Showing papers by "Sanjay P. Sane published in 2014"

Encoding properties of the mechanosensory neurons in the Johnston's organ of the hawk moth, Manduca sexta.

Abstract: Antennal mechanosensors play a key role in control and stability of insect flight. In addition to the well-established role of antennae as airflow detectors, recent studies have indicated that the sensing of antennal vibrations by Johnston's organs also provides a mechanosensory feedback relevant for flight stabilization. However, few studies have addressed how the individual units, or scolopidia, of the Johnston's organs encode these antennal vibrations and communicate it to the brain. Here, we characterize the encoding properties of individual scolopidia from the Johnston's organs in the hawk moth, Manduca sexta , through intracellular neurophysiological recordings from axons of the scolopidial neurons. We stimulated the flagellum–pedicel joint using a custom setup that delivered mechanical stimuli of various (step, sinusoidal, frequency and amplitude sweeps) waveforms. Single units of the Johnston's organs typically displayed phaso-tonic responses to step stimuli with short (3–5 ms) latencies. Their phase-locked response to sinusoidal stimuli in the 0.1–100 Hz frequency range showed high fidelity (vector strengths>0.9). The neurons were able to encode different phases of the stimulus motion and were also extremely sensitive to small amplitude (<0.05 deg) deflections with some indication of directional tuning. In many cases, the firing frequency of the neurons varied linearly as a function of the stimulus frequency at wingbeat and double wingbeat frequencies, which may be relevant to their role in flight stabilization. Iontophoretic fills of these neurons with fluorescent dyes showed that they all projected in the antennal mechanosensory and motor center (AMMC) area of the brain. Taken together, these results showcase the speed and high sensitivity of scolopidia of the Johnston's organs, and hence their ability to encode fine antennal vibrations.

Modeling Strain Sensing by the Gyroscopic Halteres, in the Dipteran Soldier Fly, Hermetia illucens

Abstract: Dipteran insects are known to receive mechanosensory feedback on their aerial rotations from a pair of vibratory gyroscopic organs called halteres. Halteres are simple cantilever-like structures with an end mass that evolved from the hind wings of the ancestral four-winged insects form. In most Diptera, including the soldier fly Hermetia illucens, the halteres vibrate at the same frequency as the wings. These vibrations occur in a vertical plane such that any rotation about this plane imposes orthogonal Coriolis forces on the halteres causing their plane of vibration to shift laterally by a small degree. This motion results in strain variation at the base of the haltere shaft, which is sensed by the campaniform sensilla. This strain variation is, therefore, a key parameter for sensing body rotations. In this paper, we present a study of the basic mechanism of soldier fly halteres to demonstrate its use as a vibratory gyroscope. First, we use a static force sensor to determine the stiffness of the haltere,...