STUDY ON THE MORPHOLOGY AND ULTRASTRUCTURE OF THE INNER EAR OF OREOCHROMIS SP.

This paper deals with the morphological structure of the inner ear of anonostariophysine fish, Oreochromis sp,from the lake of Xiamen University,using light andscanning electron microscopy.The results are as follows;1. The structure of the ear in Oreochromis sp. is the same as that of“the typical teleostear”. which consists of three semicircular canals(anterior,posterior and horizontalsemicircular canals)and three otolithic organs(utriculs,lagena and sacculus).Each fish hastwo ears between which no connection was obesrved.The bilateral mirror symmbtry of eachsaccular pair often involves divergence of the anterior ends 25-30°away from thebody-midline.2.The sacculus is particularly large and utricular-shaped, with a single large otolith fil-ling the whole otolithic sac,The saccular otolith is a laterally flattened elipsoid with a deepmedial sulcus with which the sensory epithelium is closely connected.The lagena is generallysmall and round in shape with a small and thin triangular otolith filling only half of thesacculus.The utriculus is irregular in shape. The utricular otolith is also small and has roughsurface,filling only a small part of the sacculus;3.The otolithic membrane is a thin gelatinous structure lying between the macula andthe otolith,contacting all the sensory cellshcluding those in regions not directly“undcf”theotolith.The membrane has a large number of small holes where the ciliary bunddles extendand contact the otolith.4.The results of scanning electron microscopy reveal that the maculae consist of sensoryeells and supporting cells and the surface of the sensory epithelia of each of the otolithic organs is distributed with a lot of ciliary bundles in a certain pattern. There are mainly threetypes of three ciliary bundle F1, F2 and F3.in the inner ear organs of the Oreochromis sp. Each otolithic macula can be divided into a number of regions within which all the ciliarybundles are morphologically polarized in the same two in lagenar macula and two in utricularmacula,Morphologically,the utricular macula is dish-shaped and has a lateral extension,the lagenar macula is the shape of a fat crescent and the saccular macula is elongate but widerat the rostral than the caudal end, like the shape of a tadpole.