Reproductive investment and gonad development in triploid mussels, Mytilus Edulis.

The production of triploid bivalves has elicited great interest because their reproductive investment is known to be lower than that of diploids. Reduced reproductive investment is expected to improve the survival and growth of triploid bivalves compared to diploids as the energy spared from reproduction could be used for other metabolic needs. However, the reduction of triploid fertility varies among species, therefore, its impacts on survival and growth are variable. In this study, we compared the reproductive investment of diploid and triploid mussels between two age and size groups (1-year-old ˂ 30 mm, and 2-years-old ˃ 50 mm). We measured gonadosomatic index (GSI), gonad volume fraction (GVF), gonad maturation, and sex ratio. Results demonstrated that while triploid mussels do invest part of their energy in reproduction, they had lower GSI and GVF than diploids. In all tested groups, triploid gonads were less mature than those of diploids, and their sex ratio was significantly altered, with the absence of female triploids. Furthermore, triploid gonads showed signs of gamete resorption, suggesting that the gametes of triploid mussels could serve as energy reserves. This study reveals that triploid mussels invest less energy in reproduction which suggests that the spared energy could be used to improve other metabolic need and survival. We conclude that triploid mussels could be of great interest for aquaculture because they may have better resistance to post-spawning weakness and better recovery due to gametes resorption. • Triploid mussels invest less in reproduction than diploids do. • Triploid mussels have reduced gonadosomatic index and gonad volume. • Gametes of triploid mussels do not show full maturation. • Triploid mussels have an altered sex ratio, with the absence of females. [ABSTRACT FROM AUTHOR]