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Fig. 6 | BMC Evolutionary Biology

Fig. 6

From: Ancestral role of Pax2/5/8 in molluscan brain and multimodal sensory system development

Fig. 6

Expression of Acr-Pax2/5/8 during late larval development and in settled individuals of Acanthochitona crinita. Dorsal (d)–ventral (v), apical (a)-abapical (aa), anterior (ant)-posterior (p), and left (l)-right (r) axes indicate the orientation, the red dashed circles the apical organ, and the asterisks label the mouth. Cell nuclei are labeled in blue, cilia in green in B & right inset of J). a-d Acr-Pax2/5/8 is expressed in ectodermal cells of the episphere (1), the shell fields (arrowheads in (a & c)), the dorso-lateral (2) and ventral episphere (4), and close to the apical organ (inset in c) in 35 hpf old trochophores (optical sections from dorsal (a) to ventral (d)). b A further developed, 35 hpf old, trochophore (left micrograph) and a slightly younger specimen (right micrograph) with serotonin-like immunoreactive latero-ventral ampullary cells (las), additional sensory cells (yellow dashed circles), apical organ cells (red dashed circles), and cells in the ventral hyposphere (arrowheads). e-h In competent trochophores (65 hpf) (optical sections from dorsal (e) to ventral (h)), Acr-Pax2/5/8 is expressed in cells of the shell fields (arrowheads), in cells of group 1, 2, and 4 (c.f. Fig. 4), and in two groups of cells (5) along the developing foot (f), which are connected via a slender bridge of cells. Inset in g Acr-Pax2/5/8-expressing cells close to the apical organ. i-k Lateral view of trochophore (65 hpf) shown in (e-h). j Dashed box marks location of the small inset that depicts a confocal reflection scan of Acr-Pax2/5/8-expressing subepidermal flask-shaped cells (red) in the shell fields. Right large inset: FMRFamide-like immunoreactive cell somata (red) in the shell fields (arrowheads) and close to the trochoblasts. k Acr-Pax2/5/8 expression in the posterior mantle fold (arrowhead). l No Acr-Pax2/5/8 expression was observed in postmetamorphic (settled) specimens (130 hpf). The staining of the perinotum is unspecific (arrowhead). Abbreviations: at, apical tuft; pt, prototroch. Scale bars: 20 μm (except inset in (j) 10 μm)

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