Ultrastructure, surface topography, morphology and histological observations of a new parasitic cnidarian of the marbled swamp eel from the world's largest tropical wetland area, Pantanal, Brazil

• Published in: Tissue & cell Vol. 79; p. 101909
• Main Authors: Mathews, Patrick D., Mertins, Omar, Milanin, Tiago, Aguiar, Julio C., Gonzales-Flores, Anai P.P., Tavares, Luiz E.R., Morandini, André C.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2022
• Subjects: Brazil; Histology; Morphology; Myxozoan; Ultra-structure; Wetland; Brazil; Ultra-structure; Myxozoan; Histology; Wetland; Morphology
• ISSN: 0040-8166; 1532-3072
• DOI: 10.1016/j.tice.2022.101909

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.