Impacts of multispecies parasitism on coho salmon (Oncorhynchus kisutch) in Oregon

Diseases caused by parasites are recognized as significant sources of mortality in wild fish populations. I assessed the impacts of multispecies parasitism on a threatened stock of juvenile coho salmon (Oncorhynchus kisutch). A crucial prerequisite to this research was proper identification of parasites, which can be difficult for species lacking distinct morphological features. Such was the case when I attempted to identify larval Apophallus sp. (Digenea) and a myxozoan infecting peripheral nerves, which I described as Myxobolus fryeri. The second essential step was to document the geographic distribution of infections in Oregon coastal juvenile coho salmon. I found 21 different parasite species in underyearlings and smolts from 10 different rivers. Some parasites, such as Apophallus sp., were more common in underyearlings than smolts and had a more restricted geographic distribution. Additionally, I empirically compared histology to the evaluation of wet preparations for parasite detection. The latter was more sensitive, but the former provided data on tissue level impacts. I then focused my research on parasitized coho salmon from one river, the West Fork Smith River (WFSR). The lower abundance of some parasites in smolts, compared to underyearlings suggested parasite associated mortality. Therefore, I evaluated the persistence of these parasites, as this trend could also be explained by infection recovery. The parasites in my study persisted throughout the overwintering period of these coho salmon. I also conducted a field study involving both pseudolongitudinal and retrospective approaches. Results indicated that up to 95% of parr from the lower mainstem of the WFSR had infections levels of Apophallus sp. that were associated with mortality. I also performed a laboratory study on wild fish from two consecutive year classes and fish experimentally infected with Nanophyetus salmincola. Parasite associations were evaluated for the following fish performances: size, growth, swimming stamina, and gill Na⁺,K⁺-ATPase activity. Parasites were most negatively associated with size and growth, which was remarkably consistent between study years and likely influenced swimming stamina and ATPase activity levels. Taken together, results from the population, individual, and tissue levels, all indicate that these parasites impact this threatened stock of juvenile coho salmon. These results may have implications for fishery management, as it represents a previously unrecognized limiting factor for this recovering population.Keywords: Multispecies parasitism, Histopathology, Land use impacts, Threatened populations, Macroparasite distribution, Disease ecologyKeywords: Multispecies parasitism, Histopathology, Land use impacts, Threatened populations, Macroparasite distribution, Disease ecolog

Mortality of Coho Salmon (Oncorhynchus kisutch) Associated with Burdens of Multiple Parasite Species

Multiple analytical techniques were used to evaluate the impact of multiple parasite species on the mortality of threatened juvenile coho salmon (Oncorhynchus kisutch) from the West Fork Smith River, Oregon, USA. We also proposed a novel parsimonious mathematical representation of macroparasite distribution, congestion rate, which i) is easier to use than traditional models, and ii) is based on Malthusian parameters rather than probability theory. Heavy infections of Myxobolus insidiosus (Myxozoa) and metacercariae of Nanophyetus salmincola and Apophallus sp. occurred in parr (subyearlings) from the lower mainstem of this river collected in 2007 and 2008. Smolts (yearlings) collected in 2006 - 2009 always harbored fewer Apophallus sp. with host mortality recognized as a function of intensity for this parasite. Mean intensity of Apophallus sp. in lower mainstem parr was 753 per fish in 2007 and 856 per fish in 2008, while parr from the tributaries had a mean of only 37 or 13 parasites per fish, respectively. Mean intensity of this parasite in smolts ranged between 47 - 251 parasites per fish. Over-dispersion (variance to mean ratios) of Apophallus sp. was always lower in smolts compared with all parr combined or lower mainstem parr. Retrospective analysis based on smolt data using both the traditional negative binomial truncation technique and our proposed congestion rate model showed identical results. The estimated threshold level for mortality involving Apophallus sp. was at 400 - 500 parasites per fish using both analytical methods. Unique to this study, we documented the actual existence of these heavy infections prior to the predicted mortality. Most of the lower mainstem parr (approximately 75%) had infections above this level. Heavy infections of Apophallus sp. metacercariae may be an important contributing factor to the high over-wintering mortality previously reported for these fish that grow and develop in this section of the river. Analyses using the same methods for M. insidiosus and N. salmincola generally pointed to minimal parasite-associated mortality

Survey of Parasites In Threatened Stocks of Coho Salmon (Oncorhynchus kisutch) In Oregon By Examination of Wet Tissues and Histology

We are conducting studies on the impacts of parasites on Oregon coastal coho salmon (Oncorhynchus kistuch). An essential first step is documenting the geographic distribution of infections, which may be accomplished by using different methods for parasite detection. Thus, the objectives of the current study were to (1) identify parasite species infecting these stocks of coho salmon and document their prevalence, density, and geographic distribution; (2) assess the pathology of these infections; and (3) for the first time, determine the sensitivity and specificity of histology for detecting parasites compared with examining wet preparations for muscle and gill infections. We examined 576 fry, parr, and smolt coho salmon in total by histology. The muscle and gills of 219 of these fish also were examined by wet preparation. Fish were collected from 10 different locations in 2006–2007. We identified 21 different species of parasites in these fish. Some parasites, such as Nanophyetus salmincola and Myxobolus insidiosus, were common across all fish life stages from most basins. Other parasites, such as Apophallus sp., were more common in underyearling fish than smolts and had a more restricted geographic distribution. Additional parasites commonly observed were as follows: Sanguinicola sp., Trichodina truttae, Epistylis sp., Capriniana piscium, and unidentified metacercariae in gills; Myxobolus sp. in brain; Myxidium salvelini and Chloromyxum majori in kidney; Pseudocapillaria salvelini and adult digenean spp. in the intestine. Only a few parasites, such as the unidentified gill metacercariae, elicted overt pathologic changes. Histology had generally poor sensitivity for detecting parasites; however, it had relatively good specificity. We recommend using both methods for studies or monitoring programs requiring a comprehensive assessment of parasite identification, enumeration, and parasite-related pathology.This is the publisher’s final pdf. The published article is copyrighted by the American Society of Parasitologists and can be found at: http://www.journalofparasitology.org/

Apophallus microsoma N. SP. from Chicks Infected with Metacercariae from Coho Salmon (Oncorhynchus kisutch ) and Review of the Taxonomy and Pathology of the Genus Apophallus (Heterophyidae)

Metacercariae of an unidentified species of Apophallus Luhe, 1909 are associated with overwinter mortality in coho salmon, Oncorhynchus kisutch (Walbaum, 1792), in the West Fork Smith River, Oregon. We infected chicks with these metacercariae in order to identify the species. The average size of adult worms was 197 x 57 μm, which was 2 to 11 times smaller than other described Apophallus species. Eggs were also smaller, but larger in proportion to body size, than in other species of Apophallus. Based on these morphological differences, we describe Apophallus microsoma n. sp. In addition, sequences from the cytochrome c oxidase 1 gene from Apophallus sp. cercariae collected in the study area, which are likely conspecific with experimentally cultivated A. microsoma, differ by >12% from those we obtained from Apophallus donicus (Skrjabin and Lindtrop, 1919) and from Apophallus brevis Ransom, 1920. The taxonomy and pathology of Apophallus species is reviewed.Keywords: Mortality, St. Lawrence River, Life cycle, Parasite, Perch Perca flavescens, Trematoda, Yellow perch, Brevis, Oregon, Nanophyetus salmincol

Proliferative kidney disease in Alaskan salmonids with evidence that pathogenic myxozoans may be emerging north

11 Pág.Proliferative kidney disease (PKD) of salmonids, a chronic immunopathology caused by the myxozoan parasite Tetracapsuloides bryosalmonae, is exacerbated by increased water temperatures. PKD causes economic concerns to trout farmers and contributes to the decline of wild salmonid populations in North America and Europe. The parasite occurs as far north as Norway and Iceland in Europe and was confirmed from California to southern British Columbia in the American continent. In mid-September 2011 adult chum salmon (Oncorhynchus keta) were sampled from Kantishna River, a tributary to Yukon River in Alaska. Clinical PKD was diagnosed based on the macroscopic appearance of mottled kidneys that were uniformly swollen and by the detection of tumultuous histozoic extrasporogonic and coelozoic sporogonic stages of T. bryosalmonae in renal tissue by histopathology. Archived samples provided the molecular confirmation and local strain identification, representing the first confirmed case of PKD in wild adult chum salmon, also co-infected with Parvicapsula minibicornis that represents another novel myxozoan detection in Alaska. Our investigation was extended to another case from August/September 1997, with mortality following furunculosis and ectoparasite co-infections, in sockeye salmon (Oncorhynchus nerka) pre-smolts net-pen reared in English Bay Lakes, Alaska. Immunohistochemistry on archived histological preparations confirmed T. bryosalmonae sporogonic and extrasporogonic stages, indicating a severe to resolving PKD, with concomitant Chloromyxum spp. infection. Those cases provide the first documentation that this parasite is present in Alaska and causes PKD in wild and cultured salmonids in the region. The known geographic range of T. bryosalmonae can be extended to ~267 km south of the Arctic Circle, representing the northernmost detection in America. Given the vast size of Alaska and small resident population, it is likely that T. bryosalmonae remained undetected, but more recently became evident due to the clinical manifestation of PKD, possibly linked to increasing water temperatures reported at the sample locations.This work was funded by the Commercial Fisheries and Sport Fish Divisions of the Alaska Department of Fish and Game, USA. CB was supported by the Swiss National Science Foundation, Switzerland Post-Doc Mobility grant P400PB_183824.Peer reviewe

Optimizing the Dispersion of Single-Walled Carbon Nanotubes in Sodium Dodecylbenzene Sulfonate

Carbon nanotubes, because of their remarkable mechanical, electrical, and optical properties, are among the most promising materials within nanotechnology. For most applications the carbon nanotubes must be dispersed uniformly; Van der Waal forces cause the tubes to stick together -- decreasing mechanical properties significantly. To separate the tubes from one another, they must be separated in some sort of medium often by using probe ultrasonication. Many different combinations of ultrasonication parameters --such as total time, amplitude, and concentrations of solvents -- have been used with little understanding of how these parameters affect dispersion quality. This work aims to develop such an understanding of the dispersions in sodium dodecylbenzene sulfonate by monitoring the quality of dispersion with near-infrared fluorescence to create a polymer wrapped carbon nanotube aerogel

Creating a Better Dispersion of Single Walled Carbon Nanotubes (SWNT) in Sodium Dodecyl Sulfate (SDS)

Carbon nanotubes, because of their remarkable mechanical, electrical, and optical properties, are among the most promising materials within nanotechnology. For most applications the carbon nanotubes must be dispersed uniformly in some sort of medium, often by using probe ultrasonication. Many different combinations of ultrasonication parameters, such as total time, amplitude, on/off cycling, and temperature, have been used with little understanding of how these parameters affect dispersion quality. This work aims to develop such an understanding of the dispersions in sodium dodecyl sulfate by monitoring the quality of dispersion with near-infrared fluorescence

Molecular and morphological analysis of Myxobolus spp. of salmonid fishes with the description of a new Myxobolus species

While investigating the parasite fauna of wild coho salmon. Oncorhynchus kisutch (Walbaum, 1792), histological examination provided evidence of a new species of Myxobolus (Myxozoa: Myxosporea) infecting nerves of skeletal muscle. Spores were morphologically similar to those of the intramuscular Myxobolus insidiosus Wyatt and Pratt, 1963, both having pyriform spores with clavate polar capsules. However, the former developed exclusively in the nerves of skeletal muscle rather than in myocytes. We examined both species of Myxobolus derived from coho salmon; Chinook salmon, Oncorhynchus tshawytscha (Walbaum, 1792); cutthroat trout, Oncorhynchus clarkii (Richardson, 1836); and rainbow trout Oncorhynchus mykiss (Walbaum, 1792) from freshwater in Oregon. Spore morphology, small subunit ribosomal RNA gene (rDNA) sequences, and site of infection were compared. Myxobolus arcticus Pugachev and Khokhlov, 1979 has pyriform spores, infects the central nervous system of many salmonids, and is found in the Pacific Northwest. It was therefore included in the analyses to rule out conspecificity with the new species. Together, these data show that the Myxobolus sp. from peripheral nerves in the skeletal musculature of coho salmon, rainbow trout, and cutthroat trout is a new species, described herein as Myxobolus fryeri n. sp