![stereology of the olfactory rosette in fish stereology of the olfactory rosette in fish](https://ars.els-cdn.com/content/image/1-s2.0-S2213879X14000418-fx1.jpg)
Finally, the above factors may lead the olfactory organ to have some modification in morphology, rosette structure, lamellar number and arrangement, and sensory epithelial distribution (Yamamoto 1982 Zeiske et al. 2019) and ii) pH, infective pathogens, hazard materials, and types of chemical odors as chemical factors (Ghosh and Mandal 2014) and iii) fish’s ecology (Yamamoto 1982). This organ also is a good morphological indicator to reflect aquatic habitat conditions: i) a degree of water volume, a velocity, a turbidity, and a bottom structure as physical factors (Kim et al. In fishes, the olfactory organ is an essential chemoreceptor that processes smells and deeply related to diverse ecological behaviors: prey detection, feeding, reproduction, predator risk avoidance, home recognition and migration (Hara 1986). The lamellar number and neuron’s ciliary length may be a meaningful taxonomic character for the class Petromyzonida. reissneri shows well adaptive structure of a primitive fish to slow flowing water with gravel, pebbles, and sand and a hiding habit into sand bottom at daytime. From these results, it might be considered that the olfactory organ of L. In particular, both 19 to 20 lamellae in number and olfactory receptor neuron’s quarter ciliary length of the knob diameter differ from those of P. However, the description of a pseudostratified columnar layer in the SE and Non SE is a first record, not reported in sea lamprey Petromyzon marinus. As in other lampreys, it shows same characters as follows: i) a single olfactory organ, ii) a single tubular nostril, iii) a single olfactory chamber with gourd-like form, iv) a nasal valve, v) a nasopharyngeal pouch, vi) a sensory epithelium (SE) of continuous distribution, vii) a supporting cells with numerous long cilia, viii) an accessory olfactory organ. The olfactory anatomy and histology of Lethenteron reissneri were researched using a stereo microscope, a light microscope, and a scanning electron microscope.