The Antennal Pathway of Dragonfly Nymphs, from Sensilla to the Brain

Abstract

Dragonflies are hemimetabolous insects, switching from an aquatic life style as nymphs to aerial life as adults, confronted to different environmental cues. How sensory structures on the antennae and the brain regions processing the incoming information are adapted to the reception of fundamentally different sensory cues has not been investigated in hemimetabolous insects. Here we describe the antennal sensilla, the general brain structure, and the antennal sensory pathways in the last six nymphal instars of Libellula depressa, in comparison with earlier published data from adults, using scanning electron microscopy, and antennal receptor neuron and antennal lobe output neuron mass-tracing with tetramethylrhodamin. Brain structure was visualized with an anti-synapsin antibody. Differently from adults, the nymphal antennal flagellum harbors many mechanoreceptive sensilla, one olfactory, and two thermo-hygroreceptive sensilla at all investigated instars. The nymphal brain is very similar to the adult brain throughout development, despite the considerable differences in antennal sensilla and habitat. Like in adults, nymphal brains contain mushroom bodies lacking calyces and small aglomerular antennal lobes. Antennal fibers innervate the antennal lobe similar to adult brains and the gnathal ganglion more prominently than in adults. Similar brain structures are thus used in L. depressa nymphs and adults to process diverging sensory information.

Ternary Transition Metal Complexes with an Azo-Imine Ligand and 2,2’-Bipyridine: Characterization, Computational Calculations, and Acetylcholinesterase Inhibition Activities

“…Therefore, adults are likely to have a more improved nervous system than nymphs. 39 In another literature, the differences in the activities of ACHEs obtained from different stages of Bactrocera dorsalis (H.) were appraised from two perspectives. It was papered that one of them, some alterations to the protein structure occurred during the developmental stages to meet the continuously changing demands of the development of insects, the another factor, the differences in the expression level of genes encoding specific enzymes might be resulting in changes.…”