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In consumer communities, intra‐guild predation (IGP) is a commonly observed interaction that is widely believed to increase resource density. However, some recent theoretical work predicts that resource density should first decrease, and then increase as the strength of IGP increases. This occurs because weak to intermediate IGP increases the IG predator density more than it reduces the IG prey density, so that weak to intermediate IGP leads to the lowest resource density compared to weak or strong IGP. We test this prediction that basal resource density would first decrease and then increase as the strength of IGP increase. We used a well‐studied system with two protozoa species engaged in IGP and three bacteria species as the basal resources. We experimentally manipulated the percentage of the IG prey population that was available to an IG predator as a proxy for IGP strength. We found that bacterial density first decreased (by ~25%) and then increased (by ~30%) as the strength of IGP increased. Using a modified version of a published IGP model, we were able to explain ~70% of the variation in protozoa and bacterial density. Agreement of the empirical results with model predictions suggests that IGP first increased the IG predator density by consuming a small proportion of the IG prey population, which in turn increased the summed consumer density and decreased the bacterial resource density. As IGP strength increased further, the IG predator became satiated by the IG prey, which then freed the bacterial resource from predation and thus increased bacterial density. Consequently, our work shows that IGP can indeed decrease or increase basal resource density depending on its strength. Consequently, the impacts of IGP on resource density is potentially more complex than previously thought. [ABSTRACT FROM AUTHOR]

Abstract: The morphology of Blepharisma sinuosum resting cysts and the dynamics of pigmentation at different stages of encystment are presented for the first time. Cyst morphometrics are similar to other Blepharisma species, with three‐wall layers, bacteria surrounding the ectocyst, a conical plug, and wrinkly surface toward the plug in mature stages. The vegetative moniliform macronucleus changes to a horseshoe shape, and at early stages, the cystic cytoplasm is homogeneously pigmented, comprising a contractile vacuole; later, pigments polarize toward the plug, decorate the cortical layer, and become brownish. This work reinforces the potential role of pigment dynamics on cyst biology. [ABSTRACT FROM AUTHOR]

Abstract: Blepharisma americanum, a member of the understudied ciliate class Heterotrichea, has a moniliform somatic macronucleus that resembles beads on a string. Blepharisma americanum is distinguishable by its pink coloration derived from the autofluorescent pigment blepharismin and tends to have a single somatic macronucleus with 3–6 nodes and multiple germline micronuclei. We used fluorescence confocal microscopy to explore the DNA content and amplification between the somatic and germline nuclei of B. americanum through its life cycle. We estimate that the DNA content of the macronucleus and micronucleus are 43 ± 8 Gbp and 83 ± 16 Mbp respectively. This correlates with an approximate DNA content difference of 500‐fold from micronucleus to macronucleus and a macronuclear ploidy of ~1,100 N as compared to the presumably diploid micronucleus. We also investigate a previously reported macronuclear inclusion, which is present sporadically across all life cycle stages; this inclusion looks as if it contains blepharismin based on its fluorescent properties, but its function remains unknown. We also provide additional detail to our understanding of life cycles changes in B. americanum by analyses of fluorescent images. Overall, the data analyzed here contribute to our understanding of the diversity of nuclear architecture in ciliates by providing details on the highly polyploid somatic macronucleus of B. americanum. [ABSTRACT FROM AUTHOR]

Synopsis Objective Mascara is a mild irritant that causes a range of medical problems. Animal models to predict ocular irritation have, however, been questioned at a number of levels, and there is a continued need to develop in vitro testing methods. Methods We assess changes in an easily quantifiable attribute, ciliated protozoan growth rate, as a sensitive, sublethal measure. Specifically, we test six, randomly chosen, commercial mascara products against a control (as treatments) and reveal through ANOVA ( n = 6, α = 0.05) significant differences in the specific growth rate to treatments (for both protozoa). Results We provide evidence that two easily cultured protozoa ( Paramecium caudatum, Blepharisma japonicum) should be considered as models to assess ocular irritancy (and possibly cosmetics in general) and establish the groundwork for such studies to be applied at a more commercial level. We do this by developing a bioassay for mascara toxicity and indicate the low cost (after equipment is purchased, on the order of $100s) and the ease of performing such tests (able to be conducted by undergraduate students), as a consideration for their future commercial application. We first examined dose dependence of responses, revealing that there was a need to conduct preliminary work to determine appropriate levels for sublethal responses. We then show that some products resulted in mortality at high concentrations, others decreased growth rate by >50% (compared with the control), whereas others had no significant effect, compared with the control. Conclusion We have provided a novel, quick and inexpensive means to assess mascara; the next step is to validate these ciliate bioassays by comparison with animal testing and epidemiological studies, which is beyond the scope of this fundamental 'proof-of-concept' study. [ABSTRACT FROM AUTHOR]

Abstract: The unicellular eukaryote, Blepharisma japonicum, is a light-sensitive ciliated protozoa. It possesses a photoreceptor pigment called blepharismin that plays critical roles in defensive behavior against predators and step-up photophobic response. In addition, the pigment generates reactive oxygen species such as singlet oxygen and hydroxyl radicals which contribute to photodynamic action. Previous studies reported that intense light (>300Wm−2) induced rapid photodynamic killing (necrosis) characterized by cell swelling and plasma efflux, while moderate light (3–30Wm−2) only induced pigment extrusion and photooxidation. We have found that moderate light (5Wm−2) induced apoptosis-like cell death. Microscopically it was found that >3h of moderate light irradiation induced macronuclear condensation and plasma efflux without cell swelling. Single cell gel electrophoresis assay showed that DNA fragmentation occurred between 1 and 3h of irradiation, and the condensed macronuclei contained quite fragmented DNA. Macronuclear DNA extracted from light-irradiated cells contained DNA fragments of 180–200 and 360–400bp, which were seen as apoptosis ladders. [Copyright &y& Elsevier]

Previous studies of communities implicate many potential mechanisms that can create alternate stable states. These include density-dependent foraging behavior, size refuges reached by early colonists, environmental feedback following disturbance, and different initial densities of intraguild predators. Previous work shows that alternate states of varying stability can occur in food webs containing the intraguild predators Blepharisma americanum and Tetrahymena vorax. Differences in colonization history could create the alternate states, consisting of dominance by either Blepharisma or Tetrahymena, but it was unclear whether results depended on effects of initial density or only on changes in the resource base. We manipulated initial densities of both species to determine if density effects alone could create alternate stable states. Convergence of these communities over time indicated that differences in initial density did not create alternate stable states. By default, other factors influenced by colonization history, such as resource availability, may produce alternate states. Models of alternate stable-state phenomena should incorporate differences in resource availability in addition to direct competitive and predatory interactions to provide a more complete depiction of the causes of differences in community composition in otherwise similar habitats. [ABSTRACT FROM AUTHOR]

To determine the phylogenetic position of Stentor within the Class Heterotrichea, the complete small subunit rRNA genes of three Stentor species, namely Stentor polymorphus, Stentor coeruleus, and Stentor roeseli, were sequenced and used to construct phylogenetic trees using the maximum parsimony, neighbor joining, and Bayesian analysis. With all phylogenetic methods, the genus Stentor was monophyletic, with S. roeseli branching basally. [ABSTRACT FROM AUTHOR]

We experimentally investigated effects of nutrient enrichment and trophic structure in a microbial food web consisting of mixed bacteria, two bacterivorous ciliates ( Tetrahymena sp. and Colpidium sp.) and an omnivorous ciliate ( Blepharisma sp.) feeding on both trophic levels. We assembled all possible food webs including one or more of the ciliate species and cross-classified them with four levels of enrichment of the bacterial medium. The qualitative outcome of food web interactions was independent of enrichment and always the same: Tetrahymena strongly depressed or excluded Colpidium, and Blepharisma strongly depressed or excluded both bacterivores. Consequently, in all sub-webs only the dominant ciliate species responded positively to enrichment. The total density of bacteria increased with enrichment irrespective of food web composition. In contrast, the response of single-celled bacteria to enrichment depended on food web composition and was only weakly positive in most food webs with the omnivore. Enrichment had a positive effect on the relative success of (presumably more defended) bacterial aggregates. The outcome of interspecific interactions among ciliates could not be predicted from monoculture experiments and deviated from earlier experiments in which each bacterivore coexisted separately with the omnivore. As a potential explanation we suggest that changes in experimental protocol reduced spatial heterogeneity and increased attack rates. A simple, dynamical model shows that increased attack rates can indeed greatly decrease the upper limit and range of enrichment over which intermediate consumers can coexist with omnivores. [ABSTRACT FROM AUTHOR]

Several recent studies suggest that community composition can take on alternate, apparently stable, states. For the most part, these studies are observational in nature and have not shown that alternate states arise from the order of species arrival during community assembly. Previous studies also provide little insight into the mechanisms that create alternate states, especially when direct species interactions, rather than environmental feedback, control their formation. We conducted experiments in identical physical environments to show that differences in the sequence of community assembly can create alternate species compositions that persist for many generations. Assembly sequence determined whether experimental food webs contained a single intraguild predator, or two intraguild predators. When the intraguild predator, Blepharisma americanum, became established in communities before the introduction of tetrahymena vorax, combined effects of resource depletion and intraguild predation prevented the establishment of tetrahymena. In contrast, when tetrahymena preceded blepharisma, both species frequently coexisted. Supporting experiments describe the exploitative competitive abilities of both intraguild predators, document the population dynamics of each species in less complex community modules, and determine the ability of Tetrahymena to invade Blepharisma cultures in the absence of competing prey. These results show that both competition and predation contribute to the formation of two alternate community states and confirm that one stable state resists transformation to the other. [ABSTRACT FROM AUTHOR]

The article presents information on some of the substitutes for Paramoecium caudatum for studying biology. Paramoecium is a typical one-celled animal. Paramoecium can be cultured easily. But there are certain factors which make it unsuitable as an object of study. Some of other animals which can be used for study are Stentor coeruleus, Spirostomum ambignum and Blepharisma lateritia. Stentor is a blue trumpet-shaped animal about five times the size of Paramoecium. The animal when taken on the slide attaches itself to debris or to the bristle and remains stationary if undisturbed. The powerful adoral cilia, nucleus and the cytoplasmic inclusions are clearly visible. Spirostomumis another large animal about the same length as Stentor. He has a large worm-like shape. Its cilia, oral groove and the contractile vacuole is clearly visible even by the poorest of high-school microscopists. Blepharisma is a pink or red animal and is of the same size of Paramoecium. It has a slow movement which enables students to observe it closely.