Fine structure of sunken thick-walled pegs (sensilla ampullacea and coeloconica) on the antennae of mosquitoes

Abstract

Sensilla ampullacea (pegs in tubes), a type of sensillum heretofore unknown from mosquitoes, occur on the antennae of female Anopheles stephensi Liston and Aedes aegypti (L.). Sensilla coeloconica (pegs in pits) with thick-walled pegs, previously reported from A. aegypti and Culex pipiens L. also occur on the antennae of An. stephensi.The fine structure of the sensilla ampullacea and coeloconica is similar. Each sensillum consists of a non-perforated, thick-walled peg located in either a deep tube or a pit, and is innervated by three neurons. The unbranched dendrites of two neurons extend into the lumen of the peg. The dendrite of the third neuron, which is distally folded into lamellae in all of the sensilla ampullacea and some of the sensilla coeloconica, terminates beneath the peg. Three sheath cells are associated with each sensillum.Sensilla coeloconica on the antennae of female Aedes aegypti are thermoreceptors. On the basis of similarity in fine structure, sensilla coeloconica and ampullacea of An. stephensi probably also play a role in thermoreception.