LIM homeobox gene expression during Amphimedon development. (a, c, f, h) Whole-mount micrographs; (b, d, e, g, i, j) micrographs of sectioned embryos. (a-e) The Lhx3/4 ortholog is expressed in the inner cell mass during late gastrulation, when pigment cells form a spot (a,b) and then a ring (c,d). A stronger expression domain appears transiently under the photoreceptor ring when it is forming (arrowheads in d). Expression is ubiquitous in the prehatched larva, with higher expression levels in the subepithelial layer (e). (f-j) The Lhx1/5 ortholog appears to be expressed in the outer layer at the pigment spot stage, especially around the spot (f,g). When the pigment ring forms (h,i), the gene is highly expressed in the inner cell mass, especially inside the developing ring and at the anterior end. A strong expression domain also appears in the micromeres surrounding the developing pigment ring (arrowheads in i). Expression seems to be ubiquitous in the larva before it hatches (j).