Fig. 1

Adult specimens of Timarete cf. punctata. Anti-FMRFamide (green; A), anti-serotonin (blue; B), and anti-f-actin (depth coded, legend in G; C-F) staining, confocal maximum projections, as well as SEM overviews (H-I). Anterior is left (A-D, I) respectively upper left (H). a Anterior end in ventral view, showing the brain (br), circumesophageal connectives (cc), the ventral nerve cord (vc), and the segmental nerve 2 (sn2) in each segment. The arrow indicates the circular area without FMRFamide-immunoreactivity. b Lateral view of the pro- and peristomium visualizing the orientation of the brain (br). c Anterior ventral view, showing ventral longitudinal musculature (vlm), circular musculature (cm), and the muscular pouch of the mouth opening (mp). The arrow indicates the dorso-ventral muscle fibers penetrating the brain. d Posterior end in ventro-lateral view, showing the ventral longitudinal (vlm) as well as circular musculature (cm). e, f Cross-sections of anterior (E) and posterior (F) segments showing dorsal (dlm) and ventral (vlm) longitudinal musculature, circular musculature (cm), the median ventral longitudinal muscle fiber (mlm) and the musculature associated with the parapodia (pm). Also meshwork-like musculature surrounding the intestine (in) is visible. h, i Overview of external anatomy (H) and detail of the anterior end (I), showing location and shape of prostomium (pr), peristomium (pe), the first ten chaetigers (1–10), mouth opening (mo), nuchal organ (nu), noto- (no) and neurochaetae (ne), as well as branchiae (br) and tentacles (te). Scale bars = 100 μm, except H = 200 μm