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

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Digital Gems > Biodiversity Library of Southeast Asia

Keyword: Decapoda
Grapsoidea
land crab
Epigrapsus
intraspecific variation
mitochondrial COI

Abstract: 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.