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During surveys on myxosporean parasites of Lake Balaton and River Danube fishes, two Thelohanellus spp. were found on tench (Tinca tinca) and on common nase (Chondrostoma nasus). They were identified as Thelohanellus pyriformis and Thelohanellus cf. fuhrmanni , respectively. Myxospores of T. pyriformis from tench were collected from arteria branchialis afferens of gill filaments. The mature myxospores of this species were pyriform in shape and 19 ± 0.6l (18–19.5) long, 8.2 ± 0.54 (7.5–9) wide, 7.3 ± 0.25 (7–7.5) thick containing polar tubules with 9–10 turns. The plasmodia of Thelohanellus cf. fuhrmanni were collected from under the skin of snout of the common nase. The myxospores were pyriform, 16.3 ± 0.39l (15.5–16.5) long, 6.5 ± 0.55 (6.3–7) wide, 6.3 ± 0.53 (5.8–7) thick containing polar tubules with 6 turns. Small subunit ribosomal DNA sequences of both Thelohanellus species differed from other known myxozoans. The myxospores morphology, histopathology and ssrDNA sequences supported a diagnosis of T. pyriformis from tench and T. cf. fuhrmanni from common nase. [Display omitted] • Two Thelohanellus spp. were redescribed from cyprinid fishes. • Thelohanellus pyriformis was recorded and described from the type host tench (Tinca tinca). • Thelohanellus cf. fuhrmanni was found in an atypical host, common nase (Chondrostoma nasus). • The morphology of both Thelohanellus species was supported by histology and ssrDNA sequence data. [ABSTRACT FROM AUTHOR]

Myxosporeans are a diverse group of microscopic cnidarians of wide distribution that evolved into a parasitic lifestyle. A new myxosporean species, Myxobolus sp., is herein described infecting the mandible of wild specimens of Synbranchus marmoratus , caught in the world's largest tropical wetland area, Pantanal, Brazil. Light, scanning, transmission electron microscopy and histological observations unveiled detailed taxonomic information of the new myxosporean cnidarian. Ultrastructural analysis revealed a detailed description of plasmodia structures which can be used for comparison with plasmodia from other species of myxobolids. Both histological and ultrastructural observations evidenced a connective tissue capsule surrounding the plasmodia of Myxobolus sp. as a histopathological host reaction to the infection of this parasitic cnidarian. Histology showed that tissue tropism of the new myxosporean occurs in a well-defined part of the mandible, with development of plasmodia occurring in the epidermis layer. Mature myxospores from the valvular view featured an ovoid shape and had a short prolongation of the spore valves in the posterior end. Myxospores measured 22.7 ± 1.2 µm (21.5–23.9 µm) in length, 12.5 ± 0.4 µm (12.1–12.9 µm) in width and 11.3 ± 0.5 (10.8–11.8 µm) in thickness. Polar capsules were pyriform equally-sized and measuring 4.6 ± 0.3 µm (3.9–4.3 µm) in length and 2.9 ± 0.1 µm in width (2.8–3.0 µm). Finally, this study substantiates the still hidden myxosporean diversity from South America. • First report describing infection of Symbranchus marmoratus with myxosporean cnidarian from South America. • A new myxosporean cnidarian is described using detailed features obtained from light, scanning and transmission electron micrcoscopy. • This study provides detailed descriptive ultrastructural features which could suit as a basis for accurate taxonomic identification of this new myxoxporean cnidarian. • Ultrastructural features have been described in detail for plasmodia of the new myxosporean species. [ABSTRACT FROM AUTHOR]

The article focuses on a study which developed a model for ceratomyxosis-induced mortality in Oncorhynchus tshawytscha, along with the identification of the parameters that are relevant to the persistence of myxozoan parasite Ceratomyxa shasta in Klamath River, California. The study also experimentally quantified actinospore dose and the parasite-induced mortality from such dose. Study authors described the myxospore transmission, polychaete infection and actinosphere transmission among O. tshawytscha. They concluded that their findings are relevant to understanding the ecological implications of environmental and genetic differences in ceratomyxosis-induced mortality in O. tshawytscha.

The article discusses a study on the morphologic, histopathologic and molecular characterization of Myxobolus (M.) neurophilus. In order to determine the presence of M. neurophilus in fishes, archived tissues from several fishes were examined including yellow perch Perca flavescens, walleye, and golden shiners. Examination was conducted by sectioning and staining the tissues with Giemsa or with hematoxylin and eosin. Information on the presence of mild mononuclear meningoencephalitis is also presented.