Fig. 2

Details of the fully formed sensory pits. A Optical horizontal section through the broadest area of the pits showing a fundus, pit cavity, and mucus-like discharge (double arrowheads). B Maximum intensity projection showing the nerves of the sensory pit and rostral musculature. C Maximum intensity projection showing sphincter and fundus of the sensory pit and mucus-like discharge (double arrowheads). D The schematic drawing of the sensory pits in the context of the internal anatomy of the head. Cell nuclei stained with DAPI in cyan, a signal from antibodies against tyrosinated tubulin in yellow, F-actin stained with phalloidin in green, a signal from antibodies against serotonin in red. All panels show dorsoventral sections, anterior to the top. Abbreviations: br brain, f fundus, np brain neuropile, nsp nerve of the sensory pit, ps sphincter of the sensory pit, rm rostral musculature, rn rostral nerves