title: Ptolemeba n. gen., a novel genus of hartmannellid amoebae (Tubulinea, Amoebozoa); with an emphasis on the taxonomy of Saccamoeba.
abstract: Hartmannellid amoebae are an unnatural assemblage of amoeboid organisms that are morphologically difficult to discern from one another. In molecular phylogenetic trees of the nuclear-encoded small subunit rDNA, they occupy at least five lineages within Tubulinea, a well-supported clade in Amoebozoa. The polyphyletic nature of the hartmannellids has led to many taxonomic problems, in particular paraphyletic genera. Recent taxonomic revisions have alleviated some of the problems. However, the genus Saccamoeba is paraphyletic and is still in need of revision as it currently occupies two distinct lineages. Here, we report a new clade on the tree of Tubulinea, which we infer represents a novel genus that we name Ptolemeba n. gen. This genus subsumes a clade of hartmannellid amoebae that were previously considered in the genus Saccamoeba, but whose mitochondrial morphology is distinct from Saccamoeba. In accordance with previous research, we formalize the clade as distinct from Saccamoeba. Transmission electron microscopy of our isolates illustrate that both molecularly discrete species can be further differentiated by their unique mitochondrial cristal morphology.
authors.affiliation: Department of Biological Sciences, Mississippi State University, Mississippi State, Mississippi, 39762.
authors.forename: Pamela M
authors.initials: PM
authors.lastname: Watson
authors.forename: Stephanie C
authors.initials: SC
authors.lastname: Sorrell
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Brown
mesh_terms: D004275:DNA, Ribosomal / Q000235:genetics; D016840:Lobosea / Q000145:classification* / Q000235:genetics / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000648:ultrastructure; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D004275:DNA, Ribosomal
keywords: 18S rRNA; Cashia; Hartmannella; SSU rDNA; SSU rRNA; amoeba; amoeboid; cristae; freshwater amoebae; mitochondrial morphology; terrestrial amoebae; tubulinid