Behavioral responses to visual overstimulation in the cockroach Periplaneta americana L.

Abstract

In the visual systems of insects, different types of photoreceptors contribute to specialized visual channels that mediate distinct functions and behaviors. Large compound eyes of Periplaneta americana contain photoreceptors of two spectral classes, broadband green-sensitive photoreceptors and narrow-band UV-sensitive photoreceptors. Here, we investigated how visual stimulation by UV and green light affects locomotor, resting, and grooming behaviors in P. americana under conditions when light avoidance is not possible. We show that green but not UV light stimulates locomotor activity, inducing paradoxical positive masking. Duration of resting and grooming decreased with increasing light intensity, consistent with development of behavioral stress in response to visual overstimulation. A reaction of full immobility is described under UV light and at higher intensities of green light, with relative periods of immobility and grooming strongly negatively correlated. Low-intensity UV was more effective than low-intensity green light in suppressing grooming and inducing immobility. Our results suggest that locomotor activity in P. americana is mainly regulated by green-sensitive photoreceptors, and that dim UV light can trigger behavioral immobility, whereas both wavelengths induce stress-like reactions at high intensities. Considering the intrinsic UV sensitivity of green-sensitive photoreceptors, the contrasting behavioral responses indicate antagonistic interactions between UV and green visual channels.

Changes in electrophysiological properties of photoreceptors in Periplaneta americana associated with the loss of screening pigment

“…9b). However, differences were observed in dim green light, which caused a strong increase in locomotor activity compared to dim red in wild-type cockroaches, as shown previously (Zhukovskaya et al 2017). However, W-E activity during S2 in dim green light was not different from control (S1) and they were significantly less active than wild-type cockroaches under the same conditions (Fig.…”

“…W-E cockroaches did not demonstrate any changes in exploratory behavior in dim red light, which is barely visible to human eye and practically invisible to cockroaches (Zhukovskaya et al 2017). However, there were significant changes under green light, suggesting that W-E cockroaches are overall less sensitive to light than their wild-type counterparts.…”

“…Behavioral experiments were performed using a previously described experimental setup under the same conditions (Zhukovskaya et al 2017). In brief, we recorded the activity of a single naive cockroach that entered an empty testing chamber (20x20x8 cm) from the living quarters where a group of 15 cockroaches had resided for at least two weeks.…”

“…We hypothesized that differences in absolute sensitivity between W-E and wild-type cockroaches could lead to differences in behaviour. In a previous study we showed that locomotor and other behaviours of wild-type cockroaches change with the level of illumination (Zhukovskaya et al 2017). We compared locomotor behaviours of W-E and wild-type cockroaches using the same experimental and analytical methodology.…”

The role of ocelli in cockroach optomotor performance

“…Briefly, the system consists of a projector (DepthQ ® , Lightspeed Design Inc., USA) equipped with a fisheye lens via which stimuli are produced onto the inside of a spherical projection surface covering 270° in horizontal plane. The spectrum of the projected image contains wavelengths between 400 and 700 nm (Takalo et al 2012 ), i.e., it excites almost exclusively the green receptors (Zhukovskaya et al 2017 ). An air-suspended lightweight trackball (diameter 93 mm, weight 4.8 g) is placed inside the projection sphere, so that the compound eyes of an insect walking on the trackball are at the equator of the sphere.…”