melanostomus (Teleostei: Gobiidae)

ABSTRACT This first comprehensive study of the pe-ripheral olfactory organ from a representative of the large and economically important order of teleost fishes, the Perciformes, shows a compact structure with olfactory sensory neurons distributed widely throughout the olfac-tory chamber. The spatial organization of the nasal cavity in the bottom-dwelling round goby (Gobiidae, Neogobius melanostomus) was examined using impression material injection, immunocytochemistry, and transmission elec-tron microscopy. The olfactory chamber contains a single olfactory lamella; prominent dorsocaudal lachrymal and ethmoidal accessory nasal sacs are situated ventrocaudal to the chamber. The location of the olfactory mucosa within the olfactory chamber is novel for teleost fish, as it extends beyond the ventral surface to the lateral and dorsal regions. Microvillar olfactory sensory neurons and ciliated olfactory sensory neurons were identified by transmission electron microscopy and the spatial distribu-tion of these two cell types was assessed through immu-nocytochemistry against olfactory receptor coupled G-proteins. Both Golf-immunoreactive ciliated olfactory sensory neurons and the Go-immunoreactive microvillar form were located throughout the olfactory epithelium. Ciliated crypt cells were Go immunoreactive and were found throughout the olfactory epithelium of some speci-mens. The widespread occurrence of olfactory sensory neurons in the olfactory chamber supports the idea that olfactory signaling is important to the survival of the round goby. The prominence of the lachrymal and eth-moidal accessory nasal sacs indicates the capacity to reg-ulate the flow of odorant molecules over the sensory sur-face of the olfactory sensory neurons, possibly through a pump-like mechanism driven by opercular activity associ-ated with gill ventilation. J. Morphol. 257:62–71, 2003