May function as a thiol-disulfide oxidoreductase that participates in disulfide bond formation. Involved in the regulation of reproduction during the period of rapid gonadal development. High expression levels observed in hepatopancreas, testis, ovaries and intestine. Also expressed in heart, stomach, gills, cranial ganglia, muscle and hematocytes. During reproduction, expression in ovary and testis increases rapidly and significantly at stage III-1 (August-September), with peak expression being reached in September. The highest expression level in the hepatopancreas is detected at stage IV. In hemolymph, the expression is high during stage III-1, and then decreases significantly from stage III-2 onwards. Belongs to the selenoprotein M/F family.