الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
The testis-ova or ovo-testis is the presence of female germ cells, or oocytes, within male gonads, it has been used as biomarker for detecting xenoestrogens exposure.
Two screening experiments in 2011 and 2012 were performed to detect signs of estrogenic compounds on male Nile tilapia O. niloticus fish inhabit Lake Manzala. Experimental samples were collected from five drainage endpoints areas 1) El-Bashtir, 2) El-Gamil, 3) El-Inaniya, 4) El-Sirw, and 5) El-Temsah where water was contaminated with different mixture of industrial, domestic and agriculture pollutants. In addition, Nile tilapia males were exposed to three different concentrations of estrogen like compound nonylphenol ethoxylate as a laboratory experiment. The contamination dosages of nonylphenol ethoxylate (NPE) were 25, 50 and 100 μg/l administrated for 126 days in rearing tanks, to be comparable with the data obtained from the above-mentioned locations. Eighteen to twenty wild male samples were dissected; both gonads and liver were taken the GSI and HSI was calculated and processed for histological examination.
The presence of oocytes within the testicular tissue was explicit; hence, severity index (0-4) was developed based on the number of oocytes per testicular tissue section. The number of histological section examined to clearly detect intersex in tilapia was 4-6 section per fish during the two sampling seasons; likewise, were done for the lab experiment. from each histological section, three microscopic fields were examined to determine the developmental stage in each fish; and 100% of the three sections were examined for the presence of tests-ova.
In the survey part, staging males gonads showed stages II Early spermatogenesis to stage IV Late spermatogenesis of normal histological development of the testes. Testes-ova (To) were found in all collection sites and most collected samples in both seasons with different occurrence percentage and severity. Although, females showed seasonal differences in the first season; stage (VI) spent of normal histological development of the ovaries appeared to be the common stage with almost 100% of the collected samples. Stages (III) cortical alveoli formation to stage (V) Ripe, where detected in the second season with almost all cases. A few atretic oocytes were found in both seasons due to seasonal differences and the multi-cyclic reproductive pattern of tilapia. In lab experiment, the percentages of testis-ova calculated from individuals of the experiment were 10, 28 and 50% for the treated groups 25, 50 and 100 µgl-1, respectively. Furthermore, severity on all examined samples in the lab experiment were minimal to mild (1-3 testis-ova/section). Where, overall severity was mild for 25 µgl-1 group and minimal for 50 and 100 µgl-1 groups.