Transcriptomic analysis and differential gene expression of the effects of diet and temperature in Gammarus locusta fed alternative terrestrial feeds

Gammarids and their biomass are emerging as promising candidates for the production of high-nutritional-value ingredients to replace marine ingredients derived from wild-capture fisheries. Optimising culture conditions, such as diet composition and environmental temperature, is essential to maximise both biomass yield and nutritional quality. This study evaluated the transcriptomic responses of Gammarus locusta subjected to alternative terrestrial diets (Carrot and Coconut vs. marine Fucus sp. control) in Experiment 1 and thermal gradients (5, 10, 15, and 20 °C) in Experiment 2. Using a newly assembled reference transcriptome, we performed differential gene expression (DGE) analysis to identify genes involved in lipid and fatty acid metabolism, as well as ecdysis and development. Our data indicate that alternative terrestrial diets were related with shifts in transcript abundance for key genes involved in fatty acid catabolism and transport. Concurrently, elevated rearing temperatures were associated with the upregulation of neuroendocrine and metabolic transcripts that parallel accelerated growth rates, yet coincide with reduced long-term survival. Overall, the findings from the present study provide novel candidate molecular markers for evaluating gammarid physiological status, offering an exploratory framework to aid the optimisation of sustainable culture practices for aquaculture feed applications.