We then examined the POVL using transmission electron microscopy (Fig.
We stained larvae using the NADPH diaphorase assay, generated ultrathin sections of the POVL, and identified non-ciliary band cells that contain the diformazan product (Fig.
The ultrastuctural data indicate that there are non-ciliated cells in the ciliary band lining the POVL that possess the principal characteristic of olfactory neurons: exposure to the exterior environment.
We suggest naming the POVL that we describe herein as the adoral lobe (ADL) to (i) reflect its growth toward the mouth, (ii) distinguish it from adjacent vibratile lobes (present on some larvae), and (iii) recognize a specialized function.
Therefore, while we accept the conclusion that vibratile lobes are ancestral to crown group taxa, we do not assume here that the presence of a POVL is equivalent to the presence of an ADL.
Is there a difference in morphology between a POVL and an ADL?
Because, as in other parts of the larval body, the PTB is positioned on the ridge of the POVL, an analysis of the structural elaboration of the PTB is used as a proximate measure of overall structural elaboration of this region of the larva.
Both models suggest that structural elaboration of post-oral ectoderm is not ancestral to the Echinoidea; both models indicate that structural elaboration, and hence the POVL, has been derived independently multiple times (Fig.