A new species of Choleoeimeria (Apicomplexa: Eimeriidae) from the invasive curious skink, Carlia ailanpalai (Sauria: Scincidae) from Guam, U.S. Territory.

The curious skink, Carlia ailanpalai Zug, occurs in the main group of the Admiralty Islands of Papua New Guinea but has also successfully invaded Guam, the Marianas, Yap, and Kosrae. A single coccidian, Eimeria zugi McAllister, Duszynski, Fisher, & Austin, 2013 was described from C. ailanpalai from Papua New Guinea. No additional coccidians are known from this host. Fourteen C. ailanpalai were collected from Cocos Island (Islan Dåno), Guam, U.S. Territory, and their feces examined for coccidians. A single skink (7%) was found to be passing oöcysts of a new species of Choleoeimeria. Oöcysts of Choleoeimeria cocosensis n. sp. are ellipsoidal to ovoidal with a bi-layered wall, measure (L × W) 21.1 × 12.9 µm, and have a length/width (L/W) ratio of 1.6; a micropyle and an oocyst residuum were absent but fragmented polar granule(s) was present. Sporocysts are ovoidal and measure 8.6 × 6.3 µm, L/W 1.4; Stieda, sub-Stieda, and para-Stieda bodies were absent. Sporocyst residuum was typically a loose aggregate of various-sized granules between and across the sporozoites but sometimes a dense irregular mass between and across the sporozoites. Sporozoites were elongate, with a centrally located nucleus and a large spheroidal to subspheroidal posterior refractile body, but without an anterior refractile body. The new species can be differentiated from all other choleoeimerians from skinks by possessing one of the smallest oöcysts known from the host family. We also provide an updated summation of the choleoeimerians from skinks of the world. This article was registered in the Official Register of Zoological Nomenclature (ZooBank) as urn:lsid:zoobank.org:pub:6EFDF027-0A92-43C4-9AD0-E555252E7741.