Docosahexaenoic acid (DHA); a driving force regulating gene expression in bluefin tuna (Thunnus thynnus) larvae development.

This study elucidated the role of DHA-modulated genes in the development and growth of bluefin tuna (Thunnus thynnus) larvae ingesting increasing levels of DHA in their rotifer prey. The effect of feeding low, medium, and high rotifer (Brachionus rotundiformis) DHA levels (2.0, 3.6 and 10.9 mg DHA g-1 DW, respectively) was tested on 2-15 days post hatching (dph) bluefin tuna larvae. Larval DHA content markedly (P < 0.05) increased in a DHA dose-dependent manner (1.5, 3.9, 6.1 mg DHA g-1 DW larva, respectively), that was positively correlated with larval prey consumption, and growth (P < 0.05). Gene ontology enrichment analyses of DEGs demonstrated dietary DHA significantly (P < 0.05) affected different genes and biological processes at different developmental ages. The number of DHA up-regulated DEGs was highest in 10 dph larvae (408), compared to 5 (11) and 15 dph fish (34), and were mainly involved in neural and synaptic development in the brain and spinal cord. In contrast, DHA in older 15 dph larvae elicited fewer DEGs but played critical roles over a wider range of developing organs. The emerging picture underscores the importance of DHA-modulated gene expression as a driving force in bluefin tuna larval development and growth. Overall design: To evaluate the function of DHA on the development and growth of Blue-fin tuna larvae, we fed BFT larvae with enriched rotifers at 3 doses of DHA (2.0, 3.6 and 10.9 mg DHA g-1 DW) and evaluated larval ingestion rates, growth and whole-larvae transcriptome at 5, 10 and 15 days post hatch.