The genus Antedon (Crinoidea, Echinodermata) in the Strait of Messina and the nearby Tyrrhenian Sea (Central Mediterrranean)

The high morphological variability of antedonids under different ecological conditions explains some uncertainties of their Mediterranean distribution. A comparison of Antedon specimens from the Strait of Messina and the nearby Tyrrhenian Sea documented the presence of two phenotypes, distinguished by cirral shape, articulation, and surface microsculpture, referred to the Mediterranean species Antedon mediterranea and A. bifida moroccana. The number of cirrals, the main diagnostic character in the genus Antedon, proved to be statistically discriminant at the species level as well as at lower levels, according to the population's place of origin, inside a very restricted area. These results agree with the hypothesis that the Strait of Messina is an area with high Atlantic affinity, where A. bifida moroccana tends to replace the Mediterranean endemic A. mediterranea, although the two species can be locally sympatric.