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The behavioral immune system, with disgust as its motivational part, serves as the first line of defense in organisms’ protection against pathogens. Laboratory studies indicate that disgust sensitivity adaptively adjusts to simulated environmental threat, but whether disgust levels similarly change in response to real-life threats, such as a pandemic, remains largely unknown. In a preregistered within-subject study, we tested whether the threat posed by the Covid-19 pandemic would lead to increased perceived disgust. The perception of threat was induced by testing during two phases of the Covid-19 pandemic (periods of high vs. low pathogen threat). We found heightened levels of moral disgust during a “wave” of the pandemic, but the effect was not observed in the domain of pathogen or sexual disgust. Moreover, the age of respondents and levels of trait anxiety were positively associated with pathogen and moral disgust, suggesting that variation in disgust sensitivity may be based chiefly on stable characteristics.

Disgust is an essential part of the behavioral immune system, protecting the individual from infection. According to the Compensatory Prophylaxis Hypothesis (CPH), disgust sensitivity increases in times of immunosuppression, potentially including pregnancy. We aimed to replicate a previous study observing longitudinal changes in disgust sensitivity in pregnant women. Additionally, for the first time, we explored how recent health problems influence these changes. To do this, we obtained disgust sensitivity measures from 94 women in each trimester and in early postpartum. In contrast to the original study, where disgust sensitivity was highest in the first trimester, we found that overall and animal reminder disgust increased across pregnancy and after birth. In line with the CPH, women who were recently sick in the first trimester had elevated disgust sensitivity at that time. Although disgust sensitivity was significantly higher in the second trimester and postpartum period compared to the first trimester in mothers pregnant with a male fetus, the overall results regarding the effect of fetus sex on disgust sensitivity were mixed. It seems that changing levels of disgust sensitivity during pregnancy and postpartum result from a suite of physiological and psychological changes that occur during this sensitive period of a woman’s life.

BacteriaBorrelia burgdorferi s. l. and even more the protozoanToxoplasma gondiiare known to affect the behavior of their animal and human hosts. Both pathogens infect a significant fraction of human population, and both survive in the host’s body for a long time. The resulting latent infections used to be considered clinically asymptomatic. In the last decade, however, numerous studies have shown that this view may be wrong and both infections can have various adverse effects on human health. Their specific behavioral effects may thus be merely side effects of the general impairment of patients’ health. We tested this hypothesis on a cohort of 7,762 members of internet population using a two-hour-long survey consisting of a panel of questionnaires and performance tests. Our findings confirmed that subjects infected withToxoplasmawere in worse physical and mental health and those infected withBorreliawere in worse physical health than corresponding controls. The infected and noninfected subjects also differed in several personality traits (conscientiousness, pathogen disgust, injury disgust, Machiavellianism, narcissism, tribalism, anti-authoritarianism, intelligence, reaction time, and precision). Majority of the behavioral effects associated withBorreliainfection were the same as those associated withToxoplasmainfection, but some dramatically differed (e.g., performance in the Stroop test). Path analyses and nonparametric partial Kendall correlation tests showed that these effects were not mediated by impaired health of the infected individuals. The results thus contradict predictions of the side effects hypothesis.

Toxoplasmosis is one of the most widespread human parasitoses in developed countries. Sexual transmission has been confirmed in several animal species, and indirect evidence suggests it may occur in humans. We compared the seropositivity to Toxoplasma gondii in couples who visited the Center for Assisted Reproduction in Prague from June 2016 to June 2018 and analyzed various risk factors including the serological status of sexual partner. By comparing the risk factors in men and women, we tested the hypothesis of male-to-female sexual transmission of toxoplasmosis. The prevalence of toxoplasmosis in women with infected male partners (25.6%; n = 156) was higher than in women with uninfected male partners (18.2%; n = 477; P = 0.045). Therefore, a partner’s seropositivity seems to be a risk factor for infection in women (n = 593; prevalence ratio = 1.418; P = 0.045) but not in men (n = 573; prevalence ratio = 1.058; P = 0.816). Our results support the hypothesis of the sexual transmission of T. gondii from men to women. The risk may seem relatively low, but transmission can occur during unprotected sexual intercourse, which may be at the time of conception. Because of the risk of congenital toxoplasmosis, a lower risk of infection than that observed in our study can represent a serious health problem.

About 1-2% of European population are redheaded, meaning they synthesize more pheomelanin than eumelanin, the main melanin pigment in humans. Several mutations could be responsible for this phenotype. It has been suggested that corresponding mutations spread in Europe due to a founder effect shaped either by a relaxation of selection for dark, UV-protective phenotypes or by sexual selection in favour of rare phenotypes. In our study, we investigated the levels of vitamin D precursor 25(OH)D3 (calcidiol) and folic acid in the blood serum of 73 redheaded and 130 non-redheaded individuals. In redheaded individuals, we found higher 25(OH)D3 concentrations and approximately the same folic acid concentrations as in non-redheaded subjects. 25(OH)D3 concentrations correlated with the intensity of hair redness measured by two spectrophotometric methods and estimated by participants themselves and by independent observers. In non-redheaded individuals, 25(OH)D3 levels covaried with the amount of sun exposure and intensity of suntan while in redheaded individuals, this was not the case. It suggests that increased 25(OH)D3 levels in redheaded individuals are due to differences in physiology rather than in behaviour. We also found that folic acid levels increased with age and the intensity of baldness and decreased with the frequency of visiting tanning salons. Our results suggest that the redheaded phenotype could be an evolutionary adaptation for sufficient photosynthesis of provitamin D in conditions of low intensity of UVB radiation in central and northern parts of Europe.

Toxoplasma gondii is a widely prevalent protozoan parasite in human populations. This parasite is thought to be primarily transmitted through undercooked meat and contamination by cat feces. Here, we demonstrate that Toxoplasma gondii cysts can be found within human semen, thus suggesting a potential for sexual transmission. We visualized Toxoplasma gondii cysts in ejaculates of immune-competent and latently infected human volunteers. We confirmed the encystment by probing transcription of a bradyzoite-specific gene in these structures. These observations extend previous observations of the parasite in semen of several non-human host species, including rats, dogs, and sheep. Toxoplasma gondii infection is a clinically significant infection, in view of its high prevalence, its purported role in neuropsychiatric disorders such as schizophrenia, as well as in the more serious form of congenital toxoplasmosis. Our demonstration of intact Toxoplasma gondii cysts in the ejaculate supports the possibility of sexual transmission of the parasite and provides an impetus for further investigations.ImportanceToxoplasma gondii is recognized as one of the five infections that can harm fetal health. There is also emerging evidence that toxoplasmosis is related to the development of neuropsychiatric disorders. In this context, the current report includes visual evidence of Toxoplasma gondii cyst presence in the semen of human males. It is thus plausible that this clinically significant infection can be sexually transmitted. The existence of sexual transmission in a population, and its relative importance vis-à-vis other transmission routes, remains undetermined. These possibilities are of acute relevance to human health in the context of sexual health and pregnancy management.

Human populations, especially European, are polymorphic in the RHD gene. A significant fraction of their members carries two copies of a mutated (deleted) allele, which results in their Rh-negative blood type. Theoretically, this polymorphism should be unstable. Carriers of the less frequent allele are penalized by reduced fertility because of the immunization of Rh-negative mothers by their Rh-positive babies, which results in hemolytic disease of newborns in their subsequent progeny. For about 90 years, some form of balancing selection has been suspected to sustain this polymorphism. Several recent studies showed that the Rh-positive heterozygotes express higher viability than both types of homozygotes. However, the genotype of subjects in these studies was estimated only by indirect methods. Here we compared the physical and mental health of 178 women and 86 men who were directly tested for their Rh genotype. The results showed that Rh-positive homozygotic women had worse and Rh-positive homozygotic men better physical health than Rh-negative homozygotes; the difference between Rh-negative homozygotes and heterozygotes was not significant. Our results confirmed that health of Rh-positive heterozygotes and homozygotes differ. Therefore, any result of the comparison of subjects with Rh-positive and Rh-negative phenotype depends on the heterozygote-to-homozygote ratio in the Rh-positive sample. It is, therefore, crucial to analyze the effects of Rh-genotypes, not phenotypes in future studies.

Human populations, especially European, are polymorphic in the RHD gene. A significant fraction of their members carry no copy of the coding section of RHD gene, which results in their Rh-negative blood type. Theoretically, this polymorphism should be unstable. Carriers of the less frequent allele are penalized by reduced fertility because of the immunization of RhD-negative mothers by their RhD-positive babies, which results in hemolytic disease of the fetus and newborn in their subsequent progeny. For about 90 years, some form of balancing selection has been suspected to sustain this polymorphism. Several recent studies showed that the RhD-positive heterozygotes express higher viability than both types of homozygotes. However, the genotype of subjects in these studies was estimated only by indirect methods. Here we compared the physical and mental health of 178 women and 86 men who were directly tested for their RHD genotype. The results showed that RhD-positive homozygotic women had worse and RhD-positive homozygotic men better physical health than RhD-negative homozygotes; the difference between RhD-negative homozygotes and heterozygotes was not significant. Our results confirmed that health of RhD-positive heterozygotes and homozygotes differ. Therefore, any result of the comparison of subjects with RhD-positive and RhD-negative phenotype depends on the heterozygote-to-homozygote ratio in the RhD-positive sample. It is, therefore, crucial to analyze the effects of RHD-genotypes, not phenotypes in future studies.

Leisure time and its quality use is becoming increasingly important in society. We can spend it primarily on physical activity, which offer many options, as it provides an entertainment and has a complex effect on our physical and mental health. Walking as a basis for hiking is the most accessible form of physical activity. Hiking is known as a low-level adventure activity, making it popular, and therefore, it presents an important tourism product around the world. The aim of hiking is the improvement of spiritual wealth, physical capabilities, mental resilience, and the general health of a person. An essential activity of hiking is the exploration of natural beauties and monuments. The tourist chooses a certain attractive place based on the route by which he can arrive there. The aim of this study is to provide a better understanding of the motivations of mountain hikers and to discuss the issue in wider contexts. This study examines the individual components comprising the decision-making process when choosing a hiking trail, such as slope of a terrain, relief, hiking trail surface, difficulty level of hiking trail, natural monuments, environmental attractiveness, and hiker’s internal motivation. The study contributes to contemporary literature on soft adventure hiking. Definitively, the findings provide important data in the creation of attractive and sustainable tourism products tailored to and planning for sustainable development of the territory in terms of tourism.

Background About a third of people in the world are infected with Toxoplasma gondii. This parasite has been found in the reproductive organs and semen of males of many animal species as well as humans. The effects of toxoplasmosis on sperm count, motility and morphology were confirmed in rats. A higher prevalence of toxoplasmosis has been observed in infertile men. On the other hand, no significant effect of infection on semen parameters in men was found in one already published study. Objectives To compare the prevalence of toxoplasmosis in men with and without semen pathology and to examine in detail the possible impact of infection on semen volume, sperm count, motility and morphology. Materials and methods The pre-registered cross-sectional study included 669 men who visited the Centre for Assisted Reproduction in Prague from June 2016 until June 2018. Results The incidence of fertility problems was significantly higher in the 163 Toxoplasma-infected men (48.47%) than in the 506 Toxoplasma-free men (42.29%), τ = 0.049, P = 0.029. After correction for multiple tests, we found significantly lower sperm concentration, concentration of progressively motile sperm, and concentration of non-progressively motile sperm in Toxoplasma-positive men than in Toxoplasma-negative men using partial Kendall correlation with age controlled. In addition, toxoplasmosis correlated with sperm quality in smokers but not in non-smokers. Discussion and conclusion Our results suggest that latent toxoplasmosis affects certain semen parameters (sperm count and motility), but does not seem to affect sperm morphology and semen volume. Impairment of semen parameters may be either a side effect of the presence of Toxoplasma gondii in male reproductive organs or a product of manipulation activity of the parasite aimed to increase the efficiency of the sexual route of its transmission. Tobacco smoking also appears to exacerbate the negative impact of toxoplasmosis on semen parameters.

Numerous recent studies show that vitamin D deficiency potentiates various chronic physical and psychiatric disorders and diseases. It has been shown that a similar range of disorders is also associated with latent infection with Toxoplasma gondii (Nicolle et Manceaux, 1908). For instance, among cancer, diabetes and schizophrenia patients, we find a higher prevalence of both toxoplasmosis and vitamin D deficiency. Theoretically, therefore, vitamin D deficiency could be the missing link between toxoplasmosis and these disorders. We tested this hypothesis by searching for decreased vitamin D levels in the serum of subjects infected with T. gondii (furthermore called Toxoplasma-infected subjects) in two cross-sectional and one case-control study. Results of the first cross-sectional study (N = 72) suggest that Toxoplasma-infected neurasthenic patients have non-significantly lower levels of calcidiol than Toxoplasma-free patients (study A: P = 0.26 in women, P = 0.68 in men). However, two other studies (study B: N = 400; study C: N = 191) showed a non-significantly higher concentration of vitamin D in Toxoplasma-infected subjects than in Toxoplasma-free subjects both in men (study B: P = 0.70, study C: P = 0.55) and in women (study B: P = 0.64, study C: P = 0.12). Taken together, our preliminary results thus do not support the hypothesis that toxoplasmosis could be associated with vitamin D decrease.

According to the congruency hypothesis, relationship satisfaction is predicted by the congruency (or non-congruency) between current use of oral contraceptives (OC) and their use during relationship formation. This is based on findings that OC may alter women's mate preferences, so that attraction to their partner may have changed in non-congruent women. Indeed, some studies find that women in a non-congruent state were less sexually satisfied with their partner, although they were more satisfied in non-sexual aspects of the relationship. However, some other studies have produced null results, calling the hypothesis into question. In this study, we tested the congruency hypothesis in two samples of pregnant women, and in two samples of couples attending a fertility clinic. In all four samples, couples completed questionnaires on relationship and sexual satisfaction and the women also reported their previous and current contraceptive use. In one sample of pregnant women, we found that women who used OC during relationship formation were more sexually satisfied with their partner compared to women who did not use OC at that time; this pattern has previously been interpreted as supporting the congruency hypothesis in view of certain similarities in hormonal profile between OC use and pregnancy. We did not find any significant effect of OC use during relationship formation on sexual and relationship satisfaction in the other sample of pregnant women, either sample attending the fertility clinic, or in the male partners of any of our samples. Our results thus provide mixed support for the congruency hypothesis. Finally, we discuss recommendations for future studies such as use of within-subject designs and more structured assessment of sexual satisfaction.

Toxoplasmosis is a parasitic disease widespread in the temperate zone. The definitive hosts of Toxoplasma gondii, which causes the disease, are cats. All warm-blooded vertebrates, including humans, can be intermediate hosts. A person is usually infected by ingesting oocysts, e.g. by consuming along with vegetables some contaminated soil, by drinking contaminated water, or by ingesting tissue cysts contained, for instance, in poorly cooked meat. Less common is congenital transmission or transmission via organ transplant from an infected donor. Recently, it has been suggested that toxoplasmosis could also be transmitted sexually from infected men to uninfected women. In this article, we discuss and present evidence for an alternative hypothesis, which suggests that toxoplasmosis could be transmitted by oral sex (via fellatio) from an infected man to an uninfected person (male or female), especially if the uninfected individual swallows the infected ejaculate. This hypothesis finds support in the following facts and findings: (1) Toxoplasma has been found in male ejaculate. (2) In several animal species, presence of the parasite in the seminal fluid of infected males can lead to infection of uninfected females during mating. (3) A higher prevalence of toxoplasmosis has been reported in both homosexuals and promiscuous individuals, i.e. in populations which practice a broader spectrum of sexual activities, including oral sex. (4) In heterosexual couples, a partner's infection seems to be a risk factor for infection in women but not in men. (5) A higher prevalence of toxoplasmosis in females compared to males has been observed in adolescents aged 10 to 14, where oral sex, including fellatio, is highly prevalent among those who have not yet engaged in penetrative intercourse. (6) On a theoretical level, one could expect that when an uninfected person swallows ejaculate containing Toxoplasma tissue cysts, this results in a similar infection pattern to ingestion of Toxoplasma-contaminated undercooked meat. (7) Approximately two-thirds of Toxoplasma infections in pregnant women cannot be explained by any of the known risk factors. (8) In both women and men who report practicing fellatio with men, there is a higher prevalence of toxoplasmosis than in corresponding controls. If our hypothesis is correct, an effective public health campaign with emphasis on early sexual education about the risks of unprotected oral sex will be necessary, especially in pregnant women and HIV-positive people. This route of toxoplasmosis transmission could be experimentally verified by force-feeding laboratory mice with the ejaculate of infected men.

Background: Massilia virus (MASV) is a phlebovirus isolated from Phlebotomus perniciosus in various regions of southwestern Europe. It is closely related to human pathogens such as Toscana virus and sandfly fever Naples virus. The natural cycle of phleboviruses is poorly understood. Indeed, experimental studies demonstrate that transovarial and sexual transmission are not efficient enough for the maintenance of the virus in nature and to date there is no convincing evidence that a species of vertebrates is the reservoir of the virus. Here, we studied various transmission routes of MASV taking advantage of experimental colonies representing different species of sand flies. Methodology/Principal findings: In P. perniciosus, four sources of infection were compared: (i) Virus-seeded larval food to the first instar larvae (L1), or (ii) to the fourth instar larvae (L4), (iii) virus-seeded blood meal to adult females, and (iv) virus-seeded sugar meal to adults of both sexes. From 875 adults emerged from infected L1 and L4, only three were positive. In females infected by bloodmeal the infection rate was high before defecation, then it decreased drastically, MASV RNA was detected in only 5 out of 27 post-defecation. Surprisingly, the most efficient route of infection was observed after intake of virus-seeded sugar meal: 72% of females (79/110) and 52% of males (51/99) were found to be MASV RNA-positive. In addition, MASV-infected sandflies regurgitated virus particules into the sugar drop and MASV RNA was detectable in this drop for at least 24 h after regurgitation. MASV RNA was detected in about one third of the P. perniciosus exposed to this sugar drop contaminated by regurgitation. Sugar meal infection was also tested with six other species of sand flies. In males, there were no significant differences in infection rates when compared to P. perniciosus. In females, most species tested showed high infection rate at the beginning but then significant gradual decrease in infection rate during the experiment. Conclusions/Significance: We present the first description of arboviral infection of a dipteran vector using sugar meal. In all seven sand fly species tested, MASV was detected for two weeks post-infection. Our results showed that MASV can be transmitted between P. perniciosus either through co-feeding or via an infected sugar source such as plant sap. These newly described routes of horizontal transmission may play an important role in the circulation of phleboviruses in nature.

Background: Toxoplasmosis is one of the most widespread human parasitoses in the developed countries. Toxoplasma gondii has been found in the ejaculate of various animals, including human. Sexual transmission of this zoonosis has been confirmed in several animal species but not in human. Nevertheless, a large part of infections in mothers of children with congenital toxoplasmosis cannot be explained by contact with any currently known risk factor, while high prevalence of toxoplasmosis has been observed in the fathers of children with this diagnosis. This indirect evidence supports the hypothesis of sexual transmission of toxoplasmosis in humans. Methods: We compared the prevalence of toxoplasmosis in couples and analysed various risk factors for toxoplasmosis including the infection status of sexual partner. By comparing the risk factors for Toxoplasma infection in men and women, we tested the hypothesis of man-to-woman sexual transmission of toxoplasmosis. Findings The prevalence of toxoplasmosis in women with infected male partners (25·6%; n=156) was higher than the prevalence in women with uninfected male partners (18·2%; n=477; p=0·023). Partner's infection therefore seems to be a risk factor for infection in women (n=593; odd ratio=1·602; p=0·022) but not in men (n=573; odds ratio=1·064; p=0·816). Interpretation: Our results support the hypothesis of sexual transmission of toxoplasmosis from men to women. The risk may seem relatively low, but transmission can occur during unprotected sexual intercourse, which may be the time of conception. Due to the risk of congenital toxoplasmosis, even a lower risk of infection than that observed in our study can represent a serious public health problem. Funding Statement: Charles University Grant Agency (number 104218), Czech Science Foundation Grant (number 18-13692S), Charles University Research Centre program (number 204056) and RVO-VFN64165 from the Ministry of Health of the Czech Republic. Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: Informed consent was obtained from all participants. Blood samples for serological testing for toxoplasmosis were taken during a routine examination. This research has been repeatedly approved by Ethics Committee of General University Hospital in Prague (No. 384/16; 92/17) and by Institutional review board of Faculty of Science, Charles University (No. 2015/29).

Leishmania parasites cause human cutaneous, mucocutaneous and visceral leishmaniasis. Several studies proposed involvement of certain genes in infectivity of these parasites based on differential mRNA expression data. Due to unusual gene expression mechanism, functions of such genes must be further validated experimentally. Here, we investigated a role of one of the putative virulence factors, LmxM.22.0010-encoded BTN1 (a protein involved in Batten disease in humans), in L. mexicana infectivity. Due to the incredible plasticity of the L. mexicana genome, we failed to obtain a complete knock-out of LmxM.22.0010 using conventional recombination-based approach even after ablating four alleles of this gene. To overcome this, we established a modified CRISPR-Cas9 system with genomic expression of Cas9 nuclease and gRNA. Application of this system allowed us to establish a complete BTN1 KO strain of L. mexicana. The mutant strain did not show any difference in growth kinetics and differentiation in vitro, as well as in the infectivity for insect vectors and mice hosts. Based on the whole-transcriptome profiling, LmxM.22.0010-encoded BTN1 was considered a putative factor of virulence in Leishmania. Our study suggests that ablation of LmxM.22.0010 does not influence L. mexicana infectivity and further illustrates importance of experimental validation of in silico-predicted virulence factors. Here we also describe the whole genome sequencing of the widely used model isolate L. mexicana M379 and report a modified CRISPR/Cas9 system suitable for complete KO of multi-copy genes in organisms with flexible genomes.

Phlebotomus sergenti Parrot, 1917 is the main vector of Leishmania tropica; however, its broad geographical range and molecular heterogeneity suggest possible variability in vector competence. We infected laboratory-reared P. sergenti originating from Turkey and Israel to compare their susceptibility to L. tropica. In both tested groups, heavy late-stage infections with the presence of metacyclic forms and colonization of the stomodeal valve were observed. The similar development of Leishmania in both sand fly colonies indicates that the different geographical origin of P. sergenti is not reflected by a different vector competence to L. tropica. Additionally, we tested the effect of the gregarine Psychodiella sergenti on L. tropica coinfections; no apparent differences were found between P. sergenti infected or not infected by gregarines.

The spread of leishmaniasis to areas where it was previously considered nonendemic has been recently found in the New and Old Worlds, and climate changes are suspected as a crucial factor responsible for this spread. Ambient temperature is known to significantly affect the metabolism of sand flies and their developmental times, but little is known about the effect of temperature on the Leishmania life cycle in vectors. This study assesses the effect of temperature on the development of two closely related New World Viannia species, Leishmania braziliensis and Leishmania peruviana, in the permissive vector Lutzomyia longipalpis, and on the development of New and Old World Leishmania infantum in its natural vectors Lu. longipalpis and Phlebotomus perniciosus, respectively. The mountain species L. peruviana developed well in sand fly females kept at 20°C, whereas at 26°C, most infections were lost during the defecation of bloodmeal remains; this suggests an adaptation to the slower metabolism of san...

Many high-quality genomes are available for dixenous (two hosts) trypanosomatid species of the genera Trypanosoma, Leishmania, and Phytomonas, but only fragmentary information is available for monoxenous (single-host) trypanosomatids. In trypanosomatids, monoxeny is ancestral to dixeny, thus it is anticipated that the genome sequences of the key monoxenous parasites will be instrumental for both understanding the origin of parasitism and the evolution of dixeny. Here, we present a high-quality genome for Leptomonas pyrrhocoris, which is closely related to the dixenous genus Leishmania. The L. pyrrhocoris genome (30.4 Mbp in 60 scaffolds) encodes 10,148 genes. Using the L. pyrrhocoris genome, we pinpointed genes gained in Leishmania. Among those genes, 20 genes with unknown function had expression patterns in the Leishmania mexicana life cycle suggesting their involvement in virulence. By combining differential expression data for L. mexicana, L. major and Leptomonas seymouri, we have identified several additional proteins potentially involved in virulence, including SpoU methylase and U3 small nucleolar ribonucleoprotein IMP3. The population genetics of L. pyrrhocoris was also addressed by sequencing thirteen strains of different geographic origin, allowing the identification of 1,318 genes under positive selection. This set of genes was significantly enriched in components of the cytoskeleton and the flagellum.

In this subsystem of the classical Belousov-Zhabotinskii oscillatory reaction the minimal set of reactions that still quantitatively reproduces the experimental behavior was suggested and analyzed by numerical simulations. We conclude that the reaction pathway via HOBr plays no role in the bromination of malonic acid.

The stirring effect in the BZ reaction with oxalic acid in a closed batch reactor was simulated in good agreement with experiments. Oscillations, lowering of the number of oscillations and the absence of oscillations under strong stirring were all reproduced using a simple qualitative consideration of the influence of concentration fluctuations on the rates of fast reactions.