A histological description of intersexuality in the roach

This paper is an illustrative guide to intersex in the roach Rutilus rutilu s, based on 150 intersex individuals. Most intersex roach had female germ c ells, or oocytes, within a predominantly male gonad (testis), and/or malfor med/intersex reproductive ducts. The number, pattern and developmental stag e of oocytes within testicular tissue in intersex fish varied greatly. In m ost intersex fish, a few primary oocytes, or numerous primary and secondary oocytes, were scattered randomly throughout the testicular tissue (multifo cal intersex). In other, more severely feminized individuals, large areas o f ovarian tissue were separated clearly from testicular tissue (focal inter sex). Almost all intersex individuals had a female-like reproductive duct ( ovarian cavity). In mild cases of intersex (in which the majority of the ge rm cells were male) the ovarian cavity was present together with the male s perm duct/vas deferens, whilst in certain severe cases, the sperm duct was absent or vestigial. (C) 2001 The Fisheries Society of the British Isles.