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HISTOLOGY OF GONADS IN Tilapia zillii (GERVAIS) FED - page 2 / 8





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medicine for various therapeutic purposes, anti-bacterial, anti-fungal, anti-viral and anti-fertility properties (Jegede & Fagbenro, 2007) and phytochemical analyses showed that the neem tree has more than 100 unique bio-active compounds, among which is sodium nimbinate which has potential applications as spermicide in animal care and for even regulating human fertility (NRC 1992).

Neem oil as a vaginal contraceptive inhibits the spread of micro-organisms including Candida albican, Candida tropicalis, Niesseria gonorrhoea, herpes, simplex-2 and HIV-1 as well as resistant strains of E. coli and Staphylococcus aureus, in part by boosting immune-system activity in vagina (Shakli et al.,1990). Sinna and Riai (1985) reported that Rhesus monkey and human spermatozoa became totally immobile within 30 seconds of contact with undiluted Neem oil. In vivo studies in rats (20), rabbits (8), Rhesus monkeys (14) and human volunteers (10) proved that Neem oil applied initially before sexual intercourse prevents pregnancies in all species. Neem oil also has anti implantation/abortifacient effect in rats and rabbits if applied initially on day 2-7 of expected pregnancy.

Tilapias are yet to reach their full aquaculture potential because of the problems of precocious maturity and uncontrolled reproduction, which often results in the overpopulation of production ponds with young (stunted) fish. Population control in farmed tilapias has been reviewed by Guerrero (1982), Mair and Little (1991) and Fagbenro (2002). Such control methods include monosex culture, sex reversal by androgenic hormones, cage culture, tank culture, the use of predators, high density stocking, sterilization, intermittent/selective harvesting, and the use of slow maturing tilapia species, among others. However, all these population control methods have their limitations; e.g. the use of reproductive inhibitors, such as irradiation, chemosterilants has disadvantages which are: expensive technology, hatchery facilities and skilled labour are required and hormones are expensive and difficult to obtain. There is need therefore to examine less expensive and appropriate technology to control unwanted/undesirable tilapia recruitment in ponds using natural reproductive inhibitory agents occurring in some plants.

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