Extraction of melanin from the shell and mantle and activities of enzymes related to the melanin biosynthesis in the Ruditapes philippinarum

Abstract

The shell surface of Manila clam (Ruditapes philippinarum) has a variety of colors and stripes, with diverse shell color polymorphism. As an important trait of economic shellfish, shell color plays an important role in the selection breeding of shellfish species. In this study, we extracted melanin from the shell and mantle of R. philippinarum by the hydrochloric acid method and measured the melanin content by spectrophotometry. The absorption spectrum of melanin and its absorption peak at 350 nm absorbance was determined. We found significant differences in the melanin content of clams with dark strain and light strain, as well as four different shell colors. Moreover, we further detected the activities of enzymes related to melanin synthesis in R. philippinarum mantle, such as tyrosinase (TYR), tyrosine hydroxylase (TH), dopa decarboxylase (DDC), N-acetyltransferase (NAT), and N-β- alanyldopamine (NBAD) in the mantle of R. philippinarum. The results showed that the activities of TYR, TH, DDC and NAT were positively correlated with the content of melanin. However, the activity of NBAD was negatively correlated with the content of melanin. Altogether, these results indicating that these enzymes are involved in the regulation of the melanogenesis pathway of R. philippinarum. This study provides valuable information for further research on shell color genetic mechanism and breeding of R. philippinarum.