Fig. 6. Later expression of Hro-hh in gut, body wall, reproductive tissue and nervous system. (A) Late stage 10 and (B) early stage 11 embryos (160 and 180 hours AZD) from two separate hybridization experiments. The embryo shown in B was later sectioned in a roughly transverse orientation. Selected sections, corresponding to the planes indicated by the paired arrows and arrowheads, are shown in C-G. In each embryo, Hro-hh transcripts are visible within the oral opening (black arrowhead in A,B), along the inner portion of the proboscis (inverted by this stage; extent indicated by double-headed white arrow in A) and esophagus (bracket in A), in reproductive organs (box in A), around the crop (vertical arrows in B), at the crop-intestine and intestine-rectum boundaries (white arrowheads in B) and rectum (white arrows in B). (A) The staining reaction was carried out for somewhat longer for this embryo, revealing low transcript levels in the ventral nerve cord (small arrows) and in the epidermis except for the future anterior and posterior suckers (black horizontal arrows indicate boundaries). (C) Section through the anterior portion of the proboscis (leftmost paired arrows in B) shows Hro-hh transcripts in cells near the tri-radiate lumen of the proboscis, and in a pair of neurons (arrows) in the ventral ganglion. (D) Section through a more posterior portion of the proboscis (left paired arrowheads in B) shows transcripts in a ring of longitudinally oriented fibers. (E) Section through the anterior end of the crop (middle paired arrows in B) reveals transcripts in a U-shaped pattern corresponding to the reproductive organs. (F) Section through the middle of the crop (right paired arrowheads in B) shows transcripts in visceral mesoderm and/or endoderm. (G) Section through the posterior portion of the embryo (rightmost paired arrows in B) shows transcripts in visceral mesoderm and/or endoderm of the posterior crop caeca, in muscles associated with the rectum (white arrowhead and arrows), and in the body wall bordering the posterior sucker (black arrow). (H) In later stage 11 (190 hours AZD), transcripts are largely confined to four rings of presumptive muscle surrounding the rectum (box), shown at higher magnification in I. Scale bar: 100 µm in A, B,H; 90 µm in C-G; 70 µm in I.

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