Cinnamaldehyde as a stimulant of the immune system of shrimp: Fighting against luminescence.

 Luminous vibriosis outbreaks caused by Vibrio species are among the major causes of mortality during shrimp larvae culture. Cinnamaldehyde is quorum sensing-disrupting compound that reduces virulence in Vibrio spp. The aim of this research was to evaluate cinnamaldehyde effects on Penaeus vannamei early postlarvae undergoing a luminous vibriosis outbreak under hatchery conditions. First, we determined the toxicity of cinnamaldehyde to larvae and postlarval stages. Further, we used doses that were 15 times lower than the LD50 in a luminous vibriosis outbreak at a shrimp hatchery. We determined that the LD50 of cinnamaldehyde at the Protozoea I (7.70 µM) and Mysis I stage (6.78 µM) were lower ( P <0.05) than the LD50 at postlarval stages (28.97-30.94 µM). In a luminous vibriosis outbreak at shrimp hatchery, postlarvae that received cinnamaldehyde treatment had a higher survival rate (35.8 ±15.4%) than the postlarvae without cinnamaldehyde treatment (20.6 ± 6.4%). We also observed the disappearance of luminescence in 90% of the tanks treated with cinnamaldehyde within 24 h; however, the tanks without treatment stayed luminescent for at least 4 days. We demonstrated that cinnamaldehyde at 760 µM was unable to inactivate Vibrio spp., indicating that its application in aquaculture systems, at a much lower concentration, might depend on its QS disrupting trait instead of its antimicrobial effect. One dose of cinnamaldehyde stimulated the shrimp immune system, with the highest values being registered 12 hours after the treatment. To our knowledge, this is the first report to demonstrate that a quorum-sensing disruptor protects shrimp postlarvae from luminous vibriosis infection and stimulates shrimp postlarvae immune system. .