Behavioural and cognitive influences of kairomones on an araneophagic jumping spider

In laboratory experiments, Portia fimbriata, an araneophagic salticid from Queensland, was influenced by olfactory and contact-chemical cues from Jacksonoides queenslandicus, an abundant salticid on which P.fimbriata preys. Four distinct effects were revealed: P.fimbriata (1) moved into and remained in the vicinity of J. queenslandicus, (2) performed undirected leaping, behaviour known to function as speculative hunting by inducing a turning response from not-yet-seen J. queenslandicus, (3) adopted a posture (retracted palps) known to be routine when stalking salticids and (4) showed enhanced attention to optical cues from J. queenslandicus. Laboratory experiments provided no statistical evidence that chemical cues from other prey species affected P.fimbriata, that J. queenslandicus was affected by chemical cues from P. fimbriata or that allopatric Portia were sensitive to chemical cues from J. queenslandicus.

Producing directed behaviour: muscle activity patterns of the cockroach escape response

The cockroach responds to wind from the front left by making an escape turn to the right, and vice versa. So far, no interneurones in the escape system are known that respond only to wind from the left or only to wind from the right. In this study, we used electromyographic recordings to determine whether motor neurones respond in this direction-selective manner during escape behaviour. In the mesothoracic coxal-femoral joint, whose movement direction is diagnostic for escape direction, the fast motor neurones of one muscle respond selectively to one wind direction, and those of the antagonistic muscle respond selectively to wind from the other direction, resulting in an appropriate turning response. This rules out an alternative hypothesis, a co-activation mechanism of specifying turn direction. These results suggest that it would be fruitful to search among the interneurones of the escape system for additional cells and circuit properties that could give rise to this sharp directional discrimination.

How bees exploit optic flow: behavioural experiments and neural models

Over the past thirty or so years, motion processing in insects has been studied primarily through the ‘optomotor response’, a turning response evoked by the movement of a large-field visual pattern. More recently, however, evidence is accumulating to suggest that, in addition to the optomotor pathway, there are other pathways which use motion information in subtler ways. When an insect moves in a stationary environment, the resulting optic flow field is rich in information that can be exploited to estimate the distance to a surface, distinguish between objects at different distances, land on a contrasting edge, or distinguish an object from a similarly textured background. This article reviews recent behavioural studies in our laboratory, investigating how honeybees accomplish such tasks.

A subpopulation of cerebral B cluster neurones of Aplysia californica is involved in defensive head withdrawal but not appetitive head movements

The cerebral B cluster neurones of Aplysia californica were studied under experimental conditions designed to evoke head movements in a selective fashion: either to approach an appetitive stimulus, or to withdraw from an aversive one. Intracellular recordings indicated the presence of two types of B cluster neurones: Bn cells that had fast (narrow) spikes, and Bb cells that had slow (broad) spikes. Tactile stimulation of the tentacles, rhinophores and lips excited Bn neurones, but inhibited Bb neurones. Intracellular stimulation of Bn cells evoked contractions of body wall muscles. No contractions were observed when Bb cells were fired, indicating that it is unlikely that the Bb neurones are motor neurones. Several lines of evidence indicated that the Bn type neurones are involved in withdrawal responses but not in appetitive head turning. (1) Elimination of the descending axons of the Bn cells by lesioning the cerebropleural connectives (C-Pl connectives) did not affect the head-turning response. This lesion significantly altered the head-withdrawal response by selectively eliminating an initial fast component of the withdrawal movement. (2) In chronic recordings from the C-Pl connective, unit activity was obtained which was correlated with the presentation of an appetitive stimulus rather than with evoked or spontaneous turning movements. A substantial increase in activity also occurred during head withdrawal of the animal. On the basis of these data, we postulate that separate populations of motor neurones are responsible for the aversive withdrawal of the head, and for the directed turning response towards a stimulus.

Steady Turning Stability of Partially Filled Tank Vehicles With Arbitrary Tank Geometry

Steady turning model of a partially filled tank vehicle is developed by integrating the roll plane model of the partially filled arbitrarily shaped tank with the static roll plane model of an articulated vehicle. The rollover immunity of the tank vehicle is investigated through computer simulation. The motion of the free surface of liquid and the associated load shift encountered during steady turning are computed using an iterative algorithm. The influence of tank geometry and liquid fill level on the rollover immunity of the tank vehicles is presented. Rollover threshold levels of a tractor-semitrailer vehicle with tanks of circular, modified square and modified oval cross sections are investigated for various fill levels. The influence of compartmenting of the tank on the steady turning response of the vehicle is presented and an optimal order of unloading the various compartments is determined. The study concludes that load shift encountered during steady turning has an adverse effect on the overturning limits of the articulated liquid tank vehicles. The stability of such tank vehicles may be further affected by the dynamic fluid-structure interactions, vehicle transients and driver’s reaction.

The Role of an Identified Brain Neurone in Mediating Optomotor Movements in a Moth

1. Completely unrestrained moths show an optomotor turning response to horizontal movement during pre-flight warm up or flight. 2. As the moth warms up there is a sequential recruitment of first neck, then abdominal, leg and finally some wing muscles, into the optomotor turning response. 3. Extracellular motoneurone spikes were recorded from neck muscles during optomotor stimulation. As the stimulus is oscillated from side to side, motoneurones on the ipsilateral side are excited. The latency of this response increases greatly in dim light. 4. Flight motoneurones were not observed to spike in response to movements of the optomotor stimulus, but subthreshold oscillations of 5–10 mV, in phase with the response of the identified optomotor interneurone D1, were observed. Three motoneurones, the second pleuroaxillary, the subalar and the dorsal longitudinal to the more medial, ventral fibre bundle, showed depolarizations in phase with the response of the ipsilateral D1 interneurone. Synaptic potentials in these motoneurones followed action potentials in Dl, suggesting that D1 provides a direct, excitatory input to them. 5. An excitatory postsynaptic potential (EPSP) from D1 sums with a steady depolarization of all three directly postsynaptic motoneurones to produce an action potential.