European Journal of Protistology 48 (2012) 85–88 Short communication Microscopic evidence for inclusion of Parvamoeba Rogerson, 1993 into the order Himatismenida (Amoebozoa) Alexander Kudryavtsev a,b,c,∗ a Molecular Systematics Group, Department of Genetics and Evolution, University of Geneva, 30 quai Ernest Ansermet, CH-1211 Geneva, Switzerland b Department of Invertebrate Zoology, Faculty of Biology and Soil Science, St-Petersburg State University, Universitetskaja nab. 7/9 199034, St. Petersburg, Russia c Research Group Protozoology, Institute of Biology/Zoology, Free University of Berlin, Königin-Luise-Str. 1–3, D-14195 Berlin, Germany Received 27 May 2011; received in revised form 6 July 2011; accepted 21 July 2011 Available online 26 August 2011 Abstract I have re-investigated the light-microscopic features of Parvamoeba rugata Rogerson, 1993, type strain CCAP 1556/1. The major characters of amoebae correspond to the initial description of this species. However, one peculiarity demonstrated by the cells during adhesion to the substratum, seems to have been partly underestimated previously. At the same time it is crucial for the explanation of this species’ position in the molecular phylogenetic trees and the recent system of Amoebozoa. This feature is the formation of a thin sheet of hyaloplasm on the ventral side of the cell that is used for adhesion to the substratum and locomotion, shared between Parvamoeba and members of the order Himatismenida. This explains the position of Parvamoeba as a sister clade to Cochliopodiidae in the molecular phylogenetic trees and justifies the recent inclusion of this genus into the order Himatismenida. In addition I sequenced the small-subunit ribosomal RNA of P. rugata and demonstrated that it was 99.5–99.7% similar to that of P. monoura Cole et al., 2010. This raises a question of the possible identity of these two species, however, several persistent morphological differences do not permit the unification of them, at least until more genes demonstrate identical sequences between these species. © 2011 Elsevier GmbH. All rights reserved. Keywords: Amoebae; Himatismenida; Morphology; Parvamoeba; Phylogeny; SSU rRNA; Taxonomy Introduction The genus Parvamoeba with the single species P. rugata was established by Rogerson (1993) to accommodate one of the smallest marine amoebae known to date. It was shown to ∗ Correspondence address: Molecular Systematics Group, Department of Genetics and Evolution, University of Geneva, 30 quai Ernest Ansermet, CH-1211 Geneva, Switzerland. Tel.: +41 223 793 084. E-mail addresses: gocevia@gmail.com, Alexander.Kudryavtsev@unige.ch (A. Kudryavtsev) have a rounded cell body with prominent dorsal wrinkles. It has very slow movement that is accomplished by means of a hyaline lobopodium. Based on morphology and ultrastructure Rogerson included this genus in the family Thecamoebidae. Later, another species, P. monoura, was described (Cole et al. 2010), and this is so far the only member of the genus for which a number of gene sequences including small-subunit (SSU) rRNA and actin genes were obtained (Cole et al. 2010; Tekle et al. 2008). Recent analysis of these data (Kudryavtsev et al. 2011) has shown that this species consistently branches as a sister clade to the Cochliopodium in the trees based on 0932-4739/$ – see front matter © 2011 Elsevier GmbH. All rights reserved. doi:10.1016/j.ejop.2011.07.003