Schematic representation of the nervous system shortly before (A and B) and after (C and D) metamorphosis in Aeolidiella stephanieae. Based on serial thin sections (0,5 μm/section). (A) Frontal view of the nervous system in a metamorphic competent larva (25% of development) showing five paired ganglia; cerebral- (cg), pedal- (pg), pleural- (pl), buccal- (bg), and optical ganglia (og), as well as a unpaired visceral ganglion (vg). The cerebral ganglia are joined via connectives to the pedal-, buccal-, and pleural ganglia. In close proximity to the cerebral ganglia are the eyes (e) as well as their optical ganglia. Commissures are present among cerebral-, buccal-, and pedal ganglia. The connections between the visceral ganglion and the pleural ganglia form the visceral loop; mp marks the metapodium and v the velum. (B) Lateral view of the nervous system shown in A, anterior faces upwards; cil marks the cilia, o the operculum, and s the shell. (C) Dorsal view of the nervous system in an early postmetamorphic juvenile A. stephanieae (30% of development), anterior faces upwards. The rhinophoral ganglia (rg) lie at the base of the rhinophores (r) above the newly formed cerebropleural ganglia (cpg). Note that the pleurovisceral loop (plvis) is without a visceral ganglion, which probably fused with one of the cerebropleural ganglia; jw marks the jaw. (D) Lateral view of the nervous system in C, anterior faces right. From the rhinophoral ganglion a nerve (n3) is running to the rhinophore whereas another nerve (n2) is running anteriorly from the cerebropleural ganglion to the lip. Two nerves from the pedal ganglion are innervating the foot, and one is running towards the lip, as well (p3).