The function and fine structure of the cephalic airflow receptor in Schistocerca gregaria.

Electron micrographs of parts of the sense organ showed that the dendritic axis consisted of a large and a small envelope containing microtubules as their main inclusion. The envelopes are supported by a thick-walled tube believed to be part of the ist-tier sheath cells. The small envelope is segregated from the large envelope near its apex by a fold of the tube wall. The packing of the neurotubular array within the small envelope is both more dense and more regular than within the large envelope. The tube is separated by an extracellular space from the trichogen-tormogen cell. Sections through the apex of the dendrite reveal a homogeneous cap unlikely to be part of a structure continued into the upper region of the hair shaft. No ciliary structures were visible within the dendrite, whose microtubules pass into the neuron cell body proximally. Sections through the neuron cell body reveal branched mitochondria, and numerous microtubules. Rates of discharge in sensory axons from these hair organs produced by deflexion of the hair shaft were found to be within the range 300-100 impulses/sec. There is an initial phase of rapid adaptation which gives place to a steady rate. It is suggested that the fine structure of the receptor may indicate mechano-electrical transduction at a more proximal level than is believed to be the case in some other types of receptor. The diaphragms that support the hair shaft laterally can be seen to be composed of fine cuticular strands.