Myxosoma cerebralis (Myxozoa: Myxosporea) Etiologic Agent of Salmonid Whirling Disease Requires Tubificid Worm (Annelida: Oligochaeta) in its Life Cycle

Studies of the life cycle of Myxosoma cerebralis showed that development of infectivity did not occur endogenously but that the spore “aging” process required participation of an aquatic tubificid oligochaete. Data suggestive of such involvement were derived from trials in which spores were “aged” in an array of inert, sterilized, pasteurized, or natural aquatic substrates and from examination of aquatic soils from trout hatcheries in which whirling disease was epizootic. The role of the aquatic oligochaete was confirmed two ways. First, signs of whirling disease developed, and M. cerebralis spores were produced in young rainbow trout (Salmo gairdneri) that had been fed oligochaetes harvested from pond soil taken from two hatcheries where whirling disease was epizootic. Second, when containers of pasteurized soil were populated with four genera of oligochaetes–Aeolosoma, Dero, Stylaria, or Tubifex– from a biological supply house, or with tubificid worms from trout hatcheries free of whirling disease, and then seeded with M. cerebralis spores and “aged” for 4 months, whirling disease occurred only in trout held with Tubifex and with hatchery tubificids.     

Modelling of landscape variables at multiple extents to predict fine sediments and suitable habitat for Tubifex tubifex in a stream system

1. Aggregations of fine sediments are a suitable proxy for the presence and abundance of Tubifex tubifex, one of the obligate hosts in the parasitic life cycle that causes salmonid whirling disease (Myxobolus cerebralis). 2. To determine and evaluate practical approaches to predict fine sediments (<2 mm diameter) that could support Tubifex spp. aggregations, we measured habitat features in a catchment with field measures and metrics derived from digital data sets and geospatial tools at three different spatial extents (m²) within a hierarchical structure. 3. We used linear mixed models to test plausible candidate models that best explained the presence of fine sediments measured in stream surveys with metrics from several spatial extents. 4. The percent slow water habitat measured at the finest extent provided the best model to predict the likely presence of fine sediments. The most influential models to predict fine sediments using landscape metrics measured at broader extents included variables that measure the percentage land cover in conifer or agriculture, specifically, decreases in conifer cover and increases in agriculture. 5. The overall best‐fitting model of the presence of fine sediments in a stream reach combined variables measured and operating at different spatial extents. 6. Landscape features modelled within a hierarchical framework may be useful tools to evaluate and prioritise areas with fine sediments that may be at risk of infection by Myxobolus cerebralis.     

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.     

Propagation of the myxozoan parasite Myxobolus cerebralis by different geographic and genetic populations of Tubifex tubifex: An Oregon perspective

Tubifex tubifex are obligate invertebrate hosts in the life cycle of Myxobolus cerebralis, the myxozoan parasite that causes whirling disease in salmonid fishes. This exotic parasite is established to varying degrees across Oregon’s Columbia River system (Pacific Northwest, USA) and characteristics of local T. tubifex populations likely play a role in the pattern of disease occurrence. To better understand these patterns, we collected T. tubifex from three Oregon river basins (Willamette, Deschutes, and Grande Ronde), determined their genotype (mitochondrial 16S rDNA lineage and RAPD genotype) and exposed 10 different populations to M. cerebralis in the laboratory. Four mt lineages were identified: I, III, V and VI. Lineage III was found in all river basins but dominated both central and eastern sites. The RAPD assay further divided these lineages into geographic sub-populations; no RAPD genotype was common to all basins. There was a significant difference in prevalence of infection and level of parasite production among the populations we exposed to M. cerebralis that was attributed to genotypic composition. Only lineage III worms released actinospores and only populations dominated by this lineage amplified the parasite. These populations had the lowest survival, however, the lineage dominant before exposure remained dominant despite the high prevalence of infection. The distribution and infection dynamics of susceptible T. tubifex throughout Oregon may contribute to the differences in M. cerebralis occurrence; our studies further support the influence of oligochaete genotypes on the manifestation of whirling disease in salmonid populations.     

The polyphyletic origin of the "Cheilostomata" (Bryszoa)

The relative appearance of the parietal muscles in the development of the zooids has been studied in several ctenostomatous and “cheilostomatous” species. A comparison of the different on-togenetical sequences demonstrated that a “cheilostomatous” type of organization of the zooids with a great probability has been achieved in minimum three times independentl and originated from different ctenostomatous sub-grous: the Membranidea from plesiomorgic victorelloids (ancestors of Bulbella with not yet developed peristomial tube), the Inoviceiata (Aetea) from advanced forms of victorelloids with reduced primary parietal muscles (perhaps stcies related to Pottsiella), and Penetrantia from arachnidioid or vesicularioid ancestors (?). Therefore, the classical orders ^α“Ctenostomata” and “Cheilostomata” represent only “stage groups” but no monohyletic systematical units. Because of the new concept and interpretation I propose a new name for the united group: Cteno-Cheilostomata, supra-ord. nov.     

Genus Pleistophora Gurley, 1893: An Assemblage of at Least Three Genera1

Until recently, pansporoblastic microsporidia that produce a variable and large number of sporoblasts from a sporont have been included in a single genus, namely Pleistophora Gurley, 1893. Ultrastructural studies have been used to determine whether the resemblance of these species is fundamental or superficial. The results indicated that the multisporous pansporoblastic forms belong to at least three genera and, thus, that Pleistophora is a “composite genus.” The term pansporoblast was originally used for stages in myxosporidian development. The term sporophorous vesicle adopted from Gurley is suggested for the spore-containing vesicle in the Microspora. Three species were studied: Pleistophora typicalis, the type-species; Pleistophora culicis, for which a new genus Vavraia has already been proposed; and Pleistophora simulii. P. typicalis and V. culicis have isolated nuclei throughout their development, and the sporophorous vesicle wall enveloping the sporoblasts is derived from amorphous secretions laid down during merogony external to the plasmalemma. Pleistophora and Vavraia are differentiated principally in terms of the structure of the sporophorous vesicle wall and mode of division of the sporogonial plasmodium. The nuclei of young sporonts of P. simulii are in diplokaryon arrangement and undergo meiosis to give haploid nuclei in the sporoblasts. The sporophorous vesicle wall is membranoid and is laid down external to the plasmalemma at the onset of sporogony. A new genus, Polydispyrenia n. g., is suggested for this species, the affinities of which are closer to the dimorphic species of microsporidia than to Pleistophora or Vavraia. The terms “merontogenetic sporophorous vesicle” and “sporontogenetic sporophorous vesicle” are used to distinguish between the two groups.     

A Taxonomic Study of Strains Received as “Mycobacterium” rhodochrous

A taxonomic study was carried out on 20 strains received as “Mycobacterium” rhodochrous. These strains were exceedingly similar to the strains of the genus Gordona recently proposed by the present author. Out of the 20 strains studied, 10 strains, including two strains previously named Rhodococcus rhodochrous, formed one cluster and were considered to belong to a species of the genus Gordona. The species has been named Gordona rhodochroa (Zopf; Overbeck; Gordon et Mihm) Tsukamura comb. nov. Two strains were considered to belong to the species Gordona rubra. One of the two had initially been named Mycobacterium rubropertinctum. It was considered from the facts that the specific epithet for the species should be “rubropertinta” and the name Gordona rubra be changed to Gordona rubropertincta. The other strains seemed to belong to some other species. In conclusion, the species “Mycobacterium” rhodochrous appears to be divided into several species of the genus Gordona.     

Four New Species of Myxosporidia from the Indian Fresh Water Fish Ophicephalus punctatus Bloch

SYNOPSIS. Four new species of Myxosporidia have been described from Ophicephalus punctatus , a fresh water fish of North India: Myxobolus aligarhensis n. sp., M. ophicephali n. sp., Unicauda basiri n. sp., and Henneguya zahoori n. sp. Observations have been made on some stages of their life-cycle other than the spores.     

Fine Structure of an Unidentified Protozoon in the Epithelium of Rainbow Trout Exposed to Water with Myxosoma cerebralis*

SYNOPSIS. An intracellular protozoon was discovered in the epithelium of young rainbow trout (Salmo gairdneri) exposed for as short a time as 1 hr to water known to contain infective stages of Myxosoma cerebralis. Light- and electron-microscopic examination of this tissue revealed what appeared to be a proliferative stage (presumptive schizont) of a sporozoon; other possible stages in the life cycle were also observed. The relationship of this unidentified protozoon to M. cerebralis remains unresolved.     

A web-based identification programme for Pythium species

The genus Pythium, with slightly over 140 described species, has been classified traditionally with other filamentous, coenocytic, sporangia-producing fungi as “Phycomycetes”. However, with recent advances in chemical, ultrastructural and molecular studies, Pythium spp. are now considered as “fungus-like organisms” or “pseudo-fungi” and are placed in the kingdom Chromista or kingdom Stramenopila, distinct from the true fungi or the kingdom Fungi. There is no comprehensive web-based identification key available for the identification of all described Pythium species. This article describes a web-based identification tool (which has been described by the authors under the name of Fungid) that uses morphological features. For the isolate in question, the software compares the unknown isolate with near to 90 known species submitted in the database. One or more than one species is suggested to the user by the software.     

Three new species of Myxosporidia (Myxozoa: Myxosporea) parasites of Citharinus citharus (Geoffroy Saint-Hilaire, 1809) (Citharinidae) in Chad (Central Africa)

The study of Citharinus citharus (Geoffroy Saint-Hilaire, 1809) (Teleost, Citharinidae) captured in the Chari river in Chad revealed the presence of three new myxosporidian which are described in the present paper: Thelohanellus taguii sp. nov., a systematic parasite; Myxobolus mbailaoi sp. nov., which affects operculum, skin and intestine, Myxobolus charii sp. nov., a parasite of the skin.     

An integrated environment and cost assessment method based on LCA and LCC for mechanical product manufacturing

Purpose

The purpose of this study is to provide an integrated method to identify the resource consumption, environmental emission, and economic cost for mechanical product manufacturing from economic and ecological dimensions and ultimately to provide theoretical and data support of energy conservation and emission reduction for mechanical product manufacturing.

Methods

The applied research methods include environmental life cycle assessment (LCA) and life cycle cost (LCC). In life cycle environmental assessment, the inventory data are referred from Chinese Life Cycle Database and midpoint approach and EDIP2003 and CML2001 models of life cycle impact assessment (LCIA) are selected. In life cycle cost assessment, three cost categories are considered. The proposed environment and cost assessment method is based on the theory of social willingness to pay for potential environmental impacts. With the WD615 Steyr engine as a case, life cycle environment and cost are analyzed and evaluated.

Results and discussion

The case study indicates that, in different life cycle phases, the trend of cost result is generally similar to the environmental impacts; the largest proportion of cost and environmental impact happened in the two phases of “material production” and “component manufacturing” and the smallest proportion in “material transport” and “product assembly.” The environmental impact category of Chinese resource depletion potential (CRDP) accounted for the largest proportion, followed by global warming potential (GWP) and photochemical ozone creation potential (POCP), whereas the impacts of eutrophication potential (EP) and acidification potential (AP) are the smallest. The life cycle “conventional cost” accounted for almost all the highest percentage in each phase (except “material transport” phase), which is more than 80% of the total cost. The “environmental cost” and “possible cost” in each phase are relatively close, and the proportion of which is far below the “conventional cost.”

Conclusions

The proposed method enhanced the conventional LCA. The case results indicate that, in a life cycle framework, the environment and cost analysis results could support each other, and focusing on the environment and cost analysis for mechanical product manufacturing will contribute to a more comprehensive eco-efficiency assessment. Further research on the life cycle can be extended to phases of “early design,” “product use,” and “final disposal.” Other LCIA models and endpoint indicators are advocated for this environmental assessment. Environmental cost can also be further investigated, and the relevant social willingness to pay for more environmental emissions is advocated to be increased.

     

Helicobacter pylori outer inflammatory protein A (OipA) suppresses apoptosis of AGS gastric cells in vitro

Outer inflammatory protein A (OipA) is an important virulence factor associated with gastric cancer and ulcer development; however, the results have not been well established and turned out to be controversial. This study aims to elucidate the role of OipA in Helicobacter pylori infection using clinical strains harbouring oipA “on” and “off” motifs. Proteomics analysis was performed on AGS cell pre‐infection and postinfection with H. pylori oipA “on” and “off” strains, using liquid chromatography/mass spectrometry. AGS apoptosis and cell cycle assays were performed. Moreover, expression of vacuolating cytotoxin A (VacA) was screened using Western blotting. AGS proteins that have been suggested previously to play a role or associated with gastric disease were down‐regulated postinfection with oipA “off” strains comparing to oipA “on” strains. Furthermore, oipA “off” and ΔoipA cause higher level of AGS cells apoptosis and G0/G1 cell‐cycle arrest than oipA “on” strains. Interestingly, deletion of oipA increased bacterial VacA production. The capability of H. pylori to induce apoptosis and suppress expression of proteins having roles in human disease in the absence of oipA suggests that strains not expressing OipA may be less virulent or may even be protective against carcinogenesis compared those expressing OipA. This potentially explains the higher incidence of gastric cancer in East Asia where oipA “on” strains predominates.     

Development of Caryospora bigenetica n. sp. (Apicomplexa,Eimeriidae) in Rattlesnakes and Laboratory Mice1

During a survey of the coccidian parasites of reptiles from Iowa, three specimens of Crotalus horridus L., the Timber Rattlesnake, and one of Sistrurus catenatus (Rafinesque), the Massasauga Rattlesnake, were found to be passing oocysts of a Caryospora, here described as C. bigenetica n. sp. Since these snakes (family Crotalidae) are known to subsist mainly on small mammals, oocysts from one of the Timber Rattlesnakes were fed to laboratory white mice (Mus musculus L.) to determine if mammals might be involved as alternate hosts in the life cycle. At necropsy, tissues of the tongue and dermis of the mice revealed a sequence of stages which included mature male and female gamonts, fully sporulated sporocysts, “excysted” sporozoites, and “resting” sporozoites that lay individually in solitary, cyst-like host cells termed “caryocysts.” A coccidia-free Massasauga that was fed an infected mouse, at a time when caryocysts in the mouse would have been present, later passed oocysts similar to those of the original inoculum. These results, along with the discovery of endogenous stages (asexual and sexual) in the intestine of the Timber Rattlesnake and the experimentally infected Massasauga, suggest that this parasite has a heteroxenous life cycle pattern, with sexual stages occurring both in the ophidian and the mammalian hosts.     

Relationship between Mycobacterium nonchromogenicum,Mycobacterium terrae,Mycobacterium novum and Subgroup “V” (Mycobacterium trivial)

Comparison was made among Mycobacterium nonchromogenicum, M. terrae, M. novum and subgroup “V” (M. trivial) These organisms together are differentiated from other mycobacteria of group II and group III by the following characters: (1) Sensitiveness to ethambutol; (2) Tolerance to nitrite; (3) Tolerance to Tween 80; (4) Inability to utilize glucose and succinate in the presence of glutamate. To exclude the influence of growth rate, rough colony mutants (R-type mutants) were isolated from M. nonchromogenicum, M. terrae and M. novum and compared with each other and subgroup “V” that was originally of R-type. The R-type mutants of M. nonchromogenicum were similar to those of M. terrae, with the exception of the intensity of nicotinamidase and pyrazinamidase activities. These two have been suggested to belong to the same taxon, appropriate name of which is M. nonchromogenicum. The R-type mutants of M. novum were similar to the subgroup “V”, with the exception of the intensity of arylsulfatase activity. It has been considered that subgroup “V” is an R-type mutant of M. novum. Although M. nonchromogenicum and M. novum could be differentiated from each other by the intensity of the arylsulfatase, nicotinamidase and pyrazinamidase activities and requirement of nitrogen compounds, these two organisms are differentiated from other mycobacteria by the same characteristics and are therefore considered to be closely related organisms.     

Models of stream habitat characteristics associated with tubificid populations in an intermountain watershed

Habitat assessments were conducted in an intermountain watershed at three spatial extents to explore ways to predict the presence of tubificid oligochaetes likely to support the parasite Myxobolus cerebralis, cause of salmonid whirling disease. Stream reaches with six different reach slope characteristics were selected using GIS. The aquatic habitat in 60 reaches selected at random was measured and classified into distinct habitat units. Within the habitat units, areas of microhabitat with depositional fine sediments were chosen, measured, and core samples were removed to characterize the sediments and benthic oligochaetes. Two tubificids, Tubifex spp. and Limnodrilus hoffmeisteri, were abundant and co-occurred in silt-clay and fine sand sediments in these habitats. Models were posed and tested to predict the presence and relative abundance of tubificids using habitat characteristics from the three spatial extents: reach, habitat unit, and microhabitat. At the reach extent, tubificids were associated with low-reach slope and with slow water habitats. Within habitat units, tubificids were associated with higher percentages of fine sediments and higher stream width:depth ratios. In microhabitat cores, the presence of silt-clay sediments was positively associated with higher average stream width:depth ratios. Since ecological relationships are often scale dependent and stream systems have a natural hierarchy, predictive habitat models such as these that use measures from several scales may help researchers and managers more efficiently identify and quantify aquatic communities at highest risk of infection by the M. cerebralis parasite. Handling editor: J. Trexler     

The Genus Spiniferites Mantell, 1850 (Dinophyceae)

Following the recent official rejection of proposals for conservation of the generic name Hystrichosphaera, the diagnosis of its senior synonym Spiniferites is expanded in order to incorporate additional information gained since 1850 and all species according with the expanded diagnosis are listed (24 species are transferred to Spiniferites). The cyst-family name “Hystrichosphaeraceae” is replaced by the new name “Spiniferitaceae”.     

THE STABILITY OF THE SYMBIOSIS BETWEEN DIOECIOUS FIGS AND THEIR POLLINATORS: A STUDY OF FICUS CARICA L. AND BLASTOPHAGA PSENES L.

Each Ficus species depends on a specific mutualistic wasp for pollination. The wasp breeds on the fig, each larva destroying a female flower. It is, however, not known why the wasps have not evolved the ability to use all female flowers. In “dioecious” figs, the wasp can only breed in the female flowers of the “male” trees, so that pollination of a female tree is always lethal. The wasps should therefore be selected to avoid female trees. Field data is presented showing that the fruiting phenology of the dioecious fig Ficus carica is such that this selection does not occur: syconia are not receptive at the same time on “male” and female trees. Most wasps are forced to emerge from the syconia of “male” trees at a time when they will not be able to reproduce, whether they avoid female trees or not. This aspect of the life cycle of the wasp, although noticed, has been obscured in most previous studies. It is shown that the fruiting phenology of Ficus carica, which stabilizes the symbiosis, is the result of short-term selective pressures on the male function of the trees. Such selective pressures suggest a possible pathway from monoecy to dioecy in Ficus under seasonal climates.     

Ecological Stability: Reality,Misconceptions, and Implications for Risk Assessment

Over a long time frame, an ecological system may not exhibit constancy due to successional and evolutionary changes in the species composing the system. However, over shorter time frames an ecological system exhibits a certain degree of constancy (i.e., varies within defined bounds). Traditionally, ecologists considered this short-term constancy to reflect a “balance of nature,” which was viewed akin to the simple homeostatic dynamics of physiological systems. This is an appealing perspective because the disruption of the system's “balance” (i.e., its ”health“) can be ascertained by comparing the system's current state after the imposition of a perturbation with the societally desired state (i.e., baseline). Recently, ecologists have started to develop a much more complex, and perhaps more realistic, perspective regarding ecosystem dynamics, which does not depend upon homeostasis with a single baseline state. This new view includes stochastic variation, nonlinear dynamics and alternative states, and poses a challenge for assessing environmental “health” and the risk of creating “unhealthy” ecological systems