# Genetic, Diversity, and Muscle Quality Among Red and Green Color Morphs of Asian Swimming Crab (Charybdis japonica): Implications for Accurate Species Recognition and Sustainable Management

## TL;DR

This study compares red and green color morphs of Asian swimming crabs to understand their genetic and physical differences, concluding they are the same species despite variations in color and muscle quality.

## Contribution

The study provides new insights into the genetic and morphological diversity of C. japonica color morphs, supporting their classification as a single species.

## Key findings

- Red morph crabs have higher melanocyte aggregation and lower L* and b* values compared to green morph crabs.
- Mitochondrial DNA analysis shows high sequence identity (98.96% COI, 99.71% ITS-1) between the two morphs, indicating they belong to the same species.
- Muscle texture differs between morphs, but amino acid composition remains similar.

## Abstract

In this study, two color morphs (red and green) of Asian swimming crab (Charybdis japonica) commonly distributed in the China Sea area were analyzed for their L*a*b* values, carapace and inner membrane histology, morphological characteristics, mitochondrial DNA sequences, muscle texture, and amino acid composition. The results showed that compared with the green morph group, the red morph group exhibits higher aggregation of melanocytes and fewer pigment cells in the inner membrane. In addition, L* and b* of the carapace, and L* values of the inner membrane were lower in red morph group. Both populations of C. japonica also exhibit significant differences in their morphological parameters, including carapace length, body weight, and pincer width. However, the coefficient of variation for these morphological parameters did not correspond to the subspecies level. The mitochondrial DNA analysis also revealed sequence identity of COI (98.96%) and ITS-1 (99.71%) genes in both groups, supporting them to belong to the same species. Both groups also presented significant differences in their muscle texture characteristics, including adhesiveness, springiness, and gumminess, but no significant differences were observed in the muscle amino acid composition. Overall, red and green morphs of C. japonica show differences in their body color, morphological characteristics, and muscle quality, but still belong to the same species.