Comparative morphology (SEM) of the peripheral olfactory organ in the Oxudercinae subfamily (Gobiidae, Perciformes)

The Oxudercinae (Gobiidae, Perciformes) is a young, monophyletic subfamily of specialized actinopterygians that inhabit the tidal zone. They include species adapted for periodic life out of water and also typically aquatic species. Despite close phylogenetic affinities, many differences have been described even between species from the same genus (e.g. gill modification among the various species).This study compares the structure of olfactory organs in six amphibious oxudercines: Periophthalmus argentilineatus, Periophthalmus minutus, Periophthalmus chrysospilos, Periophthalmus variabilis, Boleophthalmus boddarti, Scartelaos histophorus, and one aquatic species, Parapocryptes rictuosus. The nasal cavity in each studied species consists of a tube-like elongated canal widening to a chamber-like sac/s in the preorbital part of the head. Differences among species occur in the shape, diameter and course of the tube-like canal, the number of accessory nasal sacs, and the distribution of olfactory sensory epithelium within the sensory area. The structure of the olfactory organ may be considered as an exaptation protecting the olfactory epithelium since an analogous structure is also present in typically aquatic species.