Spoltud-1 in situ hybridization on adult and juvenile planarians shows expression in the germ line, CNS and neoblasts. (A) spoltud-1 whole mount in situ hybridization on adult planarians. Anterior is to the left. Top: dorsal view. Bottom: ventral view. Expression in testes is seen as two dorsal rows indicated by asterisks. Expression in ovaries is indicated by arrows. Arrowheads indicate CNS expression in the brain and ventral nerve cords. (B, C) spoltud-1 in situ hybridization on paraffin sections of an adult planarian showing testes, indicated by arrows (B), and parenchymal neoblasts (C). (D-G) Confocal maximum projection of a double in situ hybridization and immunohistochemistry of neoblast markers. (D) spoltud-1 mRNA positive cells in green. (E) histone H2B mRNA positive cells in red. (F) Nuclear expression of PCNA protein in neoblast cells in blue. (G) Overlay image showing colocalization of Spoltud1 mRNA and both histone H2B mRNA and PCNA protein. te, testis. Scale bars: 1 mm in A; 50 μm in B,C; 10 μm in D-G.