IMMUNOLOGY AND HOST-PARASITE INTERACTIONS - ORIGINAL PAPER The intermediate hosts of Wardium cirrosa (Krabbe, 1869) Spassky, 1961 (Cestoda, Cyclophyllidea, Aploparaksidae) in Ukraine O. Greben 1 & O. Kudlai 2 & V. V. Kornyushin 1 Received: 29 March 2019 /Accepted: 30 August 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract The metacestodes of aploparaksid cestode Wardium cirrosa Krabbe, 1869 parasitic in gulls were found in polychaetes of the family Nereidae collected off the Black Sea coast, Ukraine. Two species of polychaetes, Hediste diversicolor (prevalence 5.3%; intensity 1–3 specimens) and Neanthes succinea (prevalence 9.9%; intensity 1–39 specimens), were infected with cysticercoids that were observed either individually or in accumulations. The preliminary identification of the material based on morphological characteristics was later confirmed by experimental infection of the definitive host, Larus cachinnans (Charadriiformes: Laridae) with metacestodes, and by the identity of the partial 28S rDNA sequences of cysticercoids and experimentally obtained adults. Although previous studies suggested freshwater leeches as the intermediate host for W . cirrosa, our study provides the evidence for marine polychaetes to serve as intermediate hosts. This study is the first to present the morphological characteristics of metacestodes of W. cirrosa in addition to molecular data for this species, as well as reporting the possibility of several cysticer- coids developing from a single oncosphere. Morphology of the adult specimens obtained in the experiment was compared with adults of W . cirrosa previously collected from L. cachinnans in Ukraine. The results of our study suggest that further research focused on the elucidation of the life cycles of cestodes within the genus Wardium should consider marine invertebrates as potential intermediate hosts. Keywords Wardium cirrosa . Cysticercoid . Life cycle . DNA . Polychaeta . Ukraine Introduction Wardium cirrosa (Krabbe, 1869) Spassky, 1961 is a wide- spread parasite of various gulls and terns in the Holarctic Region (Bondarenko and Kontrimavichus 2006). It was de- scribed by Krabbe (1869) as Taenia cirrosa from Larus canus Linnaeus, 1758 in Denmark. Deblock et al. (1960) published the first detailed description of this species from Larus ridibundus Linnaeus, 1766 and L. canus in France and assigned this species to the genus Hymenolepis Weinland, 1858. Spassky (1961) transferred H. cirrosa into the genus Wardium Mayhew, 1925, which previously had been considered the junior synonym of the genus Hymenolepis. Bondarenko and Kontrimavichus (2006) in the revision of the family Aploparaksidae Mayhew, 1925 in- cluded the genus Wardium with W. cirrosa in this family. The biology of W. cirrosa was reported by Pike (1968). The metacestodes found by Pike in freshwater leeches Erpobdella octoculata (Linnaeus, 1758) in England were identified as Haploparaksis cirrosa (= W. cirrosa ) (Pike 1968 ). Illustrations and the description of the cysticercoids were pro- vided. Specimens were identified based on the hook size. The presence of the definitive hosts, gulls, in the study localities served as further evidence. To the best of our knowledg, that is the only report regarding the life cycle of W. cirrosa to date. However, the species identification of members of the genus Wardium is considered possible only through examining the morphology of the strobila in adults (Bondarenko and Kontrimavichus 2006). Wardium сirrosa was reported in countries neighboring Ukraine: Slovakia (Macko 1964), Poland (Bezubik 1956; Korpaczewska 1963; Pojmańska et al. 1984), Czechia Section Editor: David Bruce Conn * O. Greben oksana1greben@gmail.com 1 I. I. Schmalhausen Institute of Zoology, NAS of Ukraine, 15, Bogdan Khmelnitsky Str., Kyiv 01030, Ukraine 2 Institute of Ecology, Nature Research Centre, Akademijos, 2, 08412 Vilnius, Lithuania Parasitology Research https://doi.org/10.1007/s00436-019-06453-0