title: The role of juvenile hormone in dominance behavior, reproduction and cuticular pheromone signaling in the caste-flexible epiponine wasp, Synoeca surinama.
abstract: BACKGROUND
  The popular view on insect sociality is that of a harmonious division of labor among two morphologically distinct and functionally non-overlapping castes. But this is a highly derived state and not a prerequisite for a functional society. Rather, caste-flexibility is a central feature in many eusocial wasps, where adult females have the potential to become queens or workers, depending on the social environment. In non-swarming paper wasps (e.g., Polistes), prospective queens fight one another to assert their dominance, with losers becoming workers if they remain on the nest. This aggression is fueled by juvenile hormone (JH) and ecdysteroids, major factors involved in caste differentiation in most eusocial insects. We tested whether these hormones have conserved aggression-promoting functions in Synoeca surinama, a caste-flexible swarm-founding wasp (Epiponini) where reproductive competition is high and aggressive displays are common.
  
  
  RESULTS
  We observed the behavioral interactions of S. surinama females in field nests before and after we had removed the egg-laying queen(s). We measured the ovarian reproductive status, hemolymph JH and ecdysteroid titers, ovarian ecdysteroid content, and analyzed the cuticular hydrocarbon (CHC) composition of females engaged in competitive interactions in both queenright and queenless contexts. These data, in combination with hormone manipulation experiments, revealed that neither JH nor ecdysteroids are necessary for the expression of dominance behaviors in S. surinama. Instead, we show that JH likely functions as a gonadotropin and directly modifies the cuticular hydrocarbon blend of young workers to match that of a reproductive. Hemolymph ecdysteroids, in contrast, are not different between queens and workers despite great differences in ovarian ecdysteroid content.
  
  
  CONCLUSIONS
  The endocrine profile of S. surinama shows surprising differences from those of other caste-flexible wasps, although a rise in JH titers in replacement queens is a common theme. Extensive remodeling of hormone functions is also evident in the highly eusocial bees, which has been attributed to the evolution of morphologically defined castes. Our results show that hormones which regulate caste-plasticity can lose these roles even while caste-plasticity is preserved.
authors.affiliation: Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147 USA ; Present address: Department of Botany and Zoology, Stellenbosch University, Private Bag XI, Matieland, 7602 South Africa.
authors.forename: Hans C
authors.initials: HC
authors.lastname: Kelstrup
authors.affiliation: Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Universidade de São Paul, Av. Bandeirantes 3900, Ribeirão Preto, 14049-900 SP Brazil.
authors.forename: Klaus
authors.initials: K
authors.lastname: Hartfelder
authors.affiliation: Departamento de Biologia da Faculdade de Filosofia, Ciȇncias e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, Ribeirão Preto, 14040-900 SP Brazil.
authors.forename: Fabio S
authors.initials: FS
authors.lastname: Nascimento
authors.affiliation: Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147 USA.
authors.forename: Lynn M
authors.initials: LM
authors.lastname: Riddiford
keywords: Cuticular hydrocarbons; Ecdysteroids; Endocrine; Epiponini; Juvenile hormone; Swarm founding; Wasps