Comparison of the Chemical Composition of Different Body-Color Phenotypes of Perinereis aibuhitensis (Grube, 1878) (Annelida, Nereididae)

A comparative chemical analysis was conducted between P. aibuhitensis of orange and green body colors, evaluating their proximate composition, fatty acid profile, amino acid profile, astaxanthin content, lipidomic profile, and other biochemical parameters. Samples were categorized by body color into two groups, each with ten biological replicates. The samples were collected from the same local polychaete farm. The results revealed that the green phenotype had significantly higher moisture content but lower crude protein, crude lipid, and ash content compared to the orange phenotype. The orange polychaete was characterized by significantly higher concentrations of 16:0 and saturated fatty acids (SFAs), whereas the green one exhibited higher contents of n-6 polyunsaturated fatty acids (n-6 PUFAs) and a higher PUFA/SFA ratio. Regarding free amino acids, the orange polychaete had significantly higher threonine content, while the green ones had significantly higher levels of valine, isoleucine, leucine, phenylalanine, glutamate, alanine, histidine and proline. Additionally, the astaxanthin content was significantly higher in the orange phenotype. The bile acid level was significantly higher in the green phenotype compared to the orange one, but no significant differences were observed in other biochemical parameters such as total protein, total cholesterol, and triglyceride content. The lipidomic analysis revealed that glycerophospholipids were the most abundant lipid class in both phenotypes, followed by glycerolipids and sphingolipids. A total of 65 differentially abundant lipid molecules were identified between the two groups. Compared to the orange polychaete, the green one had higher levels of 59 lipids (predominantly ceramides) and lower levels of six lipids, including three triglycerides, one monogalactosyldiacylglycerol, and two phosphatidylserines. In general, the orange P. aibuhitensis showed a favorable nutritional profile for aquafeed and human nutrition, whereas the green ones had potential for targeted health applications owing to its specific lipid composition. However, direct validating experiments are required.