Morphological and molecular characterization of a new cyprinid gall bladder-infecting Chloromyxum species, Chloromyxum peleci sp. n. (Myxozoa: Chloromyxidae), from Pelecus cultratus (L.) in Russia.

Extensive sampling to get rich data is very important to resolve the current taxonomic problem of Chloromyxum genus and elucidate the nature phylogenetic relationships among congeneric species. During the parasitological survey of cyprinid fish in Gulf of Finland off the coast of St. Petersburg, a new Chloromyxum species, named as Chloromyxum peleci sp. n., was found to infect the gall bladder of sichel, Pelecus cultratus (L.). Here, we provided the morphological, ultrastructural, and molecular features to describe it. Infection was represented by mono- or disporic plasmodia and mature free-floating spores in the gall bladder. Mature spores are typical of freshwater Chloromyxum species, spherical or subspherical in lateral view, measuring 8.8 ± 0.5 µm (7.4-9.5) in length, 7.8 ± 0.3 µm (7.0-8.8) in width, and 7.5 ± 0.4 µm (6.8-8.2) in thickness. Spores have a cog-like appearance in apical view for sutural ridge, and eight to ten widely spaced extrasutural ridges per valve protrude from the spore valve margin. The surface ridge patterns of the new species are similar with those of Chloromyxum auratum and Chloromyxum cristatum, with some branching. Four polar capsules of slightly unequal in two pairs were oval in apical view and pyriform in side view, locating at the anterior end of the spores. Polar filaments coil with four to five turns. The obtained almost full length of 18S ribosomal DNA (rDNA) of Ch. peleci sp. n. does not match any sequences available in GenBank but was most closely related to that of Chloromyxum fluviatile (97.9%). Phylogenetic analysis indicated that Ch. peleci sp. n. clustered in a Chloromyxum subclade infecting the gall bladder of freshwater teleost, with robust nodal support. However, Chloromyxum sensu lato infecting gall bladder of freshwater teleost was again proved to be polyphyletic. The possible evolutionary history of Chloromyxum morphotype of Chloromyxum sensu lato was discussed based on the rDNA-referred phylogeny. This is the second Chloromyxum species from sichel.

[Henneguya wolinensis (Myxosporea: Myxobolidae), a new for Russian fauna parasite from the perch Perca fluviatilis L.].

The infection of the perch Perea fluviatilis L. with myxosporean Henneguya wolinensis Romuk-Wodoracki, 1990 has been detected. This is the second finding of this parasite after its original descriptin and the first for Russia. Plasmodium of this species develops in the epidermis under scales throughout the body causing the formation of white cysts up to 1 mm. Spores are fusiform, large, their average length constitutes 25.5 µm without the caudal appendages and 62 µm with them. Slight morphological differences in spore structure comparing to original description have been revealed.

Morphological and molecular characterization of Myxobolus mucosus sp. n. (Myxosporea: Myxobolidae) with basifilamental sporulation in two cyprinid fishes, Rutilus rutilus (L.) and Leuciscus leuciscus (L.) in Russia.

A new Myxobolus species, Myxobolus mucosus sp. n., was found in the basifilamental location of roach, Rutilus rutilus, and common dace, Leuciscus leuciscus, during the investigation of fish myxosporean fauna in Finnish Bay of Baltic Sea and Lake Ladoga in 2014. Plasmodia from the two hosts share similar morphometric and morphological features which are whitish and slightly elongated oval and measured 300-500 µm in diameter. Mature spores of M. mucosus sp. n. are ellipsoidal in frontal view and lemon shaped in sutural view, measuring 13.6 ± 0.62 (12.8-14.2) µm in length, 10.7 ± 0.51 (10.3-11.4) µm in width, 7.8 ± 0.41 (7.2-8.3) µm in thickness and 13.0 ± 0.89 (11.5-14.2) µm in length, 10.8 ± 0.77 (10.2-11.5) µm in width, 7.7 ± 0.52 (7.3-8.0) µm in thickness from roach and common dace, respectively. Polar capsules were pyriform, equal in size, converging anteriorly, with 5.9 ± 0.22 (5.7-6.3) µm in length and 3.9 ± 0.3 (3.5-4.1) µm in width and 5.6 ± 0.38 (5.1-6.2) µm in length and 3.8 ± 0.24 (3.5-4.0) µm in width from roach and common dace, respectively. Spore valves are relatively thin, symmetrical, and smooth. The most remarkable morphological character of this new Myxobolus species is the distinct mucous envelope, surrounding the full myxospore valves, up to 25 and 32 µm, respectively, in roach and common dace. The partial 18S ribosomal DNA (rDNA) sequence variation of myxospores from two hosts is very tiny (below 0.8 %) but significantly differing from all available sequences of myxosporeans in GenBank. Therefore, it can be concluded that this myxosporean from these two closely related cyprinids are conspecific by combining morphological characteristics, tissue specificity, and molecular data. Phylogenetic analysis showed that this newly described species cluster with several gill-infecting Myxobolus species from cyprinid fish inhabiting in Eastern Europe.

[THE DESCRIPTION OF MYXOBOLUS PELECICOLA SP. NOV. (MYXOZOA: MYXOBOLIDAE) FROM PELECUS CULTRATUS (CYPRINIFORMES, CYPRINIDAE)].

Morphological study of myxosporean parasites Myxobolus pelecicola sp. n. from Pele- cus cultratus (L., 1758), is presented. Presporogenic stage not observed. Polysporous, el- lipsoidal. plasmodia up to 1.2 mm in length and 0.1 to 0.4 mm in width develop in the ske- letal musculature. Mature spores elongate oval or oval form in frontal view, lens-shaped in sutural view. Length of spores 16.5 ± 0.83 (14.9-18.0), width 12.1 ± 0.63 (11.6-13.3) (n = 50), thickness 7.8 ± 0.3 (7.4-8.3) µm (n = 10). Polar capsules pyriform, unequal, length of large 8.0 ± 0.44 (7.5-8.8), small 7.6 ± 0.26 (7.2-7.8), width of large 4.5 ± 0.22 (4.2-4.7), small 4.0 ± 0.21 (3.8-4.3) µm. Five to 6 distinct filament coils oriented obli- quely to capsule length, found in polar capsule. The length of extruded (in water) filament up to 130 µm. Large, but indistinct triangular intercapsular appendix present in spores. Single rodlet inclusion is very often observed in the posterior part of spore. Mucous enve- lope is absent. The type host of Myxobolus pelecicola sp. n. is sabrefish Pelecus cultratus (L., 1758). Type locality: Finnish Bay (60°05' N 29°55' E) and Ladoga lake (60°07' N 32°19' E), Russia.

[On the methods of investigation of the actinosporean development phase of myxosporidians].

The paper describes the techniques of the actinospores investigation under field and laboratory conditions. The methylene blue solution for staining of actinospore processes and estimating of daughter cells of sporoplasm is proposed.

[On the methods of investigation of the actinosporean developmental phase of myxosporidians].

The paper describes the techniques of the actinospores investigation under field and laboratory conditions. The methylene blue solution for staining of actinospore processes and estimating of daughter cells of sporoplasm is proposed.

[Modern state of knowledge on the life cycles in Myxozoa].

A critical review of modern studies on the life cycles of Myxozoa is presented. List of myxosporidian species with known life cycles is given.