Dactylosoma sp.

Netherlands, Edward C., Cook, Courtney A., Du Preez, Louis H., Vanhove, Maarten P. M., Brendonck, Luc & Smit, Nico J., 2020, An overview of the Dactylosomatidae (Apicomplexa: Adeleorina: Dactylosomatidae), with the description of Dactylosoma kermiti n. sp. parasitising Ptychadena anchietae and Sclerophrys gutturalis from South Africa, International Journal for Parasitology: Parasites and Wildlife 11, pp. 246-260 : 253-254

3.1.2. Dactylosoma sp. from Belgium

Host: Pelophylax lessonae (Camerano, 1882) ( Anura : Ranidae ).

Site in host: Peripheral blood.

Vector: Unknown.

Localities: Haacht , Belgium (N50.979434 ̊, E4.659686 ̊) .

Voucher material – 1 × blood smear with a parasitaemia of 0.3% from Pel. kl. esculentus deposited in the protozoan collection of the National Museum, Bloemfontein, South Africa, under accession number [ NMB P 538].

Representative DNA sequences: The sequence data specifically associated with Dactylosoma sp. ex Pel. lessonae have been submitted to GenBank and are as follows: Nuclear 18S rDNA (nu 18S) partial sequence: MN 879399.

3.1.2.1. Description. Two distinct stages of merogony present in erythrocytes of Pel. lessonae ( Fig. 3 A–L ). The first stage characterised by large dactylate meronts producing up to approximately 14 clear merozoites. The second stage meronts seemingly smaller, although no clear merozoites were observed. The cytoplasm has a hyaline appearance. Parasitaemia of infected individual (n = 1) was 0.3%.

Primary merogony: trophozoites ( Fig. 3 A ) elongated to oval, usually tapering towards one end, vacuoles in some cases present ( Fig. 3 A arrow). Small round dense nuclei located at blunt end ( Fig. 3 A arrowhead), chromatin staining deep magenta. Trophozoites measure 6.3 ± 0.9 (5.3–7.4) long × 3.8 ± 0.8 (2.6–4.9) wide (n = 10).

Young primary meronts ( Fig. 3 B ) round to ovoid causing slight displacement of the host cell nucleus. Multinucleate, nuclear division located peripherally, chromatin staining bright pink to dark purple ( Fig. 3 B arrowhead). Young meronts measure 9.4 ± 1.1 (8.0–10.9) long × 8.0 ± 0.5 (7.0–8.6) wide (n = 7).

Primary meronts ( Fig. 3 C–G ) vary in form, round to pear shape, in some cases causing slight distortion or displacement of the host cell or nucleus, cytoplasm staining whitish-purple. Mature forms have dactylate appearance ( Fig. 3 F–G ). Multinucleate, normally showing more than 10 nuclei ( Fig. 3 C-E arrowhead), staining deep magenta. Meronts measure 11.3 ± 2.8 (8.4–16.5) long × 9.1 ± 1.9 (7.1–12.6) wide (n = 10).

Primary merozoites ( Fig. 3 F–H ) elongate to ovoid, hyaline cytoplasm staining white to bluish-purple. Dense nuclei chromatin centrally located, staining deep magenta ( Fig. 3 F–H , arrowhead). Merozoites ( Fig. 3 F–H , arrow) measure 4.0 ± 0.6 (3.1–5.0) long × 1.9 ± 0.6 (1.1–3.1) wide (n = 20).

Secondary merogony: young secondary meront ( Fig. 3 I ) irregular ovoid shape, cytoplasm staining bluish-purple, occasionally causing displacement of the host cell nucleus. Multinucleate, nuclei located peripherally, staining deep magenta ( Fig. 3 I , arrowhead). Young meronts measure 6.2 ± 1.1 (4.5–7.5) long × 4.5 ± 1.5 (2.7–7.3) wide (n = 7).

Secondary meronts ( Fig. 3 J ) ovoid shape, cytoplasm stains dark bluish-purple. Multinucleate, up to 6 nuclei located peripherally, chromatin staining dark purple ( Fig. 3 J , arrowhead). Secondary meronts measure 7.7 ± 0.9 (5.9–8.9) long × 6.6 ± 1.1 (5.8–8.5) wide (n = 10).

Secondary merozoites ( Fig. 3 K ) rare, short crescent shape, hyaline cytoplasm staining purple. Small round dense nuclei located peripherally, staining deep magenta ( Fig. 3 K arrowhead). Secondary merozoites measure 4.1 long × 2.3 wide (n = 1).

Gamonts ( Fig. 3 L ) elongate and slender shape, hyaline appearance, nuclei chromatin visible slightly off centre ( Fig. 3 L arrowhead). Extracellular forms often elongate with slight curvature, nucleoplasm visible slightly off centre, staining dark purplish-pink. Gamonts measure 9.8 ± 1.8 (7.9–12.1) long × 2.3 ± 0.1 (2.2–2.5) wide (n = 5).

3.1.2.2. Remarks. The species of Dactylosoma under study possesses several phenotypic characteristics mentioned in the original description of Dactylosoma splendens , later synonymised with D. ranarum , such as the round shape of the meronts and the number of primary and secondary merozoites produced (ranging approximately between 12 and five). However, this synonymisation happened over 100 years ago when knowledge of the close resemblance between different species was unknown. Unfortunately, no precise measurement data are available from the original description of D. splendens , which was described from Pel. kl. esculentus in Paris, France ( Labbé, 1894). However, based on the information of this species of Dactylosoma provided above, the parasite cannot, based on the data collected in the current study, be identified to species level.

Furthermore, this species of Dactylosoma can be characterised by its round young meront stages, the dactylate appearance of the mature meront stages, and the hyaline appearance of the cytoplasm. Although the trophozoite and gamont stages of Dactylosoma kermiti n. sp. are superficially similar in morphology and morphometrics, primary and secondary meront stages are wider (primary meront: 5.1–8.0 vs 7.1–12.6; secondary meront: 4.4–6.9 vs 5.8–8.5) and secondary merozoites stages slightly shorter (4.2–5.5 vs 4.1) in the species of Dactylosoma from Pel. lessonae . This species also conforms closely to D. sylvatica , however, the species from the current study produces more than eight merozoites in primary merogony and less than eight in secondary merogony as compared to D. sylvatica . Also the secondary meront stages are wider as compared to D. sylvatica (secondary meront: 5.9–8.9 × 5.8–8.5 vs 5.2–4.0).

Figures

Fig. 3. (A–L). Dactylosoma sp. from Pelophylax lessonae. (A–D) Primary merogony. (A) Trophozoite. (B) Young meront. (C–G) Secondary meronts. (F–H) Merozoites, arrows. (I–L) Secondary merogony. (I) Young meront. (J) Meront. (K) Merozoite. (L) Gamont. Arrowheads show condensed chromatin; arrows show vacuoles (A) and merozoites (F–H). All images captured from the deposited slide [NMB P 538]. Scale bar 10 μm.