Temperature dependence of standard metabolic rate in a temperate and a tropical species of triatomines

ROLANDI, C.; ROMERO, B.; SCHILMAN P.E.

Mendoza

Congreso; X Congreso Argentino de Entomología; 2018

Sociedad Entomologica Argentina

Environmentaltemperature is an abiotic factor with great influence on biological processesof living beings, including standard metabolic rate (SMR), and has particular importance in ectothermic animals like insects. Intropical regions, mean temperature is higher and remains relatively constantthroughout the year, contrasting with temperate regions characterized by lowermean temperatures, and higher variability on a daily and seasonal scale. Thus,ectotherms living in temperate regions could have mechanisms to cope with thesethermal characteristics. Among them, the metabolic cold adaptation (MCA)hypothesis predicts that populations or species from cooler environments (highaltitude or latitude) will have higher SMR or greater SMR sensitivity totemperature variations (Q10). The relation between temperature orthermal fluctuations effects on SMR is non-linear, and it cannot be predicted frommean constant temperatures (Jensen?s inequality). In the case of the SMR-temperaturecurve, thermal variations across the ascending portion will imply a higher overallenergy expenditure as compared to a constant mean temperature. It has beenhypothesized that species adapted to more variable environments will be able tomodulate Q10 as a response to increasing thermal variability. Rhodnius prolixus and Triatoma infestans are haematophagous vectorsof Chagas disease, with different geographical distribution across SouthAmerica. We used one tropical (R.prolixus) and one temperate (T.infestans) species to test MCA hypothesis, and potential modulatory effectsof a daily temperature fluctuation (DTF) to Q10. We usedflow-through respirometry to measure activity and CO2 production inindividual insects (as a proxy for SMR) at different temperatures -rising from10 to 35ºC by 5ºC-step-like fashion. Unfed fifth instar nymphs from bothspecies were randomly assigned to an acclimation treatment: constanttemperature (24°C), or with a DTF (17-32°C; mean = 24°C) for two weeks and theywere weighed before measurements. Our results support MCA hypothesis becausefor temperatures above 20ºC T. infestanshas a significantly (p<0.05) higher SMR and Q10 (2.63±0.10,mean±S.E) than R. prolixus (2.31±0.08).However, there is no evidence that a thermal fluctuation modulates Q10for neither species. This knowledge will notonly provide basic information to the field of insect ecophysiology, but couldalso be a useful background to develop population and disease transmissionmodels.