Short neuropeptide F receptor localization in the brain of fire ant worker subcastes: A possible role in mechanisms of division of labor and nutritional status

Red imported fire ants (Solenopsis invicta Buren, Hymenoptera, Formicidae) are eusocial insects in which the worker caste is sterile and specialized to perform tasks associated with brood care, foraging, nest construction, maintenance, and defense. Considering the large variations in body size in workers, this caste is divided into three subcastes: minors, mediums and majors. While it is believed the “fate” of these workers is influenced by environmental conditions, age and size, the molecular mechanisms of division of labor among subcastes are not very well understood. Our hypothesis is that the sNPF signaling system (NPY-like) could be involved in mechanisms of workers division of labor, nutrient sensing and foraging need. In this study we investigated the expression of the short neuropeptide F receptor (sNPFR) in the brain and subesophageal ganglion (SEG) in all worker subcastes from colonies with and without brood.  

Across subcastes, nine cell clusters expressing the sNPFR were immunolocalized near important neuropils in the brain (i.e., mushroom bodies, central complex and antennal lobes), and also in the SEG. Five of those sNPFR immunoreactive clusters are differentially expressed among subcastes. Further, in some of these five clusters, the number of cells in each cluster is different among subcastes. In addition, workers from colonies with brood showed an overall higher number of immunoreactive cells than workers from colonies without brood. These results suggest that the sNPFR is involved in neuronal networks important for worker division of labor and which are influenced by the nutritional demands of the brood.