Lifetime consequences of food protein‐carbohydrate content for an insect herbivore

Abstract

Summary1. Food protein-carbohydrate content has significant consequences for animal survival, growth and reproduction. Rarely, though, is its effect examined over an animal's entire lifetime. 2. In this study, we reared newly hatched caterpillars [Heliothis virescens Fabricus (Lepidoptera: Noctuidae)] on diets containing different protein/carbohydrate (p/c) ratios. We recorded larval survival, time to pupation, pupal mass, eclosion success, time to eclosion and pupal body lipid content. Additionally, for each treatment, we mated eclosed males and females and measured egg production and egg viability. 3. Larval performance (survival to pupation and time to pupation) was similar across all except the two most extreme treatments. In contrast, pupal performance (mass, eclosion success and time to eclosion) was best on diets that were balanced or slightly protein-biased. However, eclosion success differed between sexes. For males, it was best on diets with balanced p/c ratios, while female eclosion was strong across all but the most carbohydrate-biased diet. Pupal body lipid content in both males and females increased as the food p/c ratio decreased. 4. Egg production was best on diets with balanced or slightly protein-biased p/c ratios. 5. We also estimated the effect of food p/c ratio at the population level, using the data generated in this study. Population size was largest on diets with a balanced p/c ratio and declined steadily and strongly as the food p/c ratio became increasingly more imbalanced. 6. Our findings show, for the first time, the effect of food p/c content over an insect herbivore's entire life. Our data indicate that there is a narrow range of p/c ratios that maximize lifetime performance, and for H. virescens, this range coincides with its self-selected p/c ratio.

Revisiting macronutrient regulation in the polyphagous herbivore Helicoverpa zea (Lepidoptera: Noctuidae): New insights via nutritional geometry

“…As Fig. 5 shows, this result is much more consistent with the ITs of other lepidopterans that have been measured in GF studies and most closely matches that found for H. virescens (Lee et al, 2006;Roeder and Behmer, 2014), a generalist New World species that is closely related to H. zea. These results support our initial hypothesis that the IT for H. zea would be slightly protein-biased and be similar to that of H. virescens.…”

“…Since Waldbauer et al (1984), protein and carbohydrate regulation has been tested in several lepidopteran species using the GF, including Heliothis virescens (Lee et al, 2006;Telang et al, 2001;Roeder and Behmer, 2014), Heliothis subflexa (Lee et al, 2006), Manduca sexta (Thompson and Redak, 2005), Malacasoma disseria (Despland and Noseworthy, 2006), Plutella xyostella (Warbrick-Smith et al, 2009), Spodoptera exigua (Merkx-Jacques et al, 2008), Spodoptera exempta (Lee et al, 2004b), Spodoptera littoralis (Lee et al, 2004a), and Spodoptera litura (Lee, 2010). Across these species, the ITs range from slightly carbohydrate-biased ratio for S. exempta (0.8:1) to slightly protein-biased ratio for H. virescens (1.5:1) and S. littoralis (1.3:1), with several species selecting for a balanced 1:1 p:c ratio.…”

“…Given the IT results for other caterpillar species, especially the IT reported for the closely related H. virescens (Lee et al, 2006), we expected the IT for H. zea to be only slightly protein-biased, approximating the upper range found in these other studies. We also hypothesized that performance in the no-choice study would be best on the diet treatment that most closely matched the IT calculated from the choice experiments, given that ITs have been shown to be functionally optimal (Behmer and Joern, 2008;Roeder and Behmer, 2014).…”

Dietary phosphate affects food selection, post-ingestive P fate, and performance of a polyphagous herbivore

“…If the animal consistently consumes from these pairs in such a way that it obtains the same amount of the nutrient, the animal can be considered to be behaviorally adjusting its food selection to obtain a target quantity of the nutrient. Because numerous prior studies have demonstrated that intake targets (at least for carbohydrate:protein ratio) closely match the diet composition that maximizes fitness (Roeder and Behmer, 2014), these behavioral tests allow the animal itself to 'tell us' its optimal dietary phosphate level.…”

Nutritional physiology of life history trade-offs: how food protein-carbohydrate content influences life-history traits in the wing-polymorphic cricketGryllus firmus

“…Animals, including insects, are known to employ compensatory mechanisms when eating foods that are nutritionally imbalanced (Simpson and Raubenheimer, 1993;Simpson et al, 2002;Cook et al, 2010) or have low-nutrient concentration (Yang and Joern, 1994;Slansky and Wheeler, 1989;Lee et al, 2004). Furthermore, multiple studies have revealed that reproductive output and lifespan are also responsive to protein and carbohydrate concentrations and ratios (Maklakov et al, 2008;Lee et al, 2008, Roeder andBehmer, 2014). …”