Comparative Morphology Of The Olfactory Organs In Several Fish In Perciformes And Synbranchiformes

In the present study, olfactory organs of one single-nostril type (Tiliapia), and four double-nostril type (Pseudosciaena crocea, Terapon jarbua, Nibea albiflora and Mene maculata) were studied by some common methods of anatomy and histology. Based on our previous results which indicated the special pattern of olfactory organs, the results were proved again and the anatomic structure and histological structure of Monopterus cuchia which was congener with Monopterus albus was intensively studied for the comparation with that of M. albus. The main results were shown below:1. In Tiliapia, the olfactory sac clinged the bottom of olfactory cavity, and connected with outside through the single-nostril. The olfactory rosette in olfactory sac was composed with14-19primary lamellae, while no secondary lamellae was found. The major diameter of olfactory rosette was smaller than the eyes diameter, this may because that the activities like foraging of visual-fishes was not depends on olfactory organ but the visual organ. There were two accessory sacs connecting with each side of the olfactory cavity, and the expansion and compression of them were caused by the companding of mandibles. The histology showed many cilia on the surface of olfactory epithelium. The SEM showed that the sensory area and non-sensory area of olfactory lamellae surface was interleaving distributed. The sensory area was covered with cilia, while the surface of non-sensory area was fingerprine construction.2. There were several resemblance on the double-nostril type fish in this study (P. crocea, T. jarbua, N. albiflora and M.maculata). For example, the anterior nostril and the posterior nostril was connected, the posterior was larger than the anterior one, the anterior one is inhalant and the posterior one is exhalant; Only one olfactory rosette was found in each olfactory sac;The four species double-nostril type fishes were visual-fishes, whose major diameter of olfactory rosette was smaller than the eye diameter; In general, the number of primary olfactory lamellae of the same species increased with the bodylength growth; Two independent olfactory nerves stretched from the undifferentiated olfactory lobe connected with the olfactory rosette. The orbit diameter of the four fishes were all greater than the major diameter of olfactory rosette indecating that they were visual-fishes. In general, these fishes were the same with others in morphological structure of olfactory organ. Besides, differences were also existed. For example, the shape of posterior nostril, were meniscus, triangle, oval and long linearity-shaped respectively; The nose valve existed in both the anterior nostril and posterior nostril in T. jarbua, while no nose valve was found in both anterior and posterior nostril in M. maculata, and the existance of nose valve in P. crocea and N. albiflora were only found in posterior nostril; The four speices were also different in the shape of olfactory rosette, which shaped in oval of P. crocea, while in short ellipse of T. jarbua, and shaped in long ellipse of N. albiflora and M. maculata.The shape of raphe were still differednt, it shaped in bottle of P. crocea, while it shaped in spindle of N. albiflora and pin of T. jarbua and M. maculata.3. In this study, the important discovery in the olfactory organ of M. albus was approved again. And also indicated the resemblance on olfactory organ between M. albus and M. cuchia including that the anterior nostril was not pass through posterior nostril in M. cuchia, the olfactory sac shaped in cryptomere and occupied only little space in nasal pit, and there no any olfactory lamellae in their olfactory sac, but has a olfactory accessory sac. All the structure characters were same as the case of M. albus. Furthermore, the end of olfactory sacs both connected with the olfactory nerves according to the anatomy, but histology showed that no substantiality connection existed between them. In fact, it was only connected each other with connective tissue and olfactory nerve fiber, and this was the obvious different from M. albus. The two olfactory nerves were parallel in M. cuchia, instead, in M. albus the olfactory nerves were combined. In addition, in M. albus, left nasal pit are not pass through right one, but left one pass through right one in M. cuchia. It was indicated that both M. albus and M. cuchia were much different from other fishes in the morphological structure. The special evolvement happened on the olfactory organ of both M. albus and M. cuchia might be a special adaption to their living environment.