2016 Volume 51 Issue 1 Pages 8-14
Pathogenic studies using model animals for diseases that are found in similar diagnosis as in humans are widespreading and medaka fish Oryzias latipes is one of such animal models, however, histological studies on their diseases are still limited. In this study, we applied whole body serial tissue sectioning to adult medaka; it is similar to whole body computed tomography (CT) scanning to decide the lesion (s) location, furthermore, it can give us more precisely microscopic histological information. When adult medaka collected from a wild population were examined, we found cystic lesion (s) in their testis with a diameter of about 500 μm, filled with serous material. Because each of cysts was covered with epithelium, the lesion was found to be a true cyst. Cysts with the same histological appearance were also found adjacent to ovary and liver, and some of the medaka showed polycystic condition. This condition was seen at a high frequency in wild medaka, but it had not been found in laboratory-reared medaka. Although number of observations is small for giving conclusion, these results suggest that cysts could be a common lesion in wild medaka and whole body sectioning can be a powerful methodology for pathological examination of model animal like medaka.
