When you Like Other Algae: Adglutina synurophila gen. et sp. nov. (Moewusinia, Chlorophyceae), a Clingy Green Microalga Associated with Synura Colonies

Unicellular green biflagellates of the order Volvocales (Chlorophyceae, Chlorophyta) are common inhabitants of various types of habitats, and can also form peculiar interspecific relationships. Most of their morphological diversity has historically been assigned to the two prominent genera Chlamydomonas and Chloromonas. Ongoing reclassification of these algae, aided by molecular phylogenetics, has resulted in numerous newly proposed genera, but there are certainly brand-new taxa awaiting recognition. In this study, based on morphological and ultrastructural observations together with sequence data of the nuclear 18S and ITS2 rDNA and the plastid rbcL gene, we describe Adglutina synurophila gen. et sp. nov., a volvocalean biflagellate isolated from colonies of the golden-brown alga Synura petersenii (Chrysophyceae). Phylogenetic analyses placed Adglutina in the phylogroup Moewusinia as a sister lineage to the acidophilic “Chlamydomonas” species. It is characterised by having oval to broadly ellipsoidal cells with a low keel-shaped papilla and a cup-shaped chloroplast lacking a pyrenoid, but possessing a lateral eyespot of a variable position. The unique set of features, together with its Synura-loving nature, anchor Adglutina as a well distinguishable phylogenetic lineage within the Moewusinia. The novel alga has a widespread distribution; it has been found in three European countries to date.