Active tactile exploration for adaptive locomotion in the stick insect

Abstract

Insects carry a pair of actively movable feelers that supply the animal with a range of multimodal information. The antennae of the stick insect Carausius morosus are straight and of nearly the same length as the legs, making them ideal probes for near-range exploration. Indeed, stick insects, like many other insects, use antennal contact information for the adaptive control of locomotion, for example, in climbing. Moreover, the active exploratory movement pattern of the antennae is context-dependent. The first objective of the present study is to reveal the significance of antennal contact information for the efficient initiation of climbing. This is done by means of kinematic analysis of freely walking animals as they undergo a tactually elicited transition from walking to climbing. The main findings are that fast, tactually elicited re-targeting movements may occur during an ongoing swing movement, and that the height of the last antennal contact prior to leg contact largely predicts the height of the first leg contact. The second objective is to understand the context-dependent adaptation of the antennal movement pattern in response to tactile contact. We show that the cycle frequency of both antennal joints increases after obstacle contact. Furthermore, inter-joint coupling switches distinctly upon tactile contact, revealing a simple mechanism for context-dependent adaptation.

Spatial coordination of foot contacts in unrestrained climbing insects

“…As it is known that reaching movements of front legs may be guided by touch events of the antennae (Schütz and Dürr, 2011), stick insects appear to pass on 3D spatial information across the entire body, from the antennae to the …”

“…Furthermore, cockroaches use antennal contacts to decide whether to tunnel under or climb across obstacles (Harley et al, 2009). Stick insects use their antennae to detect the far edge of a gap (Bläsing and Cruse, 2004b), to scan the edges of obstacles (Krause and Dürr, 2012), and to guide aimed reaching movements of a front leg (Schütz and Dürr, 2011).…”

Active touch sensing

“…Dü rr & Schü tz [32] used high-speed videography methods to investigate the control of antennal movements in the Indian stick insect Carausius morosus at the level of single joint kinematics. They show that active touch sensing in this species is important for initiating climbing behaviour when the animal encounters an obstacle.…”

Single perturbations cause sustained changes in searching behavior in stick insects

“…cricket antennal movements that follow a visual cue (Honegger, 1981), but also towards transient stimuli. For example, stick insects target their front legs towards the location of preceding antennal contact (Schütz and Dürr, 2011). In some cases, targeted movements outlast the stimuli.…”

“…Rodents, for example, use whiskers to palpate objects (Diamond et al, 2008). During locomotion, many insects constantly use antennal exploration to gain information about their environment [cockroach (Camhi and Johnson, 1999;Harley et al, 2009;Baba et al, 2010); cricket (Honegger et al, 1990;Horseman et al, 1997); stick insect Schütz and Dürr, 2011)]. Insects also perform leg searching movements when losing ground contact, e.g.…”