Figure 1

Schematics of embryonic and larval development in Capitella teleta . (A) Ten stages of development representing a linear series of events from fertilization through emergence of the stage 9 metatrochophore larva prior to settlement and metamorphosis to a juvenile worm. Stages 1 to 9 each represent approximately 24 hrs at 18 to 19°C. (B) Schematics of selected embryonic and larval stages depicting endoderm development and gut formation. Stage 3 schematics are shown with anterior to the left. Stage 4 and stage 6 larvae are oriented in pairs of ventral and lateral views with anterior to the left. Gray shading represents endodermal precursor cells prior to gastrulation and during gastrulation and as definitive endoderm after gastrulation during larval development. View orientations are shown below each embryo and larva. Abbreviations: ant, anterior; bp, blastopore; br, brain; ec, ectoderm; en, endoderm; fg, foregut; hg, hindgut; mo, mouth; pos, posterior; St, stage; vcf, vegetal cross-furrow; vnc, ventral nerve cord; yo, yolk; 1 m, 1st quartet micromere; 1 M, 1st quartet macromere; 3 m, 3rd quartet micromeres; 3 M, 3rd quartet macromeres. Dotted line in stage 3 gastrula indicates the position of the blastopore. Thin solid lines internal to the contour of the body in stages 3, 4 and 6 indicate the inner boundary of regions of ectoderm distinguished by low yolk content.