Hymenolepididae Ariola, 1899

Sasaki, Mizuki, Anders, Jason Lee & Nakao, Minoru, 2021, Cestode fauna of murid and cricetid rodents in Hokkaido, Japan, with assignment of DNA barcodes, Species Diversity 26, pp. 255-272 : 261-262

Family Hymenolepididae Ariola, 1899

Genus Arostrilepis Mas-Coma and Tenora, 1997 3. Arostrilepis tenuicirrosa Makarikov, Gulyaev, and Kontrimavichus, 2011

The adult tapeworms of Arostrilepis tenuicirrosa (nos. 19AK170, 19AK439, 19AK454, and 19AK459) were found from My. rufocanus in Asahikawa and Biei. This is the first record from Japan. The following description was made based on three specimens ( Fig. 3C–E ): Scolex unarmed, 0.36–0.38 in maximum width, distinctly wider than neck. Suckers oval, four in number, 0.21–0.24 long by 0.11–0.18 wide. Rostellum absent. Mature proglottids shorter in length than width, 0.23–0.28 long by 0.95–1.20 wide. Testes pearshaped, three in number, almost equal-sized, 0.11–0.15 long by 0.14–0.21 wide, arranged in nearly a right-angled triangle. Poral testis separated from antiporal testes by female gonads. Cirrus sac 0.17–0.22 long by 0.027 –0.038 wide. Cirrus 0.09–0.10 long by 0.017 –0.022 wide, armed with spines. Genital pore opens on middle of lateral proglottid margin. Ovary irregularly lobed, 0.27–0.48 wide. Vitellarium lobed, postovarian, 0.14–0.19 wide. Gravid proglottids trapezoidal, transversely elongated, 0.51 long by 1.8–2.2 in maximum width. Uterus labyrinthine, occupying entire space of gravid proglottids.

Members of the genus Arostrilepis are widely distribut- ed in the Holarctic region, mainly using voles as definitive hosts. Arostrilepis horrida (Linstow, 1901) was once considered to be a morphologically hypervariable and geographically widespread species (Makarikov et al. 2011; Galbreath et al. 2013; Makarikov and Hoberg 2016). However, a recent molecular phylogenetic analysis using mitochondrial cytb sequences has revealed some cryptic species within the assemblage of the so-called “ A. horrida ” ( Makarikov and Kontrimavichus 2011; Makarikov et al. 2011, 2013). There are now eight species of Arostrilepis from the Palearctic region ( Makarikov and Kontrimavichus 2011; Makarikov et al. 2011, 2013): A. horrida sensu stricto, A. tenuicirrosa , A. beringiensis (Kontrimavichus and Smirnova, 1991) , A. microtis Gulyaev and Chechulin, 1997 , A. macrocirrosa Makarikov, Gulyaev, and Kontrimavichus, 2011 , A. intermedia Makarikov and Kontrimavichus, 2011 , A. janickii Makarikov and Kontrimavichus, 2011 , and A. gulyaevi Makarikov, Galbreath, and Hoberg, 2013 . Morphological differential points of these species are limited to the form and size of the cirrus, and other characters may vary and overlap among all species (Makarikov et al. 2011).

All the specimens of Arostrilepis obtained in this study were subjected to DNA sequencing of mitochondrial cox 1 and cytb. The values of pairwise divergence ranged at very low levels from 0.009 to 0.003 in both cox1 and cytb, confirming the involvement of a single species. A phylogenetic tree of cytb showed that our samples should be classified as A. tenuicirrosa ( Fig. 5 ).

Voles of Myodes spp. widely distributed from Europe to Russia serve as the definitive host for A. tenuicirrosa ( Galbreath et al. 2013) . The present study expands the distribution range to Hokkaido. There are also records of Arostrilepis horrida sensu lato from Eothenomys smithii (Thomas, 1905) and Eothenomys andersoni (Thomas, 1905) in Honshu ( Asakawa et al. 2002). Further specimens of Arostrilepis from Honshu and their DNA sequences are required to better understand the phylogeography and taxonomy of this group in Japan.

Figures

Fig. 3. Adult tapeworms of Hymenolepis sp. 1, Arostrilepis tenuicirrosa, and Microsomacanthus sp. A, Scolex of Hymenolepis sp. 1; B, mature proglottids of Hymenolepis sp. 1; C, scolex of A. tenuicirrosa; D, mature proglottid of A. tenuicirrosa; E, gravid proglottid of A. tenuicirrosa; F, whole body of Microsomacanthus sp.; G, scolex of Microsomacanthus sp.; H, mature proglottids of Microsomacanthus sp. Scale bars: A, C, G, 200µm; B, D, 500µm; E, 1mm; F, 2mm; G, 100µm.

Fig. 5. A maximum-likelihood phylogenetic tree of the genus Arostrilepis. The tree was made with sequences of mitochondrial cytb (558 nucleotide sites) under the substitutional model GTR+G+I. The isolates of this study (19AK170, 19AK439, 19AK454, and 19AK459) are shown in bold face. The DNA accession number of each taxon is shown in parenthesis. Hymenolepis diminuta (accession no. AF314223) was used as an outgroup taxon.