Figure 4.

Nco-Gsx2 expression during the growth and asexual reproduction by paratomic fission in Nais communis. Except for (E), all animals are oriented with the anterior to the left, in (E) the anterior is up. Lateral view for all panels. (A) Nco-Gsx2 is strongly expressed on the lateral and ventral sides of the newly developed segments of a growing N. communis worm. (B,C) Enlarged view of the posterior terminal region of the animal shown in (A), different focal planes. (D) Within the middle-staged fission zone, expression is detected in the cells of the new developing tail region, where a new posterior growth zone is established. (E) Enlarged view of the boxed region shown in (D), deep focal plane. (F) Nco-Gsx2 signal in the superficial cells on the lateral sides of the new developing tail region of the anterior zooid, middle stage of fission. (G) Caudal terminal region of a specimen at the middle paratomy stage. (H,I) Strong expression is observed in the cells of the new posterior growth zone and the developing, new structure of the ventral nerve cord at the late stage of paratomic fission, different focal planes. The red line marks the new developing tail region, and the green line marks the new developing head region within the fission zone. Scale bar, 45 mkm for all panels except (A,D). Scale bar in (A,D), 70 mkm.