Henneguya Thelohan , 1892

Mathews, Patrick D., Mertins, Omar, Espinoza, Luis L., Aguiar, Julio C. & Milanin, Tiago, 2023, First report of a histozoic Henneguya (Cnidaria, Endocnidozoa) infecting a synbranchid potamodromous fish from South America: Morphostructural and biological data, Zoosystematics and Evolution 99 (2), pp. 391-397 : 391

Genus Henneguya Thelohan, 1892

Species.

Henneguya sp. (We suggest that this isolate, after determination by molecular phylogenetic data, be named as ( H. atingae ) based on host species common name in Peru.

Type host.

Symbranchus marmoratus ( Teleostei: Synbranchidae ).

Site of infection.

Stratus corneum of epidermis layer of the skin.

Type locality.

Small stream, adjacent area of Oran Village, Loreto Department, Peru (3°21'0"S, 72°31'0"W).

Description.

Morphological observations by light microscopic showed mature myxospores have ovoid shape from the valvular view, measuring 32.2 ± 0.6 μm (31.6-32.8) in total length, 21.5 ± 0.3 μm (21.2-21.8) in spore body length, 11.7 ± 0.5 μm (11.2-12.2) in width and 10.6 ± 0.9 μm (9.7-11.5) in thickness (Fig. 1a, c ). Non-bifurcate caudal appendage, measuring 10.7 ± 0.4 μm (10.3-11.1) in length (Fig. 1a, c ). Two polar capsules elongated aubergine in shape, equal in size and measuring 4.9 ± 0.2 μm (4.7-5.1) in length and 3.1 ± 0.5 μm (2.6-3.6) in width (Fig. 1b, c ). Sporoplasm evidenced two nuclei in valvular view and sutural line was noticeable in side view (Fig. 1b, c ).

Surface topography analyses of mature myxospores in valvular view revealed smooth valve cell with presence of mucous in a small area (Fig. 2a ). In sutural view myxospore evidence a conspicuous sutural line (Fig. 2c ). The density of caudal appendage is likely be identical to that of its valve (Fig. 2b ). Internal ultrastructural observations showed binucleated sporoplasm contained several sporoplasmosomes and valve-forming materials in young sporoblast developmental myxospore stage (Fig. 3a ). Polar capsule with polar tubule internalized and contained seven to eight coils at a more advanced sporoblast developmental stage (Fig. 3b ). Caudal appendage and conspicuous sutural line in mature spores. (Fig. 3c ).

Histologic evidenced tissue tropism of the myxosporean under study, occurring in the stratus corneum of epidermis layer of the skin (Figure 4 ). The parasites induced no apparent tissue destruction, ulcerations, necrosis or inflammatory response. For molecular procedures, partial 18S rDNA gene was successfully amplified by PCR (Fig. 5 ), however, sequencing failed.

Figures

Figure 1. Henneguya sp. parasite from the skin of Synbranchus marmoratus. a: formalin-fixed myxospores in valvular view showing appendage caudal (large arrows) and two polar capsules in the anterior pole of spore occupied only the anterior third of the myxospore body (small blue arrows). b: mature myxospores stained with Giemsa with noticeable binucleate sporoplasm (double arrow) and polar capsules with aubergine shape (large arrow). c: schematic illustration of mature myxospore with polar tubule inside of polar capsule. Scale bars: 5 µm.

Figure 2. Surface topography by SEM of Henneguya sp. infecting skin of Synbranchus marmoratus. a: mature myxospore in valvular view showing smooth valve cell with presence of mucous (white star) in a small area and caudal appendage. Scale bar. 1 µm. b: amplified area of the caudal appendage evidencing density of caudal appendage likely to be identical to that of its valve. Scale bar. 200 nm c: myxospore evidence a conspicuous sutural line in sutural view. Scale bar: 100 nm.

Figure 3. Internal ultrastructure by TEM of myxospore of Henneguya sp. infecting skin of Synbranchus marmoratus. a: sporoblast in young developmental stage showing binucleated sporoplasm (n) contained several sporoplasmosomes (asterisk), valve-forming materials (white arrow) and polar capsules (pc) with absence of polar tubule. b: polar capsule (pc) with capsular nuclei, polar tubule internalized contained seven to eight coils (pt), sporoplasm binucleated (spl / n) and contained sporoplasmosomes (asterisk) at a more advanced sporoblast developmental stage. c: Spores with sutural lines (small arrows), sporoplasm with numerous sporoplasmosomes (asterisk) and caudal appendage (large arrow). Scale bars: 2 µm.

Figure 4. Histological sections of the host-tissue infected of Synbranchus marmoratus with Henneguya sp. a: Intact plasmodium located in the stratus corneum of epidermis layer of the skin. Scale bar. 50 µm. b: mature myxospore in sutural view with noticeable caudal appendage. Scale bar. 10 µm.

Figure 5. Agarose gel showing 18 S rDNA gene PCR amplification of Henneguya sp. from skin infected of S. marmoratus. Lane 1: DNA ladder marker, Lane 2: amplicon 1000 pb approx. (ERIB 1 / ACT 1 r), Lane 3: amplicon 1100 pb approx. (Myxgen 4 F / ERIB 10), Lane 4: Negative Control.