A revision of the genus Halosaccion (Palmariaceae, Rhodophyta) from the Russian Pacific coast with description of the genus Nothohalosaccion gen. nov.

This study evaluates the diversity and distribution of species of the genus Halosaccion along the Russian Pacific coast using morphological data and molecular analyses. Halosaccion minjaii was found to be genetically distant from other species in the genus; this and its unique morphological features – namely the development of tetrasporangia in elevated sori between long sterile filaments (which are much longer than tetrasporangia) and the mode of spermatangia formation – led to the proposal of a new genus, Nothohalosaccion, with a single species N. minjaii. Data on species distribution in the north-western Pacific were refined. Halosaccion americanum was recorded for the first time in the Okhotsk Sea. This extended the species range north-westward. In contrast, the distribution of Halosaccion microsporum was restricted to northern and western parts of the Okhotsk Sea, the eastern Kamchatka coast and western Bering Sea. The distribution patterns of species of the genera Halosaccion and Nothohalosaccion are discussed in relation to the oceanography of the region. Types of the names H. microsporum, Dumontia hydrophora (≡ Halosaccion hydrophorum) and Ulva glandiformis (≡ Halosaccion glandiforme) are designated to guarantee their unambiguous use and to stabilize the nomenclature. A new genus Nothohalosaccion for Halosaccion minjaii.First record of Halosaccion americanum in the Okhotsk Sea.Typification of specific names in the genus Halosaccion. A new genus Nothohalosaccion for Halosaccion minjaii. First record of Halosaccion americanum in the Okhotsk Sea. Typification of specific names in the genus Halosaccion.