Innervation of sheath cells of an insect sensillum by a bipolar type II neuron

A multiterminal bipolar type II neuron is situated centrally in each mandible of an elaterid larva. It is ensheathed by a glial cell to the base of the two terminal scolopophorous sensilla in the terminal mandibular tooth but its terminal branches are naked. These branches extend along the outer surfaces of the inner and outer sheath cells of and the adjacent surfaces of the epidermal cells around both sensilla. The dendrite and its branches contain longitudinal microtubules, peripheral mitochondria, and clear and variously dense vesicles. It has no ciliary region. The dense vesicles are more numerous in newly molted than in intermolt larvae. Unique plates of endoplasmic reticulum and vesiculating bodies occur in the sheath and epidermal cells adjacent to the naked dendritic branches. This neuron may control the secretory activities of the sensillar sheath cells and adjacent epidermal cells through release of appropriate chemical mediators.