Juvenile coloration and DNA barcoding of the hermit crab <i>Dardanus arrosor</i> (Herbst, 1796) (Decapoda: Anomura: Diogenidae) from Japan

Abstract Detailed descriptions of color patterns help avoid taxonomic confusion and to better understand the stages of speciation and adaptation as intraspecific differences in color patterns are common in marine crustaceans. We describe the coloration of juveniles of the hermit crab Dardanus arrosor (Herbst, 1796), a cosmopolitan species found from the Indo-West Pacific to the Atlantic Ocean and Mediterranean Sea at depths of 5–750 m. Juveniles exhibit a series of distinctive white areas that are not present in adults. This makes some color patterns present throughout development more evident, such as the oblique red stripe on the distal part of the pereiopods, much more evident in juveniles. Species identity was confirmed by phylogenetic analysis of the mitochondrial COI gene. The white color is highly prevalent among juveniles, suggesting that body coloration in ­D. arrosor changes ontogenetically and highlights the need for further studies on the adaptive significance of each color pattern across different life stages.