Increased allocation of adult-acquired carbohydrate to egg production results in its decreased allocation to sex pheromone production in mated females of the moth Heliothis virescens

• Stephen P. Foster, Karin G. Anderson and J. P. Harmon

Author Affiliations

• Entomology Department, North Dakota State University, PO Box 6050, Fargo, ND 58108-6050, USA
• Author for correspondence (stephen.foster [at] ndsu.edu)

• Received August 5, 2013.
• Accepted October 8, 2013.

Abstract

Females of most species of moths produce a volatile sex pheromone that attracts conspecific males over distance. In females of the polyandrous moth Heliothis virescens, feeding on carbohydrate (e.g. nectar) supplies precursor, via hemolymph trehalose, for both sex pheromone and egg production. With limited carbohydrate acquisition these two reproductive physiologies might compete for hemolymph trehalose, resulting in an allocation deficit to either sex pheromone or egg production. Using virgin and mated females, which have low and high egg maturation rates, respectively, we fed females a limited diet of 13C-labeled glucose daily and, using mass isotopomer distribution analysis, determined allocations of adult-acquired carbohydrate (AAC) to newly synthesized pheromone and ovarian and egg fats, our proxies for allocation to egg production. With increased number of feeds, AAC enrichment of hemolymph trehalose increased, as expected. This led to mated females increasing their proportional allocation of AAC to ovarian and egg fats, but decreasing their proportional allocation of AAC to pheromone production. By contrast, virgins increased their proportional allocation of AAC to pheromone production with increased feeds, consistent with increasing AAC enrichment of hemolymph trehalose. These results show that with limited AAC intake, enhanced egg maturation in mated females results in reduced AAC allocation to pheromone production; this does not occur in virgins because of their lower egg maturation rate. This physiological competition for AAC corresponded with decreased pheromone production in mated moths to levels unlikely to attract mates. Therefore, the availability and/or allocation of AAC may be a proximate mechanism underlying the incidence of polyandry in this and other species of moths.

KEY WORDS

• Hemolymph trehalose Pheromone biosynthesis Tradeoff Fatty acid Tracer–tracee Precursor enrichment Polyandry

FOOTNOTES

• Author contributions
  S.P.F. designed and performed the research, analyzed data and wrote the manuscript. K.G.A. performed the research, and J.P.H. analyzed the data. 
• Competing interests
  The authors declare no competing financial interests.
• Funding
  This work was funded by a Hatch grant (ND02367 to S.P.F.) from the North Dakota Agricultural Experiment Station.