Parasite diversity in painted frogs inhabiting desert oases in southern Tunisia

Data on parasites infecting amphibians in arid North-African areas are still scarce. In this study, we investigate the diversity and prevalence of parasites in a painted frog (Discoglossus pictus) population inhabiting desert oases in south-eastern Tunisia. From 120 sampled frogs, we recorded six parasite species, including three protozoa, morphologically identified as Opalina ranarum, Protoopalina intestinalis and Cepedietta gigantea, two nematodes identified as Rhabdias sp. and Cosmocercoides sp., and one trematode identified as Pleurogenoides medians. According to partial sequences of the nuclear 18S rRNA gene, the two protozoa O. ranarum and C. gigantea showed 98.64 % sequence similarity to Karotomorpha sp., and 96.62 % to P. intestinalis. The partial sequences of the mitochondrial cytochrome oxidase subunit I gene showed that nematodes morphologically identified as Rhabdias sp. featured R. bufonis with 92.35 % similarity, while those identified as Cosmocercoides sp. showed 87.44 % sequence similarity to Toxocara vitulorum, 86.30 % to Aplectana sp., and 86.20 % to Cruzia tentaculata. The single trematode morphologically identified as P. medians showed 84.76 % similarity to Characithecium sp. and 84.76 % similarity to Ancyrocephalinae sp. Moreover, 97.5 % of the sampled frogs were infected by at least one parasite species, with the nematode Cosmocercoides sp. being the most common parasite (88.44 %). Males were more frequently infected by protozoa parasites than females, and helminth infection was associated with deteriorated body condition. However, individual age, determined by skeletochronology, did not predict parasite prevalence. Overall, our findings provide knowledge that would help understand the diversity and dynamics of endoparasites associated with amphibians in North Africa.