Fatty acids and growth performance of Rugulopteryx okamurae-fed Tenebrio molitor and Acheta domesticus

Abstract This study evaluates the potential of the invasive brown seaweed Rugulopteryx okamurae as a feed supplement to enhance growth performance, fatty acid (FA) composition, and nutritional quality in Tenebrio molitor larvae and Acheta domesticus . At inclusion levels up to 70%, R. okamurae had no adverse effects on insect weight (wt), daily growth coefficient (DGC), or larval growth in either species. In T. molitor , the highest wt (0.144 g) and DGC (0.41%/day) were achieved with 70% algal inclusion. In A. domesticus , 40% algae yielded the highest wt (0.387 g), while the maximum DGC (0.54%/day) occurred with 70% inclusion. Total FA content ranged from 18.1 to 43.6% in A. domesticus and from 20.2 to 54.9 g/100 g in T. molitor . Algal supplementation increased saturated FA (SFA), particularly palmitic acid (PA, 16:0), from 24.7% (control) to 28.1% in 40%-algae-fed A. domesticus , whereas T. molitor showed no significant PA variation (13.8–16.2%). Monounsaturated FA (MUFA) peaked at 33.5% in A. domesticus with 25% algae and at 45.2% in T. molitor with 40% algae, largely due to oleic acid (OA, 18:1 n -9). The highest polyunsaturated FA (PUFA) proportions were 40.7% in A. domesticus (70% algae) and 36.0% in T. molitor (25% algae), driven mainly by linoleic acid (LA, 18:2 n -6). Docosahexaenoic acid (DHA, 22:6 n -3) was present in all groups (<1%), except in T. molitor with 40% algae (1.2%). Overall, R. okamurae improved FA profiles without altering lipid quality indices, supporting its potential as a sustainable dietary supplement for edible insects.