Thermal resistance of Pacific white shrimp fed Sargassum filipendula: A MALDI-TOF mass spectrometry approach

Abstract

Pacific white shrimp, Litopenaeus vannamei, is a tropical species known to be intolerant to cold. In our earlier work, increased thermal shock resistance caused by Sargassum filipendula raised unanswered questions about the mechanisms responsible for this resistance. Therefore, in the present work, we used MALDI-TOF mass spectrometry (MS) to assess protein and lipid profiles of intact and lysed hemocytes from Pacific white shrimp fed 0.5% of S. filipendula and submitted to thermal shock. To accomplish this, shrimp (13.0±0.4g) were reared during 15days in 800L tanks (35 shrimps tank−1), in duplicate, under constant aeration and temperature (28.5°C), 100% of daily water exchange and feeding four times day−1. At day 16, animals were submitted to thermal shock by passing from seawater at 28.5°C to 11.5°C, where they remained for 1h, and then returning to 28.5°C. Mortality was monitored during 24h. Hemolymph of 10 animals per treatment (control and 0.5% S. filipendula) was collected before and 15min after thermal shock for MALDI-TOF MS analyses. Hemocytes were processed in both intact and lysed cells. Samples were mixed (1:1) with 2,5-dihydroxy-benzoic acid matrix for lipid analysis and sinapinic acid for protein. Shrimp fed 0.5% S. filipendula showed higher signal intensity of phosphatidylcholines with unsaturated fatty acids and lower signal intensity of lysophosphatidylcholines, after thermal shock. For proteins, S. filipendula increased signals that could be associated with antimicrobial peptides and histone H2A, whereas reduced signals were related to Cytochrome c oxidase subunits. Based on these results, it can be concluded that S. filipendula increased membrane fluidity and antimicrobial defense, diminished apoptotic signaling, and modulated DNA regulation, lipid and energy metabolism of shrimp hemocytes. These mechanisms could explain, at least in part, the higher thermal shock resistance of these shrimp fed a diet with 0.5% S. filipendula.