Figure 3

Parapodial muscles. Scale bars = 50 μm, anterior is to the left. A. Ventral view, close up from Fig. 2A, phalloidin staining, depth coded (in μm). Shown are two parapodia and their muscle complexes (pmc). The ventral longitudinal muscles (VLM) lie laterally, and the median ventral longitudinal muscle (mVLM) runs along the midline. Parapodial muscles are only labeled on the right half of the body. These include chaetal muscles (chm); acicular muscles (am); inner anterior parapodial muscle (iaPM); outer anterior parapodial muscle (oaPM); inner posterior parapodial muscle (ipPM); outer posterior parapodial muscle (opPM); median ventral longitudinal muscle (mVLM); the ipPM, opPM, iaPM assemble with the mVLM (circle). Thin transverse muscle strands (tm) cross the ventral side. B. 3D-reconstruction of A, but from dorsal side, same labeling scheme. Each muscle is displayed in a unique color. The dorsal longitudinal muscle (DLM) and the anterior (adPM) and posterior dorsal parapodial muscles (pdPM) have been removed from the reconstruction of the right side of the body, to expose underlying muscles. Chaetal (chm) and acicular muscles (am) form the center of the parapodium. The outer anterior parapodial muscle (oaPM) stretches anteriorly, terminating in the vicinity of the VLM. The inner anterior parapodial muscle crosses the body-cavity and ends at the opposite side (iaPM). Both posterior parapodial muscles (ipPM, opPM) terminate at the midline in close proximity to the median ventral longitudinal muscle (mVLM). Here, the ipPM, opPM, iaPM of two adjoining pairs of parapodial muscle complexes assemble (circle). C. 3D-reconstruction of A, dorsal view, with still more overlying muscles removed to expose ventral musculature. The consecutive parapodial muscle complexes of the right body-half are shown. Labeling as in B. Three muscles, originating from either of the ventral longitudinal muscles (VLM, mVLM) stretch ventroanteriorly (asterisks). Single transverse muscle strands (tm) of the ventral side are visible. D. Same 3D-reconstruction as in C. Ventral view.