Myxobolus adrianoi, Mathews & Madrid & Mertins & Rigoni & Morandini, 2020

Mathews, Patrick D., Madrid, Rafael R. M., Mertins, Omar, Rigoni, Vera L. S. & Morandini, André C., 2020, A new Myxobolus (Cnidaria: Myxosporea) infecting the ornamental catfish Corydoras schwartzi from the Purus River in Brazil, European Journal of Taxonomy 620, pp. 1-14 : 4-6

Myxobolus adrianoi sp. nov.

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Figs 1–4

Etymology

The specific name, adrianoi , is in homage to Dr. Edson Adriano, Professor at Federal University of São Paulo, Brazil, who has been contributing to improving our knowledge on the diversity of South American Myxosporea.

Material examined

Syntypes

BRAZIL • 10+ myxospores; Amazonas State, Lábrea Municipality; 7°15′32″ S, 64°47′52″ W; air-dried slide stained with Giemsa; MZUSP 8469 .

Type host

Corydoras schwartzi Rössel, 1963 ( Siluriformes : Callichthyidae ).

Site of infection

Serosa layer of intestine.

Prevalence

From 30 examined fish, five were infected (16.6%).

Description

Mature myxospores ovoid in body shape in frontal view, showing two aubergine-shaped, elongate symmetrical polar capsules occupying more than half length of spore. Total myxospore length 22.4 ± 0.3 μm and width 16.3 ± 0.1 μm. Two polar capsules, 14.3 ± 0.2 μm in length and 6.5 ±0.1 μm in width ( Figs 2 A–D, 3).

Ultrastructural analysis showed myxospores in various stages of development. In young developmental myxospore stage, the polar filament could still be observed out of the polar capsules and valvogenic cells were readily recognized by valve-forming materials ( Fig. 4A ). In myxospores at a more advanced developmental stage, a polar filament inside the polar capsule and binucleated sporoplasms containing a moderate number of sporoplasmosomes were observed ( Fig. 4 B–C). Transverse sections of a polar capsule provided evidence of a polar filament with five coils ( Fig. 4 B–C). Sections of immature myxospores show the valvogenic cells abutting each other to form a sutural ridge, and frequently the two cells were separated by a thin layer of homogenous material ( Fig. 4D ). Almost mature myxospores showed sutural lines, valve-forming material, valves, two nuclei and sporoplasmosomes at sporoplasms ( Fig. 4 E–F). The outer surface of the myxospore valves was smooth, with no evidence of formation of ridges in the valves ( Fig. 4 E–F).

Figures

Fig. 1. Corydoras schwartzi Rössel, 1963 infected by Myxobolus adrianoi sp. nov. A. Sampled fish captured in the Purus River near Lábrea Municipality, Amazonas State, Brazil. B. Histological sections of the fish intestine showing large cyst in the serosa layer (black arrow).

Fig. 2. Light photomicrograph of mature myxospores of Myxobolus adrianoi sp. nov., parasite of the intestine of Corydoras schwartzi Rössel, 1963. A. Wet-mount mature myxospores (white arrows). B–C. Frontal view of mature myxospores stained in May-Grünwald-Giemsa, showing two equal polar aubergine-like capsules, occupying more than half the length of the myxospore. D. Mature myxospore stained, in frontal view, with the polar filament extruded (black arrow).

Fig. 3. Schematic representation of the mature myxospore Myxobolus adrianoi sp. nov., parasite of intestine of the Corydoras schwartzi Rössel, 1963. Scale bar: 10 μm.

Fig. 4 (next page). Electron micrographs of myxospores of Myxobolus adrianoi sp. nov., parasite of the intestine of Corydoras schwartzi Rössel, 1963. A. Young sporoblast showing polar filament still out of the polar capsules, abundant valve-forming material, conspicuous sutural line (large white arrow), some sporoplasmosomes (small white arrows), mitochondria and presence of pinocytic channels (white arrowheads) in the ectoplasm. B–C. Sporoblast in advanced developmental stage with polar filament (white arrows) inside the polar capsule. In B note several sporoplasmosomes (white arrows) and two nuclei at sporoplasms. In Cobserve presence of valve-formingmaterial (short white arrows),capsulogenic cell, nuclei at sporoplasm and nucleus of capsulogenic cell. D. Immature myxospore showing valvogenic cells abutting each other to form a sutural ridge and showing the two cells are separated by a thin layer of homogenous material (white arrow). E–F. Almost mature myxospores showing sutural lines (black arrows), valve-forming material (*), valves, two nuclei and sporoplasmosomes (white arrows) at sporoplasms. Abbreviations: cp = capsulogenic cell; ec = ectoplasm; mt = mitochondrion; nc = nucleus of capsulogenic cell; Nu = nucleus; pc = polar capsule; PF = polar filament; sp = sporoplasm; v = valvogenic cell/valve; vm = valve-forming material. Scale bars: 2 μm.