Figure 19

Ventral nerve cord and muscle development of P. dumerilii , 56-62 hpf, ventral view, anterior up. The age of the larvae in each row is given in the lower left corner of the first picture of each row. The displayed staining is indicated at the bottom of each column. A, G, M, S: An increasing amount of commissural axons becomes visible along the ventral nerve cord (compare A, G, M, S). B, H, N, T: A pair of serotonergic cells becomes visible in the third segment (white arrow heads), additionally to the unpaired serotonergic cell (white star) and other serotonergic cells in the first and second segment (white arrow heads). C, D, I, J, O, P, U, V: Parapodial muscles (ppm) and oblique muscles (om) increase rapidly in size. The unpaired medial ventral longitudinal muscle (mvlm) becomes visible posterior to the stomodeum and elongates posteriorly (compare C, I, O, U). E, K, Q, W: The stomodeal rosette (str) is well visible. Three pairs of parapodia (pp) become visible from around 60 hpf onwards. F, L, R, X: The second paratroch (pat2) becomes visible at the posterior boarder of the first chaetigerous segment from 56 hpf onwards. CLSM microscopy, maximum projection, Imaris surpass mode. Scale bar in all images 20 μm. Further abbreviations see abbreviations list.