Size-associated morphological changes in Epigrapsus notatus (Heller, 1865) and the taxonomic status of E. villosus Ng, 2003 (Crustacea: Decapoda: Brachyura: Gecarcinidae).

The identities of what have been referred to as Epigrapsus notatus (Heller, 1865) and E. villosus Ng, 2003, are evaluated using morphological and molecular methods. Morphological comparisons showed that the main characters used to diagnose E. villosus (viz. the setation of the carapace, the condition of the epigastric cristae, the granulation on the branchial region, and proportions of the ambulatory legs) can be attributed to the small size of the type specimen; and the extreme condition of these structures can be connected to adult forms of E. notatus through transitional phases. One morphological feature (the laterally expanded first epibranchial tooth) is seen only in the holotype of E. villosus, but it can also be regarded as a character state specific to small individuals of E. notatus, and signifying the extreme end of possible variation in that species. The analysis of mitochondrial cytochrome c oxidase subunit I (COI) reveals three haplotypes in the E. notatus/E. villosus complex, but with only as much as 0.61% of nucleotide divergence between them. In conclusion, it is clear that E. notatus undergoes dramatic morphological change during its growth, and that E. villosus should be considered a junior synonym of E. notatus. [ABSTRACT FROM AUTHOR]