Epibiotic ciliate communities on the crayfish Procambarus (Austrocambarus) sp. cultivated in a rustic aquaculture in southern Mexico.

Rustic aquaculture systems represent a sustainable production alternative in the world, providing appropriate conditions for the establishment of epibiotic ciliates on crayfish. However, the impact of epibiotic ciliates on the aquaculture production has been insufficiently studied hitherto. The objective of this work was to identify the epibiotic ciliates on the surface of the crayfish Procambarus (Austrocambarus) sp. and analyze whether there is any correlation between seasonality and environmental conditions in an artificial pond in Chiapas, Mexico. The crayfish were collected during dry and rainy seasons to investigate their ciliate epibionts. Some physical and chemical parameters of the sampled water were measured and correlation matrix analyses were applied to detect possible relationships between the presence of ciliates and environmental parameters. Thirteen species belonging to the subclasses Peritrichia and Suctoria were identified. Significant differences were found for some environmental parameters and species recorded in both seasons. The present data could help to better understand the relationship bewteen the epibiotic ciliate community on crayfish and some environmental parameters in aquaculture systems.

A tiny, long-distance hunter.

Lacrymaria olor cytoskeleton and membrane "origami" enables rapid cell hyperextension.

Incorporating mitogenome sequencing into integrative taxonomy: The multidisciplinary redescription of the ciliate Thuricola similis (Peritrichia, Vaginicolidae) provides new insights into the evolutionary relationships among Oligohymenophorea subclasses.

The evolutionary relationships among Oligohymenophorea subclasses are under debate as the phylogenomic analysis using a large dataset of nuclear coding genes is significantly different to the 18S rDNA phylogeny, and it is unfortunately not stable within and across different published studies. In addition to nuclear genes, the faster-evolving mitochondrial genes have also shown the ability to solve phylogenetic problems in many ciliated taxa. However, due to the paucity of mitochondrial data, the corresponding work is scarce, let alone the phylogenomic analysis based on mitochondrial gene dataset. In this work, we presented the characterization on Thuricola similis Bock, 1963, a loricate peritrich (Oligohymenophorea), incorporating mitogenome sequencing into integrative taxonomy. As the first mitogenome for the subclass Peritrichia, it is linear, 38,802 bp long, and contains two rRNAs, 12 tRNAs, and 43 open reading frames (ORFs). As a peculiarity, it includes a central repeated region composed of tandemly repeated A-T rich units working as a bi-transcriptional start. Moreover, taking this opportunity, the phylogenomic analyses based on a set of mitochondrial genes were also performed, revealing that T. similis, as a representative of Peritrichia subclass, branches basally to other three Oligohymenophorea subclasses, namely Hymenostomatia, Peniculia, and Scuticociliatia. Evolutionary relationships among those Oligohymenophorea subclasses were discussed, also in the light of recent phylogenomic reconstructions based on a set of nuclear genes. Besides, as a little-known species, T. similis was also redescribed and neotypified based on data from two populations collected from wastewater treatment plants (WWTPs) in Brazil and Italy, by means of integrative methods (i.e., living observation, silver staining methods, scanning and transmission electron microscopy, and 18S rDNA phylogeny). After emended diagnosis, it is characterized by: (1) the sewage habitat; (2) the lorica with a single valve and small undulations; (3) the 7-22 µm-long inner stalk; and (4) the presence of only a single postciliary microtubule on the left side of the aciliferous row in the haplokinety. Among Vaginicolidae family, our 18S rRNA gene-based phylogenetic analysis revealed that Thuricola and Cothurnia are monophyletic genera, and Vaginicola could be a polyphyletic genus.

Rhabdostylid Ciliates (Ciliophora, Peritrichia, Epistylididae) as Epibionts on Chironomid Larvae: Evidence of High Specificity and Association with Organic Pollution.

Although epibiont ciliates make up a significant part of the biomass in aquatic ecosystems and may cause perceptible alterations in the population dynamics of their hosts, studies on the extrinsic and intrinsic factors that control the abundance of these microorganisms are scarce in literature. In the present study, we investigated the colonization site and intensity of rhabdostylid epibiont upon chironomid larvae and assessed the influence of organic pollution and chironomid communities on the prevalence and abundance of epibiont ciliates at five sampling stations (two in rural areas and three in urban areas) along a neotropical urban stream over a period of 12 months. Among the 24 genera of chironomids found and the 31,976 larvae analyzed, 96.12% belonged to the Chironomus genus, of which 16.95% (5212) were colonized by Rhabdostyla aff. chironomi. The infestation intensity varied from one to 67 individuals per host with an average intensity of 4.86 (± 33.45). Ciliates were only found colonizing the chironomids' ventral tubules. The high number of chironomid larvae, high host- and site-specificity, low infestation intensity, and absence of apparent structural damage to hosts evidence an intimate relationship between epibiont and basibiont as well as a possibly long coevolutionary history. Both prevalence and abundance of epibiont ciliates were correlated to the pollution rate of the studied stream. There was an alteration in the composition and structure of the chironomid community along the sampling stations. Numeric dominance of Chironomus-tolerant chironomids and its direct correlation to infestation prevalence and to ciliates abundance highlights the predilection of both peritrich ciliates and Chironomus larvae for organically-enriched environments.

Using in situ flow cytometry images of ciliates and dinoflagellates for aquatic system monitoring / Usando imagem de citometria de fluxo in situ de ciliados e dinoflagelados para o monitoramento de sistemas aquáticos

Abstract Short-period variability in plankton communities is poorly documented, especially for variations occurring in specific groups in the assemblage because traditional analysis is laborious and time-consuming. Moreover, it does not allow the high sampling frequency required for decision making. To overcome this limitation, we tested the submersible CytoSub flow cytometer. This device was anchored at a distance of approximately 10 metres from the low tide line at a depth of 1.5 metres for 12 hours to monitor the plankton at a site in the biological reserve of Barra da Tijuca beach, Rio de Janeiro. Data analysis was performed with two-dimensional scatter plots, individual pulse shapes and micro images acquisition. High-frequency monitoring results of two interesting groups are shown. The abundance and carbon biomass of ciliates were relatively stable, whereas those from dinoflagellates were highly variable along the day. The linear regression of biovolume measures between classical microscopy and in situ flow cytometry demonstrate high degree of adjustment. Despite the success of the trial and the promising results obtained, the large volume of images generated by the method also creates a need to develop pattern recognition models for automatic classification of in situ cytometric images.

Resumo A variabilidade de curto período em comunidades do plâncton é pouco documentada, especialmente as variações que ocorrem em grupos específicos das assembleias por causa das análises tradicionais serem muito trabalhosas e demoradas. Além disso, não permitem que a alta frequência amostral necessária para a tomada de decisão. Para superar esta limitação, nós testamos o CytoSub, um citômetro de fluxo submersível. Este aparelho foi ancorado a aproximadamente 10 metros de distância da linha de maré baixa a uma profundidade de 1,5 metros por 12 horas para monitorar o plâncton em um sítio da reserva biológica da praia da Barra da Tijuca, Rio de Janeiro. A análise dos dados foi realizada a partir de gráficos de dispersão bidimensionais, pelas assinaturas ópticas individuais escaneadas (pulse shape profile) e aquisição de micro imagens. Resultados do monitoramento de alta frequência de dois grupos interessantes são apresentados. A abundância e a biomassa de carbono de um grupo de ciliados foram relativamente estáveis, ao passo que o grupo de dinoflagelado, foi altamente variável ao longo do dia. O modelo de regressão linear das medidas de biovolume entre a clássica microscopia e a citometria de fluxo in situ apresentou alto grau de ajustamento. Apesar do sucesso deste ensaio e dos resultados promissores obtidos, o grande volume de imagens geradas por este método também gerou a necessidade de se desenvolver modelos de reconhecimento de padrões para a classificação automática de imagens de citometria in situ.

Using in situ flow cytometry images of ciliates and dinoflagellates for aquatic system monitoring.

Short-period variability in plankton communities is poorly documented, especially for variations occurring in specific groups in the assemblage because traditional analysis is laborious and time-consuming. Moreover, it does not allow the high sampling frequency required for decision making. To overcome this limitation, we tested the submersible CytoSub flow cytometer. This device was anchored at a distance of approximately 10 metres from the low tide line at a depth of 1.5 metres for 12 hours to monitor the plankton at a site in the biological reserve of Barra da Tijuca beach, Rio de Janeiro. Data analysis was performed with two-dimensional scatter plots, individual pulse shapes and micro images acquisition. High-frequency monitoring results of two interesting groups are shown. The abundance and carbon biomass of ciliates were relatively stable, whereas those from dinoflagellates were highly variable along the day. The linear regression of biovolume measures between classical microscopy and in situ flow cytometry demonstrate high degree of adjustment. Despite the success of the trial and the promising results obtained, the large volume of images generated by the method also creates a need to develop pattern recognition models for automatic classification of in situ cytometric images.

Characterization of ciliate diversity in bromeliad tank waters from the Brazilian Atlantic Forest.

Bromeliads are a diverse group of plants that includes many species whose individuals are capable of retaining water, forming habitats called phytotelmata. These habitats harbor a diversity of organisms including prokaryotes, unicellular eukaryotes, metazoans, and fungi. Among single-celled eukaryotic organisms, ciliates are generally the most abundant. In the present study, we used Illumina DNA sequencing to survey the eukaryotic communities, especially ciliates, inhabiting the tanks of the bromeliads Aechmea gamosepala and Vriesea platynema in the Atlantic Forest of southern Brazil. Filtered sequences were clustered into distinct OTUs using a 99% identity threshold, and then assigned to phylum and genus using a BLAST-based approach (implemented in QIIME) and the SILVA reference database. Both bromeliad species harbored very diverse eukaryotic communities, with Arthropoda and Ciliophora showing the highest abundance (as estimated by the number of sequence reads). The ciliate genus Tetrahymena was the most abundant among single-celled organisms, followed by apicomplexan gregarines and the ciliate genus Glaucoma. Another interesting finding was the presence and high abundance of Trypanosoma in these bromeliad tanks, demonstrating their occurrence in this type of environment. The results presented here demonstrate a hidden diversity of eukaryotes in bromeliad tank waters, opening up new avenues for their in-depth characterization.

Common and Rare Taxa of Planktonic Ciliates: Influence of Flood Events and Biogeographic Patterns in Neotropical Floodplains.

After much discussion about the cosmopolitan nature of microbes, the great issue nowadays is to identify at which spatial extent microorganisms may display biogeographic patterns and if temporal variation is important in altering those patterns. Here, planktonic ciliates were sampled from shallow lakes of four Neotropical floodplains, distributed over a spatial extent of ca. 3000 km, during high and low water periods, along with several abiotic and biotic variables potentially affecting the ciliate community. We found that common ciliate species were more associated with environmental gradients and rare species were more related to spatial variables; however, this pattern seemed to change depending on the temporal and spatial scales considered. Environmental gradients were more important in the high waters for both common and rare species. In low waters, common species continued to be mainly driven by environmental conditions, but rare species were more associated with the spatial component, suggesting dispersal limitation likely due to differences in dispersal ability and ecological tolerance of species. We also found that common and rare species were related to different environmental variables, suggesting different ecological niches. At the largest spatial extents, rare species showed clear biogeographic patterns.

Ciliated protozoa community of a combined UASB-activated sludge system in southeastern Brazil.

The aims of the present study were (1) to evaluate the abundance and taxonomic composition of ciliated protozoa in the activated sludge of a full-scale combined anaerobic-aerobic system operating in a tropical country and (2) to study the relationship between the effluent quality, the physicochemical variables, and the ciliates present in the operating system. The total ciliate fauna of the activated sludge of the Piçarrão Wastewater Treatment Plant (Piçarrão WWTP) was composed of 36 morphospecies belonging to 33 genera. These included 21 species observed in the activated sludge samples on the day of collection and 15 species found in cultures. The activated sludge of the Piçarrão WWTP contained a diversified ciliate community composed mainly of indicator organisms. The most frequently occurring morphospecies were Aspidisca cicada, Vorticella spp., Gastronauta aloisi, Acineria uncinata, and Epistylis plicatilis complex. These results showed that satisfactory operating conditions prevailed at the Piçarrão WWTP. In the combined UASB-activated sludge system, the presence of Aspidisca cicada suggests the occurrence of denitrification in the process while the presence of Acineria uncinata and G. alosi indicates the removal of carbonaceous organic matter.

Anthropogenic disturbances influencing ciliate functional feeding groups in impacted tropical streams.

Anthropogenic disturbances change the trophic structure of streams, ultimately affecting ecosystem functioning. We investigated the effects of human disturbances, mainly organic pollution, on ciliate functional feeding groups (FFG) in 10 tropical streams near agricultural and urban habitats, in the dry and rainy seasons. We hypothesised that the organic pollution would affect the ciliate composition and that the richness and abundance of ciliate FFG would be associated with different disturbances, such that an increase in the load of organic matter would result in an increase in the percentage of bacterivores ciliates, while streams with low organic matter concentration and wide canopy openness will determine a higher contribution of algivorous ciliates. Our results corroborate our hypothesis of an increased development of bacterivorous ciliates with increasing organic pollution, but only in the abundance of this FFG. Also, algivorous ciliates were found to be related to riparian vegetation clearing. Thus, ciliate FFG accurately reflected different anthropogenic disturbances, revealing a change in the trophic structure of the streams. In addition, we found that organic pollution can lead to both taxonomic and functional homogenization of the ciliate community, which implies serious consequences for ecosystem functioning.

First report of predation of Giardia sp. cysts by ciliated protozoa and confirmation of predation of Cryptosporidium spp. oocysts by ciliate species.

Ciliated protozoa are important components of the microbial food web in various habitats, especially aquatic environments. These organisms are useful bioindicators for both environmental quality assessment and the wastewater purification process. The pathogenic parasitic protozoan species Giardia and Cryptosporidium represent a significant concern for human health, being responsible for numerous disease outbreaks worldwide. The predation of cysts and oocysts in 15 ciliate species from water and sewage samples collected in Campinas, São Paulo, Brazil were verified under laboratory conditions. The ciliated protozoan species were selected based on their mode of nutrition, and only bacterivorous and suspension-feeders were considered for the experiments. The species Blepharisma sinuosum, Euplotes aediculatus, Sterkiella cavicola, Oxytricha granulifera, Vorticella infusionum, Spirostomum minus, and Stentor coeruleus ingested cysts and oocysts, the resistance forms of Giardia spp. and Cryptosporidium spp., respectively. This is the first time that the ingestion of Giardia cysts by ciliated protozoa has been reported. These findings may contribute to a better understanding of the biological removal of these pathogens from aquatic environments.

Fine Structure and Molecular Phylogeny of Parametopidium circumlabens (Ciliophora: Armophorea), Endocommensal of Sea Urchins.

Metopid armophoreans are ciliates commonly found in anaerobic environments worldwide; however, very little is known of their fine structure. In this study, the metopid Parametopidium circumlabens (Biggar and Wenrich 1932) Aescht, 1980, a common endocommensal of sea urchins, is investigated for the first time with emphasis on transmission electron microscopy, revealing several previously unknown elements of its morphology. Somatic dikinetids of P. circumlabens have a typical ribbon of transverse microtubules, an isolated microtubule near triplets 4 and 5 of the anterior kinetosome, plus two other microtubules between anterior and posterior kinetosomes, a short kinetodesmal striated fiber and long postciliary microtubules. In the dikinetids of the perizonal stripe, the kinetodesmal fiber is very pronounced, and there is a conspicuous microfibrillar network system associated with the kinetosomes. A new structure, shaped as a dense, roughly cylindrical mass surrounded by microtubules, is found associated with the posterior kinetosome of perizonal dikinetids. The paroral membrane is diplostichomonad and the adoral membranelles are of the "paramembranelle" type. Bayesian inference and maximum-likelihood analysis of the 18S-rDNA gene unambiguously placed P. circumlabens as sister group of the cluster formed by ((Atopospira galeata, Atopospira violacea) Metopus laminarius) + Clevelandellida, corroborating its classification within the Metopida.

Histophagous ciliate Pseudocollinia brintoni and bacterial assemblage interaction with krill Nyctiphanes simplex. I. Transmission process.

Histophagous ciliates of the genus Pseudocollinia cause epizootic events that kill adult female krill (Euphausiacea), but their mode of transmission is unknown. We compared 16S rRNA sequences of bacterial strains isolated from stomachs of healthy krill Nyctiphanes simplex specimens with sequences of bacterial isolates and sequences of natural bacterial communities from the hemocoel of N. simplex specimens infected with P. brintoni to determine possible transmission pathways. All P. brintoni endoparasitic life stages and the transmission tomite stage (outside the host) were associated with bacterial assemblages. 16S rRNA sequences from isolated bacterial strains showed that Photobacterium spp. and Pseudoalteromonas spp. were dominant members of the bacterial assemblages during all life phases of P. brintoni and potential pathobionts. They were apparently unaffected by the krill's immune system or the histophagous activity of P. brintoni. However, other bacterial strains were found only in certain P. brintoni life phases, indicating that as the infection progressed, microhabitat conditions and microbial interactions may have become unfavorable for some strains of bacteria. Trophic infection is the most parsimonious explanation for how P. brintoni infects krill. We estimated N. simplex vulnerability to P. brintoni infection during more than three-fourths of their life span, infecting mostly adult females. The ciliates have relatively high prevalence levels (albeit at <10% of sampled stations) and a short life cycle (estimated <7 d). Histophagous ciliate-krill interactions may occur in other krill species, particularly those that form dense swarms and attain high population densities that potentially enhance trophic transmission and allow completion of the Pseudocollinia spp. life cycle.

Histophagous ciliate Pseudocollinia brintoni and bacterial assemblage interaction with krill Nyctiphanes simplex. II. Host responses.

Unlike decapod crustaceans of commercial interest, the krill defense system and its response to parasites and pathogens is virtually unknown. Histophagous ciliates of the genus Pseudocollinia interact with at least 7 krill species in the northeastern Pacific. Although they can cause epizootic events, the physiology of the histophagous ciliate-host interaction and krill (host) defenses remain unknown. From 1 oceanographic survey along the southwestern coast of the Baja California Peninsula near Bahía Magdalena and 2 in the Gulf of California, we investigated parasitoid-host physiological responses (fatty acid and oxidative stress indicators) of the subtropical krill Nyctiphanes simplex infected with the ciliate P. brintoni. All life stages of P. brintoni were associated with opportunistic bacterial assemblages that have not been explicitly investigated in other Pseudocollinia species (P. beringensis, P. oregonensis, and P. similis). Parasitoid ciliates exclusively infected adult females, which showed increased lipid content during gonad development. As the infection progressed, omega-3 eicosapentaenoic and docosahexaenoic fatty acids, which may act as energy sources to produce high numbers of ciliate transmission stages, were quickly depleted. Antioxidant enzymes, components of the crustacean defense system, varied throughout infection, but without inhibiting Pseudocollinia infection, i.e. higher levels of lipid oxidative damage were detected in late stages of infection. The ineffective response of the krill antioxidant defense system against histophagous ciliates and the bacteria associated with the ciliates suggests that Pseudocollinia ciliates are functionally analogous to krill predators and may have a strong influence on the population dynamics of krill.

Free-living ciliates from epiphytic tank bromeliads in Mexico.

The ciliate diversity of Mexican bromeliads is poorly known. We studied the ciliate community of two species of epiphytic tank bromeliads from 48 individuals of Tillandsia heterophylla and four of T. prodigiosa. The bromeliads occurred on over 22 tree host species. Samples were collected during 2009 and 2010 in a mountain cloud forest and in two coffee plantations and in a pine-oak forest. The ciliates were identified in live and protargol preparations. We recorded 61 ciliate species distributed in 39 genera grouped in eight classes. Ten species were frequent in the 52 samples (20 ± 3.2) and Leptopharynx bromeliophilus was the most frequent recorded in 25 samples. Thirty-three species are new for the fauna of Mexico, 24 species have been recorded for the first time in tank bromeliads. The classes Spirotrichea, Oligohymenophorea and Colpodea presented the highest number of species, 16, 14, and 12, respectively. Colpoda was the most species-rich genus being present with six species. A low similarity between areas and seasons was obtained with Jaccard's index. We conclude that the two bromeliads species host a rich ciliate diversity whose knowledge contributes to the question of ciliate distribution and specifically, in tank bromeliads.

The importance of protozoan bacterivory in a subtropical environment (Lobo-Broa Reservoir, SP, Brazil).

This study evaluated the importance of heterotrophic nanoflagellates (HNF) and ciliates bacterivory in a mesotrophic subtropical environment (Lobo-Broa Reservoir, Brazil) by the quantification of their ingestion rates. The in situ experiments using fluorescently labelled bacteria (FLB) were carried out bimonthly over one year (three surveys in the dry season and three in the rainy one) at the sub-surface of two sampling points that have different trophic degrees. The ingestion rates for both ciliates and HNF were higher in the meso-eutrophic region (point 2) due to the higher water temperatures, which accelerate the metabolism of protozoans and the higher bacteria densities. Concerning total protozoan bacterivory, the HNF had the greatest grazing impact on bacterial community, especially the HNF <5 µm. The data showed that HNF grazing, in addition to regulating the bacteria abundance, also induced changes to the bacterial community structure, such as increasing size and numbers of bacterial filaments. The ciliates were also important to the system bacterivory, especially in point 2, where there were high densities and ingestion rates. The protozoan bottom-up control was more important in the dry season and the top-down control was more important in the rainy season, so, these two forces are equally important to the bacterial abundance regulation in this reservoir in an annual basis.

The importance of protozoan bacterivory in a subtropical environment (Lobo-Broa Reservoir, SP, Brazil) / A importância da bacterivoria por protozoários em um ambiente subtropical (Reservatório do Lobo-Broa, SP, Brasil)

This study evaluated the importance of heterotrophic nanoflagellates (HNF) and ciliates bacterivory in a mesotrophic subtropical environment (Lobo-Broa Reservoir, Brazil) by the quantification of their ingestion rates. The in situ experiments using fluorescently labelled bacteria (FLB) were carried out bimonthly over one year (three surveys in the dry season and three in the rainy one) at the sub-surface of two sampling points that have different trophic degrees. The ingestion rates for both ciliates and HNF were higher in the meso-eutrophic region (point 2) due to the higher water temperatures, which accelerate the metabolism of protozoans and the higher bacteria densities. Concerning total protozoan bacterivory, the HNF had the greatest grazing impact on bacterial community, especially the HNF <5µm. The data showed that HNF grazing, in addition to regulating the bacteria abundance, also induced changes to the bacterial community structure, such as increasing size and numbers of bacterial filaments. The ciliates were also important to the system bacterivory, especially in point 2, where there were high densities and ingestion rates. The protozoan bottom-up control was more important in the dry season and the top-down control was more important in the rainy season, so, these two forces are equally important to the bacterial abundance regulation in this reservoir in an annual basis.

Este estudo avaliou a importância da bacterivoria por nanoflagelados heterotróficos (NFH) e ciliados em um ambiente subtropical mesotrófico (Reservatório do Lobo-Broa, Brasil) pela quantificação de suas taxas de ingestão. Os experimentos in situ utilizando bactérias marcadas por fluorescência (FLB) foram realizados bimestralmente durante um ano (três estudos no período seco e três no período chuvoso) na superfície de dois pontos de coleta que apresentam graus de trofia diferentes. As taxas de ingestão, tanto para os ciliados quanto para os NHF, foram maiores no ponto 2 (P2) devido provavelmente as maiores temperaturas da água, que aceleram o metabolismo dos protozoários, e as maiores densidades de bactérias. Em relação à bacterivoria total por protozoários, as populações de NFH causaram maior impacto de predação sobre a comunidade bacteriana do reservatório, principalmente os NFH menores que 5µm. Os dados indicaram que a predação por NFH, além de regular a abundância de bactérias, provavelmente também induziu modificações na estrutura da comunidade bacteriana, como o aumento do tamanho e da quantidade de filamentos bacterianos. Os ciliados também contribuíram significativamente para a bacterivoria no sistema, principalmente no P2, onde apresentaram altas densidades e taxas de ingestão. O controle bottom-up teve maior importância no período seco e o controle top-down maior importância no período chuvoso, assim, estas duas forças são igualmente importantes na regulação da abundância bacteriana neste reservatório em uma base anual.

The importance of protozoan bacterivory in a subtropical environment (Lobo-Broa Reservoir, SP, Brazil) / A importância da bacterivoria por protozoários em um ambiente subtropical (Reservatório do Lobo-Broa, SP, Brasil)

This study evaluated the importance of heterotrophic nanoflagellates (HNF) and ciliates bacterivory in a mesotrophic subtropical environment (Lobo-Broa Reservoir, Brazil) by the quantification of their ingestion rates. The in situ experiments using fluorescently labelled bacteria (FLB) were carried out bimonthly over one year (three surveys in the dry season and three in the rainy one) at the sub-surface of two sampling points that have different trophic degrees. The ingestion rates for both ciliates and HNF were higher in the meso-eutrophic region (point 2) due to the higher water temperatures, which accelerate the metabolism of protozoans and the higher bacteria densities. Concerning total protozoan bacterivory, the HNF had the greatest grazing impact on bacterial community, especially the HNF <5µm. The data showed that HNF grazing, in addition to regulating the bacteria abundance, also induced changes to the bacterial community structure, such as increasing size and numbers of bacterial filaments. The ciliates were also important to the system bacterivory, especially in point 2, where there were high densities and ingestion rates. The protozoan bottom-up control was more important in the dry season and the top-down control was more important in the rainy season, so, these two forces are equally important to the bacterial abundance regulation in this reservoir in an annual basis.(AU)

Este estudo avaliou a importância da bacterivoria por nanoflagelados heterotróficos (NFH) e ciliados em um ambiente subtropical mesotrófico (Reservatório do Lobo-Broa, Brasil) pela quantificação de suas taxas de ingestão. Os experimentos in situ utilizando bactérias marcadas por fluorescência (FLB) foram realizados bimestralmente durante um ano (três estudos no período seco e três no período chuvoso) na superfície de dois pontos de coleta que apresentam graus de trofia diferentes. As taxas de ingestão, tanto para os ciliados quanto para os NHF, foram maiores no ponto 2 (P2) devido provavelmente as maiores temperaturas da água, que aceleram o metabolismo dos protozoários, e as maiores densidades de bactérias. Em relação à bacterivoria total por protozoários, as populações de NFH causaram maior impacto de predação sobre a comunidade bacteriana do reservatório, principalmente os NFH menores que 5µm. Os dados indicaram que a predação por NFH, além de regular a abundância de bactérias, provavelmente também induziu modificações na estrutura da comunidade bacteriana, como o aumento do tamanho e da quantidade de filamentos bacterianos. Os ciliados também contribuíram significativamente para a bacterivoria no sistema, principalmente no P2, onde apresentaram altas densidades e taxas de ingestão. O controle bottom-up teve maior importância no período seco e o controle top-down maior importância no período chuvoso, assim, estas duas forças são igualmente importantes na regulação da abundância bacteriana neste reservatório em uma base anual.(AU)

Redescription of the Little-known Ciliate Apoamphisiella vernalis (Stokes, 1887) Berger, 2006 (Ciliophora, Hypotricha) from the Atlantic Forest, Brazil.

Apoamphisiella Foissner, 1997 is a genus of hypotrichous ciliates reported to occur in various locations in the world, but that seems particularly widespread in the Americas. In this study, the first record of Apoamphisiella vernalis for Brazil is presented based on a population from the Atlantic Forest of the Minas Gerais state. A redescription of A. vernalis made from light and scanning electron microscopy observations unveils a unique combination of diagnostic features for this species, namely the presence of green cortical granules, one contractile vacuole lacking collecting canals, and the rear end of both left and right marginal cirral rows located at same level. Moreover, A. vernalis is found to be an omnivorous predator, feeding on arcelline testate amoebae, rotifers, and other organisms.

Paratrichodina africana (Ciliophora: Trichodinidae) of wild and cultured Nile tilapia in the Northern Brazil.

The present work morphologically characterizes Paratrichodina africana from the gills of wild and farmed Nile tilapia from Northern Brazil (eastern Amazonia). Ninety fish were captured for parasitological analysis in Macapá, State of Amapá, from a wetland area bathed by the Amazon River commonly called 'Ressaca do Zerão' (n = 52), as well as from a local fish farm (n = 38). Wet smears of the skin and gills of the captured fish were air dried at room temperature and impregnated with silver nitrate by Klein's method for posterior examination of the adhesive disc structures. Total prevalence of parasitism was 16.6% (23% in fish from wetland and 7.8% in farmed fish). Characterized as a small-sized trichodinid, it presented the following measures: 33.2 ± 4.7 µm body diameter, 17.5 ± 2.1 µm adhesive disc, 10.0 ± 0.9 µm denticulate ring, and 22.6 ± 2.0 denticles. Paratrichodina africana reported in this study strongly resembles those described for other localities, but it differs by presenting greater body length. This is the fourth report of P. africana parasitizing a host fish.