Dietary effects on the reproductive performance of the sea urchin Tripneustes gratilla l: Implications for broodstock conditioning

Broadcast spawning animals often display differential parental contributions within aquaculture environments, which can influence offspring performance through a loss of genetic variation in cultured populations. This study aimed to assess the effect of different feeding regimes on the reproductive performance of Tripneustes gratilla. To achieve this, broodstock animals were conditioned on four diets [formulated feed, kelp (Ecklonia maxima), green seaweed (Ulva lacinulata) and mixture of the three diets] for four months, and various broodstock traits, including gonad development, gonad coloration, gamete (egg and sperm) quality, egg energetic components and egg fatty acids were assessed. In this study, broodstock animals fed natural feeds and a mixed feeding regime had greater gonad and egg redness indices, possibly as a result of dietary carotenoids being incorporated into their gonads. These pigments have known antioxidant, anti-inflammatory, pro-vitamin A, photoprotection and immunity-related roles. Results from this study showed that a formulated feed (20U) should not be fed in isolation for reproductive purposes, as these broodstock animals displayed lower gonad and egg quality indices. Furthermore, this diet showed poor fatty acid provisioning, with an excess linoleic acid being detected in eggs. In contrast, animals fed a mixed diet displayed the most diverse egg fatty acid profile, with a high proportion of fatty acids commonly found in sea urchins, such as palmitic acid, myristic acid and the omega-3 eicosapentaenoic acid. These results indicate that conditioning broodstock on natural feeds is advantageous for sea urchin gonad development and reproductive performance.