Amoebae of the genus Mayorella are widespread in marine, freshwater and soil habitats. These amoebae have relatively low number of morphological characters allowing species differentiation, so the number of valid species remains rather small. Representatives of the genus Mayorella are hard to maintain in culture, the very most of them are polyphagous and carnivorous. To live and multiply they require a variety of food objects, including other protists. Thus they are difficult objects for molecular studies. Only two sequences of Mayorella were available until recently in GenBank. For the present study we isolated eight strains of Mayorella from different locations worldwide, documented them with the light microscopy and obtained complete or partial sequences of their 18S rRNA gene. Results show that all members of the genus Mayorella form a robust clade within the order Dermamoebida (Amoebozoa: Discosea). The vast majority of our strains probably represent new species; this evidences that diversity of the genus Mayorella in natural habitats is high and that this genus is rather species-rich, comprising no less than 11 species. Our results show that nowadays sequence data are necessary for reliable identification of Mayorella species.
