LIM homeobox gene expression during Nematostella development. (a-d) The arrowhead (Lhx6/8) ortholog is first expressed in the apical tuft of the late planula (c) but disappears in the juvenile polyp (d). (e-h) The lin-11 (Lhx1/5) ortholog is first expressed in the putative pharyngeal endoderm in the early planula and later resolves into an endodermal ring around the pharynx (g' = oral view of g; h' = cross-section through h). (i-l) The Lmx ortholog is first transcribed in the oral ectoderm of the early planula and then spreads into the pharynx and directive mesenteries (l' = oral view of l). (m-p) The apterous(Lhx2/9) ortholog is expressed in the planula endoderm in a speckled pattern and later its expression spreads to the end of the pharynx and throughout the directive mesenteries (p' = lateral view of p). (q-t) The islet ortholog starts out in the putative pharyngeal endoderm and over time spreads into the directive mesenteries. This gene is transcribed in cells of the planula body wall endoderm and in the polyp stage there it shows restricted expression in the aboral endoderm (t' = lateral view of t).