Size related division of labor

The organization of bumblebee societies: social and molecular regulation of body size

In this project, we study the regulation of body size which underlies two of the organization principles of bumblebee societies: caste determination and worker division of labor. Smaller bumblebee workers typically perform in-nest activities such as brood care, whereas larger bees are more likely to forage outside the nest. Larger bees are more efficient in bringing pollen and nectar back to the colony and appear to be better suited for forging activities. They have better visual discrimination, odor sensitivity, learning abilities, and stronger circadian rhythms and phototactic response compared with their smaller full-sister bees. These differences in behavior are associated with relevant size-related variation in morphology and neuroanatomy. For example, larger workers have more ommatidia with wider facets in their compound eyes, elevated density of olfactory sensilla on the antennae, and additional brain neurons that are immunostained with antiserum against the circadian neuropeptide Pigment Dispersing Factor (PDF) compared with their smaller sisters. We further showed that large and small bees differ in metabolic and stress response protein levels in the brain and abdomen. Our earlier work shows that workers that are reared by the queen show shorter developmental duration and are commonly smaller compared with larvae that are reared mostly by workers (Shpigler et al. 2013). We integrate diverse cutting-edge molecular, biochemical and sociobiological approaches to explore the proximate mechanisms regulating larval development and ultimate body size. For example, we ask whether size variation is functionally significant, and try to identify the social signals and critical periods that influence size differentiation.

Recent relevant publications

  • Hamilton AR, Shpigler, H, Bloch, G, Wheeler DE, Robinson GE (2017) Endocrine Influences on Insect Societies. In: Pfaff, D.W and Joëls, M. (editors-in-chief), Hormones, Brain, and Behavior 3rd edition, Vol 2. Oxford: Academic Press; pp. 421–451.
  • Shpigler H, Tamarkin M, Gruber Y, Poleg M, Siegel AJ, and Bloch G (2013) Social influences on body size and developmental time in the bumblebee Bombus terrestris. Behavioral Ecology and Sociobiology 67: 1601-1612.
  • Wolschin F, Shpigler H, Amdam GV, Bloch G. (2012) Size-related variation in protein abundance in the brain and abdominal tissue of bumble bee workers. Insect Molecular Biology 21: 319–325.
  • Weiss R, Dov A, Fahrbach SE, Bloch G (2009) Size-related variation in Pigment Dispersing Factor-immunoreactivity in the brain of the bumble bee Bombus terrestris (Hymenoptera, Apidae). Journal of Insect Physiology 55: 479-487.

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Supported by grants from BARD (in collaboration with Gene E. Robinson and Mark Band, UIUC) and NAKFI (in collaboration with Oded Nov, NYU).