Untangling the Knotted Identities of Commercially Important Swimming Crabs

Are you sure the seafood you are consuming is what it says on the label or the menu?

In 2015, a survey of Atlantic blue crab (Callinectes sapidus) meat sold in supermarkets and restaurants in Maryland, USA, revealed that nearly 50% of the products tested were from totally different, non-Atlantic species.

DNA barcoding matched a GenBank record identified as “Portunus pseudoargentatus”, a poorly-known species described from Western Australia, and not known to be a species of commercial importance. Apparently, this species is enmeshed in a tangled web of crab names including the commercially fished species, Portunus gladiator (originally described from India in 1798) and Portunus haanii (originally described from Japan in 1858). All three have previously been deemed as the same species by crab taxonomists at some point, though there has been no consensus to date.

To shed light on the identity of these crabs, our crustacean curator, J.C.E. Mendoza, worked with Amanda Windsor and Jonathan Deeds from the United States Food and Drug Administration (US-FDA) to assemble a large collection of specimens and tissue samples sourced from the known range of these three species.

Using DNA barcoding techniques, complemented with a thorough morphological examination of the specimens and a proper reading of the International Code of Zoological Nomenclature, the team conclusively resolved the identity problem of these crabs.

Their research, recently published in ZooKeys, establishes the validity and distinctness of two species, which should now be called Monomia gladiator and Monomia haanii, with P. pseudoargentatus considered as a junior synonym of the latter.

Read the paper here.