Single perturbations cause sustained changes in searching behavior in stick insects

Abstract

SUMMARYStick insects (Cuniculina impigra) possessing only a single front leg perform untargeted stereotypical cyclic searching movements with that leg when it loses contact with the ground. When encountering an object, the animals grasp it. We hypothesized that removal of the object immediately after contact with the legʼs tibia would result in a change in searching strategy, i.e. searching movements confined to the former location of the object to regain contact. In our experimental setup, searching movements were restricted to upward and downward movements. After removal of the object, searching movements were continued. However, in post-contact searching, two movement parameters were usually changed: (1) average positions of searching movements were shifted towards the former position of the object; and (2) movement amplitudes were considerably smaller and accompanied by a decrease in cycle period. This confinement of searching movements to the location of contact was interpreted as targeting behavior. All parameters regained initial values after approximately 6s. Changes in position and amplitudes were independently controlled. Neither of the changes was under visual control, but rather depended on the presence of the trochanteral hairplate, a sensory organ that measures the coxa-trochanter joint position. Changes in average leg position were linked to changes in the ratio of electrical activity in the levator and depressor trochanteris muscles, which were based on altered activity in both or either one of the muscles. Our data demonstrate a switch in a simple behavior that is under local sensory control and may utilize a form of short-term memory.

Spatial coordination of foot contacts in unrestrained climbing insects

“…Similarly, the stick insect Medauroidea extradentata (=Cuniculina impigra) shows aimed searching movements with its front legs that repetitively wave across the space where an object is touched. Interestingly, these movements are no more directed to the former object location after ablation of the trochanteral hair field (Berg et al, 2013). The increase in swing height after ablation of the trochanteral hair field (Fig.…”

Mechanosensation and Adaptive Motor Control in Insects

“…A recent study shed light on this problem in stick insects. When a leg makes transient contact with an object, a stick insect responds by searching in a tight local pattern around the site of contact [170]. Accurate local searching behavior does not require visual input, but does require an intact hair plate at the coxa-trochanter joint, suggesting that this proprioceptive organ provides key information about the joint’s position at the moment of contact.…”

Comparative whole-body kinematics of closely related insect species with different body morphology

“…Instead, the movements were dominated by high levation of the leg and large extension of the femur-tibia joint. These characteristics also occur when Medauroidea performs a sequence of searching movements to find objects (Karg et al, 1991;Berg et al, 2013). The searching movements also affected the coordination of the other legs, leading to more protracted middle legs: whenever the front legs perform high swing movements without ground contact, the other legs must account for balance and stability.…”

“…[Carausius (Cruse, 1990;Dürr, 2005;Grabowska et al, 2012); Aretaon (Jeck and Cruse, 2007)], climbing and/or leg searchingmovements [Carausius (Cruse, 1976a;; Medauroidea (Karg et al, 1991;Berg et al, 2013); Aretaon (Bläsing and Cruse, 2004a)], catalepsy [Carausius (Godden, 1974); Medauroidea (Bässler and Foth, 1982)] and single-joint kinematics [Carausius (Cruse and Bartling, 1995); Aretaon (Frantsevich and Cruse, 1997;Jeck and Cruse, 2007)]. Because none of these data have been acquired using the same combination of setup and method, and many of them concern tethered, planar walking only, direct comparison of the results is not justified without simplifying assumptions.…”