Interactive effects of temperature and concentration of the flavonol rutin on growth, molt and food utilization of Manduca sexta caterpillars

Abstract

AbstractA factorial experiment tested the effects of varying concentrations of the flavonol rutin and daytime temperatures of 20 and 30 °C on growth, molting and food utilization efficiencies of third instar tobacco hornworms (Manduca sexta (L.)). Cool temperature prolonged both the growth (= feeding) and non‐feeding periods and consequently the relative consumption rates (RCR) and relative growth rates (RGR). Temperature had no impact on the amount of food consumed and the utilization indices of efficiency of conversion of ingested food and efficiency of conversion of digested food to larval biomass. But rutin was more concentrated in the frass of the larvae at the warm temperature. With increasing levels of rutin in the diet, the efficiency of conversion of ingested food tended to decline. Rutin reduced RCR and RGR. At the cool temperature, rutin increased the time spent in the first portion of the non‐feeding period disproportionately. Analysis of growth rate intervals within the growth period indicated that at the cool temperature rutin had no discernible impact over the first half of the growth period, during which developmental competence to molt is likely achieved. Overall, these results indicate an overlap in the growth and molting phases and suggest that rutin interferes with physiological processes at the time of molt initiation, with these effects magnified at a cool temperature.