Effect the seaweed Sargassum filipendula and Ascophyllum nodosum on the resistance of the shrimp Litopenaeus vannamei to hypothermal shock

This study investigated the resistance of Pacific white shrimp (L. vannamei) to hypothermal shock when treated with extracts from the brown seaweeds Sargassum filipendula and Ascophyllum nodosum, either by immersion for postlarvae or as a dietary supplement for juveniles. Post-larvae were exposed to seaweed extracts at concentrations of 20, 50, 100, and 200 mg*L⁻¹, while juveniles were fed diets with 0.5%, 2.0%, and 4.0% seaweed extracts for 10 days. For juveniles (~12 g), hemato-immunological and microbiological analyses were conducted after feeding with 5% seaweed diets for 15 days, all followed by hypothermal shock. Samples were collected prior to the start of thermal shock, immediately after shock (0 h), and 1 and 24 h after return to initial temperature. The aqueous extract of the seaweeds A. nodosum and S. filipendula at concentrations 100 mg*L⁻¹ and 200 mg*L⁻¹, respectively, improves the survival rates of post-larvae L. vannamei submitted to hypothermal stress. For juvenile shrimps, hypothermal shock causes significant immunodepression and reduces the bacterial community in the intestine. The addition of seaweed to the feed did not increase the survival rate and did not affect the intestinal microbiota of L. vannamei. In the case of immunological parameters, both species positively affect the agglutination titer, but no other parameters analyzed.