Transition to the doliolaria larva
During the transition from the auricularia to the doliolaria
larva, the ciliary band nerve tracts moved together with the
rearranging ciliary bands. The ciliary band nerve tracts retained
prominent immunoreactivity throughout the rearrangement, and
unlike the ciliary bands, they remained continuous and were not
segmented (serotonergic immunoreactivity is shown in Figs.
4A, B). The rearrangement was asymmetrical, especially at the
ventral side. The right anterior ventral ridge nerve tract curved
toward the ventral midline, whereas the left tract became
relatively straight (Fig. 4A). This will result in an asymmetrical
formation of the second ciliary band nerve tract in the doliolaria
larva (see Figs. 5, 6). The postoral and posterior ventral ridge
ciliary band nerve tracts elongated anteriorly, shifted to the left
(Fig. 4B). The cell bodies along the ciliary band nerve tracts
also retained serotonergic immunoreactivity and moved together
with the tracts during the transition (Fig. 4C). Immunoreactivity
to monoclonal antibody 1F9 was observed at the ciliary
band nerve tracts but not in the serotonergic nerve cell bodies
along the tracts (Fig. 4D).