Symposium on Ciliates in Memory of Denis Lynn

Denis Lynn (1947–2018) was an outstanding protistologist, applying multiple techniques and data sources and thus pioneering an integrative approach in order to investigate ciliate biology. For example, he recognized the importance of the ultrastructure for inferring ciliate phylogeny, based on which he developed his widely accepted classification scheme for the phylum Ciliophora. In this paper, recent findings regarding the evolution and systematics of both peritrichs and the mainly marine planktonic oligotrichean spirotrichs are discussed and compared with the concepts and hypotheses formulated by Denis Lynn. Additionally, the state of knowledge concerning the diversity of ciliates in bromeliad phytotelmata and amitosis in ciliates is reviewed.     

Remarkably Complex Microbial Community Composition in Bromeliad Tank Waters Revealed by eDNA Metabarcoding

To investigate patterns of biotic community composition at different spatial scales and biological contexts, we used environmental DNA metabarcoding to characterize eukaryotic and prokaryotic assemblages present in the phytotelmata of three bromeliad species (Aechmea gamosepala, Vriesea friburgensis, and Vriesea platynema) at a single Atlantic Forest site in southern Brazil. We sampled multiple individuals per species and multiple tanks from each individual, totalizing 30 samples. We observed very high levels of diversity in these communities, and remarkable variation across individuals and even among tanks from the same individual. The alpha diversity was higher for prokaryotes than eukaryotes, especially for A. gamosepala and V. platynema samples. Some biotic components appeared to be species‐specific, while most of the biota was shared among species, but varied substantially in frequency among samples. Interestingly, V. friburgensis communities (which were sampled at nearby locations) tended to be more heterogeneous across samples, for both eukaryotes and prokaryotes. The opposite was true for V. platynema, whose samples were more broadly spaced but whose communities were more similar to each other. Our results indicate that additional attention should be devoted to within‐individual heterogeneity when assessing bromeliad phytotelmata biodiversity, and highlight the complexity of the biotic assemblages gathered in these unique habitats.     

Effects of Seasonality and Dispersal on the Ciliate Community Inhabiting Bromeliad Phytotelmata in Riparian Vegetation of a Large Tropical River

This study evaluated the influence of rainfall amount on the abundance, species richness, and species occurrence and abundance distribution of the ciliate community associated with the bromeliad Aechmea distichantha. The plants were collected from a rock wall of about 10‐km long at the left bank of Paraná River. We assessed the effects of both spatial and temporal variables on the community attributes, as well as whether plants geographically closer have a similar abundance distribution and species composition. The ciliate community was substantially distinct between both hydrological periods, with greater values of species richness and abundance in the rainy period. No spatial structuring (differences in the species occurrence and abundance distribution among strata) or geographical similarity (similarity in ciliate species composition among the plants) was found. Multiple regression analysis showed a positive relationship only between the ciliate abundances and water volumes for both periods. Although few of the formulated predictions were confirmed, our study provides valuable information on the ecological aspects of the ciliate community inhabiting bromeliad phytotelmata.     

News records of phoresy and hyperphoresy among treefrogs, ostracods, and ciliates in bromeliad of Atlantic forest

The bromeliad habitat contributes to a high biodiversity and we recorded three treefrog species as new phoretic agents of ostracods, and a first case of hyperphoresy among treefrogs, ostracods and ciliates, in these habitats of Atlantic Forest. Densities of ciliates and ostracods showed significant relationships suggesting the importance of hyperphoresy for ciliate dispersion.     

Impairment of nucleoid segregation and cell division at high osmolarity in a strain of Escherichia coli overproducing the chaperone DnaK

Abstract Fourteen species of ciliates, seven of which are new, were found living in a sample of anoxic water collected from a small lake in Spain. The species belong to all six orders in which anaerobic ciliates have been described and they include the first anaerobic representatives of the order Prostomatida. This surprising diversity is probably sustained because it embraces all ciliate feeding types, and because protozoa are the only important consumers of the diversity of microbes in anoxic habitats. Six of the anaerobic ciliate species have aerobic congeners; this strengthens the contention that anaerobic ciliates evolved independently from aerobes belonging to several taxonomic groups.     

Influence of Emergent and Submerged Macrophytes on the Structure of Planktonic Ciliate Communities in Shallow Freshwater Lakes (Eastern Poland)

Data from two shallow macrophyte‐dominated lakes (Eastern Poland) sampled with standardized methods, were evaluated in order to examine the effects of various stands of macrophytes in predicting protozooplankton community structure. Differences in macrophyte structure led to two distinct groups of habitats having different patterns of ciliate distribution. The first group consists of two vegetated habitats of sparse stem density and of the open water zone, and the second of submerged macrophyte species, which were more dense and complex. The number of significant correlations was different in the studied habitats. In central zones of macrophyte habitats the number of ciliates had the strongest correlation with concentrations of total organic carbon and P_tot. On the other side in the border zone a significant correlation between the number of ciliates and the chlorophyll a concentration was found. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Intestinal ciliate composition found in the feces of the Turk rahvan horse Equus caballus, Linnaeus 1758

Species composition and distribution of large intestinal ciliates were investigated in the feces from 15 Turk rahvan horses, living in the vicinity of Izmir, Turkey. Twenty-two ciliate genera consisting of 36 species were identified. This is the first report on intestinal ciliates in Turk rahvan horses and no previously unknown species were observed. The mean number of ciliates was 14.2 ± 13.9 × 10⁴ cells ml⁻¹ of feces and the mean number of ciliate species per host was 9.9 ± 7.1. No ciliates were observed in 2 horses. Bundleia and Blepharocorys were considered to be the major genera since these ciliates were constantly found in high proportions. In contrast, Paraisotricha, Didesmis and Gassovskiella were only observed at low frequencies. The ciliates found in this survey had almost the same characteristics as those described in previous reports, suggesting that there was no significant geographic variation in the intestinal ciliate fauna of equids.     

Ciliate grazing on <Emphasis Type="Italic">Nitrosomonas europaea</Emphasis> and <Emphasis Type="Italic">Nitrospira</Emphasis><Emphasis Type="Italic">moscoviensis</Emphasis>: Is selectivity a factor for the nitrogen cycle in natural aquatic systems?

Ciliated protists are important predators of bacteria in many aquatic habitats, including sediments. Since, many biochemical transformations within the nitrogen cycle are performed by bacteria, ciliates could have an indirect impact on the nitrogen cycle through selective grazing on nitrogen-transforming bacteria. As a case study, we examined ciliate grazing on nitrifying bacteria of the genera Nitrosomonas and Nitrospira. All experiments were designed as in vitro-experiments with cultures of different bacteria and ciliate species. The nitrifying bacteria used in our experiments were Nitrosomonas europaea [Winogradsky 1892] and Nitrospira moscoviensis [Ehrich 2001]. The ciliates comprised of four species that are known as efficient bacterivores and common members of the protist community in aquatic systems: Paramecium aurelia [Müller 1773], Euplotes octocarinatus [Carter 1972], Tetrahymena pyriformis [Ehrenberg 1830] and Cyclidium glaucoma [Müller 1786]. Our experimental approach, using a combination of DAPI and FISH staining, was successful in allowing the observation of ingestion of specific bacteria and their detection within ciliate food vacuoles. However, the ciliates in this study showed no significant selective grazing. No food preferences for a any bacterial taxon or any size class or morphotype were detected. Correlation with time between ciliate abundance and bacterial abundance or biovolume, using log transformed growth rates of ciliates and bacteria, showed no significant results. On the bacterial side, neither an active defence mechanism of the nitrifying bacteria against ciliate grazing, such as changes in morphology, nor competition for resources were observed. These results suggest that in our in vitro-experiments grazing by ciliates has no influence on abundance and growth of nitrifying bacteria and nitrification.     

Two coexisting tank bromeliads host distinct algal communities on a tropical inselberg

The tank bromeliads Aechmea aquilega (Salisb.) and Catopsis berteroniana (Schultes f.) coexist on a sun‐exposed Neotropical inselberg in French Guiana, where they permit conspicuous freshwater pools to form that differ in size, complexity and detritus content. We sampled the algal communities (both eukaryotic and cyanobacterial taxa, including colourless forms) inhabiting either A. aquilega (n = 31) or C. berteroniana (n = 30) and examined differences in community composition and biomass patterns in relation to several biotic and abiotic variables. Chlorella sp. and Bumilleriopsis sp. were the most common taxa and dominated the algal biomass in A. aquilega and C. berteroniana, respectively. Using a redundancy analysis, we found that water volume, habitat complexity and the density of phagotrophic protozoa and collector‐gatherer invertebrates were the main factors explaining the distribution of the algal taxa among the samples. Hierarchical clustering procedures based on abundance and presence/absence data clearly segregated the samples according to bromeliad species, revealing that the algal communities in the smaller bromeliad species were not a subset of the communities found in the larger bromeliad species. We conclude that, even though two coexisting tank bromeliad populations create adjacent aquatic habitats, each population hosts a distinct algal community. Hence, bromeliad diversity is thought to promote the local diversity of freshwater algae in the Neotropics.     

Forest snail faunas from Crimea (Ukraine), an isolated and incomplete Pleistocene refugium

The land snail faunas of 26 forest sites and two open rocky sites in the Crimean Mountains were sampled in 2011. Of the 40 species found within the forests (about half the known fauna of Crimea as a whole), 28 were species with wide western Palaearctic distributions, and only eight were endemic to Crimea. While there were significant differences in the faunas of different sampling areas, these seemed to be a consequence of ecological differences among them rather than a product of geographical isolation and differentiation. Endemic species were large, and not entirely restricted to forest; known endemics not found in these forests are mainly typical of more open habitats. There is no local radiation of small species living in damp forest litter, as with Leiostyla species in the Transcaucasian forest refugium, and families such as the Clausiliidae with many endemic forest species in both Transcaucasia and the Carpathians are sparsely represented. The one endemic clausiliid genus, Mentissa, occurs in open as well as in wooded habitats. The present faunas are rather poor considering the soil conditions and climate, and the forests hold widespread species often associated with open habitats elsewhere. While there is evidence that these mountains provided a refuge for many animals and plants during glacial episodes further north, the forest snail fauna suggests that full forest cover did not survive throughout the Pleistocene. Rather, the present fauna contains endemics that survived in other habitats and widespread species with good powers of passive dispersal. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 424–433.     

Comparative analysis of the mitochondrial cytochrome c oxidase subunit I (COI) gene in ciliates (Alveolata,Ciliophora) and evaluation of its suitability as a biodiversity marker

The mitochondrial cytochrome c oxidase subunit 1 (COI) gene of ciliates was first successfully sequenced in species of the genera Tetrahymena and Paramecium (Class Oligohymenophorea). The sequence of the COI gene is extremely divergent from other eukaryotes and includes an insert, which is over 300 nucleotides long. In this study, we designed a primer pair that successfully amplified the COI gene of ciliates from five different classes: Heterotrichea, Spirotrichea, Oligohymenophorea, Nassophorea and Colpodea. These classes represent the diversity of the phylum Ciliophora very well, since they are widely distributed on the ciliate small subunit rRNA tree. The amplified region is approximately 850 nucleotides long and corresponds to the general barcoding region; it also includes the insert region. In this study, 58 new COI sequences from over 38 species in 13 orders are analysed and compared, and distance trees are constructed. While the COI gene shows high divergence within ciliates, the insert region, which is present in all classes, is even more divergent. Genetic distances calculated with and without the insert region remain in the same range at the intraspecific level, but they differ considerably at or above genus level. This suggests that the entire barcoding region is under similar selective constraints and that the evolutionary rate of the ciliate COI is extremely high and shows unequal rate variation. Although many problems still remain regarding standardization of barcoding methods in ciliates, the development of a universal or almost universal primer combination for the Phylum Ciliophora represents important progress. As shown in four examples, the resolution of COI at the intraspecific level is much greater than that of any nuclear genes and shows great potential to (1) identify species based on molecular data if a reliable database exists, and (2) resolve the relationships of closely related ciliate taxa and uncover cryptic species.     

The ciliated protozoa of the monomictic Lake Kinneret (Israel): species composition and distribution during stratification

The ciliate taxa from epilimnion, hypolimnion, and littoral of Lake Kinneret were studied from November to December 1987 during stratification. Two collections of planktonic and benthic ciliates were taken at each of six sampling stations. Benthic ciliates from the littoral zone were collected at seven stations along the lake shore. Densities were determined for each ciliate species and for total protozoans at each station and sampling date. Thirty-six species of ciliates, representing 31 Genera, 18 Orders and 7 Classes, were identified. Planktonic protozoans characteristic of the epilimnion included Coleps hirtus and Vorticella mayeri. The more abundant taxa of benthic ciliates in the profundal of the lake included Saprodinium dentatum, Plagiopyla nasuta and Dexiotricha plagia. The predominant ciliate in the littoral was Pleuronema coronatum. Principal component analysis, performed on the correlation matrix of both sampling stations and species, revealed that epilimnion, hypolimnion, and littoral belt were colonized by different ciliate communities.     

Genetic analysis of ciliates living on the groundwater amphipod Crangonyx islandicus (Amphipoda: Crangonyctidae)

Two endemic subterranean freshwater amphipod species have been discovered in groundwater of the volcanic active zone in Iceland, Crangonyx islandicus and Crymostygius thingvallensis. At least five different ciliate sequences were isolated from C. islandicus and the analysis of variation at the 18S ribosomal DNA gene suggests that they present previously unsequenced species, from the orders Apostomatida and Philasterida. Apostome ciliates are well known to be exuviotrophic epibionts on crustaceans. Analyses of ciliate epibionts from different groundwater amphipod species from North America and mainland Europe revealed distinct groups of ciliates and higher diversity on the epigean amphipod Crangonyx pseudogracilis. Analysis of geographic patterns of the most common ciliate within Iceland revealed population differentiation supporting limited current connectivity between the different groundwater systems. Our study reports an occurrence of previously undescribed ciliate species in a groundwater ecosystem characterized by low species diversity.     

Global diversity of polychaetes (Polychaeta; Annelida) in freshwater

A literature review of Polychaeta (Annelida) including Aphanoneura (the oligochaete-like Aeolosomatidae and Potamodrilidae), living in freshwater yielded 168 species, 70 genera and 24 families representing all of the major polychaete clades, but less than 2% of all species. The best-represented families were, in order, Nereididae, Aeolosomatidae, Sabellidae, Spionidae and Histriobdellidae. Fourteen families were represented by a single species and genus. Regions supporting the highest diversity of freshwater polychaetes were in order, Palaearctic, Neotropical, Oriental, Nearctic, Australasian, and Afrotropical. More than half of all species and genera inhabitat lakes and rivers, followed by lagoons/estuaries, which have a high proportion of euryhaline species, and inland seas. Less common, atypical polychaete habitats include subterranean waters, the hyporheic zone of rivers and plant container habitats (phytotelmata). At least three distinct ecological/historical processes appear to account for the colonisation of continental waters: invasion of a clade prior to the break-up of Gondwana, as in Aphanoneura, Namanereis, Stratiodrilus, and Caobangia; relatively recent stranding of individual species (relicts); and the temporary visitation of euryhaline species. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

How effective are non-destructive sampling methods to assess aquatic invertebrate diversity in bromeliads?

With the growing interest in small aquatic water bodies, especially as naturally replicated model systems for ecological research, aquatic invertebrate communities in phytotelmata are increasingly receiving attention these days. The recognition of the substantial contribution to the regional species pool of specialised species draws further attention to these small and often temporary habitats. The methods currently used for studying communities in some types of phytotelma, such as bromeliads, tend to be destructive, typically involving complete dissection of the plant. The expected increase in sampling intensity associated with the increasing interest in phytotelmata may result in a negative impact on plant populations in some areas, decreasing numbers in an unsustainable way, especially in locations with ongoing, intensive research. We therefore aimed to investigate whether less-destructive sampling methods can achieve sufficient data quality to allow their use as alternatives to complete plant dissection. We tested the effectiveness of three such methods in measuring the aquatic invertebrate communities in tank bromeliads (Tillandsia guatemalensis) in Cusuco National Park, Honduras. The three methods were pipetting the water out of the bromeliad, turning the bromeliad upside down and dissecting only the outer part of the plant (the oldest, often deteriorating leaves). Overall, we found that these methods were poor predictors of richness and abundance of the organisms in communities. However, we found big differences between taxonomic groups, depending in part on the ecology of the organisms, and we suggest that some less-destructive alternative methods may be appropriate for studying some specific groups (e.g. Culicidae). Based on these results and a rapid survey of the abundance of bromeliads in the national park, we question whether intensive, ongoing research into aquatic invertebrate communities in similar phytotelma populations is sustainable. From the point of view of conservation, alternative model systems need to be found.     

Feeding response of a benthic copepod to ciliate prey type,prey concentration and habitat complexity

1. Protozoans are important consumers within microbial food webs and, in turn, they represent potential prey for small metazoans. However, feeding interactions within these food webs are rarely characterised and this is especially true for freshwater sediments. 2. We aimed to quantify the feeding links between a freshwater meiofaunal copepod and ciliates in two laboratory experiments. The first experiment addressed the response of Eucyclops serrulatus towards ciliate density and type (two ciliate species of the same genus differing in terms of body size). A second experiment assessed the effect of habitat structure on feeding rates by introducing different structural complexity into the feeding arena. In contrast to the first experiment, which was run only for one time period, this experiment also tested three different total feeding times (4, 7 and 9 h). 3. Eucyclops serrulatus exhibited high ingestion rates, with 3–69 ciliates copepod^?1 h^?1 consumed depending on food concentration, food type and habitat complexity. Copepods exhibited a preference for the smaller ciliate when total ciliate concentration was low, but selected both ciliates equally when food concentrations were medium or high. However, at very high food concentration, Eucyclops preferred the larger ciliate (which was 1/3 of its own body size), suggesting that the longer handling times of the larger prey are rewarding when the large prey is present in high numbers. In terms of total numbers consumed, copepods fed on more small ciliates, but in terms of carbon units both ciliates were selected equally when total prey concentration was low or medium. However, copepods derived more carbon from the larger prey at high and very high prey concentrations (up to 0.7 μgC out of a maximum of 1.1 μgC copepod^?1 h^?1). Habitat complexity influenced the feeding of copepods when it was observed over time. 4. The copepod–ciliate link is well known from the pelagic zone of both marine and freshwater habitats. We have shown its potential importance within the benthos, where it can be influenced by food identity, food quantity and possibly by habitat complexity.     

Functional Ecology of the Ciliate Glaucomides bromelicola,and Comparison with the Sympatric Species Bromeliothrix metopoides

We investigated the ecology and life strategy of Glaucomides bromelicola (family Bromeliophryidae), a very common ciliate in the reservoirs (tanks) of bromeliads, assessing its response to food quality and quantity and pH. Further, we conducted competition experiments with the frequently coexisting species Bromeliothrix metopoides (family Colpodidae). In contrast to B. metopoides and many other colpodean ciliates, G. bromelicola does not form resting cysts, which jeopardizes this ciliate when its small aquatic habitats dry out. Both species form bactivorous microstomes and flagellate‐feeding macrostomes. However, only G. bromelicola has a low feeding threshold and is able to adapt to different protist food. The higher affinity to the local bacterial and flagellate food renders it the superior competitor relative to B. metopoides. Continuous encystment and excystment of the latter may enable stable coexistence of both species in their natural habitat. Both are tolerant to a wide range of pH (4–9). These ciliates appear to be limited to tank bromeliads because they either lack resting cysts and vectors for long distance dispersal (G. bromelicola) and/or have highly specific food requirements (primarily B. metopoides).     

Loss of phytotelmata due to an invasive bromeliad-eating weevil and its potential effects on faunal diversity and biogeochemical cycles

Epiphytic tank bromeliads are important ecosystem engineers because they form phytotelmata that create habitat, increase species richness and abundance, create water sources and nutrient reservoirs in the canopy, and collect and redirect nutrients in forest ecosystems. Native bromeliad populations have been devastated in Florida (USA) because an invasive bromeliad-eating weevil (Metamasius callizona) has been destroying the plants. Tillandsia utriculata is a tank bromeliad that was once widespread from central to south Florida. Its populations have been hit hard by the weevil and are declining rapidly. This study quantifies the mortality rate caused by the weevil in a population of T. utriculata at the Enchanted Forest Sanctuary in central Florida and estimates the associated loss of phytotelmata. Estimations of phytotelmata were calculated for the T. utriculata baseline population, the population at 6 months into the study when 87% of the population was destroyed, and at the end of the study when less than 3% of the bromeliad population remained (99% of all deaths were caused by the weevil). The baseline population contained 16,758 L of water. At six months, there were 3180 L, and at the end of the study, there were 408 L. The loss of phytotelmata results in the loss of habitat, a decrease in biological diversity, and altered water and nutrient cycles and availability.     

Aquatic life in Neotropical rainforest canopies: Techniques using artificial phytotelmata to study the invertebrate communities inhabiting therein

In Neotropical rainforest canopies, phytotelmata (“plant-held waters”) shelter diverse aquatic macroinvertebrate communities, including vectors of animal diseases. Studying these communities is difficult because phytotelmata are widely dispersed, hard to find from the ground and often inaccessible. We propose here a method for placing in tree crowns “artificial phytotelmata” whose size and shape can be tailored to different research targets. The efficacy of this method was shown while comparing the patterns of community diversity of three forest formations. We noted a difference between a riparian forest and a rainforest, whereas trees alongside a dirt road cutting through that rainforest corresponded to a subset of the latter. Because rarefied species richness was significantly lower when the phytotelmata were left for three weeks rather than for six or nine weeks, we recommend leaving the phytotelmata for twelve weeks to permit predators and phoretic species to fully establish themselves.