Macro-morphological variation among cryptic species of the moon jellyfish, Aurelia (Cnidaria: Scyphozoa)

Morphological variation in qualitative and quantitative features is compared among species of Aurelia defined a priori using molecular criteria. Macro-morphological features were more numerous than previously implied (28 cf. 17), most were variable (26 of 28), and all species were morphologically distinguishable using univariate, multivariate and phylogenetic statistics. However, due to discrepant morphological descriptions, Aurelia spp. 3, 4, and 6 could not be assigned reliably to any previously described species, and there are still insufficient macro-morphological characters and variation to reconstruct a statistically robust phylogeny for even the 12 known species of Aurelia. Yet it is shown that Aurelia aurita is most likely endemic to the boreal Atlantic Ocean and northern European seas, Aurelia labiata is neither as morphologically diverse nor widespread as recently described, and the circumglobal Aurelia sp. 1 is probably introduced across much of its range.