Oral administration of sulfated polysaccharides from Gracilaria caudata rhodophyta on tilapias post-larvae survival
Abstract
Immunostimulant agents such as sulfated polysaccharides (SP) from marine algae have been widely used to minimize stress in cultivated aquatic organisms. The objective of this work was to evaluate the effect of oral administration of SP extracted from the red marine algae Gracilaria caudata in the Nile tilapia, Oreochromis niloticus, on post-larvae (pl) survivals after the hormonally induced sexual reversion. SP were incorporated in fish ration prior the addition of synthetic androgen 17-a-methyl-testosterone which was administered to the pl's at doses of 0.05; 0.1 and 0.2 mg g-1 of pl's live weight during 28 days. Each treatment was carried out in triplicate. In the last 5 days after SP administration, severe stress was induced by removal of water aeration and renewal. Results showed that pl's survival rates at the end of the experiment were significantly higher (p < 0.05) in 0.1 and 0.2 mg g-1 doses. This study revealed that small doses of SP from marine algae G. caudata incorporated in tilapia ration were probably the main cause to increase survival rates hormonally induced sexual reversion.
