Fatty-acid and energy content of Maja brachydactyla eggs at different developmental stages (recently spawned, half-developed and ready to hatch) were analysed in order to understand what is being consumed and produced during the embryonic development. Egg volume increased during development (34%, 0.187 to 0.285 mm3, N = 270) and was negatively correlated with egg energy and fatty-acid content (r = −0.80 and r = −0.46, respectively), which decreased through embryogenesis. The most consumed fatty acids were the PUFA (21.2 μg · mg dw−1), followed by the SFA (18.8 μg · mg dw−1) and MUFA (14.9 μg · mg dw−1). Palmitic (16:0), oleic (18:1n-9) and eicosapentaenoic (EPA, 20:5n-3) acids were preferentially consumed (13.14, 9.21 and 8.67 μg · mg dw−1, respectively). The fatty acid composition found in M. brachydactyla eggs reflected the habitat and omnivorous and detritivorous scanvenger diet of the adults, although the consumption of algae was more important than previously thought, at least in the area where these adults were captured. Pre-hatching eggs have a high PUFA content (64.5 μg · mg dw−1 or 46.3% of the egg fatty-acid content). We conclude that larvae of this species might need a diet rich in PUFA, particularly EPA and DHA, for successful development. From the culture perspective, live preys commonly used in aquaculture will likely require to be enriched with DHA.