Effects of varying dietary levels of <i>Carica papaya</i> seed meal powder (PSM) on growth and histology of gonads in <i>Oreochromis niloticus</i> larvae

Abstract

Sex control in tilapia should provide an invaluable benefit to aquaculture. The effects of different dietary levels of papaya carica seed meal powder on growth and gonad histology in Oreochromis niloticus larvae were studied to prevent early maturity and uncontrolled spawning. Four (4) dietary level of seed meal powder, varying from 0 g.Kg^–1 as a control; 1 g.Kg^–1; 2 g.Kg^–1 to 3 g.Kg^–1 were each tested in triplicate. The diet were isonitrogenous and were fed to twelve (12) experimental groups of 110 larvae weighing 0.019 g at a feeding rate of 4% body weight, three times a day for 30 days with the experimental diet and then after fed with the basal diet for other 60 days of the experiment. At the end of the experiment, 24 fish from all replicates were randomly sampled, slaughtered and dissected to remove testicles and ovaries. Testicular and ovarian sampleswere fixed in 10% buffered formalin for 24 h before the histological process. After 90 days of experiment, fish weight increased from 0.019 g ± 0.09 to 32.47g ± 0.02; 30.40g ± 0.05; 34.68 g ± 0.07 and 33.83 g ± 0.09 respectively for C. papaya dosage of 0; 1; 2 and 3, respectively. In fish treated with 0 and 1 g.Kg^-1 of PSM, the testes showed different stages of spermatogenesis with germ cells moving up to the spermatozoa. Similarly, the ovaries showed follicles at different stages of folliculogenesis up to vitellogenesis. The main lesional changes observed concerned the testicles of fish fed with 2 and 3 g.Kg^-1 PSM with in particular the scarcity of germ cells and spermatozoa. For females, the only observations concern vitellogenesis which are important for treatment doses of 0 and 1 g.Kg^-1, while they decrease in the group treated with 3 g.Kg^-1.

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Keywords: Papaya seed meal powder, Performances, Gonads histology, Oreochromis niloticus