1996;Mishima and Kanzaki, 1999;Wada and Kanzaki, 2005;Kanzaki, 2007). Recent behavioural studies reported that the surge direction is modulated by the bilateral olfactory input and optic flow, and is less affected by the wind direction (Takasaki et al, 2012;Pansopha et al, 2014), suggesting that while the silkmoth decides the surge direction through osmotropotaxis, the course control is stabilized by the optomotor response (compensatory movements in response to optic flow). However, silkmoths do not show the optomotor response during the zigzagging phase , suggesting that zigzagging is simply controlled by internal mechanisms.…”

“…The wind speed in the canopy was 0.5 m s −1 , which is comparable to the air speed generated by wing fanning in untethered male silkmoths (0.3-0.4 m s −1 ; Loudon and Koehl, 2000) and was not affected by the heading of the robot in the wind tunnel. The surge direction of silkmoths is less affected by wind direction (Takasaki et al, 2012); therefore, the constant air flow in the canopy would not greatly modulate the surge direction.…”

“…We used an odour delivery system as previously described (Takasaki et al, 2012;Pansopha et al, 2014). To analyse the relationship between the stimulus side and the walking direction at behavioural onset, we applied a single puff of synthetic bombykol stimulus [(E,Z )-10,12-hexadecadien-1-ol; a principal component of the female pheromone] to one of the air suction tubes.…”