Effects of daily temperature fluctuations on physiological traits of the hematophagous bug Rhodnius prolixus

PABLO E. SCHILMAN; CARMEN ROLANDI

Tartu

Simposio; 7th International Symposium on the Environmental Physiology of Ectotherms and Plants (ISEPEP7); 2017

Environmental temperature is an abiotic factor with great influence on biological processes of living beings. Traditionally most of the studies measure the impact of constant temperatures on organisms, however, Jensen?s inequality states that for non-lineal processes such as most biological phenomena, the effects of thermal fluctuations cannot be predicted from mean constant temperatures. Thus over the past decade research has shifted in order to account for thermal variability. We studied the effect of daily temperature fluctuation (DTF) on physiological traits related to life-history in Rhodnius prolixus, a model organism in insect physiology and an important vector of Chagas disease. We measured development time from egg to adult, fecundity as the number of laid eggs, fertility as the percentage of egg´s hatching, and as an indirect measure of nutrient consumption rates we measured body mass reduction rate and survival after a single blood meal. Insects were reared at constant temperature (24ºC) or with a daily fluctuation between 17 and 32ºC (mean = 24ºC). This temperature range corresponds to the maximum DTF experienced by these insects across their geographical distribution. In addition, we tested whether this species has the ability to modulate its starvation tolerance through developmental plasticity or phenotypic flexibility. Taking into account Jensen?s inequality as well as the species tropical distribution, we predict that living in a variable thermal environment will have higher costs than inhabiting a stable one. Development time and fertility were not affected by DTF. However, fecundity was lower in females reared at DTF than females reared at constant temperature. In addition, males had lower survival and higher body mass reduction rate in the DTF regime. The higher rates of weight loss and mortality together with the lower fertility suggest that there are higher costs associated to fluctuating thermal environments, and that there is no phenotypic or developmental plasticity to mitigate its effect. At a population and epidemiological level, higher energetic costs would imply an increase in nutrient consumption rate and biting frequency, consequently increasing disease transmission from infected insects. On the contrary, lower fecundity registered in the fluctuating thermal regime could be associated with a decrease in population growth. Thus understanding the complex relations between temperature and biological parameters requires more empirical work. This knowledge will not only provide basic and fundamental information to the field of insect ecophysiology, but also could be of use as background to develop population and disease transmission models.