The life cycle of myxosporidians in fish of the Kola Peninsula

Monthly studies on the seasonal parasite fauna dynamics of pike, minnow and perch were carried out from May, 1974 to September, 1977. It was found out that the myxosporidian Henneguya creplini has a one-year life cycle. The infection of perch with this parasite takes place at a water temperature not exceeding 13 degrees. In other species (Chloromyxum esocinum, Ch. mitenevi, Myxobolus cybinae) the life cycle is shorter, in consequence of which fishes can be infected with these parasites several times a year and in different seasons. The nature of seasonal changes in abundance of myxosporidians depends to a great extent on weather conditions of each concrete year.     

An analysis of the metazoan parasitocoenoses of brown trout Salmo trutta from British Lakes

The composition of the parasite fauna of brown trout Salmo trutta in nine British lakes from varying geographical locations has been analysed with regard to several selected physico-chemical parameters of the lakes. Significant correlations existed between the size of the lake and the number of parasite species harboured by trout and between the altitude of the lake and the number of parasite species present. No significant relationships were found between the number of parasite species and the geographical position, age, degree of isolation or CaCO, levels of the lakes. Similarly no relationships existed between the proportions of the parasites with different life cycles and the parameters examined, or between the presence or absence of a particular species of parasite and the lake's limno-logical features. It is concluded that the parasites of brown trout have been, and still are, capable of rapid and widespread dissemination throughout mainland Britain, and their occurrence in any lake is a result of the combination of a number of local factors. The predictive value of the conclusions is tested and discussed with special reference to the parasite fauna of trout in reservoirs.     

Comparison of the parasitic fauna of Aplocheilus panchax and A. melastigma

The metazoan parasite fauna of two species of freshwater fishes Aplocheilus panchax and A. melastigma collected from a stream at Waltair is compared; 17 parasite species were found. Aplocheilus panchax served as a host to 13 parasite species and A. melastigma to 10 parasite species. Of the 17 parasites collected, 12 were larval helminths to which the fishes act as intermediate and paratenic hosts. This has been attributed to the interaction between terrestrial birds, mammals and fishes in determining the parasite fauna in the biocoenosis. The parasite fauna of these fishes is divided into typical and less typical according to their frequencies. Among less typical there are peripheral division parasites which are abundant in other fishes in the stream. Only six parasite species occurred in both A. panchax and A. melastigma and both fish shared most of their parasite fauna with other fishes. Differences in the parasite fauna of these fishes are attributed to the morphological, behavioural or ecological features of these fishes.     

Peculiarities of the parasitofauna of Atlantic salmon parr (Salmo salar L.), brown trout (Salmo truttae L.), and char (Salvelinus alpinus L.) in the Utsjoki River system (Northern Finland)

Data on the parasite diversity in Salmonidae fish parr from different parts of the Utsjoki River obtained during 1993-1995 and 2006-2007 are presented. Three fish species, Salmo salar L., S. truttae L., and Salvelinus alpinus L., were examined on the presence of helminthes. Twenty species of salmon parasites were found, the majority of which are the parasites with complicated life cycles. Infusorians C apriniana piscium, myxosporidia Chloromyxum januaricus and Myxobolus neurobius, metacercaria of the genera Diplostomum and Apatemon, and the nematode Raphidascaris acus larvae were the most numerous in salmon parasite fauna. Brown trout had the most number of specific parasite species, whereas char was infested by protozoan parasites only.     

Data on intestinal parasites of lower monkeys in the Adler apery

Under captive conditions, a parasite fauna connected with the changes in ecological conditions, feeding, and mode of life is usually formed in monkeys. Species composition of the intestinal parasites has been investigated in six species of the monkeys (Macaca mulatta, M. fascicularis, M. nemestrina, Ceropithecus aethiops, Papio hamadryas, and P. anubis), which were born in the Adler apery and live there for a long time. A comparison with similar investigations carried out in the Sukhumi apery, where the climatic and keeping conditions are practically identical with those in the Adler apery, was conducted. Parasite fauna of monkeys in the Adler apery was found to include three species of Nematoda (Ascaris sp., Trichocephalus sp., and Strongyloides sp.) and two species of Protozoa (Balantidium coli and Lamblia intestinalis). In our material, Trichocephalus sp. is the dominant parasite species among helminthes, and Balantidium coli is the most frequent species of Protozoa. The commonness in the transmission of these parasites and similarity in their life cycles contribute to the forming of polyinvasions in monkeys.     

Role of complex II in anaerobic respiration of the parasite mitochondria from Ascaris suum and Plasmodium falciparum.

Parasites have developed a variety of physiological functions necessary for existence within the specialized environment of the host. Regarding energy metabolism, which is an essential factor for survival, parasites adapt to low oxygen tension in host mammals using metabolic systems that are very different from that of the host. The majority of parasites do not use the oxygen available within the host, but employ systems other than oxidative phosphorylation for ATP synthesis. In addition, all parasites have a life cycle. In many cases, the parasite employs aerobic metabolism during their free-living stage outside the host. In such systems, parasite mitochondria play diverse roles. In particular, marked changes in the morphology and components of the mitochondria during the life cycle are very interesting elements of biological processes such as developmental control and environmental adaptation. Recent research has shown that the mitochondrial complex II plays an important role in the anaerobic energy metabolism of parasites inhabiting hosts, by acting as quinol-fumarate reductase.     

Patterns of intestinal parasitism in the mountain gorilla Gorilla gorilla in the Bwindi-Impenetrable Forest, Uganda

The intestinal parasite fauna of the mountain gorillas of Bwindi—Impenetrable Forest, Uganda was studied by means of faecal examination and a single post-mortem. The fauna was remarkably uniform between social groups and individuals, showing only slight differences between age groups; there is no evidence of any interaction between the parasites observed. The only protozoa were entodiniomorph ciliates; amoebae and flagellates were absent. Helminths included a single host-specific cestode species and at least five nematodes, three of which are hostspecific. The closest relatives of the host-specific parasites are found in ungulates and paenungulates, not in hosts phylogenetically related to the gorilla.
This unique and specialized parasite fauna deserves to be monitored so that any effects of the habituation of the gorillas for tourism can be assessed.     

Dynamics of infection of Bithynia tentaculata (Gastropoda: Prosobranchia) with trematodes

The dynamics of infection of Bithynia tentaculata with 7 trematode species was examined during 5 years. Stability of parasite fauna with significant changes of infection rate has been recorded. During the period of observations the infection rate of Sphaeridiotrema globulus, Notocotylus imbricatus, Holostephanus volgensis, Pleurogenoides medians and Metorchis intermedius has decreased, while that of Psilotrema tuberculata has increased. The infection rate of Plagiorchis sp. slightly fluctuated. It was found out that the infection rate of S. globulus, P. tuberculata, Plagiorchis sp., H. volgensis and M. intermedius increases by the age of hosts. Maximal infection rate of N. imbricatus was observed in mollusks of 2-3 years old. Based on peculiarities of infection dynamics during the year, 3 groups of parasites have been recognized. 1. S. globulus, P. tuberculata and N. imbricatus show an increase of infection rate from April to August with subsequent decrease. 2. Infection rate of H. volgensis increases during the Summer and reaches maximum in Autumn. Age group of host 2+ and older ones showed some decrease of infection in the beginning of Summer. 3. First cases of infection with M. intermedius occur in May, then the infection rate increases and reaches maximum in the end of July. The infection rate gradually decreases and in the end of October the mollusks infected with M. intermedius are usually absent. An emission of cercariae is usually observed in June-August. The difference in infection rate of Bithynia tentaculata males and females was not found. Based on a complex analysis of infection dynamics and population dynamics of mollusks, different aspects of the life cycle of parasites (periods of emission, maturity and longevity of local microhemipopulations) are discussed.     

Thermoregulation in the life cycle of nematodes

An unanswered question in the biology of many parasites is the mechanism by which environmental (or external) and intrinsic signals are integrated to determine the switch from one developmental stage to the next. This is particularly pertinent for nematode parasites, many of which have a free-living stage in the environment prior to infection of the mammalian host, or for parasites such as filarial nematodes, which utilise an insect vector for transmission. The environmental changes experienced by a parasite upon infection of a mammalian host are extremely complex and poorly understood. However, the ability of a parasite to sense its new environment must be intrinsically linked to its developmental programme, as progression of the life cycle is dependent upon the infection event. In this review, the relationship between temperature and development in filarial nematodes and in the free-living species Caenorhabditis elegans is summarised, with a focus on the role of heat shock factor and heat shock protein 90 in the nematode life cycle.     

Human impacts decouple a fundamental ecological relationship—The positive association between host diversity and parasite diversity

Human impacts on ecosystems can decouple the fundamental ecological relationships that create patterns of diversity in free‐living species. Despite the abundance, ubiquity, and ecological importance of parasites, it is unknown whether the same decoupling effects occur for parasitic species. We investigated the influence of fishing on the relationship between host diversity and parasite diversity for parasites of coral reef fishes on three fished and three unfished islands in the central equatorial Pacific. Fishing was associated with a shallowing of the positive host‐diversity–parasite‐diversity relationship. This occurred primarily through negative impacts of fishing on the presence of complex life‐cycle parasites, which created a biologically impoverished parasite fauna of directly transmitted parasites resilient to changes in host biodiversity. Parasite diversity appears to be decoupled from host diversity by fishing impacts in this coral reef ecosystem, which suggests that such decoupling might also occur for parasites in other ecosystems affected by environmental change.     

Metazoan parasites of the jack mackerel Trachurus murphyi (Teleostei, Carangidae) in a latitudinal gradient from South America (Chile and Peru).

The metazoa parasite fauna of the jack mackerel Trachurus murphyi Nichols 1920, obtained from seven ports from a latitudinal gradient of more than 30 degrees (From Paita Peru: 05 degrees 10' S to Talcahuano, Chile 36 degrees 40' S) was quantitatively described. 21 species of metazoan parasites were recorded (Monogenea 4, Digenea 3, Cestoda 5, Acanthocephala 2, Nematoda 4, Copepoda 2, Isopoda 1). Only four parasites (Lernanthropus trachuri, Ceratothoa gaudichaudii, Corynosoma australis, Anisakis simplex) were common to the seven ports. Only twelve species reach prevalence over 5% in at least one port. Main characteristic of the parasite fauna is the sparse of adult helminthes, specifically digenean and the dominance of larval forms, at both qualitative and quantitative levels. There are not evidence of changes in the parasite community along a latitudinal gradient, but at least Anisakis simplex (larvae) shows a trend in both, prevalence and mean intensity, increasing from north to south.     

Structure of parasite component communities of didelphid marsupials: insights from a comparative study

The parasite fauna of the gray four-eyed opossum, Philander opossum (Linnaeus, 1758), and the common opossum, Didelphis marsupialis Linnaeus, 1758, in Camp du Tigre, French Guiana, is characterized. Nine species from the gastrointestinal system were recovered from both species, which shared 80% of their parasites. The parasite fauna comprised several monoxenous species (63%) and was dominated by Aspidodera raillieti Travassos, 1914, which exhibited high levels of prevalence and abundance in both communities. Only 2 species (Moennigia sp. and Spirura guianensis) had been recorded in other species of mammals. Both species richness and taxonomic composition at the level of component communities from this locality were compared against 11 communities present in the Virginia ( Didelphis virginiana ), white-bellied (Didelphis albiventris), and common opossum from Argentina, Brazil, Mexico, and the United States. Neither host phylogeny nor taxonomy accounted for statistical differences in species richness. There was no statistical difference among species richness values among the 9 localities studied. Taxonomic similarity was analyzed by means of the Jaccard's similarity index, including all, and only common species (occurring in prevalence >10%). The results suggest that sympatric species of marsupials share more species of parasites than parasite communities occurring in conspecific marsupials from different localities. As a consequence, taxonomic composition of these parasite communities varied depending on the locality. Probably, marsupials of the monophyletic Didelphini offer the same compatibility toward their parasites, by presenting them with similar habitats. Subtle differences in lifestyles of the marsupials may determine the chance of encounter between the symbionts and prevent some parasites from completing their life cycles. Further and more rigorous tests are necessary to determine the roles of encounter and compatibility filters, as well as the role of chance, in the structuring of parasite communities in marsupials.     

The dynamics of the ectoparasite count and the protein level in the blood serum of infested carp under experimental conditions

Carps of one and two years age used for laboratory experiments were collected in winter time. 7 groups of carps of one year age were examined each 10th day during 70 days and 5 groups of two years age were examined each 15 days during 75 days. In carps of one year age the increase of different parasites was observed in different time: Dactylogyrus extensus--after 40 and 70 days, Icthyophthirius multifiliis--after 50 days, Trichodina sp.--after 60 days. In carps of two years age the increase of all parasite groups observed after 45 days, extremely great number of D. extensus was recorded after 60-70 days. Contents of proteins in a blood plasma of both age groups of carps is reliably decreased when the number of parasites is increased. Fluctuations of parasite abundance on the body and gills and some morphophysiological indices in carps of one year age in a control and in conditions of starvation were examined.     

Anthropogenic Effects of Reservoir Construction on the Parasite Fauna of Aquatic Wildlife

The creation of large freshwater reservoirs is one of the most dramatic anthropogenic impacts on the natural environment. With worldwide rising demand for water, the construction of more reservoirs is inevitable. Although the effects of reservoir construction on many medically important parasites are well known and appreciated, changes to aquatic wildlife host–parasite interactions have been largely undervalued even though a large body of literature exists. The present review examines changes in the wildlife parasite fauna during the impoundment of reservoirs, focusing on the parasites of invertebrates, fish, and birds, the effects both upstream and downstream of the reservoir, parasitic zoonoses, the associated pollution generated, and assesses the impact of the recently completed Three Gorges Dam in China on the Yangtze River’s parasite fauna.     

The effects of parasite age and intensity on variability in acanthocephalan-induced behavioural manipulation

Numerous parasites with complex life cycles are able to manipulate the behaviour of their intermediate host in a way that increases their trophic transmission to the definitive host. Pomphorhynchus laevis, an acanthocephalan parasite, is known to reverse the phototactic behaviour of its amphipod intermediate host, Gammarus pulex, leading to an increased predation by fish hosts. However, levels of behavioural manipulation exhibited by naturally-infected gammarids are extremely variable, with some individuals being strongly manipulated whilst others are almost not affected by infection. To investigate parasite age and parasite intensity as potential sources of this variation, we carried out controlled experimental infections on gammarids using parasites from two different populations. We first determined that parasite intensity increased with exposure dose, but found no relationship between infection and host mortality. Repeated measures confirmed that the parasite alters host behaviour only when it reaches the cystacanth stage which is infective for the definitive host. They also revealed, we believe for the first time, that the older the cystacanth, the more it manipulates its host. The age of the parasite is therefore a major source of variation in parasite manipulation. The number of parasites within a host was also a source of variation. Manipulation was higher in hosts infected by two parasites than in singly infected ones, but above this intensity, manipulation did not increase. Since the development time of the parasite was also different according to parasite intensity (it was longer in doubly infected hosts than in singly infected ones, but did not increase more in multi-infected hosts), individual parasite fitness could depend on the compromise between development time and manipulation efficiency. Finally, the two parasite populations tested induced slightly different degrees of behavioural manipulation.     

An Unusual Protozoal Infection of Tsetse Flies (Glossina Weidemann 1830 spp.) in West Africa

SYNOPSIS. Glossina palpalis R-D 1830 and G. pallicera Bigot 1891 in northwest Liberia were found to be infected with a flagellate parasite which never invaded the mouthparts. The parasite occurred as a number of distinctive crithidial and trypanosomal forms, and although infection was commonly confined to the midgut, it occasionally extended into the hind-gut; infections of the hindgut only were rare. The parasites also infected the coelomic cavity of the host. Attempts to produce further developmental stages in N.N.N. medium, rat, crocodile, varanid and hen failed. There are morphological similarities between the parasite and some developmental stages of Trypanosoma grayi Novy 1906, but reasons are advanced why the two forms do not belong to the same, but possibly to closely related species.     

Biogeography of helminth parasites of freshwater fishes in Mexico: the search for patterns and processes

Aim To uncover and describe patterns of biogeography of helminth parasites in freshwater fishes of Mexico, and to understand processes that determine them. Three predictions about host‐specificity, faunal exchange in transitional areas, and the biogeographical ‘core’ fauna, are evaluated, all of which follow from a fundamental hypothesis: that parasites show characteristic associations with particular host clades. The parasite fauna of the southern Mexican cichlids and of the fishes of the Mesa Central are examined as case studies that reflect Neotropical and Nearctic historical influences. Location The region covered in this study includes most of Mexico, with emphasis on six biogeographical areas: the Yucatán Peninsula (area 1), the Grijalva‐Usumacinta drainage (area 2), the Papaloapan and Pánuco drainages (area 3), the Balsas drainage (area 4), the Lerma‐Santiago drainage (area 5), and the Bravo drainage (area 6). Methods A parasite data base containing all the records of helminth parasites of freshwater fishes of Mexico was filtered to extract records of adult helminth parasites in freshwater fishes from the six biogeographical areas designated in this study. Jaccard's similarity coefficients and cluster analyses (using upgma ) were used to analyse the extent of faunal similarity between the designated biogeographical areas and between host (fish) families. Taxonomic composition of parasite assemblages in different host groups was also qualitatively compared from summary data. These data were used to test the three main predictions. Results To date, 184 species of helminths (120 as adults) have been recorded from 127 freshwater fishes in Mexico (almost 33% of the total fish diversity of Mexico). Of these parasite species, 69 are digenetic flukes, 51 are nematodes, 33 are monogeneans, 25 are tapeworms, and only six are acanthocephalans. The data and analyses from the six biogeographical areas corroborate the predictions that: (1) the adult parasite fauna is largely circumscribed by higher levels of monophyletic host taxa (families, orders, etc.), and that this pattern is independent of areas; (2) areas within a certain biogeographical region, and consequently with similar fish composition (e.g. areas 1, 2 and 3) have more similar parasite faunas compared to areas with less similar fish faunal composition; and (3) ‘core’ parasite faunas persist to some extent in transitional areas with limited host‐sharing. Main conclusions Helminth biodiversity in Mexican freshwater fishes is determined by the historical and contemporary biogeography of their hosts. Host lineage specificity, mainly at the level of the host family, appears to be an important factor in the distribution of the parasites. Most fish families (Characidae, Cichlidae, Pimelodidae, Ictaluridae, Catsotomidae, Goodeidae, Atherinidae) possess their own characteristic ‘core’ helminth fauna, with limited host‐sharing in transitional areas (e.g. areas 3 and 4). A re‐evaluation of the helminth fauna of Mexican cichlids questions the hypothesis that cichlids lost parasites during the colonization of Mexico from South America. The evidence supports the idea that they acquired new parasites by host switching, possibly from marine or brackish‐water percomorphs. In contrast, the parasite fauna of the Mesa Central remains enigmatic and reflects the region's history of endemicity with historical marine and Nearctic connections.     

Ultrastructural and physiological changes induced by different stress conditions on the human parasite <Emphasis Type="Italic">Trypanosoma cruzi</Emphasis>

Trypanosoma cruzi is the etiological agent of Chagas disease. The life cycle of this protozoan parasite is digenetic because it alternates its different developmental forms through two hosts, a vector insect and a vertebrate host. As a result, the parasites are exposed to sudden and drastic environmental changes causing cellular stress. The stress response to some types of stress has been studied in T. cruzi, mainly at the molecular level; however, data about ultrastructure and physiological state of the cells in stress conditions are scarce or null. In this work, we analyzed the morphological, ultrastructural, and physiological changes produced on T. cruzi epimastigotes when they were exposed to acid, nutritional, heat, and oxidative stress. Clear morphological changes were observed, but the physiological conditions varied depending on the type of stress. The maintenance of the physiological state was severely affected by heat shock, acidic, nutritional, and oxidative stress. According to the surprising observed growth recovery after damage by stress alterations, different adaptations from the parasite to these harsh conditions were suggested. Particular cellular death pathways are discussed.     

Trypanosome TOR as a major regulator of cell growth and autophagy

Trypanosomatid protozoa parasites are responsible for tropical diseases, and undergo complex life cycles involving developmental forms adapted to insect vectors and vertebrate hosts. During their life cycle these parasites proceed through different forms in response to dramatic environmental changes and/or developmentally regulated programs. Successful progression of the parasite through its life cycle is highly dependent on the capacity of adaptation to distinct stresses involving processes such as autophagy. In eukaryotes, Target Of Rapamycin (TOR) protein kinases act as a sensor, which integrates the nutritional and energetic status, adjusting cell metabolism and growth. Compromising cell viability in yeast and mammals leads to a reduction of TOR function, triggering processes aimed to overcome unfavourable conditions. This is partly achieved by TOR-mediated regulation of protein synthesis and recycling of cellular components by autophagy. In the last few years, autophagy has been described during developmental differentiation processes in Trypanosomatids. However, no link between TOR signalling, autophagy and differentiation has been described so far. This addendum is a commentary to the work published by our group,¹ where we discuss the possible role of TOR kinases, as a controller of cell growth and autophagy, in the regulation of differentiation processes during Trypanosomatids life cycles.