Expression of Nvi-Hox genes in nectochaetes and juvenile worms. Nvi-Hox gene expression patterns at the nectochaete stage are shown in the top row. Juvenile worms before adult head formation are in the second row. In the third, fourth, and fifth rows there are juvenile worms with 10 to 12, 15 to 20, and more than 20 segments, respectively. The anterior end is directed upwards on all panels. All views are ventral. White asterisks mark the background. Expression patterns of Nvi-Hox1 are shown in panels (Aa–Ae). Arrows show expression in peristomial cirri. Arrowheads on the panel Ae indicate Nvi-Hox1 expression in the pharynx. (Ba–Be) Expression of Nvi-Hox4. (Ca–Ce) Expression of Nvi-Hox5. (Da–De) Expression of Nvi-Lox5. (Ea–Ee) Expression of Nvi-Hox7. Red lines indicate the anterior border of Nvi-Hox7 expression in the VNC. Metameric staining in several anterior segments is a background in epithelial glands. These are pigmented and tend to bind antibodies nonspecifically (shown in higher magnification in Figure 6F). (Fa–Fe) Expression of Nvi-Lox2. The arrow shows weak expression at the nectochaete stage. Arrowheads in panel Fb point the Nvi-Lox2 expression in the pygidium area. Red lines indicate the anterior border of Nvi-Lox2 expression in the VNC. Metameric staining in several anterior segments is a background in epithelial glands. (Ga–Ge) Expression of Nvi-Post2. See text for details.