Effects of nitrofurazone on ecosystem function in marine environments: A case study on microbial fauna

To evaluate the effects of nitrofurazone on functional processes in marine ecosystems, periphytic protozoan communities were exposed to different concentrations of the antibiotic for a 10-day duration. Species trait distributions in the tested communities were observed during exposure to five concentrations of nitrofurazone. A fuzzy coding system with seven traits and seventeen categories was used to summarize the changes in functional patterns of the test organisms. Nitrofurazone had a significant influence on the function process of the periphytic ciliate communities. Bacterivores with flattened bodies were sensitive to the toxicant whereas sessile and cylindrical raptors showed a high tolerance to nitrofurazone, invariably dominating communities exposed to high concentrations. Bootstrapped-average analysis demonstrated a significant change in functional patterns at highest nitrofurazone concentrations (8 mg l^-1). Based on these findings, it is suggested that nitrofurazone may negatively influence ecosystem function in marine environments.

Ratio of abundances of ciliates behavioral groups as an indicator of the treated wastewater impact on rivers

A method for assessing the degree of impact of wastewater treatment plant discharge on receiving rivers was proposed, based on the structural indicators of the population of ciliated protozoa. It was shown that the ratio of attached, crawling and free-swimming forms in bottom sediments changes under the influence of discharge. In the points subject to organic pollution, the share of attached filter-feeding bacteriovorous ciliates increases in the assemblage of ciliated protozoa. The proposed Attached Form Index (AFI) takes this ratio into account. The use of AFI makes it possible to assess the restructuring of the assemblage of ciliated protozoa under the influence of point sources of pollution, to establish a zone of negative influence of runoff, to assess the degree of restoration of the aquatic ecosystem, as the influence of the pollution source weakened.

Improved Methods for Bulk Cultivation and Fixation of Loxodes Ciliates for Fluorescence Microscopy

Loxodes is one of the best ecologically characterized ciliate genera with numerous intriguing physiological abilities, including gravity-sensing organelles and nitrate respiration. However, these cells have been considered challenging to cultivate in bulk, and are poorly preserved by conventional fixatives used for fluorescence microscopy. Here we describe methods to grow and harvest Loxodes cells in bulk with liquid soil extract medium, as well as a new fixative called ZFAE (zinc sulfate, formaldehyde, acetic acid, ethanol) that can fix Loxodes cells more effectively than buffered formaldehyde or methanol. We show that ZFAE is compatible with immunofluorescence and the nuclear stain DAPI. Loxodes is thus now amenable to long-term maintenance, large-scale growth, and modern cell biology investigations of monoclonal strains in laboratory conditions.

Hydrodynamic dissection of Stentor coeruleus in a microfluidic cross junction

Stentor coeruleus, a single-cell ciliated protozoan, is a model organism for wound healing and regeneration studies. Despite Stentor's large size (up to 2 mm in extended state), microdissection of Stentor remains challenging. In this work, we describe a hydrodynamic cell splitter, consisting of a microfluidic cross junction, capable of splitting Stentor cells in a non-contact manner at a high throughput of ∼500 cells per minute under continuous operation. Introduction of asymmetry in the flow field at the cross junction leads to asymmetric splitting of the cells to generate cell fragments as small as ∼8.5 times the original cell size. Characterization of cell fragment viability shows reduced 5-day survival as fragment size decreases and as the extent of hydrodynamic stress imposed on the fragments increases. Our results suggest that cell fragment size and composition, as well as mechanical stress, play important roles in the long-term repair of Stentor cells and warrant further investigations. Nevertheless, the hydrodynamic splitter can be useful for studying phenomena immediately after cell splitting, such as the closure of wounds in the plasma membrane which occurs on the order of 100-1000 seconds in Stentor.

Community assembly and co-occurrence network complexity of pelagic ciliates in response to environmental heterogeneity affected by sea ice melting in the Ross Sea, Antarctica

In the Southern Ocean, the living environment of organisms has changed due to the dramatic increase in melting sea ice and the loss of glaciers, which have consequently caused substantial changes in biodiversity. Samples of pelagic ciliates from 13 sites were collected as bioindicators to demonstrate the relationship between spatial distribution patterns and environmental heterogeneity affected by sea ice melting and to reveal the community assembly mechanisms in the Ross Sea. Univariate analyses and multivariate analyses were effective tools demonstrating clear spatial patterns and providing a sufficient explanation to interpret strong correlations between pelagic ciliate communities and environmental variations, especially the distribution pattern of nutrients and Chl a. Moreover, environmental heterogeneity might affect the co-occurrence network complexity of ciliate communities. Furthermore, our results also indicated that stochastic processes play a significant role in the community assembly of pelagic ciliates. This study examined the controlling mechanisms of environmental heterogeneity affected by sea ice melting on pelagic ciliate communities and provided explanations for the community assembly of pelagic ciliates in polar marine ecosystems.

Scuticociliatosis caused by Philasterides dicentrarchi

The ciliate Philasterides dicentrarchi has been previously identified as a new agent of scuticociliatosis in marine fish. The parasite can cause high mortalities in fish reared on farms or kept in aquariums. P. dicentrarchi is usually a free-living protozoan but can become an opportunistic histophagous parasite causing rapid lethal systemic infections in cultured fish. This review provides information about the morphology and biology of the scuticociliate P. dicentrarchi, as well as information about the pathological and immunological reactions of the host in response to the infection with the parasite. The epidemiology and the control strategies of the disease are also reviewed.

Landscape configuration affects probability of apex predator presence and community structure in experimental metacommunities

Biodiversity is declining at an unprecedented rate, highlighting the urgent requirement for well-designed protected areas. Design tactics previously proposed to promote biodiversity include enhancing the number, connectivity, and heterogeneity of reserve patches. However, how the importance of these features changes depending on what the conservation objective is remains poorly understood. Here we use experimental landscapes containing ciliate protozoa to investigate how the number and heterogeneity in size of habitat patches, rates of dispersal between neighbouring patches, and mortality risk of dispersal across the non-habitat ‘matrix’ interact to affect a number of diversity measures. We show that increasing the number of patches significantly increases γ diversity and reduces the overall number of extinctions, whilst landscapes with heterogeneous patch sizes have significantly higher γ diversity than those with homogeneous patch sizes. Furthermore, the responses of predators depended on their feeding specialism, with generalist predator presence being highest in a single large patch, whilst specialist predator presence was highest in several-small patches with matrix dispersal. Our evidence emphasises the importance of considering multiple diversity measures to disentangle community responses to patch configuration.

Effect of Predation by Colpoda sp. in Nitrogen Fixation Rate of Two Free-Living Bacteria

Biological nitrogen fixation is limited to several groups of prokaryotes, some of them reduce nitrogen as free-living nitrogen-fixing bacteria. Protozoa predation on these latter releases sequestered nitrogen that may enhance the formation of new bacterial biomass and possibly increase nitrogen fixation within soil microbial communities. We aim to evaluate the predation effect of Colpoda sp. on two nitrogen fixers: Azospirillum lipoferum and Stenotrophomonas sp. during their lag, early exponential, and exponential phases. The kinetics of bacterial population growth was determined in the predators' presence or absence and the effect of predation on the rate of N fixation was evaluated through the reduction of acetylene to ethylene technique. Colpoda sp. showed a non-significant difference in preferences between the two species offered as prey. Consequently, the abundance of A. lipoferum and Stenotrophomonas sp. decreased significantly due to predator's pressure and both species responded by increasing their specific growth rate. Likewise, predation promoted greater nitrogen fixation rate by CFU during the lag phase in A. lipoferum (0.20 nM/CFU with predation vs 0.09 nM/CFU without predation) and Stenotrophomonas sp. (0.22 nM/CFU vs 0.09 nM/CFU respectively). During early exponential phase (29 h), the rate diminished to 0.13 and 0.05 nM/CFU in A. lipoferum and to 0.09 nM/CFU and 0.05 nM/CFU in Stenotrophomonas sp. Finally, during the exponential phase (52 h), only A. lipoferum without predation produced 0.003 nM/CFU of ethylene. Thus, the nitrogenase activity was higher in the lag and the early exponential phases when predator activity was involved.

Quantitative detection of parasitic ciliate Cryptocaryon irritans in seawater with an optimized sample processing method

The protozoan Cryptocaryon irritans is one of the most important ectoparasites of marine fish, causing 'white spot disease' and mass mortality in aquaculture. To accurately predict disease outbreaks and develop prevention strategies, improved detection methods are required that are sensitive, convenient and rapid. In this study, a pair of specific primers based on the C. irritans 18S rRNA gene was developed and used in a real-time PCR (qPCR) assay. This assay was able to detect five theronts in 1 L of natural seawater. Furthermore, a linear model was established to analyse the log of Ct value and parasite abundance in seawater (y = -2.9623x + 24.2930), and the coefficient of determination (R² ) value was 0.979. A lysis buffer was optimized for theront DNA extraction and used for storage sample. This method was superior to the commercial water DNA kit, and there was no significant degradation of DNA at room temperature for 24-96 hr. A dilution method was developed to manage qPCR inhibitors and used to investigate natural seawater samples in a net cage farm with diseased fish, and the findings were consistent with the actual situation. This study provides a valuable tool for assisting in the early monitoring and control of cryptocaryoniasis in aquaculture.

How do microalgae in response to biological pollution treat in cultivation? A case study investigating microalgal defense against ciliate predator Euplotes vannus

Microalgae have significant amounts of proteins, lipids, carotenoids, vitamins, minerals, and unique pigments. However, with the gradual expansion of microalgae cultivation, hostile biological pollution seriously restricted the large-scale microalgae cultivation and limited the exploitation of its biological resources. Moreover, protozoan poses the greatest threat to microalgae cultivation. Here, the relationship between six marine economic microalgae populations and their ciliate predator Euplotes vannus was examined. And four concentrations were designed for each type of microalgae to carry out the experiment. It was revealed that four species of microalgae inhibit the ciliate population growth at high density. Furthermore, the experiment which was the influence of microalgae at three different growth stages on the growth of the ciliates for these four kinds of high-density inhibitory microalgae was designed. The microalgae inhibitory effects were already exhibited at the end of the exponential growth phase, and it was significantly inhibited during the stationary growth phase. As the microalgae concentration increased, the inhibitory effect became more pronounced. This study provides fundamental data for screening protozoan-inhibiting microalgae and shows potential to be used in algae cultivation.

Insights for monitoring surveys into influence of tidal events on protozoan periphyton fauna along the tidelines of Yellow Sea, Northern China

To explore the influence of tidal events on protozoan periphyton fauna along tidelines, a 1-month baseline survey for bioassessment was conducted in an intertidal zone of the Yellow Sea, Northern China. A total of 27 protozoans species were identified among five sampling sites along five tidelines (sites A-E). The periphytic protozoans showed a significant variation in species distribution and community pattern along five tidelines. Species richness decreased from the high tideline (site A) and reached the minimum value at the middle tideline (site C), followed by an increase up to the low tideline (site E). Individual abundances peaked at site C and leveled off at the other four tidelines. Species richness, evenness, and diversity showed low value at site C compared with those at the other four sites. These findings suggest that periphytic protozoan fauna was shaped by tidal events along the tidelines of marine ecosystems.

Use of protozoan periphytons for evaluating of environmental heterogeneity in intertidal zones of marine ecosystems

As an important biological indicator, multivariate dispersion in homogeneity of an observed community is a useful parameter for bioassessment of environmental heterogeneity. To identify the influence of tidal events on homogeneity of protozoan periphyton fauna from the highest tideline to the lowest, a 1-month baseline survey was carried out along five tidelines (sites A-E) in an intertidal zone of the Yellow Sea, northern China. There was a significant influence of tidal events on the homogeneity in both compositional and community structure among five tidelines. The β-diversity measures generally decreased from the highest tideline to the lowest. The biodiversity indices of the protozoans dropped sharply from the highest to the middle tidelines, followed by an increase until to the lowest tideline. These findings suggest that the homogeneity of protozoan periphyton in both species composition and relative abundance was significantly shaped by the environmental heterogeneity in intertidal zones of marine ecosystems.

Use of functional units of periphytic protozoa for monitoring water quality in marine ecosystems: bioindicator redundancy

Although periphytic protozoan communities have long been used for the bioassessment of water quality, their utility is hampered by functional redundancy, leading to high "signal-to-noise" ratios. In this study, a 1-year baseline survey of periphytic protozoan communities was carried out in coastal waters of the Yellow Sea, northern China, in order to determine redundancy levels in conditions of differing water quality. Samples were collected at four sampling sites along a pollution gradient. Environmental variables such as salinity, chemical oxygen demand (COD), and concentrations of dissolved oxygen (DO), soluble reactive phosphates (SRP), ammonium nitrogen (NH₄-N), and nitrate nitrogen (NO₃-N) were measured to compare with biotic factors. A total of 53 functional units (FUs) were identified from 144 observed protozoan species based on four biological traits, i.e., feeding type, body size, movement type, and source of food supply. For reducing the "signal-to-noise" ratios of species-abundance/biomass data, the peeling procedure was used to identify the bioindicator redundancy levels based on these FUs. Three consecutive subsets of response units (RU1-RU3) with correlation coefficients > 0.75 of the full FU dataset were identified, comprising 12 FUs, 21 FUs, and 9 FUs, respectively. Algivores and bacterivores were dominant in RU1 and RU2 among the polluted sites, whereas raptors were dominant in RU3 at the unpolluted site. In terms of relative abundance, RU1 was the primary contributor to the protozoan communities during the 1-year cycle and its relative abundance increased with the increasing pollution, whereas RU2 and RU3, with complementary temporal distributions, generally decreased with increasing pollution. Ordinations based on bootstrapped average analyses revealed a significant variation in the functional pattern of all three RUs among the four sampling sites. Biological-environmental match analysis demonstrated that the variability was driven by the increasing concentrations of nutrients (e.g., NH₄-N, NO₃-N, and PO₄-P) and decreasing concentrations of DO (P < 0.05). There were high levels of functional redundancy among periphytic protozoan communities which could be used as bioindicators of marine water quality.

Can tidal events influence analysis on colonization dynamics in body-size spectrum of periphytic ciliates for marine bioassessment?

The tidal influence on body-size spectrum of the protozoan periphytons was explored by using the conventional slide system (CS) and the polyurethane foam enveloped slide system (PFES) in coastal waters during a 1-month study. During the colonization process, clear temporal patterns of the body-size spectrum were observed using the two sampling methods. In terms of relative species number and frequency of occurrence, the rank S4 represented a more stable temporal variability in the PFES system than the CS system during the colonization. Additionally, the small forms (e.g., S1, S2, and S3) were more abundant in the PFES system. The clustering and bootstrapped average analyses demonstrated differences in body-size spectrum of protozoans between the two sampling systems. Our results imply that the body-size spectrum of protozoan periphytons may be impacted by tidal events during colonization process in marine waters.

Heterosigma akashiwo does not serve as prey and chloroplast donor for the toxic dinoflagellate, Dinophysis acuminata

In laboratory culture, the toxic dinoflagellate Dinophysis acuminata acquires plastids from the ciliate, Mesodinium rubrum, which, in turn, acquires plastids from the cryptophyte, Teleaulax amphioxeia. Reports of D. acuminata from field samples found plastids of the raphidophyte, Heterosigma akashiwo within D. acuminata cells, suggesting a broader range of prey. Dinophysis blooms often co-occur with H. akashiwo in Delaware's inland bays. In the study presented here, predation on H. akashiwo by D. acuminata was investigated. Growth rates of D. acuminata were measured when cultured with H. akashiwo either alone or with its known prey, M. rubrum. M. rubrum was also cultured with H. akashiwo to examine predation by the ciliate as a vector for Heterosigma plastids. Ingestion rates by D. acuminata were measured when presented with H. akashiwo as prey, and retention of plastids from H. akashiwo was investigated by measuring chlorophyll a fluorescence intensities in D. acuminata cells presented with H. akashiwo as prey compared to M. rubrum. Additionally, a fluorescence-based method was developed to identify the presence of the accessory pigment fucoxanthin from H. akashiwo plastids in cells of D. acuminata. Results showed that the growth rate of D. acuminata was significantly lower when offered H. akashiwo as prey compared the growth rate when offered M. rubrum as prey. Likewise, no predation was observed when D. acuminata was offered H. akashiwo as prey. Intensity of chlorophyll a fluorescence was lower when H. akashiwo was offered as prey compared to M. rubrum, and fucoxanthin was not detected in any of the Dinophysis cells examined after incubation with H. akashiwo. Results of this investigation do not support the hypothesis that D. acuminata preys on H. akashiwo and highlight the need for further research on factors that stimulate the growth of Dinophysis in field populations.

Insights into the ecotoxicity of nitrofurazone in marine ecosystems based on body-size spectra of periphytic ciliates

In ecotoxicological studies, some biological responses known as biomarkers can be used as powerful tools to evaluate the ecotoxicity. In this study, we investigated the disparity of responses shown by body-size spectra of periphytic ciliate communities when used as biomarkers to detect the toxicity of the broad-spectrum veternary antibiotic nitrofurazone. Briefly, in chronic exposure experiments ciliate communities were exposed to different concentrations (0, 1, 2, 4 and 8 mg ml^-1) of nitrofurazone. Relative Abundance of ciliates in all body-size categories decreased significantly, whereas their frequency of occurrence and probability densities showed hormetic-like responses in a dose dependent manner. Additionally, body-size distinctness indices were influenced by toxic stress and significantly departed from an expectation at higher nitrofurazone concentrations. Taken together, our results demonstrated that body-size spectra and body-size distinctness offered clear evidence of nitrofurazone toxicity in periphytic ciliates. Body-size spectra can therefore be used as a pivotal biomarker to determine the ecotoxicity of nitrofurazone in aquatic environments.

Disentangling the relative roles of natural and anthropogenic-induced stressors in shaping benthic ciliate diversity in a heavily disturbed bay

Coastal areas are facing biodiversity loss and degradation of habitats due to intensified human activities. However, our understanding of the relative contribution of natural gradients and human induced disturbance to biodiversity is limited. Here, we investigated the response of three facets of alpha and beta diversity of benthic ciliates to environmental gradients in a highly disturbed estuarine bay in China. We used linear regression and distance-based redundancy analysis to determine the key driving factors for biodiversity. Variation partitioning was further used to examine the relative influence of natural gradients and anthropogenic disturbances on ciliate communities. Our results revealed that ciliate alpha diversity and functional composition remained similar despite notable variation in species composition along salinity gradient. Sediment grain size, together with heavy metals were the strongest determinants in shaping both alpha and beta diversity. After controlling for the effect of natural factors, heavy metals still had significant impacts on beta diversity. Human induced nitrogen enrichment was positively correlated with algivorous functional group with possible impacts on benthic food webs. These results suggest that beta diversity is overall more sensitive to anthropogenic stressors than alpha diversity and give important insights into the role of anthropogenic disturbance on coastal diversity, being also useful for developing ecosystem protection and conservation strategies.

Comparative Study of Rumen Ciliate Fauna of Goat and Sheep in Libya

OBJECTIVE

This study aims to provide comparative information on the rumen ciliate fauna of goat (Capra aegagrus hircus) and sheep (Ovis aries) living in Zawiya, Libya.

METHODS

We obtained rumen samples from 16 goats and 17 sheep after the slaughter in Zawiya, Libya between June and August 2016. We immediately fixed the well-mixed samples with an equal volume of 18.5% formalin. We filtered and stained the samples in the laboratory with methyl green formalin saline solution to determine the nuclei and added 2% Lugol's iodine solution to visualize the skeletal plates.

RESULTS

We found that the mean number (± standard deviation) of ciliates in the rumen contents from goats and sheep was 70.9±61.6×10⁴ cells mL^-1 (minimum-maximum value, 4.0-187.0×10⁴ cells mL^-1) and 96.3±49.3×10⁴ cells mL^-1 (minimum-maximum value, 19.5-235.0×10⁴ cells mL^-1), respectively. Results also showed that the total number of species per goat and sheep was 1-17 (mean, 8.2±4.7) and 1-13 (mean, 7.9±3.8), respectively. We identified 10 genera, 19 species, and 11 morphotypes in goats and 9 genera, 16 species, and 13 morphotypes in sheep. Additionally, we found that Entodinium simulans prevalence in all goats and sheep was 100%. On the other hand, we observed Hsiungia triciliata and Ostracodinium gracile in only one goat (6.3% prevalence) and Polyplastron multivesiculatum in only one sheep (5.9% prevalence). Overall, the ruminal ciliate fauna of goat and sheep in Libya comprised Entodinium species (mean for goats, 85.9%; mean for sheep, 83.5%).

CONCLUSION

This study recorded Hsiungia triciliata as a new endosymbiont in goats. To our knowledge, this study is the first to report all of the species detected in goats from Libya. Similarly, this is the first to detect Diplodinium anisacanthum, Entodinium bursa, E. ellipsoideum, E. longinucleatum, E. simulans, Isotricha prostoma, Ophryoscolex caudatus, Ostracodinium gracile, and Polyplastron multivesiculatum in sheep from Libya.

Predator Chemical Cue Effects on the Diel Feeding Behaviour of Marine Protists

We have assessed the effect of copepod chemical cues on the diel feeding rhythms of heterotrophic and mixotrophic marine protists. All phagotrophic protists studied exhibited relatively high diurnal feeding rates. The magnitude of the diel feeding rhythm, expressed as the quotient of day and night ingestion rates, was inversely related to the time that phagotrophic protists were maintained in the laboratory in an environment without predators. In the case of the recently isolated ciliate Strombidium arenicola, the rhythm was lost after a few months. When challenged with chemical alarm signals (copepodamides) from the copepod Calanus finmarchicus at realistic concentrations (0.6-6 pM), S. arenicola partially re-established diurnal feeding. Conversely, the amplitude of the diel feeding rhythm for the ciliate Mesodinium rubrum was not affected by copepodamides, although the 24-h integrated food intake increased by approximately 23%. For the dinoflagellates Gyrodinium dominans and Karlodinium armiger, copepodamides significantly reduced the amplitude of their diel feeding rhythms; significant positive effects on total daily ingestion were only observed in G. dominans. Finally, the dinoflagellate Oxyrrhis marina, isolated >20 years ago, showed inconsistent responses to copepodamides, except for an average 6% increase in its total ingestion over 24 h. Our results demonstrate that the predation risk by copepods affects the diel feeding rhythm of marine protists and suggests a species-specific response to predation threats.

Influence of tidal events on the body-size spectrum of periphytic ciliates for marine bioassessment using artificial substrata

As an internal functional trait of a community, the body-size spectrum is a highly informative indicator for bioassessment of water/environmental quality in aquatic ecosystems. To determine the influence of tidal events on body-size spectra of protozoan periphytons, a 3-month baseline survey was conducted in Korean coastal waters using the polyurethane foam enveloped slide system (PFES) and conventional slide system (CS). The body-size spectrum of the protozoans showed a clear temporal pattern during the study period using both sampling systems. However, the temporal dynamics showed significantly different trajectories in the body-size spectrum between the two sampling methods during the study period. The bootstrapped average analysis revealed that the patterns of the body-size spectrum were significantly different between the PFES and CS systems, especially in terms of frequency of occurrence. These findings suggest that the tidal events may significantly influence body-size spectrum of periphytic ciliates for bioassessment in marine ecosystems.

Signals from the deep-sea: Genetic structure, morphometric analysis, and ecological implications of Cyclothone braueri (Pisces, Gonostomatidae) early life stages in the Central Mediterranean Sea

Cyclothone braueri (Stomiiformes, Gonostomatidae) is a widely distributed fish inhabiting the mesopelagic zone of marine tropical and temperate waters. Constituting one of the largest biomasses of the ocean, C. braueri is a key element in most of the ecological processes occurring in the twilight layer. We focused on the ecological processes linked to early life stages in relation to marine pelagic environmental drivers (temperature, salinity, food availability and geostrophic currents) considering different regions of the Central Mediterranean Sea. A multivariate morphometric analysis was carried out using six parameters with the aim of discerning different larval morphotypes, while a fragment of 367 bp representing the 12S ribosomal RNA gene was used to perform molecular analyses aimed at determining the intraspecific genetic variability. Analysis highlighted two geographically distinct morphotypes not genetically discernible and related to the different nutritional conditions due to spatial heterogeneities in terms of temperature and food availability. The body depth (BD) emerged as an appropriate morphometric parameter to detect the larval condition in this species. Molecular analysis highlighted a moderate genetic divergence in the fish population, showing the recurrence of two phylogroups not geographically separated.

Insights into seasonal shift in the homogeneity of periphytic protozoan fauna in coastal waters of the Yellow Sea, northern China

The seasonal shift in the homogeneity of the periphytic protozoan fauna was studied based on a four-season baseline survey in the coastal waters of the Yellow Sea, northern China. Samples were collected using glass microscope slides as an artificial substratum at a depth of 2 m after the immersion time of 14 days during each of the four seasons (winter, spring, summer, and autumn, 2017). The protozoan fauna showed a clear seasonal shift in species composition and a significant variation in homogeneity in terms of both compositional and community structure during four seasons. The dispersion measures and β-diversity index represented an increase in the trend from spring to winter. These findings suggest that the homogeneity of the periphytic protozoan fauna was subject to a significant variability shaped mainly by species composition during a four-season cycle in marine ecosystems.

Prey type constrains growth and photosynthetic capacity of the kleptoplastidic ciliate Mesodinium chamaeleon (Ciliophora)

Kleptoplastidic, or chloroplast-stealing, lineages offer insight into the process of acquiring photosynthesis. By quantifying the ability of these organisms to retain and use photosynthetic machinery from their prey, we can understand how intermediaries on the endosymbiosis pathway might have evolved regulatory and maintenance mechanisms. Here, we focus on a mixotrophic kleptoplastidic ciliate, Mesodinium chamaeleon, noteworthy for its ability to retain functional chloroplasts from at least half a dozen cryptophyte algal genera. We contrasted the performance of kleptoplastids from blue-green and red cryptophyte prey as a function of light level and feeding history. Our experiments showed that starved M. chamaeleon cells are able to maintain photosynthetic function for at least 2 weeks and that M. chamaeleon containing red plastids lost chlorophyll and electron transport capacity faster than those containing blue-green plastids. However, likely due to increased pigment content and photosynthetic rates in red plastids, M. chamaeleon had higher growth rates and more prolonged growth when feeding on red cryptophytes. For example, M. chamaeleon grew rapidly and extensively when fed the blue-green cryptophyte Chroomonas mesostigmatica, but this growth appeared to hinge on high levels of feeding supporting photosynthetic activity. In contrast, even starved M. chamaeleon containing red plastids from Rhodomonas salina could achieve high photosynthetic rates and extensive growth. Our findings show that plastid origin impacts the maintenance and magnitude of photosynthetic activity, though whether this is due to variation in ciliate control or gradual loss of plastid function in ingested prey cells remains unknown.

Water mass shapes the distribution patterns of planktonic ciliates (Alveolata, Ciliophora) in the subtropical Pearl River Estuary

Ciliates comprise essential components of microzooplankton in diverse marine environments. However, the extent to which environmental variables shape the distribution of planktonic ciliates in complex estuarine systems remains unclear. Here, 52 samples were collected from the Pearl River Estuary, China to reveal the influence of environmental variables on planktonic ciliate communities. Distinct community compositions of ciliates were found in three identified water masses: Pearl River diluted water mass, South China Sea surface water mass, and South China Sea bottom water mass. Significant differences in abundance, biomass, cell size, and oral diameter structure of ciliates were also detected among the three water masses. The partial Mantel test showed that water mass (as represented by water temperature and salinity) surpassed other environmental variables to be the primary factor driving the dynamics of the ciliate community. This study revealed the controlling mechanisms of planktonic ciliate communities in a subtropical, hydrographically complex estuarine ecosystem.

Scuticociliate (Philasterides dicentrarchi) infection cluster in a multispecies marine aquarium system

Scuticociliatosis, caused by ciliated protozoa of the subclass Scuticociliatia, has been associated with high mortalities in marine fish. Environmental factors such as an increase in water temperature can enhance this disease. The aim of the present report is to describe the occurrence of a cluster of cases of scuticociliatosis in a multispecies marine cold-water system in a public aquarium. Philasterides dicentrarchi was identified by PCR in formalin-fixed tissues of some of the fish showing meningitis or meningoencephalitis, dermatitis and myositis with intralesional protozoa. An increase in water temperature of approximately 2°C was identified as a potential contributing factor for this cluster of infections. Higher temperature may have enhanced the propagation or pathogenicity of scuticociliates or increased host susceptibility of some species of fish, especially wolf-eel Anarrhichthys ocellatus and spotted ratfish Hydrolagus colliei. This report also highlights the complexity of dealing with mixed species systems housing fish from different natural ecozones.