Fig. 3

Tubulin⁺ elements in the early mitraria. CLSM images of DAPI (cyan) and beta-tubulin (a–j) and alpha-acetylated tubulin (k–m) (yellow or white) at 24 hpf. Insets in (f–g) are close ups of the peripheral neuron in e. a–c Lateral views with beta-tubulin⁺ axons extending from the apical organ (ao) anteriorly (fn), dorsally (dn) and laterally (rpn, lpn; orange arrowheads) towards the prototroch ring. The polar bodies (pb) are still visible at this stage in the blastocoel space between the apical organ and the midgut (mg). Beta-tubulin is also staining the cell boundaries across the body of the larva, like in c. d–g Ventral views showing at least one beta-tubulin⁺ monociliated cell (magenta arrow) in the prototroch that presumably connects to the apical organ via a peripheral nerve (rpn1). h–j Two bilateral peripheral nerves (rpn1–rpn2 and lpn1–lpn2) branch out on each side of the episphere towards the tubulin⁺ prototrochal ring (pr). k–m Most of the beta-tubulin⁺ axons are also with acetylated tubulin. ao: apical organ; at: apical tuft; dn: dorsal nerve; fn: frontal nerve; lpn1–lpn2: left peripheral nerves 1–2; mg: midgut; mo: mouth; pr: prototrochal ring; pt: prototroch; rg: refringent globule; rpn1–rpn2: right peripheral nerves 1–2