Henneguya voronini, Borkhanuddin & Cech & Molnár & Shaharom-Harrison, 2020

Borkhanuddin, Muhammad Hafiz, Cech, Gábor, Molnár, Kálmán & Shaharom-Harrison, Faizah, 2020, Henneguya (Cnidaria: Myxosporea: Myxobolidae) infections of cultured barramundi, Lates calcarifer (Perciformes: Latidae) in an estuarine wetlands system of Malaysia: description of Henneguya setiuensis n. sp., Henneguya voronini n. sp. and Henneguya calcarifer n. sp., Parasitology Research (85) 119 (1), pp. 85-96 : 89-90

Henneguya voronini n. sp.

Type host: barramundi, Lates calcarifer (Bloch 1790) .

Site of infection: Base of the gill filament.

Type locality: Setiu Wetlands , Terengganu, Malaysia .

Prevalence of infection: 2.8% (1/35).

Type material: Digital images of syntype spores and histological sections were deposited in the parasitological collection of the Zoological Department, Hungarian Natural History Museum, Budapest, collection no. HNHM-71893. The 18S rDNA sequence was deposited in GenBank under accession number MH743110 .

Etymology: The species is named in honour of V. A. Voronin, an eminent Russian fish parasitologist.

Description of spores: Myxospores symmetric, with two equal caudal appendages and equal-sized polar capsules ( Fig. 2 ). Spore wall thin (0.3–0.4 μm), smooth and composed of 2 equal valves. Apical end of spore body blunt, the caudal end tapers and extends into the caudal appendages. Total length 35–39 μm, length of spore 9.9 ± 0.3 (9.5–10.3) μm and width 5.9 ± 0.3 (5.8–6.0) μm; thickness could not be measured as no spores were observed in sutural plane. Polar capsules pear shaped, blunt at the posterior end and tapered anteriorly, length 3.7 ± 0.2 (3.5–4.0) μm and width 2.1 ± 0.1 (2.0–2.2) μm. Polar tubules coiled in 6 turns perpendicular to the long axis of the polar capsules. Sporoplasm binucleate, with a small iodinophilous vacuole. Caudal appendages straight, tapering, length 27.2 ± 1.4 (25.0–29.0) μm, about 4 times as long as the spore body. Plasmodium ellipsoidal 250– 300 μm × 130–150 μm.

Remarks: Myxospores of H. voronini n. sp. could not be distinguished morphometrically using most measurements with the two other species observed in the host. Both H. voronini n. sp. and H. setiuensis n. sp. were found in the gills but the specific tissue locality differed: the large ellipsoidal plasmodia (up to 300 μm) of H. voronini n. sp. were localized to the cartilaginous base of the gill filaments, while the smaller spherical plasmodia of H. setiuensis n. sp. (up to 75 μm) developed between lamellae of the gill filaments. Considering Henneguya spp. from other Lates species, spores of H. voronini n. sp. could be differentiated in at least two dimensions (Table 2).

Molecular analysis: 1696 bp 18S rDNA were sequenced, including the primers. A BLAST search indicated that highest sequence similarities were to other Henneguya species in GenBank, but all <90%. Pairwise analysis showed H. voronini n. sp. was molecularly very similar to H. calcarifer n. sp. (97.7%; 1658/1969 bp; p -distance 0.013), described from the same fish (below).

Histology: Ellipsoidal plasmodia were located in the cartilaginous gill arch between gill filaments ( Fig. 4c ). We suspect that development began in the multilayered connective tissue covering the gill arch and then a large part of the plasmodium moved into the gill filaments and was covered by a multilayered epithelium as it matured.

Microscopy: SEM revealed that the valve cell surfaces were smooth, which is a morphological feature typical of genus Henneguya .

Figures

Fig. 2 Henneguya voronini n. sp. (a–b) Line drawings of mature myxospores in frontal view showing polar capsules with coiled polar tubules. (c) Fresh, unstained myxospores in frontal view showing the two pyriform polar capsules. (d) Scanning electron microscope image of the spores showing simple, smooth valve cell surfaces, each contiguous with a caudal process; features typical of the genus

Fig. 4 Histological sections of gill filaments from Lates calcarifer infected by plasmodia of H. setiuensis n. sp. and H. voronini n. sp. (a) Plasmodia of H. setiuensis n. sp. (arrows) producing compression and damage to the lamellae (*). (b) Development of plasmodia of H. voronini n. sp. (arrows) in the sub-epithelial layer at the base of the filament. Note that the plasmodia also impinge into the gill arch (g)