Factors affecting locomotor plasticity in Rhodnius prolixus

Triatomines are vectors of Trypanosoma cruzi, the causative agent of Chagas disease. Their locomotor activity is influenced by endogenous and exogenous factors, but whether individual behavioral profiles persist across developmental stages remains unclear. This study evaluated non-oriented locomotor activity in Rhodnius prolixus under varying nutritional states (short-fasting, long-fasting, fed), developmental stages (5^th instar nymphs and adults), sex (males and females), and light phase (photophase vs. scotophase). In a longitudinal design using actometers, we recorded the movements of 81 insects (42 males, 39 females) over 24-hour periods at specific time points through their 5^th instar and adult stage. Results revealed significant variability in activity, but statistical modeling indicated that individual differences contributed minimally to activity variation, with sex, daytime, nutritional state, and developmental stage being the primary determinants. Females were consistently more active than males and both sexes presented higher movement levels during the scotophase compared to the photophase. Adults exhibited greater activity than nymphs. While fed adults displayed higher activity levels than starved individuals, possibly linked to mating or shelter-seeking behaviors, nymphs maintained consistently low activity regardless of nutritional state, indicating a potential energy-conserving starvation-survival strategy. These findings suggest that R. prolixus locomotor activity is not an individually intrinsic trait but rather one dynamically modulated by physiological and environmental conditions, with sex- and light-phase-dependent differences shaping dispersal and survival strategies across life stages.