We describe a new protosteloid amoeba, Luapeleamoeba hula. Protosteloid amoebae, sometimes called protostelids, are sporocarpic amoebae that make fruiting bodies that consist of a stalk and one to a few spores. This new taxon was cultured from dead leaves of mamaki (Pipturus albidus) from the Manuka Natural Area Reserve, Hawai`i, USA. Light microscopic examination showed that this amoeba has a short, rigid stalk with a small apophysis and a spore that changes shape continuously until it is shed and crawls away from the stalk. In addition, this amoeba was initially observed to maintain a diurnal rhythm in which fruiting body formation occurred primarily in the late afternoon. This new species is unique in both its amoebal and fruiting body morphology. Spore deciduousness appears to be a result of shape changes in the spore itself. This is the fourth species of protosteloid amoeba described with a clearly described diurnal rhythm. In addition, previous molecular phylogenetic analyses suggested that this new species has SSU rRNA gene sequences that clearly separate it from any other protosteloid amoebae and place it as sister to Protacanthamoeba bohemica among the Acanthamoebidae family in Centramoebida of Amoebozoa. Because this new species’ amoebae do not fit into any of the centramoebid genera, we have proposed a new genus—Luapeleamoeba.

A new soil urostylid ciliate, Birojimia soyaensis nov. spec. was discovered from Soya Island, Incheon, South Korea. The species is described based on live and stained specimen observations, and 18S ribosomal RNA gene sequence analysis. Birojimia soyaensis nov. spec. is characterized by the following features: body slender, elongate, and somewhat twisted; body size in vivo 170–200 μm × 40–50 μm; contractile vacuole located at middle of left cell margin; cortical granules present; 37–48 adoral membranelles; 3 frontal and 2 frontoterminal cirri present; III/2 and buccal cirrus present; midventral pairs only; pretransverse ventral and transverse cirri present; 1 left and 4 right marginal rows, including 3 compound rows; 5 long dorsal kineties with 3 additional shortened kineties in anteriorly compound rows; 8–11 caudal cirri; 53–69 macronuclear nodules; and 2 or 3 micronuclei. Birojimia soyaensis nov. spec. is distinguished from B. terricola by cortical granule size (0.4–1.2 μm in diameter vs. 2–3 μm × 1–2 μm), cortical granule shape (mostly spherical vs. broadly ellipsoid to lenticular, respectively); number of caudal cirri (8–11 vs. 2–7), and number of dorsal bristle rows (8 vs. 6–7). Phylogenetic analysis suggests this new species is most closely related to the genus Hemicycliostyla.

Shell composition is considered an important functional trait in testate amoebae community. Differences in the composition of shells may represent adaptations of these organisms to changes in the availability of environmental resources. We aimed to evaluate the influence of these environmental resources on the presence of different testate amoeba species, based on observation of one important functional trait (shell composition), in floodplain environments. We hypothesised that species diversity would increase with increased availability of food (chlorophyll-a; a critical environmental requirement). We also predicted that a higher concentration of suspended inorganic material would contribute to the occurrence of species that have an exogenous shell. Testate amoeba samples were taken between 2002 and 2011 in plankton of ten floodplain environments. A significant positive correlation was noted between the concentration of chlorophyll-a and the diversity of testate amoeba species according to a simple regression analysis. Furthermore, non-metric multidimensional scaling showed distinct groups with lower and higher concentration of suspended inorganic material. The occurrence of testate amoeba species with smaller exogenous shells was the most influenced by environments with higher concentrations of suspended inorganic material. Thus, our results emphasised that the evaluated environmental resources are important as assembly factors to shell traits in testate amoebae community.

Among the most prolific invasive plant species posing threats to the ecological balance of ecosystems in North America and Europe is Japanese knotweed (Fallopia japonica). In order to identify the potential role of protists in the invasive capacity of Japanese knotweed the winter abundances of naked amoebae in soils from three roadside thickets of Japanese knotweed were compared to nearby non-invaded sites. Japanese knotweed soils had higher abundances (t = 5.43, df, 16, p < 0.001) of amoebae than comparison sites. This is one of the first studies to document higher abundances of soil naked amoebae associated with an invasive plant, and may indicate more generally that below-ground abundances of amoebae can promote soil fertility and support the successful adaptation and expansion of some invasive plant species. Moreover, analysis of encysted vs. trophic forms of naked amoebae in the winter soil, provided evidence of freezeresistant, amoeba resting cells in soil samples from the natural environment in support of prior findings that were based solely on laboratory experimental evidence. Overall, high densities of naked amoebae in the winter soils of Japanese knotweed, some as resting cells capable of forming rapidly activated trophic stages, likely increase soil fertility and strengthen the species’ invasive capacity.

Members of the genus Trichodina are mostly found on fish, but have also been recorded from a variety of other aquatic organisms, including calanoid copepods. So far, it appears that all the trichodinid populations collected from calanoids in various parts of the world are the same species, i.e. Trichodina diaptomi Šrámek-Hušek, 1953. This paper reports on a new record of T. diaptomi from Metadiaptomus meridianus in a large reservoir in South Africa, as well as on a new host species, Metadiaptomus transvaalensis, and the first record of T. diaptomi from pools in an ephemeral river in northern Botswana, therefore adding a new country to the distribution of this species. We used the history of the discovery of T. diaptomi in different parts of the world and came to the conclusion that it is a cosmopolitan species, exclusively associated with copepods of the order Calanoida. Based on existing information, T. diaptomi does not appear to have a reservoir host. Against this background, we provide a discussion on the possibility that, although no dormant stage has been recorded for any trichodinid, it may be possible that T. diaptomi possesses some form of diapause and that this might be related to that of calanoid copepods.

The response of ciliate communities to cyanobacterial bloom was investigated in a shallow, hypertrophic reservoir in Slovakia, central Europe. Seasonal dynamics of ciliate communities corresponded negatively with course of water bloom formation. The highest numbers and abundances of ciliate species occurred during the spring season when cyanobacterial bloom was not fully developed, while there was an abrupt decrease in both numbers and abundances at the beginning of summer when water bloom culminated. Cyanobacterial blooming thus significantly lowered diversity and equitability of ciliate communities: many rare and sporadic species disappeared and few common taxa flourished and dominated. Nonetheless, these leading ciliates formed a functionally diverse assemblage whose members showed mostly positive contemporaneous and only rarely time-shifted interactions. There were fine filter feeders (Cinetochilum margaritaceum, Dexiotricha granulosa, Paramecium caudatum and Spirostomum teres) grazing heterotrophic bacteria and picocyanobacteria, omnivorous fine to coarse filter feeders (Frontonia leucas) as well as hunters (Coleps hirtus, Holophrya teres and Loxophyllum helus) looking for an individual prey. Also a comparatively rich, anaerobic coenosis comprising various bacterivorous armophoreans and plagiopyleans, developed at the bottom of the reservoir. Our study documents that ciliates form functionally diverse communities with potential to control cyanobacterial blooms in hypertrophic reservoirs.

Respiratory CO2 emissions from laboratory freshwater microcosms enriched with organic C (glucose and amino acids) and kept in the dark at 24°C were compared to control microcosms without C enrichment for two different freshwater pond sources. The purpose was to estimate experimentally the rate of respiratory CO2 emission from organically polluted freshwater ecosystems compared to non-enriched water. Experiment One, used pond water collected at the Lamont-Doherty Earth Observatory campus; and Experiment Two used pond water, inoculated with natural detritus, obtained from North Carolina. At peak respiration, the net efflux of CO2 (enriched minus control) to the atmosphere was ~ 90 nmol min–1 L–1 (Day 7, Experiment One) and ~ 240 nmol min–1 L–1 (Day 3, Experiment Two). The corresponding net efflux of C to the atmosphere was 25 nmol C min–1 L–1 (Day 7, Experiment One) and 65 nmol C min–1 L–1 (Day 3, Experiment Two). Peak CO2 emissions from the organic-enriched microcosms expressed as μmol m–2 s–1 (as more typically reported for natural bodies of water) were 0.20 for Experiment One, and 0.42 for Experiment Two, at a surface layer depth of approx. 20 cm, i.e. the microcosm depth. There was a relatively large correlation between respiratory CO2 emission and bacterial densities in the organic-C enriched microcosms (r = 0.76), but a smaller correlation (r = 0.32) in the non-enriched, control microcosm. Further broad scale research, robustly sampling natural bodies of organically polluted water, is needed to confirm and better establish the results of the research reported here using microcosms.