Characterization of S elenaion koniopes n. gen., n. sp., an Amoeba that Represents a New Major Lineage within Heterolobosea, Isolated from the W ieliczka Salt Mine

A new heterolobosean amoeba, S elenaion koniopes n. gen., n. sp., was isolated from 73‰ saline water in the W ieliczka salt mine, Poland. The amoeba had eruptive pseudopodia, a prominent uroid, and a nucleus without central nucleolus. Cysts had multiple crater‐like pore plugs. No flagellates were observed. Transmission electron microscopy revealed several typical heterolobosean features: flattened mitochondrial cristae, mitochondria associated with endoplasmic reticulum, and an absence of obvious G olgi dictyosomes. Two types of larger and smaller granules were sometimes abundant in the cytoplasm—these may be involved in cyst formation. Mature cysts had a fibrous endocyst that could be thick, plus an ectocyst that was covered with small granules. Pore plugs had a flattened dome shape, were bipartite, and penetrated only the endocyst. Phylogenies based on the 18S rRNA gene and the presence of 18S rRNA helix 17_1 strongly confirmed assignment to Heterolobosea. The organism was not closely related to any described genus, and instead formed the deepest branch within the H eterolobosea clade after P haryngomonas , with support for this deep‐branching position being moderate (i.e. maximum likelihood bootstrap support—67%; posterior probability—0.98). Cells grew at 15–150‰ salinity. Thus, S . koniopes is a halotolerant, probably moderately halophilic heterolobosean, with a potentially pivotal evolutionary position within this large eukaryote group.