Yuri A. Mazei

Testate amoebae are valued for their functional significance and application as indicators of environmental conditions, particularly in peatland ecosystems. Research on testate amoebae has increased dramatically in recent years but there are still large parts of the world which have seen very little research. Here we consider testate amoeba communities of the West Siberian Lowland, the world’s largest peatland region and therefore one of the largest potential habitats for testate amoebae. Extensive sampling identified 89 taxa and showed that testate amoeba communities are structured by their physical and biological environment. We identified significant relationships between amoeba communities and both moisture content and vegetation composition. Despite the assemblages containing many widely-distributed species, some taxa considered typical of peatlands (e.g. Archerella flavum and Hyalosphenia papilio) were comparatively rare or absent, paralleling findings further south in Asia. We suggest that testate amoebae in this region deserve further study and may have useful applications in palaeoecological reconstruction and as bioindicators of the impacts of oil and gas extraction. 

The morphology and infraciliature of five trachelocercid ciliates: Tracheloraphis huangi spec. nov., T. colubis (Kahl, 1933) comb. nov., T. phoenicopterus (Cohn, 1866) Dragesco, 1960, T. oligostriata (Raikov, 1962) Foissner and Dragesco, 1996 and Trachelocerca incaudata Kahl, 1933, isolated from the intertidal zone of a beach at Qingdao, China, were studied in live and protargol impregnated specimens. Tracheloraphis huangi spec. nov. was distinguished from its congeners mainly by its single nuclear group composed of 25–30 round macronuclei and 29–37 somatic kineties. The poorly known T. colubis is redescribed including for the first time information on its infraciliature. An improved diagnosis is also provided. In light of its infraciliature, T. colubis is transferred to Tracheloraphis from the genus Trachelocerca. Additional data on other three species is supplied based on the Qingdao populations.

Testate amoebae in Vietnam are still poorly investigated. We studied species composition of testate amoebae in 47 waterbodies of South Vietnam provinces including natural lakes, reservoirs, wetlands, rivers, and irrigation channels. A total of 109 species and subspecies belonging to 16 genera, 9 families were identified from 191 samples. Thirty-five species and subspecies were observed in Vietnam for the first time. New species Difflugia vietnamica sp. nov. is described. The most species-rich genera are Difflugia (46 taxa), Arcella (25) and Centropyxis (14). Centropyxis aculeata was the most common species (observed in 68.1% samples). Centropyxis aerophila sphagniсola, Arcella  discoides, Difflugia schurmanni and Lesquereusia modesta were characterised by a frequency of occurrence >20%. Other species were rarer. The species accumulation curve based on the entire dataset of this work was unsaturated and well fitted by equation S = 19.46N0.33. Species richness per sample in natural lakes and wetlands were significantly higher than that of rivers (p < 0.001). The result of the Spearman rank test shows weak or statistically insignificant relationships between species richness and water temperature, pH, dissolved oxygen, and electrical conductivity.

The composition (143 species and forms) of testate amoebae communities from 68 samples of soils and lake sediments from South Vietnam (Cat Tien National Park) was investigated. In most terrestrial habitats, hydrophilous, soil and even xerophilous testaceans were co-occurring. The likely reason for this phenomenon are sharp seasonal changes in hydrological regime including temporal overwetting or inundation. Typical members of soil communities were Plagiopyxis callida, Tracheleuglypha acolla, Euglypha cristata, E. tuberculata, Trinema complanatum. The fauna was composed mainly of eurybiont species. Less abundant but still common were moss-dwelling species from the genera Heleopera, Hyalosphenia, Nebela and Sphenoderia. Calciphilous species were also present, including Centropyxis plagiostoma, Geopyxella cf. sylvicola, Schwabia terricola, Plagiopyxis callida, P. intermedia v. cyrtostoma, Heleopera petricola v. humicola. Species from the genera Hoogenraadia, Planhoogenraadia, Apolimia were found in this region of South-East Asia for the first time. The variations in the species composition and diversity of testate amoebae in soils was likely caused by several mechanisms including local variations in hydrological regime, the differences in chemical and physical properties and decomposition rates of plant litter, and mineralogical features of soils. The fauna of lake sediments was very distinct with characteristic species Difflugia bacillariarum, Lesquereusia modesta, Arcella gibbosa, Euglypha acanthophora. In the relatively uniform lake sediments local microcommunities were rich in species but very similar in species composition (low beta-diversity). In contrast, in soil samples the micro-scale heterogeneity was usually very pronounced, though the alpha-diversity was lower than in lake sediments. The updated list of testate amoebae of Vietnam includes 237 taxa. Taxa with restricted geographical distribution form up to one tenth of the total species richness.

Two new species of Deharvengia and Assulina are described from samples in the mountain forests of Honshu Is. (Japan). Morphometric analysis showed low variability of their morphological characteristics with coefficients of variation ranging between 1.4 and 9.1% for the two new species. An amended description of the genus Deharvengia is provided

We studied the diversity of heterotrophic flagellates from the sandy sediments of the Yangtze River, sandy and silty sediments of Donghu Lake, soil, moss and litter from the Luojiashan and Moshan hills as well as litter from the floodplain near Donghu Lake in April 2010. Sixty-seven heterotrophic flagellate species were identified by means of phase and interference contrast light microscopy and transmission electron microscopy. The majority of the observed flagellates were bacterivorous. Local species richness of river sediment communities was significantly lower than that of lake sediments and terrestrial habitats. The communities from the terrestrial habitats were more heterogeneous than those from freshwater sediments. Common species for the aquatic habitats were Rhynchomonas nasuta, Paraphysomonas sp., Neobodo designis, N. curvifilis, Bodo saltans and Spumella spp. In the soils only Spumella spp. was found in the majority of samples. Most characteristic taxa for the lake sediments were Helkesimastix faecicola, Petalomonas minuta, P. pusilla, Diphylleia rotans, Amastigomonas caudata. Amoeboflagellates such as Cercomonas angustus, C. granulifera, Paracercomonas crassicauda were specific for the terrestrial habitats. There were no specific taxa in the river sediments. The majority of the heterotrophic flagellates identified in this survey have been noted in China earlier. They are common (and usually predominant) for other regions in both freshwater and soil habitats.