Effect of Sargassum wightii fucoidan on growth and disease resistance to Vibrio parahaemolyticus in Penaeus monodon post-larvae

Abstract

The polysaccharide – fucoidan was extracted from brown seaweed Sargassum wightii and its antibacterial activity was screened by agar well diffusion method. The maximum zone of inhibition observed was 15.66 mm in 20 mg mL−1 concentration against Vibrio parahaemolyticus. The Minimum Inhibitory Concentration (MIC) of the fucoidan was 12 mg mL−1 against V. parahaemolyticus. The fucoidan was then enriched with Artemia nauplii at four different concentrations such as 100, 200, 300 and 400 mg L−1 for 12 h. The enriched Artemia nauplii were fed to Penaeus monodon post-larvae for 20 days and the growth performance was assessed. The weight gain and SGR of the control group were 0.2432 g and 15.78%, respectively. But, in experimental groups fed with fucoidan enriched Artemia nauplii, the weight gain and SGR were increased and were respectively ranged from 0.2602 to 0.3161 g and from 16.11 to 17.05%. The P. monodon post-larvae were challenged with V. parahaemolyticus for a period of 30 days showed a reduction in mortality percentage of experimental groups over the control group and it was ranged between 36.97 and 89.86%. During the challenge test, the V. parahaemolyticus load was also enumerated from the infected shrimp at every 10 day intervals. In the control group, the Vibrio load showed a linear increase in hepatopancreas and muscle tissues from 10th to 30th days of challenge test, whereas in the experimental groups, the Vibrio load established a declining trend with the advancement of challenged test.