Electrophysiological identification of thermo- and hygro-sensitive receptor neurons on the antennae of the dragonfly Libellula depressa

Recent ultrastructural investigations on Odonata antennal flagellum describe two types of sensilla styloconica, T1 and T2. The styloconic sensilla are located in pits, at the bottom of deep cavities, and share common features typical of thermo-hygroreceptors. In order to ascertain if the Odonata antennae are involved in hygroreception and thermoreception, we carried out electrophysiological recordings (single cell recordings, SCR) from adult males and females of Libellula depressa L., 1758. After contact was established, the antenna was stimulated by rapid changes in temperature and humidity. The present research shows the occurrence of a dry (DC), a moist (MC) and a cold (CC) receptor neurons on the antennal flagellum of L. depressa. These data demonstrate for the first time the presence of functional thermo-hygroreceptors on the antennal flagellum of dragonflies. The present results extend our knowledge of the not visual sensory modalities of Odonata, a field of research unexplored so far.

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► Odonata are well known for their ability to thermoregulate.
► Hygro- and thermoreception have never been electrophysiologically investigated in these insects.
► We present recordings from the sensory neurons of Libellula depressa, stimulated by rapid changes in temperature and humidity.
► These recordings (SCR) show the presence of a dry (DC), a moist (MC) and a cold (CC) receptor neurons on the antenna.
► Our data demonstrate for the first time the ability to perceive temperature and humidity in Odonata.