Figure 4

Expression of MaDfd, MaScr, and MaLox5 in M. alaskensis larval development. All images and diagrams show lateral views with larval anterior up and future juvenile anterior to the left. Asterisk marks apical organ. (A) MaDfd expression is not evident during the trunk-discs stage anywhere in the larval or juvenile body, including the trunk discs (td), the cephalic disc (cd), and stomach (st). (B) MaDfd is first clearly expressed during the head-and-trunk stage in small domains of each trunk rudiment (tr) and in a portion of the dorsal disc (dd). The head rudiment (hr) is indicated for reference. (C) In torus-stage larvae, MaDfd is expressed in a very narrow ring of the juvenile posterior. Proboscis rudiment (pb) marked for reference. (D) MaScr expression is not evident during the trunk-discs stage anywhere in the larval or juvenile body. (E) The onset of MaScr expression occurs during the head-and-trunk stage in domains of each trunk rudiment (tr) and in a portion of the dorsal disc (dd). (F) In torus-stage larvae, MaScr is expressed in a ring of the juvenile posterior with an additional few small spots of expression laterally towards the anterior of the juvenile (arrowheads). (G) MaLox5 expression is not evident during the trunk-discs stage anywhere in the larval or juvenile body. Faint background staining is observed in both pairs of discs. (H) The onset of strong MaLox5 expression occurs during the head-and-trunk stage in domains of the each trunk rudiment (tr) and in a portion of the dorsal disc (dd). Faint background staining persists in all juvenile rudiments, including head rudiment (hr) as well as portions of the stomach. (I) MaLox5 is expressed in a patch near the posterior end of the juvenile in extended-proboscis-stage larvae. (A’-I’) diagrammatically illustrate expression patterns in the three respective developmental stages.