The last alien reaching Sicily: Isognomon legumen (Gmelin, 1791) (Mollusca Bivalvia Isognomonidae)

The finding of some living specimens of an alien bivalve of the genus Isognomon Lightfoot, 1786 (Mollusca Bivalvia Isognomonidae) attached to rocks is here reported in Sicily for the first time. This is the last of a series of numerous finding of alien molluscs reports in the same area, for which a human-mediated model was supposed. An attempt to indicate the age of the specimens are here furnished on the basis of the number of byssus filaments. Some further environmental notes underline how in recent times these alien species seem better integrated inside the indigenous benthic communities in the Southern Mediterranean coasts, being better allowed in the first settlement by the recent climatic changes and resulting ecologically well organized and structured as in the tropical environments of provenance.