Stage 34
At the Early Body Axis Rotation Stage (CirobuD:0000057), the stalk continues to elongate and forms, with the endostyle axis, an angle of about 90° (Stage 34). The strong actin intensity in the trunk region associated to the tail remnants indicates that the latter is tightly packed.
Adult organs proceed with their differentiation. In the digestive system, the pyloric caecum (CirobuA:0000630) is differentiating evagination of the stomach. The latter starts to enlarge.
The oral cavity (CirobuA:0000802), representing the oral siphon lumen (os in AIII, B-BI), extends to the rim of the velum (CirobuA:0000900) and tentacles (CirobuA:0000741, now recognizable (Hozumi et al., 2015; Mackie et al., 2006; Manni et al., 2005; Veeman et al., 2010). The oral siphon lumen is in continuity with the branchial chamber (CirobuA:0000863; synonym: branchial sac, branchial cavity) lumen. Tunic cells are also in the tunic covering the inner oral siphon epidermis.