Histopathological effects of environmental pollutants beta-HCH and methyl mercury on reproductive organs in freshwater fish.

From various environmental pollutants studied so far, specific effects on the reproductive system of small fish species Poecilia reticulata (guppy) and Oryzias latipes (medaka) were noted in the case of beta-hexachlorocyclohexane (induction of vitellogenesis and hermaphroditism, both indicative of estrogenic activity; 32 micrograms/l) and methyl mercury (impaired spermatogenesis; 1.8 micrograms/l). The latter effect was attributed to a disturbance of mitosis.

Sexuality and hermaphroditism in fishes. I. Synchronous functional hermaphroditism in the serranid fish Serranus scriba L.

Anatomical and histological examination of Serranus scriba L. showed the existence of primary females (67%), hermaphrodites (31%) and primary males (2%). Synchronous functional hermaphroditism is described on the basis of an anatomical and histological study of the gonads. Although they function simultaneously, the testicular and ovarian parts of hermaphrodite gonads have completely separate ducts. Females and hermaphrodites have the same annual reproduction cycle. In hermaphrodites, the testicular part matures one month sooner than the ovarian part. Cross fertilization between primary females and hermaphrodite individuals and between two different hermaphrodites probably occurs, while self-fertilization is less likely. The testicular tissues of primary males are of the acinar type and those of hermaphrodites are of the radial type. It is possible that primary males do not take part in reproduction. Serranus scriba in Egyptian Mediterranean waters is a longperiod spawner, which spawns from June to the end of October, i.e. it is a summer-autumn spawner.