Myxobolus freitasi n. sp. (Myxozoa: Bivalvulida), a parasite of the brain of the electric knifefish in the Brazilian Amazon region

A total of 30 specimens of the Amazonian electric knifefish, Brachyhypopomus beebei Schultz, 1944 (Gymnotiformes: Hypopomidae), were collected from the Peixe-Boi River in the state of Pará, Brazil (1°06’59” S; 47°18’26” W). Fragments of the brain tissue were extracted for analysis via optical microscopy, and 18 specimens (60%) presented microparasites of the genus Myxobolus, with unequal capsules. The spores were 18.6 µm (17.7-19.8 µm) long and 8.6 µm (8.4-9.0 µm) wide; the largest polar capsule was 13.0 µm (12.4-13.4 µm) long and 5.6 µm (5.3-6.0 µm) wide, and the smallest capsule was 5.0 µm (4.5-5.3 µm) long and 2.5 µm (2.3-2.6 µm) wide. Infected brain fragments were extracted for histological processing and staining with hematoxylin-eosin and Ziehl-Neelsen. Some fragments were conserved in ethanol for molecular genetics analysis. A partial sequence of the 18S DNA gene was obtained from the spores, which did not correspond to any other sequences deposited in GenBank, although it did form a clade with other Myxobolus parasites of the nervous system. The morphological data, together with molecular phylogeny, supported the designation of a new species Myxobolus freitasi n. sp.

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.

A new Myxobolus (Cnidaria: Myxosporea) infecting the ornamental catfish Corydoras schwartzi from the Purus River in Brazil

A new microscopic cnidarian is described, infecting five of thirty (16.6%) specimens of Corydoras schwartzi caught in the Purus River, State of Amazonas, Brazil. Histological analysis showed that cyst development occurred in the serosa layer of the intestine. Mature myxospores are ovoid in body shape in frontal view, 22.4 ± 0.3 μm in total length and 16.3 ± 0.1 μm in width. Internally, two aubergine-shaped, elongate symmetrical polar capsules occupy more than half the length of the spore, 14.3 ± 0.2 μm in length and 6.5 ± 0.1 μm in width. Ultrastructural analysis provided evidence of five polar filament coils inside the polar capsule and binucleated sporoplasm containing a moderate number of sporoplasmosomes. The valvogenic cells abutting each other form a sutural ridge and frequently a thin layer of homogeneous material separates the cells. The outer surface of the myxospore valves is smooth, with no evidence of formation of ridges in the valves. Immature myxospores in various stages of development were observed. This study is the first report of a myxosporean parasitizing C. schwartzi and the first report of a myxosporean infection in the intestine of an ornamental fish from South America.

Phylogenetic characterisation of seven Unicapsula spp. (Myxozoa: Myxosporea: Multivalvulida) from commercial fish in southern China and Japan

The myxozoan genus Unicapsula Davis, 1924 (Myxosporea: Multivalvulida: Trilosporidae) is characterized as having one functional polar capsule (PC) and two rudimentary PCs in a three-valved myxospore. The plasmodia of Unicapsula spp. grow either in the myofibres or in the gills, oesophageal walls and urinary organs of marine fish. Few studies have investigated the taxonomy of Unicapsula spp. including the type species Unicapsula muscularis. Accordingly, the taxonomy of the genus was explored in the present study by using 15 new isolates of seven Unicapsula spp. (U. muscularis, U. galeata, U. andersenae, U. pyramidata, U. pflugfelderi, and two new species) that had formed pseudocysts in the trunk myofibres of commercial fish collected in southern China and Japan from November 2015 to January 2019. Two new species Unicapsula trigona n. sp., and Unicapsula motomurai n. sp. exhibited unique myxospore morphologies (semi-triangular and spherical myxospores, respectively) and 18S and 28S rDNA sequences that were distinct from those of the other Unicapsula spp. Phylogenetic analysis of the 18S and 28S rDNA sequences confirmed the monophyletic status of Unicapsula.

Morphological and molecular characteristics of Kudoa scomberomori (Myxosporea: Kudoidae) firstly foundfrom the muscles of info-pacific king mackerel Scomberomorus guttatus in Quang Binh province, Vietnam

The genus Kudoa includes about 100 described species. In Vietnam, so far, only one species, Kudoa monodactyli, has been reported. During servey for parasites of marine fish in Quang Binh province, Vietnam in 2017, we found Myxozoan samples in 8 out of 15 Indo-Pacific king mackerel (Scomberomorus guttatus). They are identified as K. scomberomori based on the results of morphological and molecular analyses. A great number of individual spores form white pseudocysts with thin membrane within the muscle fibre. The pseudocysts were 0.1-0.3 × 0.4-0.7 mm. The shape of fresh spore like a flower petal. The spore of K. scomberomori was 6.65 ± 0.09 (6.53-6.76) µm in length, 7.42 ± 0.13 (7.29-7.58) µm in width and 6.55 ± 0.11 (6.40-6.65) µm in thickness. Each spore has six shell valves with same size. Each shell valve contained one polar capsule measuring 3.42 ± 0.09 (3.32-3.48) µm in length and 1.30 ± 0.14 (1.14-1.46) µm in width. This is the first report of K. scomberomori in Vietnam and Indo-Pacific king mackerel is recorded as a new host for this species. Citation: Nguyen Ngoc Chinh, Ha Duy Ngo, Nguyen Huu Duc, Nguyen Thuy Linh, Pham Ngoc Doanh, 2017. Morphological and molecular characteristics of Kudoa scomberomori (Myxosporea: Kudoidae) firstly foundfrom the muscles of info-pacific king mackerel Scomberomorus guttatus in Quang Binh province, Vietnam. Tap chi Sinh hoc, 40(1): x-xx. DOI: 10.15625/0866-7160/v40n1.10671. *Corresponding author: [email protected] Received 13 September 2017, accepted 2 December 2017

Morphological, histopathological and molecular characterization of Thelohanellus pathankotensis n. sp. (Cnidaria: Myxosporea: Myxozoa) infecting an Indian minor carp, Labeo dero Hamilton, 1822 from a cold water wetland in Punjab (India)

A new myxobolid, Thelohanellus pathankotensis parasitizing gill lamellae and caudal fins of the Indian minor carp Labeo dero has been described using light microscopy, histopathology and molecular analyses. The fish host was collected from a cold water wetland, Ranjit Sagar Wetland, Punjab, India located 32 ̊ 26 ̍ 30 ̎ N Latitude and 75 ̊ 43 ̍ 30 ̎ E Longitude. The prevalence of infection was 30%. The plasmodia were located in the gill lamellae and the caudal fins were cylindrical and whitish, 0.8–1.0 mm in size containing about 150–300 myxospores. The myxospores had a mean length of 9.70 ± 0.50 µm, width 3.85 ± 0.27 µm, mean length of polar capsule 3.0 ± 0.15 µm, width 2.68 ± 0.08 µm. The 18S rDNA nucleotide with 1098 bp of Thelohanellus pathankotensis n. sp. (accession number KU516661) clustered phylogenetically with other myxozoan parasites, with the species most closely related was T. sp. PBS- 2015 with 92% homogeneity and T. boggoti with 98% homogeneity. The intensity of infection or the mean abundance was determined by the gill plasmodial index (GPI) based on the number of countable plasmodia. The myxospores of the present species differed from others previously described infecting the hosts of family Cyprinidae, same tissue location and geographical location.