Zschokkella hildae Auerbach, 1910: phylogenetic position, morphology, and location in cultured Atlantic cod

Occurrence of Myxobolus spp. (Myxozoa) in the blood of Metynnis lippincottianus (Osteichthyes: Serrasalmidae) from eastern Amazon, Brazil

Myxozoans are obligatory parasites and can be found in various organs and bloodstreams of fish, thus, the objective of this work was to describe the occurrence of Myxobolus spp. in the circulating blood of Metynnis lippincottianus from River Curiaú, Macapá City, eastern Amazon, Brazil. The samples of M. lippincottianus (11) were caught using cast net and gillnets. The fish blood was collected by puncturing the caudal vessel, using needles and syringes containing 10% of EDTA solution. Blood smear were prepared and panchromatic stained with a combination of May Grunwald-Giemsa-Wright, for observation and examination of the parasitic structures in optical microscope. Tissues from the kidney was examined using specific stereoscopic binoculars to check for the presence of cysts, lesions and parasites. The prevalence of Myxobolus spp. infecting the circulating blood of the fish was 36.36% (4/11) and 15 spores of mixosporyds were visualized. Myxobolus spp. had a prevalence of 54.55% (6/11) in host's kidney tissue and the morphometric spores data converge with observed in the blood. The morphological characteristics of the spores in the blood samples revealed two morphotypes of Myxobolus spp. This is the sixth occurrence recorded of Myxobolus spp. infecting fish blood in Brazil.

Zschokkella epinepheli n. sp. (Myxosporea: Myxidiidae) infecting the gallbladder of the white grouper Epinephelus aeneus (Serranidae) from Tunisian waters

A new coelozoic myxosporean species, Zschokkella epinepheli n. sp., collected from the gallbladder of the white grouper Epinephelus aeneus (Perciformes: Serranidae) from the bay of Bizerte, Tunisia, is described based on morphological and molecular characteristics. Myxospores and plasmodia were observed floating free in the bile. Mature plasmodia were polysporic and subspherical in shape, measuring 85.0-94.0 μm long and 70.0-82.0 μm wide. Mature myxospores were ovoid in valvular view, measuring 10.0 ± 1.7 (8.0-11.0) μm in length and 7.0 ± 0.3 (6.6-7.5) μm in width. Polar capsules were pyriform and equal in size, measuring 3.0 ± 0.2 (2.8-3.6) μm in length and 2.3 ± 0.3 (1.8-2.7) μm in width. Myxospore valves had 12-14 longitudinal striations. Based on the small subunit rDNA, the new species Z. epinepheli n. sp. differs from all other Zschokkella species for which there is a DNA sequence deposited in GenBank. Phylogenetic analysis revealed that Z. epinepheli n. sp. clustered in the marine subclade of Zschokkella species within the biliary tract IV clade. This is the first report of a Zschokkella species from the gallbladder of an epinephelin fishes.

Synopsis of the species of the genus Zschokkella Auerbach, 1910 (Myxozoa: Bivalvulida: Myxidiidae)

A synopsis of the species of Zschokkella Auerbach, 1910 (Myxozoa: Bivalvulida: Myxidiidae) is presented, including 94 nominal species from piscine hosts and 3 additional nominal species from amphibian or reptilian hosts. The most relevant morphological and morphometric features of both myxospores and trophozoite stages (when available) are presented for each species in tabulated format.

Taxonomy on three novel species of Sphaeromyxa Thélohan 1892 (Myxozoa, Bivalvulida, Sphaeromyxidae) with insight into the evolution of the genus

Three new myxosporeans of the genus Sphaeromyxa Thélohan 1892 were discovered from the coastal waters off Xiamen in the East China Sea and characterized based on morphological and SSU rDNA data. Sphaeromyxa photopectoralis sp. n. was described from Photopectoralis bindus, and Sphaeromyxa sebastisca sp. n. was described infecting both Sebastiscus marmoratus (type-host) and Scorpaenopsis cirrosa. These two species are morphologically consistent with the "balbianii" group, possessing straight myxospores and truncated ends, but are distinct from one another genetically and by myxospore dimensions. A third myxosporean infecting Siganus fuscescens was described as Sphaeromyxa xiamenensis sp. n., and this species is morphologically consistent with the "incurvata" group, bearing arcuate myxospores with rounded ends. The molecular phylogeny and estimated rRNA secondary structure suggest that marine sphaeromyxids are probably derived from freshwater myxidiids, and "incurvata" and "balbianii" groups might each represent independent evolutionary lineages. The present study also shows that S. limocapitis phylogenetically nested in "incurvata" group.

The description of two new species of Chloromyxum from skates in the Argentine Sea reveals that a limited geographic host distribution causes phylogenetic lineage separation of myxozoans in Chondrichthyes

During a survey on the myxosporean fauna of Rajiformes from the Atlantic coast of Argentina, in waters off Buenos Aires Province (34°-42°S; 53°-62°W), the gall bladders of 217 specimens belonging to seven species of skates, representatives of two families, were examined. As a result, three species of Chloromyxum Mingazzini, 1890, namely C. atlantoraji n. sp., C. zearaji n. sp. and C. riorajum Azevedo, Casal, Garcia, Matos, Teles-Grilo and Matos, 2009 were found infecting three endemic host species, the spotback skate Atlantoraja castelnaui (Arhynchobatidae), the yellownose skate Zearaja chilensis (Rajidae) and the Rio skate Rioraja agassizii (Arhynchobatidae), respectively. These species were described based on myxospore morphology and morphometry characterization, as well as by providing their small subunit ribosomal DNA (SSU rDNA) sequences. The SSU rDNA-based phylogenetic analyses showed that these three species constituted a well-established monophyletic subclade within the marine Chloromyxum clade, while branches subtending the other Chloromyxum species were poorly resolved or unresolved, independently of the host taxonomic identities (Carchariniformes, Myliobatiformes, Orectolobiformes, Pristiophoriformes, Rajiformes, Squaliformes and Torpediniformes) and/or host geographic distribution (Atlantic coast of Portugal, Atlantic coast of the USA, Australian waters or Mediterranean Sea). The possible causes of these discrepancies are discussed, providing new insights into the phylogeny of the marine Chloromyxum clade.

Morphology, seasonality and phylogeny of Zschokkella trachini n. sp. (Myxozoa, Myxosporea) infecting the gallbladder of greater weever Trachinus draco (L.) from Tunisian waters

We describe a new myxosporean species, Zschokkella trachini n. sp., infecting the gallbladder of greater weever Trachinus draco Linnaeus 1758 from Tunisia. This is the first record of Zschokkella species in T. draco. Plasmodia were polysporic producing six to eight mature spores; they were attached to the gallbladder epithelium or free floating in the bile. Mature spores were sub-ovoid in the frontal view, measured 15.2 ± 0.6 (14.4-16.0) μm in length and 9.8 ± 0.7 (9.0-10.8) μm in width. Two equal spherical polar capsules 4.0 ± 0.4 (3.6-4.5) μm in diameter, were located separately at the spore's extremities. The prevalence of infection ranged from 23.5 to 87.7 %. Morphological data and molecular analysis of the small subunit rDNA gene identified this parasite as a new species of Zschokkella. Neighbour joining clustered the parasite in a sub-clade containing other Zschokkella species parasiting the gallbladder of marine fish hosts, located within the coelozoic clade of the major freshwater clade. This is the second Zschokkella species reported from Tunisia.

Morphological characterisation and phylogenetic relationships of Zschokkella candia n. sp. from the gall-bladder of Sparisoma cretense (L.) (Perciformes: Scaridae) in the Sea of Crete off Greece

A new myxosporean parasite, Zschokkella candia n. sp., from the gall-bladder of the wild parrotfish Sparisoma cretense (L.) (Perciformes: Scaridae) is described based on light and scanning electron microscopy. Mature spores are elliptical, with mean dimensions 11.2 ± 0.5 × 7.8 ± 0.1 μm and possess spherical polar capsules with mean diameter of 2.3 ± 0.3 μm. The new species is differentiated from other similar species of the genus based on spore morphology, its coelozoic life-style and molecular data. The phylogenetic tree constructed using maximum likelihood analysis of small subunit (SSU) rDNA sequence data complements the characterisation of Zschokkella candia n. sp. by defining its phylogenetic position among the species of Zschokkella Auerbach, 1909 sequenced to date. The phylogenetic analysis supports the existing knowledge on the complicated polyphyletic relationships among the members of the genus Zschokkella.

A parvicapsulid (Myxozoa) infecting Sprattus sprattus and Clupea harengus (Clupeidae) in the Northeast Atlantic uses Hydroides norvegicus (Serpulidae) as invertebrate host

A myxosporean producing actinospores of the tetractinomyxon type in Hydroides norvegicus Gunnerus (Serpulidae) in Denmark was identified as a member of the family Parvicapsulidae based on small-subunit ribosomal DNA (SSU rDNA) sequences. Myxosporean samples from various Danish and Norwegian marine fishes were examined with primers that detect the novel myxosporean. Sprattus sprattus (Linnaeus) and Clupea harengus Linnaeus (Teleostei, Clupeidae) were found to be infected. The sequences of this parvicapsulid from these hosts were consistently slightly different (0.8% divergence), but both these genotypes were found in H. norvegicus. Disporic trophozoites and minute spores of a novel myxosporean type were observed in the renal tubules of some of the hosts found infected through PCR. The spores appear most similar to those of species of Gadimyxa Køie, Karlsbakk et Nylund, 2007, but are much smaller. The actinospores of the tetractinomyxon type from H. norvegicus have been described previously. In GenBank, the SSU rDNA sequences of Parvicapsulidae gen. sp. show highest identity (82%) with Parvicapsula minibicornis Kent, Whitaker et Dawe, 1997 infecting salmonids (Oncorhynchus spp.) in fresh water in the western North America. A phylogenetic analysis places P. minibicornis and Parvicapsulidae gen. sp. in a sister clade to the other parvicapsulids (Parvicapsula spp. and Gadimyxa spp.).

Sinuolinea infections in the urinary system of Cynoscion species (Sciaenidae) and phylogenetic position of the type species of Sinuolinea Davis, 1917 (Myxozoa: Myxosporea)

Myxosporean infections that we diagnosed frequently in the urinary tract of Cynoscion nebulosus (Cuvier, 1830) and Cynoscion regalis (Bloch and Schneider, 1801) (Sciaenidae) collected in the estuarine systems of SC, USA, are described together with their etiological agent. Based on the morphology of spores and plasmodial stages, we identified the agent, in both fish host species, as Sinuolinea dimorpha (Davis, 1916), which is the type species of the genus. Based on sequences of SSU rDNA generated in this study from type host material, this species of SinuolineaDavis, 1917 has found its place in the current phylogenetic reconstruction of Myxozoa and enlarged the limited number of myxosporean genera represented in phylogenetic analyses by sequences of type species. Sequences of SSU rDNA of S. dimorpha from Cynoscion host species formed two clusters, irrespective of their host species, and also revealed differences within each cluster. These findings contribute to the acknowledgement of myxosporean cryptic species diversity, an important topic that emphasizes the general necessity of species delimitation and of continued effort to improve our knowledge of Myxosporea based on both morphology of spores and molecular data.

Ultrastructural and phylogenetic description of Zschokkella auratis sp. nov. (Myxozoa), a parasite of the gilthead seabream Sparus aurata

A new myxosporean, Zschokkella auratis sp. nov., infecting the gall bladder of the gilthead seabream Sparus aurata in a southern Portuguese fish farm, is described using microscopic and molecular procedures. Plasmodia and mature spores were observed floating free in the bile. Plasmodia, containing immature and mature spores, were characterized by the formation of branched glycostyles, apparently due to the release of segregated material contained within numerous cytoplasmic vesicles. Mature spores were ellipsoidal in sutural view and slightly semicircular in valvular view, with rounded ends, measuring 9.5 ± 0.3 SD (8.7-10.3) µm in length and 7.1 ± 0.4 (6.5-8.0) µm in width/thickness. The spore wall was composed of 2 symmetrical valves united along a slightly curved suture line, each displaying 10 to 11 elevated surface ridges. Two equal subspherical polar capsules, 3.7 ± 0.3 (3.0-4.1) µm long and 3.0 ± 0.2 (2.6-3.2) µm wide, were located separately at the spore's extremities. Each polar capsule contained a polar filament forming 4 to 5 coils. The sporoplasm was binucleate and contained numerous sporoplasmosomes. Morphological data, tissue tropism, and molecular analysis of the small subunit rDNA gene identified this parasite as a new species of Zschokkella. Maximum parsimony, neighbor-joining, and maximum likelihood inferences clustered the parasite in a subclade containing other Zschokkella species parasitizing the gall bladder of brackish and marine fish hosts, located within the coelozoic clade of the major freshwater clade; this supports the existence of a marine subclade within the 'freshwater' clade, as well as the existence of a correlation between tissue tropism and myxosporean phylogeny.

Sphaerospora sensu stricto: taxonomy, diversity and evolution of a unique lineage of myxosporeans (Myxozoa)

Myxosporeans (Myxozoa) are eukaryotic parasites, primarily of fish, whose classification is in a state of flux as taxonomists attempt to synthesize the traditional morphology-based system with emerging DNA sequence-based phylogenies. The genus Sphaerospora Thélohan, 1892, which includes pathogenic species that cause significant impacts on fisheries and aquaculture, is one of the most polyphyletic taxa and exemplifies the current challenges facing myxozoan taxonomists. The type species, S. elegans, clusters within the Sphaerospora sensu stricto clade, members of which share similar tissue tropism and long insertions in their variable rRNA gene regions. However, other morphologically similar sphaerosporids lie in different branches of myxozoan phylogenetic trees. Herein, we significantly extend taxonomic sampling of sphaerosporids with SSU+LSU rDNA and EF-2 sequence data for 12 taxa including three representatives of the morphologically similar genus Polysporoplasma Sitjà-Bobadilla et Álvarez-Pellitero, 1995. These taxa were sampled from different vertebrate host groups, biogeographic realms and environments. Our phylogenetic analyses and statistical tests of single and concatenated datasets revealed Sphaerospora s. s. as a strongly supported monophyletic lineage, that clustered sister to the whole myxosporean clade (freshwater+marine lineages). Generally, Sphaerospora s. s. rDNA sequences (up to 3.7 kb) are the longest of all myxozoans and indeed metazoans. The sphaerosporid clade has two lineages, which have specific morphological, biological and sequence traits. Lineage A taxa (marine Sphaerospora spp.) have a single binucleate sporoplasm and shorter AT-rich rDNA inserts. Lineage B taxa (freshwater/brackish Sphaerospora spp.+marine/brackish Polysporoplasma spp.) have 2-12 uninucleate sporoplasms and longer GC-rich rDNA inserts. Lineage B has four subclades that correlate with host group and habitat; all Polysporoplasma species, including the type species, cluster together in one of these subclades. We thus suppress the genus Polysporoplasma and the family Polysporoplasmidae and emend the generic diagnosis of the genus Sphaerospora. The combination of morphological, biological and DNA sequence data applied in this study helped to elucidate an important part of the taxonomic puzzle within the phylum Myxozoa.

A new host record of Sphaerospora epinepheli (Myxosporea: Bivalvulida) occurring on orange-spotted grouper Epinephelus coioides from Thailand: epidemiology, histopathology and phylogenetic position

In 1991, the first record of Sphaerospora epinepheli was described as a kidney parasite of wild and cultured malabar grouper, Epinephelus malabaricus, along coastlines of Thailand, the Gulf of Thailand and the Andaman Sea. However, the present study detected high infection of this parasite in kidney renal tubes of orange spotted grouper, Epinephelus coioides, collected from Andaman Sea. The highest infection rate of 36.82% was observed during the rainy season in 2009 in Phang-Nga Bay, in the north of Andaman Sea, which is an important grouper production site in Thailand. The biological and histopathological data of the parasite in this new host record are presented. Species classification is described based on morphological data of mature spore and molecular analysis of myxosporean 18S rDNA phylogeny including that of S. epinepheli which infected E. malabaricus. The genetic position of this parasite found in two host species was also studied. The phylogenetic tree analysis of small-subunit rDNA sequences of S. epinepheli from both infected hosts was constructed using two algorithms, maximum likelihood (ML) and Bayesian inference (BI). They were placed in the clustered basal sphaerosporid clade that contain four long SSU rDNA sphaerosporid species including Sphaerospora truttae, Sphaerospora elegans, Sphaerospora ranae, Sphaerospora fugu and Bipteria formosa with strong bootstrap supports. Histopathologically, renal intratubular myxosporean spores were associated with tubulonephosis, tubular necrosis, chronic interstitial nephritis and mimic membranoproliferative glomerulonephritis. This myxosporean parasite appears to be a significant pathogen on the basis of pathological changes in the renal tubules and is highly distributed in orange-spotted grouper.

Phylogenetic position of Sphaerospora testicularis and Latyspora scomberomori n. gen. n. sp. (Myxozoa) within the marine urinary clade

An amendment of the family Sinuolineidae (Myxosporea) is proposed in order to include a newly described genus Latyspora n. gen. The type species Latyspora scomberomori n. gen. n. sp. is a coelozoic parasite in the kidney tubules of Scomberomorus guttatus. In addition to the morphological and molecular characterization of L. scomberomori n. gen. n. sp., we also present novel SSU rDNA data on Sphaerospora testicularis, a serious parasite of Dicentrarchus labrax. Performed phylogenetic analyses revealed that both species cluster within the marine urinary clade encompassing the representatives with a shared insertion within their V4 SSU rRNA region and grouping according to the shape of their spores' sutural line and their similar tissue tropism in the host. Sphaerospora testicularis is the closest relative to Parvicapsula minibicornis within the Parvicapsula subclade and L. scomberomori n. gen. n. sp. is the basal species of the Zschokkella subclade. The phylogenetic position of S. testicularis, outwith the basal Sphaerospora sensu stricto clade, and its morphology suggest it being a non-typical Sphaerospora. The sequence data provided on S. testicularis can help in future revisions of the strongly polyphyletic genus Sphaerospora. We recommend re-sequencing of several sphaerosporids as an essential step before such taxonomic changes are accomplished.

Infection dynamics of two renal myxozoans in hatchery reared fry and juvenile Atlantic cod Gadus morhua L

In order to study the infection dynamics of 2 renal myxozoans, Zschokkella hildae Auerbach, 1910 and Gadimyxa atlantica Køie, Karlsbakk and Nylund, 2007 in cultured Atlantic cod, Gadus morhua L. aged 3-19 months, a specific single-round PCR assay and a double-label in situ hybridization protocol were developed. The results demonstrated that the 2 myxozoans show spatial separation of their development with regard to spore formation inside the renal tubules versus the collecting ducts and ureters, as well as temporal separation with Z. hildae proliferating and developing spores only once the G. atlantica infection decreases, despite the presence of both myxozoans in the smallest fry studied. These results strongly suggest within-host competition of the 2 myxozoans with potential suppression of Z. hildae by G. atlantica until G. morhua acquires immunity against G. atlantica. The quantification of the G. atlantica infection inside the renal tubules before and after a 29-day experimental growth performance study using fry from hatcheries with differing filtration systems showed that the intensity of infection with G. atlantica seems to be controlled if prolonged exposure to the myxozoan transmission stages takes place from hatching onwards. Surprisingly, growth rates in the trial were inversely affected suggesting that G. atlantica does not negatively influence cod fry growth performance.