Figure 5

AmphiSyn expression in amphioxus larvae. All embryos are oriented with the anterior side to the left. Cross sections are viewed from the caudal end of the animal. Whole mount and cross section scale bars are 50 and 25 μm, respectively. A: Side view of 24-hour larva. AmphiSyn expression was found in the most rostral region of the cerebral vesicle. Expression also occurs in the two-third of the nerve cord. B, C: Enlargement of the rostral region of specimen in A in dorsal and lateral views. The latter shows clearly two large epidermal cell bodies localized around the preoral organ. D, E: Cross sections trough levels shown in A. In the rostrum, some positive epidermal cells near the blastopore were visible (D) (arrow). All sensory cells at this stage were localized only in the epidermal sheet (black arrowheads). F: 36-hour larva in lateral view. Sensory cells were visible in the rostrum and in the lateral body. A high concentration of labeled sensory cells was found in the middle of the body. G: High power view of the head of the specimen in F, showing AmphiSyn expression in rostral cells located more ventrally. I-K: Cross sections through levels shown in F. AmphiSyn-positive photoreceptor cells of frontal eye complex (arrowheads) were visible. Presumptive cells located under the epidermis surface in the ventral portion of the rostrum were visible in I and J (arrows). Such cells could correspond to the precursors of corpuscles of de Quatrefages. H: Enlargement of the most caudal region of the specimen in F with in focus epidermal sensory cells located mid-laterally along the flanks of the body. L-O: Cross sections through levels shown in F. In M, photoreceptor cells of dorsal ocellus express AmphiSyn (arrows).