Abstract
It has been attracting Public attention that there is an increasing number of malformed sweetfish both in the river and in the cultivating farm. The author studied the external configuration of malformed sweetfish through X-ray investigation. A series of X-rayobservations was conducted by using SOFTEX X-ray machine.
The X-ray photograph showed that the malformed sweetfish had distortion in jaw bones and deficit of opercle, dorsal and ventral fins, lordosis and shorterned vertebrae throughout the entire body. The relative ratio of the body length to the head lenghth and that of the body Iength to the distance between the ethomoid and the vertical strip were smaller in thesh orterned vertebrae than in the normal sweetfish. The ratio of the head length to the headdepth was larger in the normal sweetfish than in the malformed sweetfish, while the former showed a smaller value of the head depth to the head width. Furthermore, it was observed that the malformations at the upper and lower jaws, opercle and pelvic girdle of the rnalformed sweetfish often took place almost at the same period and that the dorsal and ventral fins lost the intemeural spins and the pelvic girdle at the same time. It was also observed that the sweetfish malformed in the upper and lower jaw bones and in the ventral fin had 2 or 3 fewer vertebrae than the normal sweetfish, while the shorterned vertebra has the same number of vertebrae as that of the normal sweetfish, except for the length of vertebrae in the caudal vertebra which was shorter than that in the normal sweetfish.
