Comparative analyses within Gyrodactylus (Platyhelminthes: Monogenea) mitochondrial genomes and conserved polymerase chain reaction primers for gyrodactylid mitochondrial DNA.

In this study, we describe the complete mitochondrial genomes of Gyrodactylus brachymystacis and Gyrodactylus parvae infecting rainbow trout (Oncorhynchus mykiss) and the invasive topmouth gudgeon (Pseudorasbora parva), respectively. The two circular genomes have a common genome organization found in other Gyrodactylus species. Comparative analyses of mitochondrial genomes from six Gyrodactylus species were carried out to determine base composition, codon usage, transfer RNA and ribosomal RNA genes, major non-coding regions, and nucleotide diversity within the genus. We also provide the first universal models of the secondary structures of rrnS and rrnL for this group thereby promoting utilization of these genetic markers. Universal primers provided herein can be used to obtain more mitochondrial information for pathogen identification and may reveal different levels of molecular phylogenetic inferences for this lineage.

Identification of transferrin in Atlantic cod Gadus morhua epidermal mucus.

The previously unreported presence of transferrin in Atlantic cod Gadus morhua epidermal mucus is described. A less destructive sampling method, which may result in decreased epidermal tissue damage, is discussed.

Taxonomy and host-specificity of Gyrodactylus aideni n. sp. and G. pleuronecti (Monogenea: Gyrodactylidae) from Pseudopleuronectes americanus (Walbaum) in Passamaquoddy Bay, New Brunswick, Canada.

Wild and cultured winter flounder Pseudopleuronectes americanus (Walbaum) from Passamaquoddy Bay were surveyed for species of Gyrodactylus Nordmann, 1832. Two species were found: G. pleuronecti Cone, 1981 and G. aideni n. sp, both members of Malmberg's 'groenlandicus group'. Although the hard parts in the haptor are very similar in the two species, hamuli of G. aideni are consistently shorter than those of G. pleuronecti. The two species differed by 35 base pairs in the ITS 1, 5.8 and ITS 2 region. A BLAST search identified a variety of species of Gyrodactylus from marine fishes in the Atlantic Ocean as closest matches, indicating the 'groenlandicus group' is part of a major marine lineage within Gyrodactylus (sensu lato) that has successfully radiated among coastal percid, pleuronectid, cottid and anarhichadid fishes. Exposure experiments suggested that winter flounder is the primary host of both species of parasites and that three other pleuronectid species in the bay may potentially serve only as occasional transport hosts.

The placement of Gyrodactylus salmonis (Yin & Sproston) in the molecular phylogeny of studied members of the Gyrodactylus wageneri-group parasitizing salmonids.

The molecular phylogeny of Gyrodactylus salmonis from brook charr, Salvelinus fontinalis, rainbow trout, Oncorhynchus mykiss, cutthroat trout, O. clarkii, and Atlantic salmon, Salmo salar, in Canada is presented using sequences from ITS-rDNA and the mitochondrial COX 1 gene. Sequence variation among G. salmonis specimens from the different North American hosts was consistent with within-species variation reported for other Gyrodactylus. Sequence data are compared to those from other members of the wageneri group parasitizing salmoniform fishes in northern Europe (G. derjavini, G. derjavinoides, G. lavareti, G. salaris, G. salvelini, G. teuchis and G. truttae) and Asia (G. brachymystacis). Sequence divergence between G. salmonis and the recently described G. salvelini on Arctic charr, Salvelinus alpinus, in Finland was consistent with within-species levels of variation in Gyrodactylus; however, phylogenetic analyses and morphological comparisons provided evidence of their distinctiveness such that they appear to be sister species. They grouped with G. lavareti (a parasite of a coregonid) to form a clade separate from European and Asian species of the wageneri lineage known from salmonid fish. Further study of gyrodactylids from across salmonid, coregonid and thymallid fish in the northern hemisphere would shed more light on the phylogeography of these parasites and serves as an important backdrop to understanding the evolution of their emergent virulence.

Divergence between Asian, European and Canadian populations of the monogenean Pseudodactylogyrus bini indicated by ribosomal DNA patterns.

The monogenean Pseudodactylogyrus bini parasitizes the gills of eels belonging to the genus Anguilla. Circumstantial evidence suggests that the parasite has been spread accidentally from the Pacific area (East Asia) to Europe by the intercontinental eel trade. This is based on early descriptions of the parasites from Asian regions and the lack of records of the parasites in Europe before 1977. In addition, the susceptibility of European eels to infections with the parasite is significantly higher compared to that of Japanese eels, which could indicate that the European eel had not undergone co-evolution with this parasite. The present study was undertaken to elucidate the origin of the parasite by using molecular tools. Parasite samples were obtained from Europe (Germany), Asia (Taiwan) and Nova Scotia, the latter of which is the first record of P. bini in Canada. Sequencing of rDNA comprising part of the internal transcribed spacer 1 (ITS1) gene, 5.8S and part of ITS2 (1323 bp) showed that P. bini isolates from the first two regions showed high variability. One sequence was found both in a number of Asian parasites and with one to a few transitions in European parasites, which could indicate that they were split recently into the two regions. Other sequence variations suggested that one or a few genotypes of P. bini were imported on one occasion from Asia to Europe and that the two geographic isolates subsequently developed differently in the two regions. The Nova Scotian/Canadian isolates showed no variation and were found to be unique compared to the European and Taiwanese forms, indicating that this population is independent in origin. This could indicate that the Canadian parasites were introduced to North America on another occasion and independently of the European colonization.

First record of Anguillicoloides crassus (Nematoda) in American eels (Anguilla rostrata) in Canadian estuaries, Cape Breton, Nova Scotia.

In the summer of 2007, American eels, Anguilla rostrata, from 2 localities on Cape Breton Island, were found to be infected with the swim bladder nematode Anguillicoloides crassus. This is the first documented report of this highly invasive parasite in Canadian waters. More than half of the yellow eels in Mira River (6 of 10), and 1 eel (of 5) from Sydney Harbour were infected. Parasite intensity ranged from 1 to 11 worms per eel. The occurrence of A. crassus at these 2 localities suggests the need for a more extensive survey on the distribution of this exotic parasite in eel populations throughout Cape Breton Island.

Morphological and molecular comparison of Myxobolus procerus (Kudo, 1934) and M. intramusculi n. sp. (Myxozoa) parasitising muscles of the trout-perch Percopsis omiscomaycus.

Inter- and intracellular cysts from a presumed single species, Myxobolus procerus (Kudo, 1934), parasitising the trout-perch Percopsis omiscomaycus were compared with respect to their spore morphology and small subunit 18S ribosomal DNA. The two cyst types have similar pyriform spores and comparable ranges in spore length and width, size of the polar capsules and number of filament coils. However, fixed spores of the intracellular cysts are significantly shorter (p<0.05) in mean length than those from intercellular cysts, giving them a broader appearance. Comparing 991 base pairs of 18S rDNA revealed a 20 bp difference between the two cyst types (97.9% similarity), 10 due to base substitutions and 10 due to the presence or absence of a base. The described morphological differences and consistent 2.1% difference in the 18S rDNA reveal that the intracellular form is a separate species, which is described herein as Myxobolus intramusculi n. sp. M. intramusculi n. sp. and M. procerus may be sister species and it is suggested that the two species arose through sympatric speciation involving a switch in site specificity within a single host species.

Initial infection, distribution, and seasonal occurrence of Hoferellus gilsoni (Myxozoa) within a population of Anguilla rostrata (Anguillidae) in southern Nova Scotia.

Recently transformed elvers of Anguilla rostrata, entering the mouth of the East River in the Timber/Connaught Lake watershed (Nova Scotia) from the sea in mid-May, did not develop infections of the urinary bladder parasite Hoferellus gilsoni (Myxozoa) after nearly 3 mo in captivity. However, 40% of elvers collected from the mouth of the river in early June and 80% in late June exhibited patent infections by mid-August. It is speculated that given this initial level of infection, the summer run of elvers (estimated to be 208,000-963,000 individuals annually) represents a significant upstream dispersal of spores. Infections in yellow eel, which has a limited home range, probably contribute to spore dispersal within the home range and downstream through spore drift. Sporogenesis occurred in samples of yellow eel collected over an 8-mo period from April to November. Eel length was similar in 3 widely separated sampling locations in the watershed. Prevalences at these localities were 44, 36, and 57% in April and, by June, reached 76, 70, and 90%, respectively. Prevalences remained near the June levels until sampling ceased in November 1998. Studies on captive fish suggest that H. gilsoni can overwinter in the eel. Data from the study indicate that immediate infection of young elvers entering the system, effective spore dispersal, and a seasonally extended sporogenesis all contribute to the ubiquitous presence of the parasite in the eel population.

Myxozoan communities parasitizing Notropis hudsonius (Cyprinidae) at selected localities on the St. Lawrence River, Quebec: possible effects of urban effluents.

Late summer myxozoan infra- and component communities parasitizing 73 Notropis hudsonius at 5 sites on the St. Lawrence River upstream and downstream from the island of Montreal are described from study of histological sections of individual fish. Community membership included Myxobolus sp. A (intracellular in striated muscle fibers), Myxobolus sp. B (intracellular in striated muscle fibers), Myxobolus sp. C (brain), and Thelohanellus notatus (Mavor, 1916) Kudo, 1929 (loose connective tissue), all of which are histozoic myxobolids displaying strict tissue specificity for trophozoite development. Mean infracommunity richness in fish at the separate localities was estimated to be 0.4 +/- 0.5 to 1.3 +/- 0.7, with a maximum richness of 3 in any 1 fish. Component community richness in host samples was 2 to 4. It is argued that these are relatively high levels of diversity for freshwater fish parasites but that the values are probably conservative because of the study of only portions of individual fish. The percentage of fish infected with myxozoans of any species and infracommunity richness was significantly greater below the island of Montreal compared with above it. It is suspected that increased oligochaete populations at these sites, resulting from sewage-caused organic enrichment of sediments, may have accounted for the observed increased prevalence of infection.

Infections of Unicauda clavicauda (Kudo, 1934) (Myxozoa) in the skin of Notropis hudsonius (Cyprinidae) from Montana, with a synopsis of the genus Unicauda Davis, 1944.

Infections of Unicauda clavicauda (Kudo, 1920) Davis, 1944 (Myxozoa) are described from Notropis hudsonius (Clinton) in Montana. Plasmodia form beneath scales of the body and produced spores within a loosely-defined matrix. Fixed spores are oval in front view, 11-14 microm long and 9-10.5 microm wide, and contain a posterior appendage that is up to 26 microm long. The polar capsules are 4-6 microm long and 2.5-4 microm wide. The study represents the first report of U. clavicauda since the original species description and a new host and geographical record. The taxonomic history of Unicauda Davis, 1944 is summarised and it is concluded the following 10 species are valid members of the genus: U. aristichthydis Zhao et Ma, 1995, U. brachyura (Ward, 1919), U. caudatus (Gogebashvili, 1965), U. clavicauda, U. crassicauda (Kudo, 1934), U lumae Rahemo, 1976, U. macrura (Gurley, 1893), U. magna Minchew, 1981, U. pelteobagrus Ma, 1998, and U. wuhanensis Xiao et Chen, 1993. All of these species have circular, subcircular, or oval spores in frontal view and all parasitise fish of the superorder Ostariophysi. As a group they are known from temperate freshwater locations in North America, Europe and Asia. A list of 16 species described or transferred to Unicauda at one time or another, but not recognised as members of the genus in the present study, is provided.

Species of Myxobolus (Myxozoa) from the bulbus arteriosus of centrarchid fishes in North America, with a description of two new species.

Three species of Myxobolus (Myxozoa, Myxosporea) occur in heart tissue of centrarchids. Myxobolus paralintoni Li and Desser, 1985 from Lepomis gibbosus in Algonquin Park and in Lake Erie, Ontario, has subcircular spores (in plane of spore length) in frontal view (11-13 microm long, 9-10 microm wide, and 5 microm thick) with a width-to-length ratio of 1:1.2. Myxobolus jollimorei n. sp. from Lepomis macrochirus in Lake Erie and in the Pascagoula River System, Mississippi, has subcircular spores (in plane of spore width) in frontal view (10.0-11.5 microm long, 12.0-14.5 microm wide, and 6.5-8.0 microm thick) with a width-to-length ratio of 1:0.8. Myxobolus manueli n. sp. from Pomoxis nigromaculatus in Lake Erie has spores (10-11 microm long, 8-10 microm wide, and 6.5-7.0 microm thick) that are nearly circular in frontal view but that have 2 distinct sublateral knobs along the sutural ridge and a width-to-length ratio of 1:1.2. All 3 species occur in the bulbus arteriosus of their hosts where they form small, saucer-shaped pseudocysts. Free spores were found free in the lumen of the heart and bulbus arteriosus, in bile, and in kidney tissue presses.

Comparison of richness and diversity of macroparasite communities among eels from Nova Scotia, the United Kingdom and Australia.

Species richness and diversity of macroparasite assemblages were compared among American eels (Anguilla rostrata) from Nova Scotia, European eels (A. anguilla) from the United Kingdom (Kennedy, Bush & Aho, 1986; Esch et al. 1988; Kennedy, 1990, 1993), and Australian eels (A. reinhardtii) from Queensland (Kennedy, 1995). Community richness and diversity of the macroparasite fauna of American and European eels did not differ significantly for total parasite component communities, intestinal parasite component communities, and intestinal parasite infracommunities. The similarities in richness and diversity between the parasite communities of American and European eels are not surprising given the common, recent origin of these sister species. However, differences in species composition were noted between Nova Scotia and the UK. Both species of eels were infected by a nearly identical suite of specialists, but differences occurred in the species number and composition of generalist parasites. In addition, generalist species were rarely dominant in Nova Scotia, but commonly so in the UK. These differences can be attributed to the differences in the freshwater fish fauna and their parasites that occur between Nova Scotia and the UK. American and European eels are derived from a common ancestor and, whereas they have carried with them a common suite of specialist parasites during their brief period of independence, they acquired different suites of generalists apparently from their respective continental faunas after they diverged. In contrast, parasite communities of American and European eels were significantly less diverse and speciose than those of Australian eels regardless of scale (total component community, intestinal component community, intestinal infracommunity). These results support the notion that parasite communities have had more time to evolve and/or that tropical conditions have promoted parasite speciation in Australian eels.

Myxobolus petenensis n. sp (Myxosporea) from the circumorbital integument of Dorosoma petenense (Clupeidae) in Kentucky Lake.

Myxobolus petenensis n. sp. is described from the circumorbital integument of threadfin shad (Dorosoma petenense) in Kentucky Lake, Kentucky. Preserved spores are subspherical in frontal view and measure 10.1-13.1 microm long and 12.0-15.8 microm wide. The polar capsules are pyriform and often unequal in size, with the larger capsule measuring 6.6-8.0 microm long and 4.8-5.7 microm wide and the smaller capsule 5.7-7.4 microm long and 4.2-5.5 microm wide. Examination of several clupeids, skipjack herring (Alosa chrysochloris), gizzard shad (D. cepedianum), and threadfin shad revealed M. petenensis to infect only threadfin shad. This report of M. petenensis is the first known species of Myxobolus infecting a species of freshwater fish of the family Clupeidae in North America.

Report of spores of Henneguya salminicola (Myxozoa) in human stool specimens: possible source of confusion with human spermatozoa.

The spores of Henneguya salminicola, a common tissue parasite of salmonid fishes in the northern hemisphere, were observed in stool specimens from two different patients with diarrhea. The spores' superficial resemblance to human spermatozoa resulted, in one instance, in an incorrect report, leading to suspicion of sexual abuse. H. salminicola spores and human spermatozoa can be differentiated on the basis of size, morphology, and staining characteristics. Laboratory personnel who perform microscopic examinations of stool specimens for ova and parasites should be aware that spores of H. salminicola may be seen from time to time.

Myxobolus mississippiensis n. sp. (Myxosporea) from gills of Lepomis macrochirus in Mississippi.

Myxobolus mississippiensis n. sp. is described from gill lamellae of the bluegill (Lepomis macrochirus) inhabiting the Pascagoula River System, Mississippi. Fresh spores measure 16.4-18.7 microns long, 3.9-6.2 microns wide, and 4.7-6.2 microns thick. Spore width to length ratio is 1:3.2. Polar capsules are 5.5-7.8 microns long and 1.5-2.3 microns wide, with 9-10 filament coils that when extruded measure 42.1 +/- 4.2 microns. This parasite is unique among known species of Myxobolus in having spores that are lenticular in frontal view.

Parasite communities as indicators of ecosystem stress.

Many parasites have complex life cycles and for transmission depend on the presence of a variety of vertebrate and invertebrate intermediate hosts, including members of the benthos and zooplankton. Thus, food web dynamics and trophic interactions have a powerful influence on parasite community structure. In addition, many parasites possess free-living stages that are also susceptible to environmental conditions. Therefore, the parasite community within a single host species such as a fish is indicative of environmental stress, trophic structure, and biodiversity. We show that parasite communities of American eels (Anguilla rostrata) in Nova Scotia respond to acid conditions in rivers. Parasite species richness was greater and there were more multiple infections in eels from an experimentally limited river compared to those from an adjacent acidified river. Digeneans were absent in eels from the acidified river. The study was expanded to include 28 sites in the Southern Upland and adjacent regions of Nova Scotia, encompassing a pH gradient increasing from southwest to northeast. Survey results support those obtained by experimental manipulation. Parasite diversity in eels as measured by species richness, Shannon-Wiener Index, and Hill's Number decreased when pH < 5.4. Digeneans were absent from the southwest, where pH < 4.7. Parasite distributions among rivers in adjacent watersheds corresponded to fluctuations in pH in those rivers. These results support the hypothesis that parasite communities are good indicators of environmental stress and biodiversity, because they reflect the presence of many different types of organisms based on the variety of complex life cycles displayed by the different parasite taxa.

Food webs: a plea for parasites.

Parasites have the capacity to regulate host populations and may be important determinants of community structure, yet they are usually neglected in studies of food webs. Parasites can provide much of the information on host biology, such as diet and migration, that is necessary to construct accurate webs. Because many parasites have complex life cycles that involve several different hosts, and often depend on trophic interactions for transmission, parasites provide complementary views of web structure and dynamics. Incorporation of parasites in food webs can substantially after baste web properties, Including connectance, chain length and proportions of top and basal species, and can allow the testing of specific hypotheses related to food-web dynamics.

On the distribution and abundance of eel parasites in Nova Scotia: local versus regional patterns.

Site-to-site variation in macroparasite species distribution and richness was observed in eels (Anguilla rostrata) among 7 sites in the Timber Lake drainage system, Nova Scotia. There was a positive relationship between maximum local species distribution, as measured by maximum prevalence at a site, and regional distribution, as measured by the number of sites in which a parasite was found within the watershed and among 28 sites across Nova Scotia. Species richness increased with spatial scale. However, the species richness of host-specific parasites approached a maximum at the spatial scale of the watershed, whereas that of generalist parasites continued to increase with increasing scale. The near-peak in species richness of eel specialists at the watershed level suggests that in a functional sense for these parasites it is the spatial scale of the watershed that serves as a species pool from which local species richness is derived.