Anele EU et al. (2026), Distributions of Xenopus species and their helm...

XB-ART-61849

PLoS One 2026 May 19;215:e0348516. doi: 10.1371/journal.pone.0348516.

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Distributions of Xenopus species and their helminth parasites in ecological zones of Nigeria.

Anele EU, Nock IH, Gadzama IMK, Kia GSN, Premachandra T, Jackson JA, Tinsley RC, Evans BJ.

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African clawed frogs (Xenopus species) are distributed across sub-Saharan Africa, live in water, and are hosts to diverse parasites whose distributions and host-specificities are incompletely characterized. To better understand this host/parasite biodiversity, we used morphology and Sanger sequencing to characterize Xenopus species and their helminth parasites in several ecological zones of Nigeria. Five Xenopus species were identified in Nigeria (X. fraseri, X. fischbergi, X. poweri, X. tropicalis, and X. calcaratus), and one - Xenopus fraseri - was found to have a wide ecological tolerance in four different savanna ecological zones. Thirteen species of helminths from two phyla and five major lineages were isolated: camallanoid and seuratoid nematodes (roundworms), and cestode, digenean, and monogenean platyhelminths (flatworms). Based on our sample, the nematodes exhibited higher host generalism than the platyhelminths by infecting several host species and occurring in a wider breadth of ecological zones. In this study, all parasite species specialized either to a specific tissue (e.g., the bladder or pericardium) or a similar pair of tissues (e.g., esophagus and stomach or the lower intestine and rectum), which underscores the distinctiveness if different tissue ecosystems within a host. This study provides novel and molecularly confirmed insights into host and parasite species diversity, distributions, and ecological specificities in several ecological zones of Nigeria. Future efforts should focus on transition zones between ecological zones in Nigeria.

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Species referenced: Xenopus tropicalis
Genes referenced: mt-rnr2
GO keywords: detection of nematode

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	Fig 1. Distribution of ecological zones in Nigeria following [20] (top left), host Xenopus species (top right), and four major groups of Xenopus parasites (bottom row). Numbered ecological zones are: (1) Sahel Savanna, (2) Sudan Savanna, (3) Guinea Savanna, (4) Jos Plateau, (5) Montane Forest, (6) Derived Savanna, (7) Lowland Rainforest, (8) Freshwater Swamp Forest, and (9) Coastal Vegetation. A small red box on the inset in the top left panel shows the location of Nigeria; the large red box on this panel demarcates the area depicted in other panels, which illustrate sampling localities of frogs (top right) and parasites (bottom row). Parasite species are labeled except the nematodes where species are represented by the following symbols: Camallanus kaapstaadi: blue diamonds; Chabaudus leberrei: green circles; Batrachocamallanus occidentalis: red triangles; Batrachocamallanus xenopodis: orange star.
	Table 1. Observed distributions of parasites in Xenopus host species, Nigeria ecological zones, and Xenopus host organs.
	Fig 2. Photographs of (a) a female Camallanus kaapstaadi; (b) a male Batrachocamallanus sp.; (c) a female Batrachocamallanus xenopodis; (d, e) a female and male Batrachocamallanus occidentalis, respectively; (f,g,h,i) anterior & posterior views of a male and femaleChabaudus leberrei, respectively; (j,k,l) scolex, immature proglottid, and gravid proglottid of Cephalochlamys compactus,, respectively; (m,n,o) scolex, immature proglottid, and gravid proglottid of Cephalochlamys namaquensis, respectively; (p) Protopolystoma xenopodis; (q) Protopolystoma microsclera; (r) Protopolystoma occidentalis; (s) Diplodiscus fischthalicus; (t) Progonimodiscus doyeri; (u) Oligolecithus elianae; (v) Strigeatoid metacercaria (a larvae of an unidentified digenetic trematode). The scale bar of 5 mm for all panels is in (a).
	Fig 3. Phylogenetic inferences among Sanger sequences of Nigerian Xenopus species (top left insert) and their helminth parasite (Nematoda, Platyhelminthes: Cestoda, Trematoda (Digenea) Monogenea); black circles over nodes indicate bootstrap support of at least 90%, except for terminal nodes where this is omitted for clarity. For the host phylogeny, two divergence time estimates are provided based on mitochondrial (mtDNA) and nuclear DNA (nDNA) data, as described in [8].