The rare Calappa tuerkayana Pastore, 1995 is a juvenile stage of the common Calappa granulata (Linnaeus, 1758) (Brachyura: Calappidae)

In the Mediterranean Sea, four species of the genus Calappa (Family Calappidae) are known, namely Calappa granulata (type species of the genus by subsequent designation), Calappa pelii, Calappa rosea, and Calappa tuerkayana. We hereby first tested the status of C. tuerkayana as a valid species through an integrative approach, thus analyzing morphologically and genetically specimens of both C. tuerkayana and C. granulata and comparing them with congeners. Molecular analyses based on mitochondrial and nuclear markers suggested that they account for a single species. Absence of ovigerous females in C. tuerkayana and presence of middle-sized specimens showing intermediate morphology in carapace and sexual organs between the two taxa point to the evidence that C. tuerkayana was described on a juvenile stage of C. granulata. The present paper makes C. tuerkayana a junior synonym of C. granulata, fills a gap in the knowledge of the ontogenetic changes of the common Mediterranean shame-faced crab during its various life stages, and first offers a redescription of C. granulata that includes its juveniles.