Schematic representation of nervous system development of Carinina ochracea.

Serotonin-like (5HT-lir) and FMRFamide-like (RFa-lir) immunoreactivity are color coded in magenta and green respectively; the general nervous system architecture as outlined by synapsin-like immunoreactivity (syn-lir) is shown in grey. All larval stages are drawn to scale with apical tuft (at), epidermal cilia, fronto-lateral epidermal invaginations (fi), midgut (mg), mouth opening (mo), and the pigmented larval eye (pe) serving as landmarks (cilia of the frontal epidermal invaginations, the stomodaeum, the midgut, and epidermal cilia in the aspect of view omitted), apical is up. A and B: left: lateral view from right, right: ventral view. Transitory neuronal/neuritic elements are indicated by stippling/dotted lines. A: Post-gastrula stage larva at one day post-fertilization (1-dpf). B: Larva at 2-dpf. C: Larva at 3-dpf. From left to right: lateral view from right, ventral view, dorsal view, lateral view from left. Since the nervous system is roughly symmetrical, only one side is shown (left: 5HT-lir, right: RFa-lir). For clarity, the peripheral plexus is not shown. Further explanations, see text.–bd, dorsal brain neuron; br, brain-ring; bv, vental brain neuron; an1, 1^st apical median (transitory) neuron; an2, 2^nd apical medio-ventral (transitory) neuron; nc, lateral nerve cord; cn1, 1^st caudal median (transitory) neuron; cn2, 2^nd caudal medio-dorsal (transitory) neuron; nm, dorso-median neurite mass.