Thecamoeba aesculea n. sp. was isolated and described from the surface of the bark of Aesculus hippocastanum and from terrestrial mosses growing on it. This amoeba is superficially similar to Thecamoeba sphaeronucleolus, but comparison of the newly isolated strain with the photographs and video records of the type strain of this species reveals differences which show that the two strains do not belong to the same morphospecies. The data obtained indicate the necessity of further comparative studies on the diversity of thecamoebian ‘morphospecies’ to outline clearer borders between them.

Three new, minute testate amoeban species smaller than 15 μm, including one new genus, are described from the plankton of the River Danube (Hungary) using high resolution video micrography. Pseudodifflugia klarae nov. spec. is characterised by an oval/pyriform, rigid, slightly compressed, scarcely or densely agglutinated test with a length of 8–14 μm. Its aperture is irregular in outline and inconspicuous; the nucleus contains one nucleolus and a few bent rods in the nucleoplasm. Bereczkya nov. gen., an incertae sedis cercozoan, has a minute spherical cell enclosed in a thin, rigid, more or less agglutinated organic test that is filled entirely by the cytoplasm. Its test bears an irregular and inconspicuous aperture. A collar-like ectoplasmic rim is situated in the aperture, from which a pseudopodial stem with filopodia is erected. The nucleus is slightly irregular, without a central nucleolus, but it contains rod-shaped granules in the nucleoplasm. Bereczkya minuta nov. spec. (test length: 3.5–8 μm, the diameter of the ectoplasmic rim: 0.8–2.3 μm) has a spherical test with asymmetric swellings and depressions, agglutinated with refractile mineral and other flat or irregularly-shaped xenosomes that may sometimes be almost entirely absent. Paramphitrema muelleri nov. spec. has a tubular or lemon-like test (length: 13–17 μm), which tapers towards the rigid apertures. The test is rigid, agglutinated and ism circular in cross section. The nucleus is vesicular. Thin filopodia, as well as 1–2 thick, straight, unbranched, tubular pseudopodia are produced.

Lieberkuehnia wageneri Claparède et Lachmann, 1859, a poorly known freshwater foraminiferan, was re-discovered after 38 years in a moss sample from an oak-hornbeam forest in Malé Karpaty Mts. (Western Slovakia). The species was taxonomically revised, re-described using light microscopical observations, and its occurrence and ecology were reviewed. Its locomotive form is typical with membranous and flexible ovoid test having a single terminal aperture from which a broad pseudopodial network emerges on a pseudopodial peduncle. Additional data and details are described, illustrated and discussed. Lieberkuehnia wageneri is known from various freshwater, soil and marine habitats in Western and Middle Europe, suggesting a high ecological tolerance and wide distribution. It is hoped that the observations reported in this paper will aid the identification of this species based on the locomotive morphology at the light microscopical level.

A new testate amoeba Scutiglypha cabrolae sp. n. is described from a small lake located in the caldera of Licancabur volcano, central Andes, at 5916 m above sea level. Its morphology was investigated using light and scanning electron microscopy. The main characteristics of the new species are: thick-set ovate test, length/width ratio 1.4; relatively small size, mean length × width: 69 × 48 μm; 3–4 rows of apertural plates, apertural plates of first row lozenge-shaped, oral margin with median tooth and (5)–6 lateral toothlets; body-plates scutiform, broad, with weakly crenulated oral and aboral margin.

The taxonomic identity in microbial eukaryotes remains an impediment to discussing ecology, biogeography and phylogeny, mainly due to a lack of standards in organism descriptions and few comparative works. The lobose testate amoebae (Arcellinida) present an ideal study system, as progress is severely hindered due to taxonomic confusion. In the present survey, we have examined the morphology, biometry and ecology of 2400 individuals in the genus Arcella Ehrenberg, 1832, collected from the Tiete River in Sao Paulo, Brazil. We then contrasted these new data with 26 previously described species, varieties and forms, looking for consistencies and trying to establish distinct entities. Using a combination of morphology and multivariate statistics we were able to determine 4 distinct taxa (Arcella hemisphaerica, Arcella discoides, Arcella gibbosa and Arcella brasiliensis), each of them encompassing a number of other non-distinct nominal taxa. We describe in detail each of the 4 taxa with notes on ecology and biogeography, and list the indistinguishable names in an effort to make identification and taxonomy in the testate amoebae a more objective and precise exercise by clarifying the taxonomic identity.

Shell ultra-structure and morphometrical variability of Nebela tenella were investigated using scanning electron microscopy (SEM). N. tenella was isolated from two widely separated populations, one from Switzerland and another from Canada. The shell’s structural elements were similar to those of the other nebelids, but N. tenella has a characteristic peculiarity – always present depressions on the shell surface, which makes an uneven outline of the shell. Moreover, light microscopy and SEM study showed that the collar of the N. tenella represents a turned-over continuation of the neck, which is covered by the same idiosomes as on the shell body. The biometrical analysis showed that the majority of the basic characters of N. tenella vary moderately and give continuous series of transition forms. According to the shell depth and the ratio depth/width both populations were significantly different of each other. Variation coefficients showed that the variability of the characters differs in both populations and the Swiss population is more stable than the Canadian one. All new obtained data for N. tenella raise the question whether the shell’s size, cross section and ultramorphology are reliable enough as characters for the differentiation of N. tenella and N. griseola, and whether they are two distinct species or should just be considered as ecophenotypic variation within one species?

Genus Amphidinium Claparède et Lachmann (Gymnodiniales, Dinophyceae) sensu lato has recently undergone a reappraisal using extended microscopical methods and genetic comparisons, with the type species and morphologically similar species used for the redescription of the genus Amphidinium sensu stricto. Within the latter concept of the genus, the new species Amphidinium thermaeum is established using light and scanning electron microscopy in combination with LSU rDNA phylogeny. This species was isolated from the Thermaikos Gulf in Greece, and its description is largely based on observations of cultured material. The main diacritic features distinguishing A. thermaeum from related taxa were: shape, size and plasticity of the cell, position of distal and proximal cingulum ends, site of longitudinal flagellar insertion, sulcal course, pusule details, plastid characteristics, and mode of cell division. Genetic phylogeny applying Bayesian Inference, Maximum Likelihood, and Neighbor-Joining analyses, places A. thermaeum in an independent position within the Amphidinium sensu stricto monophyletic group, and the new species is closely related to its small and morphologically similar siblings (A. massartii, A. klebsii, A. trulla, A. gibbosum, A. carterae).

Three marine peritrichous ciliates, Zoothamnium alrasheidi spec. nov., Z. marinum Kahl, 1933 and Z. vermicola Precht, 1935, were isolated from littoral areas near Qingdao, China. The living morphology, infraciliature and silverline system were studied in living and silver-impregnated specimens. Zoothamnium alrasheidi is distinguished from its congeners by the giant, leaf-shaped colony, the differentiation of zooids, the structure of the infundibular polykineties and in having 57–75 silverlines between the oral area and the trochal band and 24–42 between the trochal band and the scopula. Zoothamnium marinum and Z. vermicola are reported for the first time in over 70 years. Each was identified by its zooid shape and size, colony shape, the branching pattern of its stalk and its marine habitat. As a result of the present study, additional features for characterizing these species now include the structure of infundibular polykinety 3 and the number of silverlines between the aboral trochal band and (a) the scopula, and (b) the peristomial lip. Redescriptions and improved diagnoses of both species are supplied based on the Chinese populations.

Ortholinea africanus Abdel-Ghaffar et al., 2008 is re-described using light and scanning electron microscopy (SEM) to reveal the external ornamentation of the spores. Present spores matched the original description in morphology but were larger in all dimensions. They measured 9.6 ± 0.8 (8.1–10.9) μm in length, 9.5 ± 0.6 (8.8–10.9) μm in width and 8.9 ± 0.4 (8.6–9.1) μm in thickness. Polar capsules were 3.9 ± 0.3 (3.0–4.3) μm in length with polar filaments turned 4–6 turns. The pattern of polar filament coils was different in each of the polar capsules. In the same spore, one capsule contained oblique filament turns to the longitudinal axis of the capsule, while the other capsule contained perpendicular turns. SEM revealed completely different shell ridge patterns than those described by light microscopy in the original description. This emphasizes the necessity of SEM in the reliable description of any myxosporean genera with external shell ornamentation like Ortholinea and Chloromyxum. The present species is considered the first (purely) freshwater Ortholineadescribed from a proper freshwater host. Three different methods of isolation and preparation of coelozoic spores for SEM were evaluated. The best combination was using a syringe filter holder with a membrane filter of 5 μm pore nucleopore filters.