Figure 8

Early development of the nervous and muscle systems in Maritigrella crozieri. CLSM micrographs of fluorescently labeled wholemounts from 55-70% development time (phalloidin - white, 5HT - magenta). (A) Left - anterior view, right - posterior view. Early development of apical circular myofibrils (acm) and posterior circular muscles (pcm) around the stomodeum (st). 5HT immunoreactivity in the developing epidermal eye (ee) and it's associated nerve (een). (B) Dorsal view showing the primary longitudinal muscles (plm) and their position relative to the epidermal eye, apical circular muscles and anterior primary circular muscle (apcm). Rudiments of the commissural cell bodies (ccb) are developing. (C) Left lateral view showing further development of circular muscles (cm) and 5HT expression in caudal perikarya (cp). (D) Anterior and left lateral view show neuropil condensation. An apical ring (ar) of 5HT expressing cells in the epidermis sits between the cerebral eyes (asterisks) and above the apical circular muscles, the commissural cell bodies and nerves are below the body wall muscles. The dorso-lateral (dlc) and ventro-lateral (vlc) connectives migrate posteriorly and the ring commisures extend dorsally (double arrowheads). Several longitudinal muscles (arrowheads) form and early mouth retractor muscles (mrm) grow from the apical complex posterior-ventrally to the mouth. (E) Ventral view shows predominance of circular muscles and the first signs of 5HT expression under the ciliary band (cb). (F) Anterio-lateral view shows the establishment of the orthogonal body wall musculature with the development of up to 12 longitudinal muscles. The mouth retractor muscles (mrm) are visible on the ventral side and increasing numbers of rhabdites (rb) develop in the epidermis Scale bars 100 μm.