A new species of the genus Monoecocestus (Cestoda: Anoplocephalidae) from Lagidium viscacia (Rodentia: Chinchillidae) from the high-altitudes of Peru.

Anoplocephalidae (Cestoda: Cyclophyllidea) is a diverse family, with the subfamily Anoplocephalinae comprising 59 genera that primarily parasitize the digestive tract of rodents and birds. Monoecocestus threlkeldi was originally described from the northern vizcacha, Lagidium peruanum, in Junin, Peru, and subsequently reported in cricetids (Holochilus spp.) in Argentina and Bolivia. In the present study, we describe a new species of the genus Monoecocestus parasitizing the southern vizcacha, Lagidium viscacia, based on specimens collected in Puno, Peru, at an elevation of 3932 m a. s. l. A total of 45 specimens of the new species were obtained and processed for morphological and molecular analysis. For molecular analysis, DNA sequences of three markers were generated: the nuclear 18S, 28S, ITS, and mitochondrial cox1. The molecular data were compared with sequences available in GenBank, confirming its inclusion in the genus Monoecocestus. Morphologically, the new species is similar to M. threlkeldi, but it can be distinguished by its smaller body size, scolex, cirrus pouch, and number of proglottides. The description of the new species Monoecocestus viscaciae improves our understanding of the diversity of cestodes in high-altitude Andean ecosystems and provides new insights into host specificity within the genus Lagidium.