Morphological and molecular characterization of a new ciliate Nyctotheroides grimi n. sp. (Armophorea, Clevelandellida) from Chinese frogs
Graphical abstract
Introduction
The nyctotherids are a large group of clevelandellid ciliates (Armophorea: Clevelandellida), mainly inhabiting the digestive track of both invertebrates and vertebrates, including oligochaetes, insects (cockroach), myriapods (centipede, millipede), molluscs (shipworm), fishes, amphibians (frogs and toads) and reptiles (Albaret 1975; Jankowski 2007; Lynn 2008). They have been discovered thus far in marine, freshwater and terrestrial habitats as endocommensals of the fore-mentioned hosts.
The nyctotherids are classified into 15 genera within the family Nyctotheridae (Lynn 2008), being Nyctotheroides and Nyctotherus the most important ones. Nyctotheroides is restricted to amphibian hosts and Nyctotherus to invertebrates and non-amphibian vertebrates, such as reptiles (Albaret 1975; Lynn and Wright 2013). It is generally accepted that these genera can be distinguished by the apical kinetal suture systems (“système secant”): there are kinetal sutures on the right and left apical sides in Nyctotheroides, while Nyctotherus has a kinetal suture only on the right apical side (Albaret 1975; Affa'a et al. 2004). There are other suture systems in Nyctotheroides, but they are not present in all species and Affa'a (1980, 1988) proposed to subdivide the species of this genus into four lineages (cordiformis, judesi, anomalus and bisecatus).
There are more than 70 species described in Nyctotheroides (Albaret 1975; Edwards et al. 1982; Kalavati et al. 1991; Fokam et al. 2013) but to date, genetic data have been obtained from only five of them (van Hoek et al. 1998; Affa'a et al. 2004; Li et al. 2016, 2017). In the present study, we attempt to contribute to the knowledge of the genus Nyctotheroides by describing a new species discovered from the rectum of the frog Fejervarya limnocharis (=Rana limnocharis), based on both detailed morphological information and molecular data.
Section snippets
Host collection and ethical statement
The frogs (F. limnocharis) were captured from Diaocha Lake (30°24′-30°48′N; 113°42′-113°58′E), Hubei Province, China in May to August 2015. All the experimental procedures and animal care were performed according to the protocols approved by the Institutional Animal Care and Use Committee of the Institute of Hydrobiology, Chinese Academy of Sciences (PAOIHB12519, 5/2012). The frogs were transported alive to the laboratory for further examination. All frogs were euthanized with MS-222 and
Results
Based on our survey, 74 (22.8%) of 325 examined F. limnocharis were found to be infected with a new ciliate species described now. About 150 trophozoites/ml were found in average in the recta of examined frogs.
Species name: Nyctotheroides grimi n. sp.
Type Host: Fejervarya limnocharis Gravenhorst, 1829
Type Locality: Diaocha Lake (30°24′-30°48′N; 113°42′-113°58′E), Hubei Province, China.
Infection site: Rectum.
Type material: Protargol stained specimens have been deposited in the Key Laboratory of
Discussion
The occurrence of a new Nyctotheroides species inhabiting Chinese anuran amphibians is recorded herein, with its morphological and genetic data presented in detail. Nyctotheroides grimi is quite unique considering its noteworthy knob-like projection at left-posterior end, which can distinguish it from almost all other Nyctotheroides species. Nictotheroides pyriformis could also present a knob-like projection at the posterior end in some cells, but much less significant than that of N. grimi;
Conclusions
A new species of clevelandellid ciliate, Nyctotheroides grimi, is described from the rectum of the frog Fejervarya limnocharis. It has clear morphological differences with related species, but the genetic similarity in the SSU rDNA and the ITS region indicates a recent phylogenetic divergence. There are no differential genetic features (such as indels, sequence motifs, or extra helices in the secondary structure) in the SSU rDNA or in the ITS region that could be useful for genus barcoding in
CRediT authorship contribution statement
Ming Li: Conceptualization, Investigation, Methodology, Data curation, Formal analysis, Validation, Writing - original draft, Writing - review & editing. Guangran Hu: Investigation, Methodology. Can Li: Investigation, Methodology. Wei-shan Zhao: Investigation, Methodology. Hong Zou: Formal analysis, Validation. Wen-xiang Li: Formal analysis, Validation. Shan-gong Wu: Formal analysis, Validation. Gui-tang Wang: Funding acquisition, Resources, Supervision. Francisco Ponce-Gordo: Data curation,
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was supported by the National Natural Science Foundation of China (No. 31772429, 31471978), the Youth Innovation Promotion Association CAS (No. Y82Z01) and the earmarked fund for China Agriculture Research System (No. CARS-45-15).
References (34)
- et al.
Supplemental description of Nyctotheroides pyriformis n. comb. (= Macrocytopharynxa pyriformis (Nie, 1932) Li et al. 2002) from frog hosts with consideration of the validity of the genus Macrocytopharynxa (Armophorea, Clevelandellida)
Eur. J. Protistol.
(2017) - et al.
Sicuophora (Syn. Wichtermania) multigranularis from Quasipaa spinosa (Anura): morphological and molecular study, with emphasis on validity of Sicuophora (Armophorea, Clevelandellida)
Parasite
(2018) - et al.
The characterization of enzymatically amplified eukaryotic 16S-like rRNA-coding regions
Gene
(1988) - et al.
Genetic heterogeneity in internal transcribed spacer genes of Balantidium coli (Litostomatea, Ciliophora)
Protist
(2011) Nyctotheroides nouveaux ou peu connus du Cameroun (premièe série)
Ann. Fac. Sci. Yaoundé
(1980)Nyctotheroides nouveaux ou peu connus du Cameroun (deuxième série)
Ann. Fac. Sci. Yaoundé (Bio. Biochim.)
(1988)Observations morphologiques sur deux nyctothères (ciliés hétérotriches) commensaux de batraciens anoures du Québec
Can. J. Zool.
(1991)- et al.
Phylogenetic position of species in the genera Anoplophrya, Plagiotoma , and Nyctotheroides (Phylum Ciliophora), endosymbiotic ciliates of annelids and anurans
J. Eukaryot. Microbiol.
(2004) Description de cinq espèces nouvelles du genre Nyctotheroides Grassé, ciliés hétérotriches parasites de batraciens anoures malgaches
Bull. Mus. Nat. Hist. Nat.
(1972)Etude systématique et cytologique sur les ciliés hétérotriches endocommensaux.
Bull. Am. Mus. Nat. Hist.
(1975)
The Ciliated Protozoa: Characterization, Classification, and Guide to the Literature
Phylogenetic study of Class Armophorea (Alveolata, Ciliophora) based on 18S-rDNA data
Gen. Mol. Biol.
Taxonomic affinities of Cryptocaryon irritans and Ichthyophthirius multifiliis iferred from ribosomal RNA sequence data
Dis. Aquat. Org.
Index-Catalogue of Medical and Veterinary Zoology
Description of two new species of Sicuophoridae and Nyctotheridae (Heterotrichina), endocommensal in the rectal ampulla of Bufo regularis (Amphibia: Anura) from the Northwest of Cameroon
Protistology
Sur quelques Nyctotherus (infusoires hétérotriches) nouveaux ou peu connus
Ann. Protistol.
Class Armophorea Lynn 2002
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