Fig. 9

Schematic representation of SLI pattern in the investigated pycnogonids and inferred minimal pattern in the last common ancestor. The left column shows the largely corresponding SLI pattern of the ventral half of all four walking leg ganglia, the middle column depicts the pattern characteristic for the dorsal half of walking leg ganglia 2–4, and the right column for the slightly deviating dorsal half of walking leg ganglion 1 only. All neurons shown in black have been consistently identified in the respective species. Neurons in gray were only inconsistently identified. In the case of the ALNs of P. litorale, five neurons are shown in black (minimum number observed) and the additional gray neurons indicate that higher numbers are frequently observed, but no clearly fixed maximum cell number was assessable. The lowest row illustrates the reconstructed minimal pattern of the common ancestor, including only those neuron types and neuron numbers that have been reliably recovered and therefore homologized across the three investigated pycnogonid species