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Parasites specif i c to centipedes form a new major lineage of terrestrial gregarinesTatiana S. Miroliubova 1,2? , Kirill V. Mikhailov 3,4 , Timur G. Simdyanov 5 , Vladimir V. Aleoshin 3,4,5 , ?inh Th? D?ng 2 & Aleksandra I. Kudriavkina 1,2Gregarines from the families Dactylophoridae and Trichorhynchidae parasitize exclusively centipedes and have a distinct morphology among other terrestrial eugregarines, but their evolutionary relationships have not yet been studied with molecular methods. Here we obtain rDNA operon sequences for the dactylophorids and trichorhynchids. We describe a new species Trichorhynchus efeykini sp. n. from a scutigeromorph Thereuopoda longicornis from Vietnam. Phylogenetic analyses with combined SSU, 5.8S and LSU rDNA dataset support the previously proposed separation of Trichorhynchus to the Trichorhynchidae based on morphology and recover the dactylophorids and trichorhynchids as sister groups in a monophyletic clade. This clade appears sister to the clade of the Actinocephaloidea and Stylocephaloidea, and represents a new major lineage of terrestrial gregarines that we designate as a new superfamily Dactylophoroidea.Terrestrial gregarines are parasites that have been known for almost 200 years 1 . Th ey infect a wide range of terrestrial and freshwater invertebrates, including annelids and arthropods 2 . Metagenomic data shows their high abundance in soil communities, which points to their signif i cant yet currently underestimated role in terrestrial ecosystems 3,4 . However, their evolutionary relationships remain largely unclear and taxonomy is still mainly based on morphological data, since many genera and even families do not have a single sequenced representative. Two of such families are Dactylophoridae Léger, 1892 and Trichorhynchidae Ormières, Marquès & Puisségur, 1977. Recent phylogenies have outlined four lineages of terrestrial gregarines, which have been designated as superfamilies Actinocephaloidea Léger, 1892, Gregarinoidea Labbé, 1899, Stenophoroidea Clopton, 2009, and Stylocephaloidea Clopton, 2009 5–8 , but it is unclear how dactylophorids and trichorhynchids are related to these superfamilies.T h e members of Dactylophoridae and Trichorhynchidae parasitize exclusively centipedes (Chilopoda). Th e dactylophorids infect Geophilomorpha, Lithobiomorpha, and Scolopendromorpha centipedes, while the only described trichorhynchid, Trichorhynchus pulcher Schneider, 1882, infects Scutigeromorpha centipedes 2 .Dactylophorid trophozoites have a remarkable distinctive feature—an asymmetrical and dilated protomerite carrying an attachment apparatus in the form of a number of digitiform or fi liform processes—rhizoids, instead of a single epimerite as in the majority of eugregarines 9–11 . At fi rst, Trichorhynchus pulcher was placed in the family Dactylophoridae as a centipede parasite 12 . Later, Ormières and colleagues studied the ultrastructure of T. pulcher trophozoites 13,14 and found signif i cant morphological dif f erences from other dactylophorids, including the absence of rhizoids, a lobed epimerite anchored close to the basal lamina of the host intestinal epithelium, a well-developed neck—an elongated anterior end of protomerite deeply immersed in the host intestinal epithelium, and the presence of multiple cytopilia on the cell surface instead of a typical eugregarine epicyte (multiple pellicular folds) 2 . Based on this, they separated Trichorhynchus into a monotypic family Trichorhynchidae 13 . Yet in addition to the closely related hosts, there is another feature bringing Trichorhynchidae closer to Dactylophoridae: they have similar (but not identical) mechanisms of the gametocyst dehiscence involving a dilating cytoplasmic residuum, the pseudocyst 13,15 . In order to determine the relationship between the Dactylophoridae and Trichorhynchidae and their position among other gregarines, we obtained rDNA operon sequences of the dactylophorids Echinomera hispida (Schneider, 1876) Labbé, 1899 and Grebnickiella 1 Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Leninsky Ave. 33, Moscow, Russian Federation119071. 2 Joint Vietnam-Russia Tropical Science and Technology Research Center, Hanoi, Vietnam. 3 Belozersky Institute for Physico-Chemical Biology, Lomonosov Moscow State University, Leninskiye Gory 1, bldg. 40, Moscow, Russian Federation119991. 4 Kharkevich Institute for Information Transmission Problems, Russian Academy of Sciences, Bolshoy Karetny Ln. 19, bldg. 1, Moscow, Russian Federation127051. 5 Faculty of Biology, Lomonosov Moscow State University, Leninskiye Gory 1, bldg. 12, Moscow, Russian Federation119234. ? email: provorosenok@gmail.comOPENScientif i c Reports | (2025) 15:192 1 | https://doi.org/10.1038/s41598-024-83990-4www.nature.com/scientificreports