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

ROLANDI, C.; SCHILMAN, P.E.

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

Environmentaltemperature is an abiotic factor with great influence on biological processesof living beings. Traditionally most of the studies measure the impact of constanttemperatures on organisms, however, Jensen?s inequality states that fornon-lineal processes such as most biological phenomena, the effects of thermalfluctuations cannot be predicted from mean constant temperatures. Thus over thepast decade research has shifted in order to account for thermal variability. Westudied the effect of daily temperature fluctuation (DTF) on physiologicaltraits related to life-history in Rhodniusprolixus, a model organism in insect physiology andan important vector of Chagas disease. We measured development time from egg toadult, fecundity as the number of laid eggs, fertility as the percentage ofegg´s hatching, and as an indirect measure of nutrient consumption rates we measuredbody mass reduction rate and survival after a single blood meal. Insects werereared at constant temperature (24ºC) or with a daily fluctuation between 17and 32ºC (mean = 24ºC). This temperature range corresponds to the maximum DTF experiencedby these insects across their geographical distribution. In addition, we testedwhether this species has the ability to modulate its starvation tolerance throughdevelopmental plasticity or phenotypic flexibility. Taking into accountJensen?s inequality as well as the species tropical distribution, we predictthat living in a variable thermal environment will have higher costs thaninhabiting a stable one. Development time and fertility were not affected by DTF.However, fecundity was lower in females reared at DTF than females reared atconstant temperature. In addition, males had lower survival and higher bodymass reduction rate in the DTF regime. The higher rates of weight loss andmortality together with the lower fertility suggest that there are higher costsassociated to fluctuating thermal environments, and that there is no phenotypicor developmental plasticity to mitigate its effect. At a population andepidemiological level, higher energetic costs would imply an increase innutrient consumption rate and biting frequency, consequently increasing diseasetransmission from infected insects. On the contrary, lower fecundity registeredin the fluctuating thermal regime could be associated with a decrease inpopulation growth. Thus understanding the complex relations between temperatureand biological parameters requires more empirical work. This knowledge will notonly provide basic and fundamental information to the field of insect ecophysiology,but also could be of use as background to develop population and diseasetransmission models.