Metabolism and water loss rate of the haematophagous insect,Rhodnius prolixus: effect of starvation and temperature

Abstract

Haematophagous insects suffer big changes in water needs under different levels of starvation. Rhodnius prolixus is the most important haematophagous vector of Chagas disease in the north of South America and a model organism in insect physiology. Although there have been some studies on patterns of gas exchange and metabolic rates, there is little information regarding water loss in R. prolixus. We investigated whether there is any modulation of water loss and metabolic rate under different requirements for saving water. We measured simultaneously CO 2 production, water emission and activity in individual insects in real time by open-flow respirometry at different temperatures (15, 25 and 35°C) and post-feeding days (0, 5, 13 and 29). We found: (1) a clear drop in metabolic rate between 5 and 13 days after feeding that cannot be explained by activity and (2) a decrease in water loss rate with increasing starvation level, by a decrease in cuticular water loss during the first 5 days after feeding and a drop in the respiratory component thereafter. We calculated the surface area of the insects and estimated cuticular permeability. In addition, we analysed the pattern of gas exchange; the change from a cyclic to a continuous pattern was affected by temperature and activity, but it was not affected by the level of starvation. Modulation of metabolic and water loss rates with temperature and starvation could help R. prolixus to be more flexible in tolerating different periods of starvation, which is adaptive in a changing environment with the uncertainty of finding a suitable host. KEY WORDS: Flow-through respirometry, Respiratory water loss, Cuticular permeability, CO 2 emission rate INTRODUCTIONDesiccation resistance is vital for survival and colonization of terrestrial habitats. In insects in particular, there must be a fine and efficient control of water loss because of their high surface area to volume ratio. Insects lose water through various pathways: transpiration through the cuticle, evaporation along open spiracles through the tracheal system, and excretion (Edney, 1977;Hadley, 1994). The contribution of each of these pathways to overall water loss is variable but cuticular water loss (CWL) generally accounts for a high proportion of the total water loss (Gibbs and Johnson, 2004;Hadley, 1994). The contribution of respiratory water loss (RWL) to dehydration has been analysed mostly in insects showing discontinuous gas exchange (DGE) (e.g. Chown and Davis, 2003;Lighton, 1992;Quinlan and Lighton, 1999 techniques that enable CWL and RWL to be distinguished in insects with continuous gas exchange: the regression method (Gibbs and Johnson, 2004) and the hyperoxic switch method . Using these techniques, it was observed that spiracular control under continuous gas exchange can modulate RWL as effectively as DGE (Schilman et al., 2005;Gray and Chown, 2008).Haematophagous insects that do not drink free water show big changes in water balance under different levels of starvation (Benoit and Denlinger, 2010)....

Ecological and physiological thermal niches to understand distribution of Chagas disease vectors in Latin America

“…The metabolic rate of triatomines can be modified by extrinsic variables such as temperature (Rolandi et al ., ), as well as intrinsic variables such as insect mass. Because there were significant differences of mass across the species studied (Table ; F 6,88 = 136.08, P < 0.0001), we analysed the thermo‐limit parameters of mass‐independent metabolic rate to compare differences across species (Table ; see S4 in File S1 for mass‐independent conversion).…”

“…For insects, temperature affects most of the physiological processes; in fact, it is probably the most important abiotic factor determining species geographical distribution (Chown & Nicolson, ; Angilletta, ). There are many studies about the effects of temperature on physiological and behavioural processes of Chagas disease vectors (Blaksley & Carcavallo, ; Schilman & Lazzari, ; Rolandi et al ., , among others), and several about the abiotic factors explaining their distributions (Carcavallo et al ., ; Gorla, ). However, there are only a few studies linking physiological traits of one (de Souza et al ., ) or two species of triatomines (de la Vega et al ., ) to their geographical distribution.…”

Haematophagy is costly: respiratory patterns and metabolism during feeding inRhodnius prolixus

“…Different blood-sucking arthropod species have been analysed in terms of metabolic activity, such as fleas, bedbugs, ticks and mosquitoes (Lighton et al, 1993;Bradley, 2003, 2006;DeVries et al, 2013). However, the species that has been best characterized in terms of respiration dynamics and metabolism is the triatomine Rhodnius prolixus Bradley, 2009, 2010;Rolandi et al, 2014;Heinrich and Bradley, 2014). Hence, this bug constitutes a good model system with which to evaluate the energetics of feeding in blood-sucking insects.…”

Progressive behavioural, physiological and transcriptomic shifts over the course of prolonged starvation in ticks

“…This balance is critical for blood-feeding arthropods that rely on blood as the sole resource for both somatic and gametic processes (Benoit & Denlinger, 2010). Cimex and Rhodnius mitigate energetic losses by depressing metabolic rates as starvation progresses (DeVries, Kells, & Appel, 2015;Rolandi, Iglesias, & Schilman, 2014). Additionally, feeding status affects the host-seeking behaviours of a variety of other blood-feeders (Reisenman, Lee, Gregory, & Guerenstein, 2013;Takken, Van Loon, & Adam, 2001;Wang et al, 2017).…”