Black-spotted pond frog Pelophylax nigromaculatus as a new host for the renal coccidian genus Hyaloklossia (Alveolata: Apicomplexa)

Hyaloklossia Labbé, 1896 (Apicomplexa: Sarcocystidae) is a renal coccidium that infects anuran species. The genus consists of two species: H. lieberkuehni, recorded from Pelophylax kl. esculentus, Pelophylax ridibundus, and Rana temporaria in Europe; and H. kasumiensis, recorded from Pelophylax porosus porosus in Japan. However, there have been no reports of Hyaloklossia in the other anurans in Japan. On June 2021, we examined a total of 58 adult frogs comprising 2 P. p. porosus, 23 Pelophylax nigromaculatus, 8 Rana japonica, 3 Glandirana rugosa (Ranidae), 13 Fejervarya kawamurai (Dicroglossidae), and 9 Buergeria buergeri (Rhacophoridae) for infection by Hyaloklossia. Microscopic examination of kidney tissues revealed a high infection incidence of 47.8% (11/23) in P. nigromaculatus, but the other frog species were negative for Hyaloklossia. Morphological and molecular analyses using nuclear ribosomal and mitochondrial genes confirmed the infective species as H. kasumiensis. This is a new host record for H. kasumiensis.