Sarcocystis muricoelognathis Qin & Ortega-Perez & Wibbelt & Lakim & Ginting & Khoprasert & Wells & Hu & Jäkel 2024, sp. nov.
Creators: name: Qin, Tao
name: Ortega-Perez, Paula
name: Wibbelt, Gudrun
name: Lakim, Maklarin B.
name: Ginting, Sulaiman
name: Khoprasert, Yuvaluk
name: Wells, Konstans
name: Hu, Junjie
name: Jäkel, Thomas
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Chromista
Miozoa
Eucoccidiida
Sarcocystidae
Sarcocystis
Sarcocystis muricoelognathis

description: Taxonomic summary of Sarcocystis muricoelognathis sp. nov.   
 (Sarcocystis sp.: Figs. 1, 2, 3, 4, 5, 6, Additional file 1: Table S1).    Diagnosis   
 Oocyst containing two sporocysts with four sporozoites each; sporocysts measuring on average 10.1–10.3 × 7.2– 7.5 µm; sarcocysts microscopic with striated cyst wall in fresh preparations (similar to S. singaporensis but cyst wall protrusions not resting on stalks), cigar-shaped with slightly pointed ends in older cysts; in skeletal musculature except heart; native sarcocysts in rats infected experimentally for 5 months measured 400–700 × 70–90 µm, in wild-caught rats 770–1580 × 87–123 μm; cyst wall with palisade-like, villar protrusions, 8 to 11 µm long and 2–4 µm wide at their base; protrusions at the tips of the sarcocyst often longer, 10–16 µm; banana-shaped, live cystozoites on average 5.9–6.5 µm long and 2.1–2.2 µm in diameter; ultrastructurally, villar protrusions palisade-like, attached upright to the cyst (if not bent by preparation), sometimes slightly broadened towards the apical ends, delimited by a knob-like lining and filled with fine, electron-light granular material; cystozoites with only two rhoptries throughout distribution range.    Type natural definitive hosts   
 Coelognathus radiatus (holotype), Coelognathus flavolineatus (paratype).    Type experimental intermediate host   
 Rattus norvegicus (holotype)    Type natural intermediate hosts   
 Maxomys whiteheadi (paratype); Rattus norvegicus (paratype)    Type localities   
Holotype: central Bangkok, Tailand; paratypes: Chumphon, southern Tailand; Poring Hot Springs, Northern Borneo, Sabah, Malaysia; Anning and Nanjian Prefectures, China.  
  Other locations and natural hosts not included in type series Sarcocysts with the same ultrastructure recorded from Rattus argentiventer and Bandicota indica in Tailand  [2] and reported from Rattus rattus in Singapore [15].    Etymology   
Species name in reference to the intermediate and definitive hosts.   Type specimens deposited   
 Holotype deposited at the Department of Parasitology, University of Hohenheim, Emil-Wolff-Str. 34, 70599 Stuttgart-Hohenheim, Germany, accession number DP/ R41C961764: Resin-embedded sarcocyst from Rattus norvegicus infected with sporocysts from Coelognathus radiatus; paratype from Borneo deposited at the Sabah Parks Museum, Kinabalu Park, Sabah, Malaysia, accession number SP/EAC/00102: sarcocyst in musculature from Maxomys whiteheadi; paratypes from China deposited at the Zoological Specimen Museum of Yunnan University, Kunming, accession number Prot202302: formalin-fixed tissue containing sarcocysts as well as photomicrographs.    Sequences deposited at GenBank   
 18S rRNA: OR976520, OR976521; 28S rRNA: isolates from China OR979639, OR979640, OR979641, OR979642, and Borneo OR979643; ITS1 - 5.8S- ITS2: OR977565, OR977566, OR977567, OR977568; cox1: PP033596.    ZooBank Registration   
 Tis article has been submitted to ZooBank under the Life Science Identifier (LSID) urn:lsid:zoobank. o r g: p u b: E 8 6 A 1 F E F - 6 1 8 9 - 4 E 2 8 - A 6 2 7 - 1 1 A B - FAA635AC. Te LSID for the new species name Sarcocystis muricoelognathis is urn:lsid:zoobank. org:act: 000AF647-D4AC-4609-914D-61C1449A2DAA.   Discussion  Taxonomic remarks  
 Since the ultrastructure of the sarcocyst wall is in many cases a useful criterion for distinguishing between species of Sarcocystis [40], we show here that S. muricoelognathis is clearly distinct from two similar species, S. zuoi and S. murinotechis. In the case of S. zuoi, its villar protrusions of the cyst wall are bent by a certain angle, which is also visible in live sarcocysts when the surrounding host tissue has been removed, and exhibit a reticulate base [11]. In contrast, S. muricoelognathis shows upright protrusions with a largely non-reticulate base. Compared to S. murinotechis from Australia [7], the two former species have markedly longer protrusions (roughly twice as long). Although only two electron micrographs of the sarcocysts of S. murinotechis exist in the original species description, the accompanying text characterizes them as possessing “short, broad protrusions” that were about 6 µm in length [7]. Relatively short protrusions are also visible in a histological section of a sarcocyst of S. cf. murinotechis from Rattus lutreolus [18] supporting the observations on S. murinotechis published by these authors 2 years later. All in all, we propose that the sarcocyst ultrastructure of S. muricoelognathis could be categorized under group 10a of the common cyst wall classification system for Sarcocystis [40]. Additionally, the sizes of the transmission stages, sporocysts and cystozoites, were significantly different among the three species discussed above. Notably, sporocysts of S. murinotechis exhibited a shape index different from S. muricoelognathis and S. zuoi: Size differences of sporocysts can be regarded a suitable indicator for the potential presence of different Sarcocystis species [41]. Regarding intraspecific variability, cystozoites of S. muricoelognathis were remarkably constant in size independent of geographic location and intermediate host and consistently showed two rhoptries at the ultrastructural level. Tese characteristics underscore the uniqueness of S. muricoelognathis compared to other species with striated cyst walls, which we have discussed previously [20]. At the light microscopic level, sarcocysts of S. muricoelognathis may be easily confused with S. singaporensis, because both species are microscopic, show a striated cyst wall with relatively long protrusions, exhibit pointed sarcocyst ends and share similar geographic distributions and rodent hosts. However, the cyst wall protrusions of the latter species rest on typical stalks, which appear as a thin, basal layer of the striated wall at lower magnification in live and histological preparations [2]. Molecularly, S. muricoelognathis can be unequivocally identified using its 28S rRNA and ITS1 sequences, whereby the partial 28S rRNA gene (≥ 600 bp) is already sufficient for differential diagnosis if the variable expansion segments D1 and D2 are included (as discussed below).   
 In a taxonomic context, we think we provided substantial molecular evidence for the proposition that the rRNA sequences from Tailand deposited under accession number KU341120 [19] do not belong to S. zuoi but represent S. muricoelognathis. Although a high degree of sequence identity between partial sequences alone may be insufficient for species discrimination, we must add here that the 28S rRNA gene sequence of S. muricoelognathis from Borneo included the variable expansion segments D1 and D2 of the rRNA molecule according to the predicted secondary structure of the reference sequence of T. gondii (L25635, [27]). Especially, domain D2 has been shown to be highly variable [42]. Moreover, the overlapping parts of the alignments of partial sequence KU341120 with the (almost) full-length 28S rRNA sequences of S. muricoelognathis from China included expansion segments D1–D6, which, in view of an identity score of 99%, strongly suggested that these sequences belong to the same species. Furthermore, both taxa clustered together in the ITS1 phylogenetic tree, which is increasingly used for discriminating between closely related Sarcocystis spp. (e.g. [43]) and shows much greater evolutionary rates than other rRNA markers [28]. Given that the sequences under KU341120 have been included in major rRNA databases under the species name ‘ Sarcocystis zuoi ’ and are frequently cited in the context of Sarcocystis of rodents (e.g. [44, 45]), it will probably take some time until any annotation in line with our proposal could be expected. Moreover, based on the observations here and a previous study [6], it can be safely assumed that the sequences KU341118/19/21 also do not represent S. zuoi but belong to a different species, because they clustered in a clade apart from the original S. zuoi sequences.
description: Published as part of Qin, Tao, Ortega-Perez, Paula, Wibbelt, Gudrun, Lakim, Maklarin B., Ginting, Sulaiman, Khoprasert, Yuvaluk, Wells, Konstans, Hu, Junjie & Jäkel, Thomas, 2024, A cyst-forming coccidian with large geographical range infecting forest and commensal rodents: Sarcocystis muricoelognathis sp. nov., pp. 1-19 in Parasites & Vectors (135) (135) 17 (1) on pages 13-14, DOI: 10.1186/s13071-024-06230-8, http://zenodo.org/record/11552183