Sphaerospora festivus n. sp., a parasite of the flag cichlid, Mesonauta festivus (Teleostei: Cichlidae) from eastern Amazon, Brazil

The present study describes a new species of the genus Sphaerospora found in the urinary bladder of the flag cichlid, Mesonauta festivus collected in Corre Água district of the municipality of Macapá, Amapá State (Brazil). The study includes morphological and phylogenetic analyses of the new parasite, to determine the relationship of the new species with related myxosporean species. The new species has polysporous plasmodia, which vary in size and shape. The mature myxospores are subspherical shape in valvar view. In the sutural view, the myxospores are 5.3±0.2 (5.2-5.6) μm in length and 7.0±0.7 (6.3-7.7) μm in width, with two piriform polar capsules equal size, 2.5±0.2 (2.3-2.8) μm in length and 1.8±0.2 (1.6-2.0) μm in width. The phylogenetic analyses of a partial sequence of the 18S rRNA gene confirmed the status of the new species and determined the relationship of the new species and related myxosporean species.The sum of the evidence indicates that, Sphaerospora festivus n. sp. belongs to the family Sphaerosporidae, and is the first record of the genus Sphaerospora from Brazil.

Myxobolus jialingensis n. sp. (Myxozoa: Myxobolidae) infecting urinary bladder and hepatopancreas of yellowhead catfish Tachysurus fulvidraco from China

In the present study, we described a novel myxosporean species, Myxobolus jialingensis n. sp. (Myxozoa: Myxobolidae), which infected the urinary bladder and hepatopancreas of yellowhead catfish Tachysurus fulvidraco in China. The mature spores of M. jialingensis n. sp. were pyriform with the length of 15.8 ± 0.7 (15.4–17.0) μm and width of 8.0 ± 0.3 (7.8–8.9) μm. Two pyriform polar capsules were slightly unequal in size: the larger polar capsule was 7.4 ± 0.3 (6.7–8.0) μm in length and 3.1 ± 0.2 (2.8–3.6) μm in width; and the smaller polar capsule measured 7.3 ± 0.3 (6.6–8.1) μm in length and 3.3 ± 0.2 (2.9–3.6) μm in width. The polar capsules were directed toward the apex of the spore, packing seven to eight spirals of the polar filaments. The small subunit ribosomal RNA gene (18S rDNA) sequence of M. jialingensis n. sp. was unique among all myxozoans, and the highest similarity was 96.1% with M. voremkhai. Phylogenetic analysis based on 18S rDNA sequences revealed that myxosporeans infecting the close host affinity (belonging to the same order) had close phylogenetic relationship and, some myxosporeans infecting the same host order might have multiple origins.

History of formation and peculiarities of Ponto-Caspian fish myxosporean fauna

History of formation of Ponto-Caspian basin fish myxosporean fauna is examined. This work is based on our own material on myxosporean parasites of fish from the Black Sea (collected in 1987–2018) and the Sea of Azov (1997–2016). Totally, we have investigated 15 368 specimens of 87 species of fish (14 297 specimens of 80 species of fish in the Black Sea and 1071 specimens of 19 species of fish in the Sea of Azov). The material was collected by the method of incomplete parasitological dissections and treated by generally accepted methods. Also, all available literary sources on the myxosporean parasites of fish from the Black Sea, the Sea of Azov, and the Caspian Sea are analyzed (references list contains the most significant publications). A comparative analysis of fish myxosporean fauna in the Black Sea, the Sea of Azov, and the Caspian Sea is performed. It is stated that 108 parasite species are known in the Black Sea, 42 – in the Sea of Azov, and 68 – in the Caspian Sea. Number of myxosporean parasite species common for the Sea of Azov and the Black Sea is 32, for the Caspian and Black seas – 32, and for the Sea of Azov and the Caspian Sea – 20. Totally 16 species of myxosporean parasites are registered in all the mentioned seas. To date, of 108 myxosporean species of Black Sea region, 29 are registered only in freshwater fish in the estuaries with considerable brackish water. For 79 myxosporean species, marine fish species serve as hosts; they are registered mainly in full-salt sea part, and 17 of them are of freshwater origin: 7 species are registered in freshwater fish and in euryhaline mullets; 1 parasitizes on freshwater and marine salmon fishes; the only hosts for 9 species are mullets or other marine fish species. Marine forms are represented by Pontic (22 species), Ponto-Azov (3), and Ponto-Caspian (2) endemics, as well as by Mediterranean invaders (35). Among freshwater myxosporeans, only 1 species is Black Sea endemic; 1 species is Ponto-Azov endemic, and most other species are widely represented in freshwater reservoirs. Among Mediterranean invaders, 23 species found in the Mediterranean Sea should be noted; 12 species still have not been registered in the Mediterranean Sea, mainly due to very few studies on this group of parasites. The fauna of Sea of Azov fish parasites includes 42 myxosporean species; 32 of them are found in the Black Sea, 20 – in the Caspian Sea. Totally 19 species belong to freshwater ones, and they are parasitic only in freshwater fish species. Ten species are of freshwater origin but can be registered in marine fish species (mostly in mullets, and one – in gobies). Of the freshwater species, one is Ponto-Azov endemic. Totally 13 myxosporean species are marine ones: 2 species are Sea of Azov endemics; 3 species are Ponto-Azov endemics; 8 species are Mediterranean invaders. Caspian Sea fauna includes 68 species of myxosporeans: 8 are marine ones (1 is ancient marine species; 1 is Ponto-Caspian endemic; 6 are brackish-water myxosporeans), and 60 are freshwater species. Five endemics of the Caspian Sea are known (2 of marine origin and 3 of freshwater origin). When moving from west to east (from the Black Sea to the Caspian Sea), a gradual impoverishment of marine myxosporean fauna and its replacement by freshwater myxosporean species are observed. Impoverishment of Myxosporea species composition of the Sea of Azov and the Caspian Sea in comparison with the Black Sea one is also found.

First Record of Six Myxosporean Species (Myxozoa: Myxosporea) in Iraq from Gills of the Mugilid Fish Planiliza abu (Heckel, 1843)

Sampling of Planiliza abu specimens were done from July 2015 until the end of March 2016, a total of 118 specimens were collected weekly from Tigris River near Al-Graiat region in Baghdad province. The examination of gills of these fishes showed the occurrence of six myxosporean species which were documented for the first time in Iraq. These included: Myxobilatus baicalensis (Dogiel, 1957), Myxobolus bizerti Bahri & Marques, 1996, M. branchialis (Markevich, 1932), M. chuatsi (Dogiel &Akhmerov in Akhmerov, 1960), M. dermatobius (Ishii, 1916) and M. niei Shul'man, 1962. The description and measurements of these parasites were given as well as their illustrations.

Malacosporean myxozoans exploit a diversity of fish hosts

Myxozoans are widespread and common endoparasites of fish with complex life cycles, infecting vertebrate and invertebrate hosts. There are two classes: Myxosporea and Malacosporea. To date about 2500 myxosporean species have been described. By comparison, there are only five described malacosporean species. Malacosporean development in the invertebrate hosts (freshwater bryozoans) has been relatively well studied but is poorly known in fish hosts. Our aim was to investigate the presence and development of malacosporeans infecting a diversity of fish from Brazil, Europe and the USA. We examined kidney from 256 fish belonging variously to the Salmonidae, Cyprinidae, Nemacheilidae, Esocidae, Percidae, Polyodontidae, Serrasalmidae, Cichlidae and Pimelodidae. Malacosporean infections were detected and identified by polymerase chain reaction and small subunit ribosomal DNA sequencing, and the presence of sporogonic stages was evaluated by ultrastructural examination. We found five malacosporean infections in populations of seven European fish species (brown trout, rainbow trout, white fish, dace, roach, gudgeon and stone loach). Ultrastructural analyses revealed sporogonic stages in kidney tubules of three fish species (brown trout, roach and stone loach), providing evidence that fish belonging to at least three families are true hosts. These results expand the range of fish hosts exploited by malacosporeans to complete their life cycle.