Figure 4

Capitilla teleta-zic (Ct-zic) expression in the lophotrochozoan C. teleta. Expression of Ct-zic at cleavage (M), stage 3 (A and B), stage 4 (C, D and N), stage 5 (E, F and O), stage 6 (G and H), stage 7 (I and, J) and stage 8 (K, L, P and Q). Views are as indicated except that H is a ventral-lateral view; M is an animal view; N and O are anterior views; P is a lateral view; and Q is a ventral view. In all lateral and ventral views the anterior is to the left and the ventral is down in all lateral views. An asterisk (*) indicates the relative mouth position. Ct-zic is detectable in micromeres on animal pole (M). Ct-zic mesodermal expression is detected in the anterior mesodermal band on the ventral side of stage 3 animals (A and B) and in two bilateral mesoderm domains adjacent to the foregut at stages 4 and 5 (C and E, arrowheads). The mesodermal expression expands around the foregut during stages 6 (G) and 7 (I, notched arrowhead). At stage 5, four lateral mesodermal domains (F, arrowheads) are detected. At stage 7, lateral mesoderm domains form two longitudinal rows along the anterior-posterior (A-P) axis (J, arrowheads). At stage 8, the longitudinal domains are clearly mesoderm associated with chaetae (L, arrowheads, and P), but not the chaetal sac (P, arrows). Ct-zic is expressed in presumptive brain ectoderm in all stages (B, arrow, C-L and N). Ventrolateral expression at the lateral edge of ventral neural ectoderm is detected at stage 4 (C, arrow) and stage 5 (F and O, arrows). The lateral neural ectoderm domain is down-regulated in an A-P wave apparent at stage 6 (G, white line demarcates anterior border of expression) but remains expressed in the growth zone (I and J, arrows). Ct-zic is also detectable in neurons in the brain (H, arrow) and, beginning at stage 6, in the ventral nerve cord (VNC; G, white arrowhead). VNC expression persists through stage 8 (K, arrowhead, and Q). Medial and lateral ganglions are detected in each segment (Q, which is a higher magnification of L). In Q, the white lines demarcate segmental boundaries.