Species Demarcation and Comparative Analysis of Amino Acid and Fatty Acid in Four Scylla Species: Unveiling the Nutritional Profiles

This study examined four species of Scylla genus (S. paramamosain, S. olivacea, S. serrata, and S. tranquebarica) morphologically and molecularly. Morphologically, distinct frontal lobe spine shapes and colorations were observed. Using HRM genotyping with CSN9 primers, we identified clear species-specific melting curve distinctions. The Tm values of S. serrata, S. paramamosain, S. tranquebarica and S. olivacea are 79.55℃, 80.12℃, 78.12℃ and 82.04℃, respectively. Sequencing data validated these results, revealing 28 SNPs and 9 haplotypes. Amino acid analysis showed arginine dominance in S. paramamosain, which was 40.64 mg g⁻¹, and a TFAA range of 135.70 – 149.65 mg g⁻¹. A total of 26 fatty acids were identified, while S. paramamosain showed the highest concentration (P < 0.05). EPA was a major component (16.17% – 23.26%), while S. paramamosain exhibited the highest levels. Principal component analysis and cluster analysis highlighted distinct species groupings based on amino acid and fatty acid profiles. These findings provide comprehensive insights into Scylla species' morphological, molecular, and biochemical diversities.