Fig. 8

Schematic of i-cell distribution and cell proliferation in Nanomia bijuga. Shades of blue indicate density of i-cells, as indicated by co-localized expression of the examined genes. Magenta dots indicate cell proliferation. a Siphosomal growth zone and anterior part of the siphosome. Two gastrozooids (gc) are represented as cross sections. I-cells (blue) get restricted to deeper layers of the basigaster. nanos-2 (green) continues to be expressed in outer layers of the basigaster, and vasa-1 (yellow) continues to be expressed within the developing hypostome. b Older siphosomal stem fragment with a mature gastrozooid, two palpons, and developing gonozooids. Cell proliferation is spatially restricted to tentacle and palpacle bases and to developing gonophores. b bract, fg female gonodendron, g gastrozooid, gc gastrozooid cross section, goc gonodendral i-cell cluster, h horn, mgo male gonophore, p palpon, pa palpacle, sst siphosomal stem, te tentacle