Sugar feedingviatrehalose haemolymph concentration affects sex pheromone production in matedHeliothis virescensmoths

Abstract

SUMMARYLong-distance, female-produced sex pheromones are widespread among moths. Larval feeding provides most of the nutrients for development of these insects but is not thought to influence the de novo production of the fatty-acid derived compounds used as pheromones by most species. Feeding on plant nectar (sugar) by adult moths is important for increasing female fitness and also for the pollination of many plant species. In this paper, I show that feeding on sucrose solution, as opposed to water, increases sex pheromone titre in mated, but not virgin, female Heliothis virescens. Mating caused a rapid decrease in haemolymph trehalose concentration, which was restored to near-virgin levels by sugar ingestion. When isolated mated female abdomens were cultured with different concentrations of trehalose, pheromone titre increased with increasing trehalose concentration. This effect was not observed when abdomens were cultured on saline containing the sugar rhamnose, which insects cannot metabolise to glucose. Virgins injected with the juvenile hormone (JH) analogue, methoprene, showed the same effects as mated females with respect to pheromone titre and haemolymph trehalose concentration. Thus, following mating increases in JH titre increase demand for, and lowering of, blood sugar to develop oocytes, which can be compensated for by sugar ingestion. Haemolymph trehalose concentration probably influences glycolysis in gland cells and, consequently, levels of cytosolic citrate and acetyl-CoA for pheromone biosynthesis. This increase in pheromone titre in sugar-fed, mated females may facilitate further mating and increased fecundity. Thus, exogenous sugar feeding is behaviourally and physiologically integrated with endogenous JH titre to maximise female fitness.

Sex pheromone of a coccoid insect with sexual and asexual lineages: fate of an ancestrally essential sexual signal in parthenogenetic females

“…These findings indicate that the pheromone is produced only during a limited period even by the sexual mealybugs, which may save a cost of continuous production. Most pheromones are biosynthesized de novo in specific organs [65,66] and thus require nutrient resources [67]. Terpenoid pheromones of coccoids are considered to be de novo biosynthesized, because their structures are unique, and no compounds with similar skeletons are found in host plants [68].…”

Sex pheromones in mate assessment: analysis of nutrient cost of sex pheromone production by females of the mothHeliothis virescens

“…Adult Lepidoptera commonly feed on carbohydrate in plant nectar, which typically increases female fecundity (Wäckers et al, 2007). In the polyandrous moth Heliothis virescens Fabricius (Lepdioptera, Noctuidae), this adult-acquired carbohydrate (AAC) is also used for pheromone biosynthesis via uptake to hemolymph (as trehalose), followed by glycolysis and pyruvate oxidation to cytosolic acetyl CoA (Foster and Anderson, 2011;Foster, 2009;Foster and Johnson, 2010). Although this demonstrates that pheromone can be made from carbohydrate, we do not know whether this is the sole nutrient used or the relative importance of adult-versus larval-acquired nutrients.…”

Changes in the calling behaviour of female Spodoptera littoralis (Lepidoptera: Noctuidae) as a function of body weight and adult feeding

“…Although the cost of calling is assumed to be low (Cardé & Baker, 1984;Alberts, 1992) there is indirect evidence that signalling using pheromones is costly. The decrease in pheromone production associated with resistance to pesticides (Delisle & Vincent, 2002), the use of trehalose and fatty acids as metabolic reservoirs for pheromone biosynthesis (Foster, 2005), the enhancement of sex pheromone production after feeding on sucrose (Foster, 2009;Foster & Johnson, 2010) and the reduced fecundity and survival associated with calling (Harari et al, 2011) all indicate that calling is metabolically expensive. The long period spent calling by large starved females may thus be due to their having greater metabolic reserves and consequently being more able to sustain long and costly periods of calling.…”

“…The increase in the time spent calling by females fed on sucrose may be a consequence of increased rates of pheromone production. Foster (2009) andJohnson (2010) have demonstrated that females fed on sucrose produce more sex pheromone. Regardless of their body weight, moths are expected to utilize sucrose in several ways.…”

“…In addition to providing energy for mating, development of eggs and oviposition (O'Brien et al, 2000), another benefit of feeding during the adult stage could be an enhancement of the likelihood of mating resulting from females increasing their calling activity. Foster (2009) andJohnson (2010) have shown that virgin and mated females that are fed sugar produce more sex pheromone, indicating that feeding during the adult stage affects calling behaviour. However, it is Abstract.…”