New taxonomic insights into three cyathostomine nematodes of Sumatran elephant (Elephas maximus sumatranus).

Elephants harbour intestinal nematode infections, particularly cyathostomine nematodes (Cyathostomini: Strongylidae). Monitoring helminths in rare and endemic species is crucial, as infections can contribute to population declines. The Sumatran elephant (Elephas maximus sumatranus), a subspecies of the Asian elephant, is native exclusively to the island of Sumatra, Indonesia. The studies on nematodes of Sumatran elephants remain limited. In this study, three cyathostomine nematodes not previously reported from Indonesia - Quilonia renniei, Murshidia (Murshidia) falcifera, and M. (M.) murshida - were redescribed using light microscopy and scanning electron microscopy. This approach enabled the observation of previously unreported morphological features of taxonomic significance and corrected existing errors. Our SEM observations showed for the first time the detailed morphology of the cephalic extremity and the bursa of Murshidia (M.) falcifera, and M. (M.) murshida. Additionally, we provide the first molecular data on the nuclear DNA region (ITS1, 5.8S, and ITS2) of Q. renniei, the first mitochondrial partial cytochrome c oxidase I (COI) sequences for M. (M.) murshida and M. (M.) falcifera, and newly generated COI data for Q. renniei. These sequences were used to construct a phylogenetic tree of the elephant nematodes belonging to the Tribe Cyathostomini. The ITS phylogeny supported the monophyly of Murshidia and Quilonia and placed Khalilia sameera as a basal lineage, whereas the COI dataset failed to resolve relationships at the generic level. The ITS tree also confirmed the identity of Q. renniei, which appeared as sister to Q. africana.