Cystodiscus elachistocleis, Vieira & Úngari & Alcantara & Emmerich & Santos & Silva, 2021

Vieira, Diego Henrique Mirandola Dias, Úngari, Letícia Pereira, Alcantara, Edna Paulino De, Emmerich, Enzo, Santos, André Luiz Quagliatto, O'Dwyer, Lucia Helena & Silva, Reinaldo José Da, 2021, Description of Cystodiscus elachistocleis sp. nov. (Cnidaria: Myxosporea) parasitizing the gallbladder of Elachistocleis cesarii from Brazil, based on morphological and molecular analyses, European Journal of Taxonomy 775, pp. 107-118 : 110-113

Cystodiscus elachistocleis sp. nov.

urn:lsid:zoobank.org:act:E2AE8907-E225-4804-A2F9-E3920AD6298D

Figs 1–3

Type host

Elachistocleis cesarii (Miranda-Ribeiro, 1920).

Site of infection

Gallbladder.

Etymology

The species epithet is derived from the genus Elachistocleis of the host.

Material examined

Hapantotypes BRAZIL • 10+ myxospores; Mato Grosso State, Araguaiana municipality; 14°35′5.29″ S, 51°41′19.15″ W; glycerogelatin slide; GenBank MZ645740 - MZ645741 ; INPA79 .

Description

Numerous pseudoplasmodia were found free in the bile. Pseudoplasmodia ( Fig. 1C ) of approximately 2 mm were rounded in shape, appeared to be formed by a ʻgelatinousʼ substance, and were floating in the host’s bile containing several myxospores in its interior. The morphology of myxospores found in the gallbaldder of E. cesarii corresponded to the genus Cystodiscus . The myxospores ( Figs 1A–B , 2 ) were ellipsoid to ovoid. The two myxospore valves were joined by a raised ridge that appeared straight or slightly curved (S-shaped in sutural view) along the medial axis of the myxospore. Transverse depressions on the surface of the myxospores appeared connected to the sutural ridge depression. Their measurements presented as mean ± SD (range) were: myxospore length 10.6 ± 0.3 (9.8–11.2) μm, myxospore width 6.2 ± 0.5 (5.6–6.6) μm. The polar capsules were pyriform and equal in size, situated each one in a myxospore extremity and measured 3.6 ± 0.4 (2.8–4.3) μm in length and 2.6 ± 0.3 (2.2– 3.1) μm in width. The polar filament present within the polar capsule had 2–4 coils. The myxospores showed 3–5 transverse ridges and a binucleated sporoplasm. Filiform polar appendages were not observed.

Remarks

Cystodiscus elachistocleis sp. nov. was morphometrically compared to all Cystodiscus spp. described worldwide ( Table 2 ). The species that most resembled C. elachistocleis sp. nov. was C. haldari (Sarkar, 1982) , which showed similarity in all measurements available for comparison. However, the geographical distance ( Brazil vs India) and the different type host (E. cesarii vs Hyla arborea (Linnaeus, 1758)) allow us to separate the two species. Furthermore, C. haldari does not present any comparative values such as the number of turns of the polar filament and the number of transverse ridges, which could differentiate the two species. Cystodiscus thyponius Gray (1993) also presented measures of length and width of myxospores similar to those found in C. elachistocleis sp. nov. However, differences were observed in the polar capsule width (2.6 ± 0.3 (2.2–3.1) vs 3.6 (3.3–5.2)) and the number of transverse ridges (3–5 vs 9–11).

Regarding the Cystodiscus spp. described from Brazil, C. elachistocleis sp. nov. was morphometrically compared with two species parasitizing the gallbladder of Rhinella marina (Linnaeus, 1758) . Cystodiscus immersus, Kudo & Sprague (1940) presented a longer body length than that found in C. elachistocleis sp. nov. (11.8–13.3 vs 10.6 ± 0.3 (9.8–11.2)), in addition to a greater number of transverse ridges (7–9 vs 3–5). Cystodiscus lyndoyense Carini, 1932 showed the length of the body (11.0–12.0 vs 10.6 ± 0.3 (9.8– 11.2)) and the body width (7.5–8.0 vs 6.2 ± 0.5 (5.6–6.6)) longer than that found for C. elachistocleis sp. nov. The other Cystodiscus spp. already described presented a body length longer than that observed in C. elachistocleis sp. nov.

Molecular analyses

Fragments of 1730-bp and 1916-bp of the SSU rDNA gene were generated. The fragments showed 100% similarity when aligned. The BLAST search of the sequences did not reveal a direct match with myxozoan sequences available in GenBank. The genetically closest species was C. immersus , which exhibited a similarity of 97.3%, and a difference of 24 out of 885 nucleotides ( Table 3 ).

A well-supported phylogenetic tree divided into three main groups was obtained ( Fig. 3 ).A monophyletic group composed of Sphaeromyxa Thélohan, 1892 spp. that parasitizes fish, a polyphyletic group composed of Zschokkella Auerbach, 1909 and Myxidium Bütschli, 1882 spp. that infect fish, and finally a monophyletic group composed of Cystodiscus spp. that parasitize amphibians. Still, there is a small monophyletic group composed of Myxidium ssp. found in reptiles, fish, and birds. Cystodiscus elachistocleis sp. nov. appears as a sister species of Cystodiscus cf. immersus 1, in a subclade formed by species that parasitize the amphibians gallbladder.

Figures

Fig. 1. Myxospores and pseudoplasmodia of Cystodiscus elachistocleis sp. nov. (INPA79) found parasitizing the gallbladder of Elachistocleis cesarii (Miranda-Ribeiro, 1920) from Araguaiana, Mato Grosso State, Brazil. A. Front view ofC. elachistocleis sp. nov.B. Front and side view ofC. elachistocleis sp. nov.C. Pseudoplasmodium (P) containing several myxospores of C. elachistocleis sp. nov. highlights myxospores (M) through the pseudoplasmodium-forming tissue.

Fig. 2. Schematic drawing of Cystodiscus elachistocleis sp. nov. (INPA79) found parasitizing the gallbladder of Elachistocleis cesarii (Miranda-Ribeiro, 1920) in front and side view.

Fig. 3. Phylogenetic tree of Bayesian analysis based on partial SSU rDNA partial sequences showing the position of Cystodiscus elachistocleis sp. nov. (INPA79) among genetically similar species. Node numbers represent the Bayesian posterior probabilities and bootstrap (BI/ML). Values less than 0.7 are represented by dashes. The scale bar represents the number of substitutions per site.