Structure of the pecten neuropil pathway and its innervation by bimodal peg afferents in two scorpion species
Fig 4
Position and morphology of the pecten neuropils in Mesobuthus eupeus (A-C) and Heterometrus petersii (D-F). Maximum projections of cLSM stacks, showing neuropilar regions in grey (synapsin-immunoreactivity). (A) Horizontal section of the posterior part of the synganglion of M. eupeus. The associated neuropils of the pecten extend from the most posterior region anteriorly to the level of the third walking leg neuromere (WLN3). The pecten neuropil is divided into the anterior pecten neuropil (APN) and the posterior pecten neuropils 1–3 (PPN 1–3). (B) Frontal section of the PPN and synganglion located just dorsally. The PPN1 appears to be layered, with “onion peel”-like arches that are smaller in dorsal direction and wider in ventral direction. The area between the hemiganglia is slightly torn (asterisk). (C) Sagittal section of the synganglion of M. eupeus. PPN protrudes ventrally from the synganglion. (D) Horizontal view of PPN of H. petersii. Immunolabelling appears stronger in PPN than in the remaining synganglion. PPN1 has a stronger synapsin-immunoreactivity in the outer cortex, compared to the central region. These subcompartments are not as differentiated as in M. eupeus. APN is ellipsoid and heterogeneously structured, exhibiting a weaker immunoreactivity of synapsin than PPN. (E) Frontal section of the synganglion of H. petersii. The outer cortex of PPN1 appears to be more nodular than the inner layers with stronger synapsin immunoreactivity. (F) Sagittal section of the synganglion of H. petersii. APN is very prominent and positioned ventrally at the level of the WLN3. PPN protrudes ventrally from the synganglion. Abbreviations: a: anterior; APN: anterior pecten neuropil; d: dorsal; p: posterior; PPN1-3: posterior pecten neuropil 1–3; v: ventral; WLN3-4: walking leg neuromere 3–4.