Morphological and molecular analysis of Henricia Gray, 1840 (Asteroidea: Echinodermata) from the Northern Atlantic Ocean

The asteroid genus Henricia Gray, 1840 is notorious for intraspecific morphological variation, which complicates species identification within the genus. We examined 796 Henricia sampled in by-catch programmes on Greenland and Iceland as well as research cruises and diving in Norway for diagnostic morphological features. Based on their morphology, individuals could be easily assigned to either the 'pertusa group' (470 specimens) or 'perforata group' (286 specimens) as defined by Madsen (1987), but some samples could only be assigned to genus level (40 specimens). Seventy-eight specimens were used for DNA bar coding, employing sequences from the cytochrome c oxidase subunit I gene and the 16S ribosomal gene. Five well-supported genetic clades (A-E) were revealed in maximum likelihood analysis of the DNA sequence data sets. Three of the clades were consistent with the species H. oculata, H. perforata and H. pertusa. The other two clades contained individuals with variable morphology, which could represent several known species, precluding species assignment to these clades. Given the morphological variation within Henricia, a combination of morphological study and DNA barcoding is useful for species identification.