Widespread infection, diversification and old host associations of Nosema Microsporidia in European freshwater gammarids (Amphipoda).

The microsporidian genus Nosema is primarily known to infect insects of economic importance stimulating high research interest, while other hosts remain understudied. Nosema granulosis is one of the formally described Nosema species infecting amphipod crustaceans, being known to infect only two host species. Our first aim was to characterize Nosema spp. infections in different amphipod species from various European localities using the small subunit ribosomal DNA (SSU) marker. Second, we aimed to assess the phylogenetic diversity, host specificity and to explore the evolutionary history that may explain the diversity of gammarid-infecting Nosema lineages by performing a phylogenetic reconstruction based on RNA polymerase II subunit B1 (RPB1) gene sequences. For the host species Gammarus balcanicus, we also analyzed whether parasites were in excess in females to test for sex ratio distortion in relation with Nosema infection. We identified Nosema spp. in 316 individuals from nine amphipod species being widespread in Europe. The RPB1-based phylogenetic reconstruction using newly reported sequences and available data from other invertebrates identified 39 haplogroups being associated with amphipods. These haplogroups clustered into five clades (A-E) that did not form a single amphipod-infecting monophyletic group. Closely related sister clades C and D correspond to Nosema granulosis. Clades A, B and E might represent unknown Nosema species infecting amphipods. Host specificity seemed to be variable with some clades being restricted to single hosts, and some that could be found in several host species. We show that Nosema parasite richness in gammarid hosts is much higher than expected, illustrating the advantage of the use of RPB1 marker over SSU. Finally, we found no hint of sex ratio distortion in Nosema clade A infecting G. balcanicus. This study shows that Nosema spp. are abundant, widespread and diverse in European gammarids. Thus, Nosema is as diverse in aquatic as in terrestrial hosts.

A new microsporidian parasite, Microsporidium theragrae n. sp., infecting Alaska pollock Gadus chalcogrammus (Teleostei: Gadidae).

A new microsporidian infecting Gadus chalcogrammus Pallas, 1814 (Gadidae), is described based on morphological, ultrastructural, and molecular studies. This microsporidian parasite develops inside intramuscular spindle-shaped lesions measuring approximately 1-2 mm in width and 4-8 mm in length. Infected cells encapsulated by a host-produced wall containing a sponge-like acellular zone. Sporogony presumably proceeds via segmentation of sporogonial plasmodium, resulting in a variable number of spores. Sporogonial stages develop in sporophorous vesicles (SVs), abutting a moderately electron-dense thick walled coat of a homogeneous amorphous material. SVs space contains rare granular and tubular inclusions. Neighboring SVs often interconnected by bridges of the host cell cytoplasm that were limited by membrane comparable with SV coat. The elongate-ovoid spores, measuring 4.29 ± 0.38 × 2.51 ± 0.26 µm (N 104), possess a bipartite polaroplast and polar tube with 15-16 coils arranged in 2-3 layers. The angle of tilt of the polar tube coils is less than 30°. The sequence analysis of SSU rDNA coding region showed that the studied microsporidians differs from other fish muscle-infecting species at least in 17 bp (2.58%) and is closely related to Microsporidium cypselurus Yokoyama et al. (2002) infecting the flying fish from East China Sea. The parasite is provisionally positioned as Microsporidium theragrae sp. n.

Pathogens and other symbionts of the Amphipoda: taxonomic diversity and pathological significance.

With over 10000 species of Amphipoda currently described, this order is one of the most diverse groups of freshwater and marine Crustacea. Members of this group are globally distributed, and many are keystone species and ecosystem engineers within their respective ecologies. As with most organisms, disease is a key factor that can alter population size, behaviour, survival, invasion potential and physiology of amphipod hosts. This review explores symbiont diversity and pathology in amphipods by coalescing a range of current and historical literature to provide the first full review of our understanding of amphipod disease. The review is broken into 2 parts. The first half explores amphipod microparasites, which include data pertaining to viruses, bacteria, fungi, oomycetes, microsporidians, dinoflagellates, myxozoans, ascetosporeans, mesomycetozoeans, apicomplexans and ciliophorans. The second half reports the metazoan macroparasites of Amphipoda, including rotifers, trematodes, acanthocephalans, nematodes, cestodes and parasitic Crustacea. In all cases we have endeavoured to provide a complete list of known species that cause disease in amphipods, while also exploring the effects of parasitism. Although our understanding of disease in amphipods requires greater research efforts to better define taxonomic diversity and host effects of amphipod symbionts, research to date has made huge progress in cataloguing and experimentally determining the effects of disease upon amphipods. For the future, we suggest a greater focus on developing model systems that use readily available amphipods and diseases, which can be comparable to the diseases in other Crustacea that are endangered, economically important or difficult to house.

Histological and ultrastructural study of Myxobolus mugchelo (Parenzan, 1966) with initial histopathology survey of the Liza ramada host intestine.

This paper provides histological and ultrastructural data on Myxobolus mugchelo (Myxozoa), a parasite of the intestinal wall of thinlip mullet Liza ramada from the Comacchio lagoons (Northern Adriatic Sea, Italy). About 80% of the examined mullets were infected with this myxozoan. In histological sections, the plasmodia appeared rounded to ovoid and spindle shaped, measured 181.61 ± 97 × 122.79 ± 53.16 µm (mean ± standard deviation, SD) in size. Early sporogenic plasmodia were located primarily in the muscle layer where no pronounced inflammatory response was detected. Plasmodia containing mature spores were situated closer to mucosal folds and were encircled by numerous immune cells, especially mast cells. Mature spores were generally oval and 6.06 ± 0.40 × 3.48 ± 0.92 µm in size. The spores showed symmetrical and smooth valves. The anterior end of the spores contained two equal pyriform polar capsules measuring 2.19 ± 0.47 × 1.59 ± 0.29 µm. Inside the polar capsules, an isofilar polar filament displayed 5-6 coils perpendicular or slightly oblique to the longitudinal axis. The wall of the polar capsule was filled with a hyaline substance contrasting with the very dense internal matrix. The mucus layer surrounded the spore surface. A thorough comparison with the Myxobolus species infecting intestine of fish is provided. This is the first report on occurrence of this myxozoan species in L. ramada population of the North Adriatic Sea.

Study of Loma acerinae (Microsporidia) detected from three Ponto-Caspian gobies (Gobiidae) in Ukraine.

A previously recognized Glugea-belonging Microsporidia (G. melanostomi, G. markievichi, G. naidenovi) were found in the intestinal mucosa of Neogobius melanostomus, N. fluviatilis, and Proterorhinchus semilunaris (Teleostei, Gobiidae) from lower Dnieper River and Black Sea coastal inlets, Ukraine. Light microscope observations demonstrated small spherical xenomes about 0.35 mm in diameter filled by developmental stages of parasites. Mature spores were ellipsoidal, slightly narrowed at anterior pole, sometimes ovoid or elongate in shape approximately 3.1-4.5 × 2.0-2.9 µm in size. The stained spores were elongate ovoid that are measured about 2.3-4.3 × 1.6-3.4 µm. Ultrastructural study showed that xenoma wall consisted of finely granular layer up to 350 nm wide. Numerous host-derived collagenous fibers adhered to the xenoma wall were noticed. Microtubular inclusions about 40 nm in diameter occupied the episporontal space. Mature spores displayed the polar filament arranged in one row. One to two last turns of polar filament were sharply tapered to half of diameter. The number of polar filament turns varied depending of host infected from 10 (9 + 1) in N. melanostomus to 13 (11 + 2) in N. fluviatilis and 14 (13 + 1) in P. semilunaris. The endospore thickness varied depending of host infected from 30-35 nm in case of N. fluviatiis to 40-50 nm in P. semilunaris and 60-80 nm in N. melanostomus. SSU 16S rRNA sequence analysis, blast searches, and ultrastuctural data revealed similarity of all studied microsporidians with Loma acerinae (Jirovec, 1930).

Parasitization of invasive gobiids in the eastern part of the Central trans-European corridor of invasion of Ponto-Caspian hydrobionts.

Four gobiid species, Babka gymnotrachelus, Neogobius melanostomus, Neogobius fluviatilis, and Proterorhinus semilunaris, were parasitologically studied in different localities of the Dnieper and Vistula river basins. The highest number of parasitic species was found in N. fluviatilis (35 taxa). The parasite fauna of N. melanostomus, B. gymnotrachelus, and P. semilunaris consists of 23, 22, and 15 taxa, respectively. The species accumulation curves show stable accumulation of parasite species by all four fish hosts along the studied part of the corridor, from the Dnieper Estuary to the Vistula River delta. The plot reveals also that the studied gobies lose the parasites common in the host native range and accept new parasites from the colonized area. In the case of N. melanostomus, it complies with the enemy release hypothesis, as the parasite load was low in the invaded area if compared to the native range. The three other alien gobies are vector for Gyrodactylus proterorhini in the Baltic basin. Moreover, populations of this alien monogenean tend to be more abundant in their new range in comparison with the Black Sea basin. In general, the number of parasite species in the colonized area was of the same rank as in the native one for N. fluviatilis, and even higher for B. gymnotrachelus. This results from accumulating new parasite species along the gobiid invasion route. In particular, the N. fluviatilis, B. gymnotrachelus, and P. semilunaris lost some of their native parasites and gained the local ones after entering the post-dam part of the Vistula River; it can be interpreted as a partial escape from parasites.

Orthosomella lipae sp. n. (Microsporidia) a parasite of the weevil, Liophloeus lentus Germar, 1824 (Coleoptera: Curculionidae).

A new microsporidium, Orthosomella lipae sp. n., was isolated from the outer ovariole sheath, trophic chambers, oocytes, somatic tissues and eggs of adults of the weevil, Liophloeus lentus Germar, 1824 (Coleoptera: Curculionidae) from southern Poland. Morphological and life cycle characteristics revealed using light and electron microscopy, place this new species within the Unikaryonidae. However, the 16S rDNA phylogeny indicates that it is associated with the genus Orthosomella.

Database on eukaryotic symbionts of native and invasive gammarids (Crustacea, Amphipoda) in the Baltic region of Poland with information on water parameters for sampling sites.

This dataset documents the diversity of eukaryotic endo- and epibiotic organisms from 612 host individuals of seven gammarid (Amphipoda) species (Gammarus pulex, Gammarus zaddachi, Gammarus roeselii, Gammarus tigrinus, Dikerogammarus villosus, Pontogammarus robustoides, Echinogammarus ischnus) of native and invasive origin in the Baltic region of Poland. We identify 60 symbiotic species of nine phyla from 16 localities of freshwater and brackish habitats. Twenty-nine symbiotic species belonged to the Ciliophora, 12 to Apicomplexa, 8 to Microsporidia, 3 to Platyhelminthes, 2 to Acanthocephala, 2 to Nematoda, 2 to Rotifera, 1 to Choanozoa and 1 to Nematomorha. The material in this Data in Brief paper is composed of three Microsoft® Excel files. The first file represents the raw data on the number of individuals (infrapopulation size) of each eukaryotic symbiont taxa recorded in each host individual and location. The data set contains information on the assemblage of symbionts per host individual in one table-matrix; macro- (host) and symbiont taxa name, host length, the date of collection, the geographic coordinates and locality name in columns; and amphipod host specimens in lines. The second file reports the symbiont species list (the species breakdown by phyla in spreadsheets) with information on host species, sampling date, locality and geographic coordinates, infection site, obtained sequences (if the case), brief morphological characteristics and microphotographs. The third file reports measured water parameters, habitat features and host density per sample. We generate the present dataset to evaluate the richness, diversity, population and community features of symbiotic organisms in native and invasive gammarid hosts in Poland. Biological sciences: ParasitologyEnvironmental Science: Ecology; Hydrology and Water Quality.

Gregarines (Apicomplexa) and microsporidians (Microsporidia) of native and invasive gammarids (Amphipoda, Gammaroidea), occurring in Poland.

The goal of our study was to recognize microparasites of alien gammarids inhabiting Polish inland and coastal waters versus those infecting local species. Twenty two localities including the Vistula, Oder and Bug Rivers, Vistula Lagoon, Goslawskie Lake, littoral of the Baltic Sea, as well as small rivers draining directly to the sea were investigated. In total, over 5000 individuals of 14 species of gammarids were collected and analyzed using light and electron microscopy. The studies have revealed five named and seven unnamed species of gregarines (Apicomplexa, Gregarinidae) as well as three named and seven unnamed species of microsporidians (Microsporidia, Nosematidae, Thelohaniidae) infecting six native and four invasive gammarid host species. All the above microparasites were new to Poland. Four species of gregarines (Uradiophora ramosa, U. longissima, Cephaloidophora similis, C. mucronata) and four microsporidians (Nosema dikerogammari, N. pontogammari, Thelohania sp. 2, Thelohania sp. 5) were associated with hosts of Ponto-Caspian origins. Evidently, these microparasites were transported to the area through the range expansion of their invasive hosts. Gregarines Cephaloidophora sp. 1 and Uradiophora sp. 1 were registered only in North American Gammarus tigrinus. Uradiophoera ramosa infects Ponto-Caspian (P. robustoides, D. villosus) and North-Americah hosts (G. tigrinus).

Europe-wide reassessment of Dictyocoela (Microsporidia) infecting native and invasive amphipods (Crustacea): molecular versus ultrastructural traits.

Microsporidia are common parasites infecting animals and protists. They are specifically common pathogens of amphipods (Crustacea, Malacostraca), with Dictyocoela spp. being particularly frequent and highly prevalent, exhibiting a range of phenotypic and ecological effects. Until now, seven species of Dictyocoela were defined, predominantly based on the genetic distance. However, neither the taxonomic status of this provisionally erected genus (based on eight novel sequences and one micrograph of the spore), nor its internal phylogenetic relationships have been clearly revealed. The formal description of the genus and of most of the putative species are still lacking. Here we aimed to fill this gap and performed both ultrastructural and molecular studies (based on SSU, ITS and partial LSU) using different species delimitation methods. As a consensus of these results and following conservative data interpretation, we propose to distinguish five species infecting gammarid hosts, and to keep the names introduced by the authors of the type sequences: Dictyocoela duebenum, D. muelleri, D. berillonum and D. roeselum. We provide full descriptions of these species. Moreover, thanks to our extensive sampling, we extend the known host and geographic range of these Microsporidia.

Microparasites of worldwide mullets.

The present review is focus on parasitic organisms, previously considered as protozoans. Viral, prokaryotic and fungal parasites caused diseases and disorders of worldwide mullets were also observed. Most of the known viruses associated with a high mortality of mullets were detected in Mugil cephalus. Prokaryotic microparasites were registered in M. cephalus, Moolgarda cunnesiu, Liza ramada and Mugil liza. Fungal pathogens were associated with representatives of the genera Aphanomyces, Achlya, Phialemonium, Ichthyophonus. Ichthyophonus sp. can be considered as a potential threat for marine fish aquaculture, especially in culture conditions. A new hyperparasitic microsporidium like organism was recorded in myxozoan Myxobolus parvus infecting grey mullet Liza haematocheilus in the Russian coastal zone of the Sea of Japan. The protozoan representatives of the phyla Dinoflagellata, Euglenozoa, Ciliophora and Apicomplexa were reviewed and analyzed. The review of myxosporean parasites from grey mullets includes 64 species belonging to 13 genera and 9 families infecting 16 fish species

[Systematics meanders of microsporidia]. / Meandry systematyki mikrosporydiów.

Meanders of systematics of Microsporidia. Taxonomical questions of Microsporidia, its systematic position and evolutionary relationship with other Eukaryota are discussed. Utilizations of modern methods of investigations of microsporidians cause new taxonomical troubles. At the present time it is difficult to create a clear hypothesis concerning the phylogeny and evolution of Microsporidia. Most likely they are representatives of a new kingdom of Eukaryota. Existing problems will not be dissolved until new detailed data concerning the new and common species are obtained.

Genetic diversity of the feminising microsporidian parasite Dictyocoela: new insights into host-specificity, sex and phylogeography.

Microsporidia of the genus Dictyocoela are parasites of gammarid amphipod Crustacea. They typically exhibit low virulence and efficient vertical transmission and at least some strains are capable of feminising their hosts. Sequencing of a region of the 16S rDNA of Dictyocoela spp. from various gammarid host species and localities in Europe and northern Asia indicates that Dictyocoela is genetically diverse and that different strains predominate in different host species. However, the presence of intermediate sequences casts doubt upon previous attempts to describe Dictyocoela spp. on the basis of rDNA divergence alone. Phylogenetic analysis provides little support for coevolution between gammarids and Dictyocoela. Furthermore, observations of heavily infected individuals, together with genetic evidence of recombination, suggest that some strains of Dictyocoela may be horizontally transmitted and are sexually reproducing. These findings suggest that Dictyocoela may be phenotypically, as well as genotypically, diverse, with the potential to exhibit a range of different interactions with its host populations.