Fig. 1

Larval asymmetry of amphioxus. a Left lateral view of premetamorphic larva showing streamlined shape. b Magnification of oral region showing mouth and preoral pit on left and gill openings on right side. c Schematic illustration of early knife-shaped larva showing organ formation in anterior region and previously suggested location of mouth opening (arrow). anp; anterior neuropore; ch, notochord; csg, primordial club-shaped gland; es, primordial endostyle; g, gut; lld, left lateral diverticulum (= pp, preoral pit); m, mouth; nc, neurenteric canal; pgs, primary gill slit; rld, right lateral diverticulum (= rc, rostral coelom); 1-10s, 1st-10th somite. Scale bars, 1.0 mm for (a), 0.5 mm for (b)