THE OLFACTORY ORGAN OF THE HARDHEAD SEA CATFISH, ARIUS-FELIS (L) - GROSS MORPHOLOGY AND FINE-STRUCTURE

The olfactory organ of the hardhead sea catfish, Arius felis (L.), was investigated morphologically by means of light and electron microscop y (SEM, TEM). The two rather large nostrils of each side lie close tog ether, surrounded by upstanding margins. The olfactory rosette consist s of a midline raphe with two rows of lamellae. The sensory epithelium on the lamellae is almost continuous and contains receptor cells of b oth the ciliated and the microvillous type. Ciliated non-sensory cells are scattered throughout the sensory epithelium. Accessory ventilatio n sacs are lacking. The shape, position and size of the nostrils indic ate that forward motion of the fish creates the water current through the olfactory organ (kolymbosmates). The scattered nonsensory cilia ma y aid in ventilation. The olfactory organ of A. felis differs from tha t of the other marine catfish, Plotosus lineatus, and from those of fr eshwater catfishes. The morphological differences are discussed with r espect to species-specific behavioural activities.