Int.J.Curr.Microbiol.App.Sci (2020) 9(8): 636-649 636 Original Research Article https://doi.org/10.20546/ijcmas.2020.908.071 Effect of Fucoidan of Brown Seaweeds on the Immuno-haematological Change and the Disease Resistance against Aeromonas hydrophila in Tilapia Oreochromis mossambicus V. Rani * , P. Jawahar, R. Jeyashakila and A. Srinivasan Fisheries College and Research Institute, Tamil Nadu Dr. J. Jayalalithaa Fisheries University, Thoothukudi - 8, Tamil Nadu, India *Corresponding author ABSTRACT Introduction The native seaweeds are dominantly abundant along the coast of Gulf of Mannar but are not effectively exploited either for commercial application or human health or agriculture and aquaculture purposes. Seaweed products like k-carrageenan and liquid fertilizer have received greater demand in the market, after the culture practice of exotic red seaweed, Kappaphycus alverazii has witnessed a positive sign as through implementation by self-help groups rather than corporate farms (Mantri et al., 2017). Among the three major groups of seaweeds, brown seaweeds contain more biological properties compared to red and green seaweeds (Seafood Plus, 2004) and specifically used to produce polysaccharides International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 9 Number 8 (2020) Journal homepage: http://www.ijcmas.com An experiment was conducted to study the influence of dietary fucoidan from brown seaweeds viz., Padina tetrastromatica and Sargassum oligocystum on the innate immunity and disease resistance of fish Oreochromis mossambicus. Fucoidan was supplemented with fish feed at different concentrations such as 0.1, 0.2 and 0.3% to observe hematological changes and non-specific immunological properties for a period of 60 days. The results indicated that fucoidan supplemented diet had no significant effect on hematological changes whereas, the lysozyme activity was significantly increased in the fishes fed with fucoidan of P. tetrastromatica (4012 ± 2198 IU ml -1 ) on 30 th day and S. oligocystum (2412 ± 221 IU ml -1 ) on 15 th day at 0.2% and 0.3% concentration, respectively. NBT activity was found to be highest at 15 th , 30 th and 45 th days in fishes fed with 0.1, 0.2 and 0.3% of fucoidan derived from P. tetrastromatica. The results stated that the fucoidan derived from S. oligocystum has relatively lower lysozyme and NBT activity than from P. tetrastromatica but higher than the control. The fish O.mossambicus challenged with A. hydrophila, feeding offucoidan extracted from the seaweeds invariably increased the survival upto 75%, 80% at 0.2 and 0.3% and 65, 70% respectively than the control. Keywords Brown seaweeds, fucoidan, Hematological changes, Innate immunity, Oreochromis mossambicus, Aeromonas hydrophila Accepted: 10 July 2020 Available Online: 10 August 2020 Article Info