An evidence of intersex males in Jajroud River Loach, Oxynoemacheilus bergianus (Derjavin, 1934)

In the present study, JajroudRiverloach, Oxynoemacheilus bergianus (Derjavin, 1934), was examined monthly for a previous observation of oocyte presence within testes tissues. Accordingly, the gonad development in O. bergianus is examined histologically. Although our data show typical fish gonad development and differentiation in female and some male individuals, some males show intersexuality. Gonad histology and development of females’ ovaries were carried out to provide comparative data on oocyte staging in testes. Intersex males were observed throughout the year except in March and July, especially in individuals larger than 5.3 cm total length. Occurrence of intersex males seems to be associated with sex ratios and their deviation from 1:1 and fish age at different times of the year. As no real ovotestes were observed, histological changes were considered to be a transient stage in the testicular tissue with no evidence of sex change in fish. In the absence of testes fully transformed to ovaries, this type of change was considered as intersex.