Gonadotropic and physiological functions of juvenile hormone in Bumblebee (Bombus terrestris) workers

• Published in: PloS one 2014-06, Vol.9 (6), p.e100650-e100650
• Main Authors: Shpigler, Hagai, Amsalem, Etya, Huang, Zachary Y, Cohen, Mira, Siegel, Adam J, Hefetz, Abraham, Bloch, Guy
• Format: Article
• Language: English
• Subjects: Age; Animal behavior; Animals; Apis mellifera; Bees; Bees - physiology; Behavior, Animal; Biology and Life Sciences; Biosynthesis; Bombus; Bombus terrestris; Bumblebees; Corpora Allata - surgery; Division of labor; Dufour's gland; Ecology; Egg laying; European honeybee; Eusociality; Evolution; Fat body; Female; Females; Fertility; Foraging behavior; Gene Expression; Gonadotropins; Gonadotropins - metabolism; Hemolymph; Hemolymph - metabolism; Homology; Honey; Hormones; Hypotheses; Influence; Insects; Juvenile hormones; Juvenile Hormones - metabolism; Lasioglossum zephyrum; Life sciences; Oogenesis; Pheromones; Physiology; Pituitary (anterior); Reproduction; RNA, Messenger; Secretion; Signal Transduction; Signaling; Studies; Transcription; Tribolium castaneum; Vitellogenin; Vitellogenins - genetics; Vitellogenins - metabolism; Workers; Workers (insect caste); Zoology
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0100650

The evolution of advanced sociality in bees is associated with apparent modifications in juvenile hormone (JH) signaling. By contrast to most insects in which JH is a gonadotropin regulating female fertility, in the highly eusocial honey bee (Apis mellifera) JH has lost its gonadotrophic function in adult females, and instead regulates age-related division of labor among worker bees. In order to shed light on the evolution of JH signaling in bees we performed allatectomy and replacement therapies to manipulate JH levels in workers of the "primitively eusocial" bumblebee Bombus terrestris. Allatectomized worker bees showed remarkable reduction in ovarian development, egg laying, Vitellogenin and Krüppel homolog 1 fat body transcript levels, hemolymph Vitellogenin protein abundance, wax secretion, and egg-cell construction. These effects were reverted, at least partially, by treating allatectomized bees with JH-III, the natural JH of bees. Allatectomy also affected the amount of ester component in Dufour's gland secretion, which is thought to convey a social signal relating to worker fertility. These findings provide a strong support for the hypothesis that in contrast to honey bees, JH is a gonadotropin in bumblebees and lend credence to the hypothesis that the evolution of advanced eusociality in honey bees was associated with major modifications in JH signaling.