Leptomyxa mirabilis n. sp. – A new species of the genus Leptomyxa (Amoebozoa, Tubulinea) with a remarkable floating form and unusual cyst structure

Abstract

Variable body shape and significant variations in cell size make it difficult to distinguish species belonging to the genus Leptomyxa. At present, molecular data are becoming crucial for the identification of these amoebae. Among leptomyxids, the divergence of the 18S rRNA gene, mainly used to distinguish species, is low. Morphologically distinct species may have very similar 18S rRNA gene sequences and vice versa. However, some species exhibit remarkable morphological characters that can be combined with gene sequences to distinguish them reliably. In this paper, we describe a new terrestrial species of the genus Leptomyxa isolated from the Russian Far East, Leptomyxa mirabilis n. sp. Amoebae of this species are reticulate, flattened, and branched. This species has a unique floating form, previously undescribed among leptomyxids, and a remarkable cyst structure. The cysts of the studied species are often lobed or have a complex branched shape resembling the plasmodiocarps of some mycetozoa. Cysts can be single-walled or double-walled. The outer wall of a double-walled cyst encloses one or two multinucleate endocysts. In some cases, the wall of mature cysts is complex and multilayered. In addition, Leptomyxa mirabilis n. sp. differs from related leptomyxid species in the sequence of the 18S rRNA gene.