Effects of a novel marine probiotic, Lactobacillus plantarum AH 78, on growth performance and immune response of Nile tilapia (Oreochromis niloticus).

AIMS: Evaluation of the efficacy of marine lactic acid bacteria, Lactobacillus plantarum AH 78, on growth performance and immune response of Nile tilapia (Oreochromis niloticus) challenged with Aeromonas hydrophila. METHODS AND RESULTS: Marine probiotic, Lact. plantarum AH 78, was incorporated in Nile tilapia diets at 0·0, 0·5, 1·0 or 2·0% (w/w). The diets were fed to juvenile Nile tilapia for 40 days, after which they were challenged with pathogenic bacterium, Aer. hydrophila. The best growth rates and feed efficiency were obtained at 0·5% probiotic, while fish survival was not affected by dietary probiotic. After challenge with Aer. hydrophila immunological responses and survival were recorded at 1·0% probiont. Likewise, significant up-regulation of the expression of cytokine genes, IL-4, IL-12 and IFN-γ, in fish livers was found at 1·0% probiont, compared to the control diet. Concomitantly, AH 78 colonized the intestinal mucosa of treated fish, even after reverting to the control diet, and remained viable in the feed stored at 4°C up to 12 months. CONCLUSIONS: Marine Lact. plantarum AH 78 at 0·5-1·0% inclusion level conferred the best performance and immune response of Nile tilapia challenged with Aer. hydrophila. SIGNIFICANCE AND IMPACT OF THE STUDY: Marine Lact. plantarum AH 78 could be considered as a potential probiotic to control disease outbreaks in farmed Nile tilapia.

Structural and functional effects of early exposure to 4-nonylphenol on gonadal development of Nile tilapia (Oreochromis niloticus): a-histological alterations in ovaries.

The present study investigated the gonads alterations of mature female Oreochromis niloticus caused by different concentrations (0, 40, 60, 100 µg/L) of 4-nonylphenol (NP) and also its effect on steroidogenesis. A tendency for a dose-dependent reduction in the gonadosomatic index, fecundity and oocytes diameter in the NP-exposed groups was observed. Histological examination revealed that NP impairs gonadal growth clearly shown in the oocyte development and differentiation. Also, the estrogenic activity of such NP was identified through 11-ketotestosterone, 17b-estradiol and vitellogenin which were affected significantly by the applied concentrations. The study indicates that NP has estrogenic potency-induced marked alteration in the sexual development including gonadal maturation, spawning time and egg production.

Structural and functional effects of early exposure to 4-nonylphenol on gonadal development of Nile tilapia (Oreochromis niloticus): b-histological alterations in testes.

The present study investigates the effects of different doses (0, 40, 60, 100 µg/L) of 4-nonylphenol (NP) on testis histology and sperms motility of mature Oreochromis niloticus. A tendency for a dose-dependent reduction in the gonado-somatic index (GSI) in the NP-exposed groups was observed. Histological examination revealed that high doses of NP (60 and 100 µg/L) cause hyperplasia of interlobular connective tissue components coincide with decrease in the size of seminiferous lobules and amount of lumen spermatozoa in comparison with the control and low-dose (40 µg/L)-exposed groups. In addition, within the seminiferous lobules, rupture of spermatogenic cysts, vacuolation and necrosis of primary spermatocytes due to damage of sertoli cells were clearly observed and lead to decrease in advanced spermatogenic cells. The highest dose caused significant decrease in the GSI associated with appearance of testis-ova (intersex) state. The percentage of abnormal sperms increased with increasing the dose of NP reaching to 96 % for those subjected to 100 µg NP/L, while it was only 11 % for the control group specimens. The study indicates that NP has estrogenic potency induced marked alteration in the sexual development including inhibition in testicular growth and deformation in the sperms.