Figure 5

Mlglis and Mlgli expression during the Mnemopsis leidyi development. Expression of Mlglis at 4 high power field (hpf; A), 5hpf (B), 7hpf (C), 8hpf (D), 9hpf (E), 14hpf (F and G) and 24hpf (H) and the expression of Mlgli at 24hpf (I and J). The aboral view (A-F, H-J) and the lateral view (G and all insets) are shown. Oral is down in the lateral views and dashed lines indicate the tentacular axis on the aboral views. Mlglis expression detected at mid-gastrula in two ectodermal domains flanking aboral pole (A) in the presumptive apical organ domain. Domains expand by late gastrula (B) and assume a dumbbell shape over the next three hours (C and D). By comb row formation, each domain splits resulting in four distinct domains (E), which are maintained through the hatching (F and G) and cydippid (H) stages. The four domains are associated with the balancing cilia at the hatching stages (G arrows) and, in the cydippid larva, optical cross-sections of the balancing cilia are clearly aligned with the centre of each of the four Mlglis domains (H arrows). Mlgli expression is first detected at 24hpf in four groups of cells along the adesophageal plane of the apical organ (I and J). Unlike Mlglis, these cells are not associated with the balancing cilia but are in domains consistent with previously described photoreceptor-like cells [25].