Genetic diversity of Loma acerinae (Microsporidia: Glugeida) from different fish hosts and localities - Short communication.

Loma acerinae is a xenoma-forming fish microsporidium described from common ruffe Gymnocephalus cernua (Perciformes: Percidae) and also found in Ponto-Caspian gobies (Gobiiformes: Gobiidae). This casts doubt on the strict host specificity of this parasite. The largest subunit RNA polymerase II (rpb1) was used as a genetic marker of the parasite isolated from six host species of Perciformes (G. cernua from the Baltic Sea), Atheriniformes (Atherina boyeri from the Azov Sea) and Gobiiformes (Neogobius spp. and Zosterisessor ophiocephalus from the Black Sea and Ponticola kessleri from the Caspian Sea basin). Two major rpb1 haplogroups were found with 98.5% identity between the groups. Notably, Haplogroup I was associated with Neogobius spp. samples (n = 6) only, whereas Haplogroup II included the samples from other host species (n = 7). These findings confirm the broad distribution and host range of L. acerinae, but also indicate that certain patterns of host-driven intraspecific polymorphism may exist. Furthermore, the study revealed low similarity between the ribosomal RNA gene sequences of L. acerinae and the type species, Loma morhua (as well as other species of the genus). This suggests loose genetic association within the genus, and may raise the need for the taxonomic revision of L. acerinae.

Common dace (Leuciscus leuciscus) - A new host of the myxozoan fish parasite, Myxobolus elegans (Cnidaria: Myxozoa) - Short communication.

This paper reports the detection of the myxozoan species Myxobolus elegans Kashkovsky 1966 in common dace (Leuciscus leuciscus) that has not been previously listed as its host. The problem of differentiation of phenotypically similar Myxobolus species is addressed. During parasitological survey of common dace from the desalinated part of the Gulf of Finland at the city of Sestroretsk, Russia, numerous oval-shaped plasmodia, 0.2-0.4 mm in size, filled with Myxobolus spores were found on the gills. Pear-shaped myxospores were 15.4 (14.8-16.0) × 10.2 (9.6-10.9) µm in size with a rib on each valve. On the basis of spore morphology, the species appeared to be similar to M. elegans and Myxobolus hungaricus Jaczó, 1940. In order to identify the species, molecular genetic analysis was performed, and the species was identified on the basis of morphological characteristics and 18S rDNA data. The results obtained indicate that the Myxobolus species observed on the gills of dace is M. elegans. Thus, common dace is another valid host of M. elegans besides the type host, ide (Leuciscus idus).

Myxobolus pelecicola Voronin et Dudin 2015 is a junior synonym of Myxobolus ladogensis Rumyantsev et Schulman 1997 (Myxosporea: Myxobolidae) infecting the skeletal muscle of sichel Pelecus cultratus (Actinopterygii: Cyprinidae) in Russia.

Myxobolus pelecicola Voronin et Dudin, 2015 was recently described from the skeletal musculature of sichel Pelecus cultratus. However, another species, Myxobolus ladogensis Rumyantsev et Schulman, 1997, was described previously from the same host, displaying identical tissue localization and spore morphology as in M. pelecicola. Unfortunately, M. ladogensis was overlooked when M. pelecicola was described, resulting in the superfluous description of the latter species, which, according to the International Code of Zoological Nomenclature, is a junior synonym of M. ladogensis. The description of M. ladogensis is supplemented with SSU rDNA sequence analysis supporting the conspecificity with M. pelecicola. The closest relatives of Myxobolus ladogensis (syn. M. pelecicola) include several muscle-infecting Myxobolus spp. with sequence similarity below 97%.

Ultrastructure and molecular phylogenetics of Helmichia lacustris, a microsporidium with an uncoiled isofilar polar filament.

The description of Helmichia lacustris Voronin (Parazitologiya 34:327-331 1998) is supplemented with morphogenesis and ultrastructure of the extrusion apparatus. Formation of the anterior (made up by rare short lamellae) and posterior (made up by spongy matter or small vesicles) regions of the polaroplast is preceded by granulated spheres and agglomerations of bean-like bodies, respectively. The anchoring disc is formed by an oval structure of moderate electron density, sometimes possessing a granular texture. The parasite development occurs within the cisterns of granular endoplasmatic reticulum (ER) of the host cell. Each group of spores is enclosed within a two-layered sheath, including the smooth inner membrane of the sporophorous vesicle and the outer ribosome-encrusted membrane (which originates from the host cell ER) of the parasitophorous vacuole. Two microsporidia, H. lacustris (GenBank accession number GU130406) and Euplotespora binucleata (GenBank accession number DQ675604) share 78.1% of 16S rRNA gene sequence similarity. Both parasites are characterized by an uncoiled isofilar polar filament. They form a cluster nested among terrestrial and aquatic microsporidia with well-developed coiled polar filaments, suggesting that an uncoiled polar filament in this species is a result of reduction, rather than a "primitive" character.

Life cycle, ultrastructure, and molecular phylogeny of Crispospora chironomi g.n. sp.n. (Microsporidia: Terresporidia), a parasite of Chironomus plumosus L. (Diptera: Chironomidae).

The life cycle, ultrastructure, and molecular phylogeny of a new microsporidium Crispospora chironomi g.n. sp.n., a parasite of the midge Chironomus plumosus, are described. The parasite infects the gut epithelium of the host larvae and possesses sporogonies of two types, polysporoblastic and disporoblastic, respectively, proceeding within the same host cell. In the sporogonial sequence of the first type, dozens of spherical monokaryotic spores within a thick-walled capsule are formed. The spores are 1.5-2.0 µm in diameter; the exospore possesses two to three bundles of tubular protrusions. In the sporogonial sequence of the second type, diplokaryotic oval spores, 2.5 × 1.5 µm in size, are formed within a compartment, partially surrounded with multilayered membranes. Spores of both types are similar in respect to inner structure, possessing a well-developed extrusion apparatus with (a) the anterior vesicular part of the polaroplast covering the lamellar posterior one and (b) isofilar polar filament with several coils in one row. Small subunit ribosomal DNA phylogeny showed position of the new microsporidium in a cluster uniting microsporidia of terrestrial origin infecting diverse hosts, nested within Clade IV, corresponding to Class Terresporidia sensu Vossbrinck and Debrunner-Vossbrinck (Folia Parasitol 52:131-142, 2005).

Ultrastructure and molecular phylogeny of Anisofilariata chironomi g.n. sp.n. (Microsporidia: Terresporidia) from Chironomus plumosus L. (Diptera: Chironomidae).

Larvae of Chironomus plumosus, collected in North-Western Russia in September 2008, were infected with a microsporidium possessing broadly oval uninucleate spores in sporophorous vesicles. Sporogony and spore ultrastructure of this microsporidium differed from that of known microsporidian species, suggesting establishment of a new species, Anisofilariata chironomi, being a type species of a new genus. Sporogony di-, tetra-, octo-, and 16-sporoblastic. Fixed and stained spores are 4.7-6.8 x 3.4-5.4 microm in size, the spore measurements varying depending upon the number of spores in the sporophorous vesicle. The polaroplast is bipartite, with anterior and posterior parts composed of very thin and thick lamellae, respectively, and occupies the major volume of the spore. The polar filament is anisofilar, with two broad proximal and 10-13 narrow distal coils arranged in 2-4 layers. The sporophorous vesicle is bounded by a thin membrane and contains multiple tubular structures. Small subunit ribosomal DNA phylogeny showed basal position of the new microsporidium to a cluster uniting microsporidia infecting ciliates (Euplotespora binucleata), microcrustaceans (Glugoides intestinalis, Mrazekia macrocyclopis), lepidopteran insects (Cystosporogenes spp., Endoreticulatus spp.) and human (Vittaforma corneae), nested within Clade IV sensu Vossbrinck and Debrunner-Vossbrinck (2005 Folia Parasitol 52:131-142). No close phylogenetic relationships were found between A. chironomi and microsporidia from other dipteran hosts.

Taxonomy of Neoperezia chironomi and Neoperezia semenovaiae comb. nov. (Microsporidia, Aquasporidia): Lessons from ultrastructure and ribosomal DNA sequence data.

We did a comparative analysis of the small subunit ribosomal DNA (rDNA) for two species of Microsporidia, Semenovaia chironomi and Neoperezia chironomi, both parasites of Chironomus plumosus (Diptera, Chironomidae). These two microsporidial species have been described previously on the basis of light and electron microscopic studies. The former species is dimorphic, producing both single diplokaryotic spores and uninucleate spores in sporophorous vesicles (SPVs) in packets of 16, while the latter species is monomorphic, disporoblastic, producing only uninucleate spores in SPVs. Based on their life cycles, S. chironomi and N. chironomi were assigned to two different families, Burenellidae and Neopereziidae. However, molecular analysis shows 96.7% sequence similarity for the small subunit rDNA between these two species. Remarkable similarities of the spore ultrastructure (mainly of the extrusion apparatus) justify a transfer of S. chironomi to Neoperezia, establishing a new combination, Neoperezia semenovaiae. Neoperezia belongs to Clade V, Class Aquasporidia sensu Vossbrinck and Debrunner-Vossbrinck (2005), and is in its spore ultrastructure similar to its closest relatives, namely Bryonosema, Schroedera, Pseudonosema, Trichonosema and Janacekia. We therefore conclude that similarities in spore ultrastructure reflect the phylogenetic relatedness of these Microsporidia, as opposed to the strikingly diverse life cycles.