Figure 8.

Nco-Cdx1 expression during the growth and asexual reproduction by paratomic fission in Nais communis. Except for (C), all animals are oriented with the anterior to the left; in (C) the anterior is up. Lateral view for all panels. (A) Nco-Cdx1 is strongly expressed in epidermal cells on the lateral and ventral sides at the posterior end of a growing N. communis worm. (B) An additional domain of Nco-Cdx1 expression (arrow) is visible in the fission zone already at the very early stage of paratomy. (C,D) Expression becomes broader at the middle stage of paratomy. (E) At the late stage of fission zone formation, Nco-Cdx1 mRNA marks the newly formed growth zone and pygidium. (F,G) Enlarged view of the posterior end of a growing adult, different focal planes. (H) Expression of Nco-Cdx1 at the early stage of paratomy. (I) Expression of Nco-Cdx1 at the middle stage of paratomy. (J) Expression of Nco-Cdx1 in epidermal cells of the new developing tail region of the anterior zooid at the late stage of paratomy. (K) Expression of Nco-Cdx1 in the new developing tail region of the anterior zooid at the late stage of paratomy, deep focal plane. 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 in (A,B), 70 mkm; in (F–K) 45 mkm.