Study of the olfactory epithelium in the developing sturgeon. Characterization of the crypt cells

In acipenserids, crypt cells (CCs) have only been observed in juvenile specimens, and it has not been clarified whether they differentiate along with olfactory receptor neurons (ORNs) during the lecithotrophic stage or during later development stages. Furthermore, no detailed optical microscopy (OM) or electron microscopy study on the development of CCs has been published to date. In the present study, we used OM and electron microscopy to follow the development of CCs in Acipenser naccarii from hatching to the establishment of exogenous feeding. Based on these observations, we can affirm that CCs are present from the first few posthatching (PH) days. CCs appear with their nucleus close to the basal lamina of the epithelium and enveloped by supporting cells. In addition, from the beginning of day 2 PH, we observed cells with highly similar characteristics to those of CCs (absence of knob, abundant mitochondria and filamentous material in apical cytoplasm, numerous microtubules, and envelopment by supporting cells) but with cilia still remaining on their noninvaginated apical surface. We conclude that these cells may correspond to immature CCs in which the crypt, the final feature of their morphological differentiation, has not yet formed.