The immunolocalization analyses of the sNPF receptor in the ovaries of fire ant queens. Receptor signal was observed in mid- and early-oogenesis oocytes. A: In mated queens in a colony, the sNPF receptor signal was detected in the posterior end of oocytes at the mid-oogenesis stage (arrow, oocyte in follicle number three), but not in oocytes at the late-oogenesis stage in which nurse cells are reduced in size (big stars, oocytes in follicles number 1 and 2). F1, 2 and 3: follicle numbers counted from the calyx (Ca). B: In newly-mated queens (24 h after mating flight), the receptor signals were also detected in a similar stage of developing oocytes as in A. C: A higher magnification merged image of the oocyte posterior end from newly-mated queen ovaries shows a clearly receptor signal (red) in the oocyte membrane, but not in the follicle cells (nuclei in blue, DAPI label). D: The receptor signals were also detected in the early-oogenesis stage oocytes (oocyte size < 20 μm) of mated queens in a colony. E: In virgin queen ovaries, the receptor signals were detected in the early-oogenesis stage oocytes, similar to the mated queen oocytes shown in D. No signal was detected in negative controls using either antigen-preabsorbed antibodies (F and G) or a preimmune antiserum (H).