Electron Microscopical Investigations of a New Species of the Genus Sappinia (Thecamoebidae, Amoebozoa), Sappinia platani sp. nov., Reveal a Dictyosome in this Genus

The genus Sappinia belongs to the family Thecamoebidae within the Discosea (Amoebozoa). For long time the genus comprised only two species, S. pedata and S. diploidea, based on morphological investigations. However, recent molecular studies on gene sequences of the small subunit ribosomal RNA (SSU rRNA) gene revealed a high genetic diversity within the genus Sappinia. This indicated a larger species richness than previously assumed and the establishment of new species was predicted. Here, Sappinia platani sp. nov. (strain PL-247) is described and ultrastructurally investigated. This strain was isolated from the bark of a sycamore tree (Koblenz, Germany) like the re-described neotype of S. diploidea. The new species shows the typical characteristics of the genus such as flattened and binucleate trophozoites with a differentiation of anterior hyaloplasm and without discrete pseudopodia as well as bicellular cysts. Additionally, the new species possesses numerous endocytobionts and dictyosomes. The latter could not be found in previous EM studies of the genus Sappinia. Standing forms, a character of the species S. pedata, could be formed on older cultures of the new species but appeared extremely seldom. A loose layer of irregular, bent hair-like structures cover the plasma membrane dissimilar to the glycocalyx types as formerly detected in other Sappinia strains.