Figure 1.

Schematic diagrams of the general anatomy of starfish (Asterias rubens) larvae (modified after, Murabe et al., 2008) (top half) and main neuronal aggregations of the nervous system (bottom half). In all diagrams anterior is uppermost with the overall body structure shown in yellow and the digestive system shown in orange. (A) bipinnaria larva; dorsal view. (B–D) brachiolaria larva. (B) dorsal view. (C) frontal (ventral) view. (D) left lateral view with ventral side on the left and dorsal on the right. (E) bipinnaria larva; dorsal view. (F) bipinnaria larva; ventral view. (G–I) brachiolaria larva. (G) dorsal view. (H) frontal (ventral) view. (I) left lateral view with ventral side on the left and dorsal on the right. The areas of main neuronal aggregations are highlighted in red in (E–I). The lateral ganglia start to develop at the bipinnaria stage and are located at the base of the anterior projection (solid black arrow labels the left lateral ganglion and dotted black arrow labels the right lateral ganglion; Moss et al., 1994; Elia et al., 2009). Neurons are also concentrated in several regions along ciliary bands, especially in the preoral ciliary band near the mouth (small black arrowhead; Moss et al., 1994; Byrne et al., 2007). In addition to these regions, the brachiolaria stage develops neuronal aggregations in the brachia tips (black arrowheads) and stems (white arrowheads), in the adhesive disk (double arrow), and in the basi-epithelial nerve plexus underlying the disk (white arrow; Barker, 1978; Murabe et al., 2008; Elia et al., 2009). a, anus; abr, anterior brachium; ad, adhesive disk; ap, anterior projection; ar, adult rudiment; ba, bipinnaria arms; e, esophagus; g, gut; m, mouth; lbr, lateral brachium; pol, postoral lobe; prl, preoral lobe; s, stomach.