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Fig. 7 Regional specification of the body axis in type-A embryos appears to be unaffected by the UV treatment. UV retarded type-A and control embryos were stained with various digoxigenin-labeled RNA probes to assess the regional specification in the truncated axes. (A,B) UV-treated and control embryos at the 2-somite stage stained with an antisense RNA probe directed against the Zf[pax-b] gene. Expression of Zf[pax-b] is confined to the anlage of the mesencephalon in the neural plate at the 2-somite stage. View onto animal pole is shown, dorsal is at the bottom. (C,D) UV-treated and control embryo at the 8-somite stage labelled with the Zf[pax-b] antisense probe. os, optic stalk; m: mesencephalon; o: otic vesicle; p: pronephros. (E,F) UV-treated and untreated control embryo stained with the ZF[pax-A]. gene. Staining in the diencephalon and the hindbrain is marked by d and h, respectively. (G,H) UV-treated and control embryo at the 4- somite stage. Embryos were stained with the ZFcad1 probe. t points out the tail bud in control embryo. (I) An 80% epiboly control embryo stained with ZFcad1 for comparison with staining in G. Embryos, with exception of A and B, are oriented anterior up and dorsal to the right. Blastoderm margins are highlighted by black or white dots. UV embryos were exposed to 3.6 mJ/cm2 UV.