The effect of commercial, natural and grape seed extract supplemented diets on gene expression signatures and survival of greenlip abalone (Haliotis laevigata) during heat stress

Summer mortality is a phenomenon associated with high temperature water spikes that can result in mass mortalities of abalone and other molluscs. This is a particular concern for aquaculture industries due to the economic impacts of such events. Diets containing algal supplements have been suggested as pre-emptive solutions for preventing these mass mortalities. The same has also been suggested for diets containing grape seed extract. This is due to their potential as a source of antioxidative compounds, which reduce the accumulation of harmful reactive oxygen species. This study aimed to identify functional genes associated with high survival in abalone fed diets high in antioxidative compounds during heat stress. Tentacle transcriptomes of 40 greenlip abalone (Haliotis laevigata) were investigated to determine the combined effects of differing diets and temperature on the gene expression responses by abalone. Here we compare the functional gene expression changes at 22 degrees C and 25 degrees C in abalone fed common commercial, live macroalgal (Ulva lactuca) and grape seed extract supplemented commercial diets as a means to understand the resulting high survival of abalone fed grape seed extract during heat stress. Twenty-four genes were differentially expressed between high survival promoting diets (macroalgae or grape seed extract supplemented commercial) relative to the purely commercial diet. Many of these genes have been suggested to be involved in antioxidant and innate immunity responses. The identification of these genes and their functional roles has enhanced our understanding of processes that contribute to summer stress resilience in abalone. Our study supports the hypothesis that diet and gene expression signatures may be indicative of the survival capabilities of abalone when exposed to heat stress.