Sex determination in blue mussels: Which method to choose?

• Mussel sex determination should start by the histology of the mantle.
• Methods that rely on gamete presence were not effective in determining mussel sex during the sexual rest period.
• To determine mussel sex in the sexual rest period, the best method is the RT-PCR analysis of sex-specific gene.

Sexing methods of blue mussels are mostly based on the presence or absence of gametes, and do not take into account reproductive cycle stages. Exposure effects can be affected by the sex of mussels, thus the aim of this study is to determine an efficient sex determination protocol taking into account the reproductive cycle stage. Eight mussel sexing methods were compared. This study demonstrates that the first step in discerning sex in blue mussels should be assessing the reproductive stage, which can be done by mantle histology. During gametogenesis, histology allows the differentiation of males from females by the observation of gametes. However, when mussels are in sexual rest, the only method that should be used is the sex-specific gene method.

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