Parvicapsula irregularis, Kodádková & Dyková & Tyml & Ditrich & Fiala, 2014

Kodádková, Alena, Dyková, Iva, Tyml, Tomáš, Ditrich, Oleg & Fiala, Ivan, 2014, Myxozoa in high Arctic: Survey on the central part of Svalbard archipelago, International Journal for Parasitology: Parasites and Wildlife 3 (1), pp. 41-56 : 47-48

Parvicapsula irregularis comb. nov. ( Kabata, 1962) ( Fig. 1C ).

Synonyms: Sphaerospora irregularis Kabata, 1962 ; Myxoproteus irregularis ( Kabata, 1962) ; Ortholinea irregularis ( Kabata, 1962) .

Type host: H. platessoides (Fabricius, 1780) , American plaice (syn. Drepanopsetta platessoides Fabricius, 1780 ); average standard length 10.6 cm.

Other hosts: unknown.

Type locality: Northern North Sea .

Other localities: Greenland Sea, part of the Billefjorden, Isfjorden, Petunia Bay in the central part of Svalbard archipelago (78° 69 Ɩ N, 16° 53 Ɩ E).

Description of sporogonic stages: disporic plasmodia of various shapes i.e. round, oval or irregular with protrusions; pseudopodia with rounded ends; for dimensions see Table 1.

Description of myxospores: spore shape roughly pyriform with considerable degree of irregularity, widest diameter of spore about middle of the long axis, narrowing somewhat towards the poles, particularly towards the anterior pole; slightly flattened in the sutural plane; spherical PCs close together located anteriorly; single sporoplasm occupying more than three quarters of the spore, sporoplasm with two nuclei; for dimensions see Table 1.

Localization of sporogonic stages: coelozoic, renal tubules, urinary bladder.

Prevalence: 44% (4 of 9 urinary bladders; 2 samples co-infected with Schulmania aenigmatosa ).

Pathology: no material available for evaluation the species pathogenicity.

Materials deposited: DNA sample (nr. 1376) stored in – 80 °C in the Laboratory of Fish Protistology, Institute of Parasitology, BC ASCR; SSU (GenBank accession No. KF874229) and LSU (GenBank accession No. KF874226) rDNA sequences.

Remarks: Kabata (1962) described Sphaerospora irregularis from American plaice in northern North Sea. This species was later assigned to other genera: Myxoproteus ( Gaevskaya and Kovaleva, 1984) , and Ortholinea ( Arthur and Lom, 1985) . After re-examination, KØie et al. (2007b) suggested S. irregularis may belong to Parvicapsula . Despite S. irregularis was reported from another host, Pleuronectes platessa ( MacKenzie et al., 1976) , this report most probably corresponds to Parvicapsula bicornis later described from this host ( KØie et al., 2007b). Unfortunately, the report of ‘‘ S. irregularis ’’ by MacKenzie et al. (1976) lacked sufficient morphological documentation and comparison with similar species. Therefore, P. bicornis from P. platessa was regarded as syn. part. of S. irregularis ( KØie et al., 2007b). Since this species is now re-examined and molecularly characterised we claim that P. bicornis and the re-described P. irregularis are two morphological and molecularly different species. S. testicularis as the closest relative of P. irregularis has a wider and thicker spore.

3.2.2. Description of new taxa

Zschokkella siegfriedi n. sp. ( Fig. 1I–K , Figs. 4–6 ).

Family Myxidiidae Thélohan, 1892 .

Genus Zschokkella Auerbach, 1910 .

Type host: B. saida (Lepechin, 1774) , Polar cod (officially accepted common name; commonly used name Arctic cod for B. saida is valid for Arctogadus glacialis (Peters, 1872) ( Froese and Pauly, 2013) ; average standard length 14.4 cm.

Other host: unknown.

Type locality: Greenland Sea , part of the Billefjorden , Isfjorden, Petunia Bay in the central part of Svalbard archipelago (78° 69 Ɩ N, 16° 53 Ɩ E) .

Other localities: none.

Description of sporogonic stages: plasmodia mostly di-, rarely polysporic; round to oval in shape; clear differentiation between smooth ectoplasm and granular endoplasm; for dimensions see Table 1.

Description of myxospores: shape of spores considerably variable, from spores with one side vaulted appearing almost rounded triangular to spores of ellipsoidal shape; suture line irregularly oblique, two shell valves completely asymmetrical; subspherical to spherical PCs located in the spore ends and discharging to opposite sides parallel with axis of the spore from the apical view, 7 coils of polar filament; for dimensions see Table 1.

Localization of sporogonic stages: coelozoic, renal tubules.

Prevalence: 43% (6 of 14 kidney samples).

Pathology: regressive changes of importance developed in the epithelial cells of infected renal tubules manifested as pronounced changes of staining properties of individual cells in semithin sections; mitochondria with various degrees of mitochondrial electron-density suggestive of necrotic changes revealed in ultrathin sections ( Fig. 5 , Fig. 6 ).

Materials deposited: DNA sample (nr. 1608) stored in – 80 °C and blocks in resin nrs. 541a and 543a in the Institute of Parasitology, Laboratory of Fish Protistology, BC ASCR; SSU rDNA sequence (GenBank accession No. KF874231).

Etymology: The species name of Z. hildae , type species of the genus Zschokkella , refers to Hilda (a shorten version of the German name) used by author Auerbach (1910) in honour of his wife. We name Z. siegfriedi n. sp. according to the German heroic poem ‘‘The Song of Nibelungs’’ with the lovers Siegfried and Kriemhilda (Hilda) reflecting the close phylogenetic relationship between Z. hildae and our new species.

Remarks: We found Zschokkella siegfriedi from the kidney of polar cod to be genetically distinct (2.8% of dissimilarity) (Supplementary Table 1) from Z. hildae SSU rDNA sequence from G. morhua . Zschokkella hildae , the type species of the genus Zschokkella , typically infects fish from the family Gadidae and was previously reported from B. saida without providing any molecular data ( Aseeva, 2002; KØie, 2009). In the light of the new data, we suggest B. saida was most likely either infected with Z. siegfriedi in the report of Aseeva (2002) or this host is susceptible for both Z. hildae and Z. siegfriedi species. The spores of Z. hildae possess some degree of pleiomorphy during maturation; morphologically, Z. hildae and Z. siegfriedi are indistinguishable. However, Z. hildae was found to infect the host’s urinary bladder and collecting duct of the kidney, unlike Z. siegfriedi which develops in the upper excretory system and the renal tubules. Nevertheless, we expect Z. siegfriedi to infect also urinary bladder as reported for Z. hildae since we were not able to cheque the urinary bladder of B. saida . We determined that Z. siegfriedi is a distinct species based on biology and genetics; biologically, Z. siegfriedi has (i) significant genetic difference based on SSU rDNA; (ii) localization of sporogonic stages in renal tubules vs collecting duct; (iii) different but very closely related host species to that of Z. hildae .

Figures

Fig. 1. Mature spores and plasmodia. (A-N) Myxospores and myxosporean plasmodial stages as seen in Nomarski differential interference contrast. Measurements are listed in Table 1. (A) Mature spore of Ceratomyxa porrecta. (B) Spores of Schulmania aenigmatosa with focus on polar capsules (left) and sinuous valve suture (right). (C) Plasmodial stages (left) and mature spore of Parvicapsula irregularis (right). (D) Mature spores of Parvicapsula petuniae. (E) Mature spore of Myxidium gadi. (F) Mature spore of Myxidium finnmarchicum. (G, H) Spores of Sinuolinea arctica in frontal (G) and sutural (H) view. (I, J) Plasmodial stages of Zschokkella siegfriedi. (K) Mature spores of Zschokkella siegfriedi. (L) Plasmodial stage of Latyspora-like organism. (M, N) Latyspora-like organism spores with focus on polar capsules and part of valve suture, respectively.

Fig. 4. Line drawing of Zschokkella siegfriedi, sutural view. Scale bar = 10 µm.

Fig. 5. Histology of Zschokkella siegfriedi infection. (A–C) Zschokkella siegfriedi infection in renal tubules of Boreogadus saida as seen in semithin sections stained with toluidine blue. (A) Infected segment of renal tubule with plasmodial stages in its lumen and densely stained cells in its epithelial lining. (B) Advanced plasmodial stages and amorphous material completely filling the lumen of renal tubule. All epithelial cells are densely stained. (C) Almost mature spores localised in the lumen of renal tubule. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 6. Ultrastructure of Zschokkella siegfriedi infection. (A–C) Details of ultrastructure of Zschokkella siegfriedi as seen in transmission electron microscope. (A) Early developmental stage (EDS) localised within epithelium of renal tubule. Epithelial cells (EC) differ substantially in electron-density due to differences in density of mitochondria. Arrows mark basal membrane of renal tubule, NEC nucleus of epithelial cells, M mitochondria. (B) Almost mature spore in longitudinal section. VC valvogenic cell, NVC nucleus of VC, CC capsulogenic cells, NCC nucleus of CC, S sporoplasm, NS nucleus of S, PPF primordium of polar filament, M mitochondria. C. Valves (V), the polar capsule wall (PCW), and some sections of the polar filament coils.