Umbraculum umbraculum (Lightfoot, 1786) (Gastropoda, Opisthobranchia, Tylodinoidea) and the synonymy of U. mediterraneum (Lamarck, 1812)

Abstract

Specimens of Umbraculum Schumacher, 1817 from the North Atlantic (Great Meteor Bank and Azores), the Mediterranean Sea and from the southwest Pacific (Australia, Solomon lds, New Zealand) were investigated anatomically and histologically to clarify whether U. mediterraneum (Lamarck, 1812) and U. umbraculum (Lightfoot, 1786) are two distinguishable species or only one. Additional molecular analyses of one specimen each from Australia, the Azores and the Great Meteor Bank were performed, using 18S rRNA, 16S rRNA and COl genes. The morphological and molecular investigations give no evidence supporting their separation into two species. We therefore consider U. mediterraneum to be a junior synonym of U. umbraculum, and follow the assumptions of Bum (1959) that there is only one species of Umbraculum, with a wide spread distribution in tropical and warm temperate waters.