Waveforms from stylet probing of the mosquito Aedes aegypti (Diptera: Culicidae) measured by AC-DC electropenetrography

Abstract

Electropenetrography (EPG) has been used for many years to visualize unseen stylet probing behaviors of plant-feeding piercing-sucking insects, primarily hemipterans. Yet, EPG has not been extensively used with blood-feeding insects. In this study, an AC-DC electropenetrograph with variable input resistors (Ri), i.e., amplifier sensitivities, was used to construct a waveform library for the mosquito arbovirus vector, Aedes aegypti (Linneaus), while feeding on human hands. EPG waveforms representing feeding activities were: 1) electrically characterized, 2) defined by visual observation of biological activities, 3) analyzed for differences in appearance by Ri level and type of applied signal (AC or DC), and 4) quantified. Electrical origins of waveforms were identified from five different Ri levels and AC versus DC. Mosquitoes produced short stylet probes ('bites') that typically contained five waveform families. Behaviors occurred in the following order: surface salivation (waveform family J), stylet penetration through the outer skin (K), penetration of deeper tissues and location of blood vessels/pathway activities (L), active ingestion with engorgement (M), and an unknown behavior that terminated the probe (N). Only K, L, and M were performed by every insect. A kinetogram of conditional probabilities for waveform performance demonstrated plasticity among individuals in L and M, which were alternated. Now that EPG waveforms for mosquito feeding have been defined, EPG can be used as a tool for improved biological understanding of mosquito-borne diseases.