High temperature treatment causes complete loss of germ cells in the ovaries leading to permanent sterilization in Nile tilapia. Histology of ovaries of the 9-dah group
fish exposed to control and 37C. (A) Histology of the control fish ovary after 45 days of treatment, with ovarian cavity and few oocytes at the perinucleolar stage. (B)
Histology of the section of 37C treated fish ovary after 45 days of treatment, with complete absence of germ cells. (C) Magnified version of (B) (inset). (D) Ovaries of control
fish with mature oocytes after extended rearing in the water at normal temperature for 6 months. (E) A section of the control fish ovary. (F) A section of the control fish ovary,
showing Vasa immunopositive reaction on germ cells. The arrowheads indicate the immune-reaction. (G) Ovaries of 37C treated fish after extended rearing in the water at
normal temperature for 6 months. (H) A section of the 37C exposed fish ovary, with complete absence of germ cells. (I) A section of the fish treated at 37C for 45 days,
showing no immunopositive reaction to Vasa indicating absence of germ cells. PO = oocytes at the perinucleolar stage; OC = ovarian cavity; VO = oocytesat the vitellogenic
stage; SC = steroid producing cells. Scale bars represent 20lm.