Catenotaenia Janicki, 1904

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 : 264-265

Genus Catenotaenia Janicki, 1904 6. Catenotaenia sp.

The adult tapeworms of Catenotaenia sp. (nos. 18AK131, JA212, JA317, AMU, and O36) were found from My. rufocanus in Asahikawa, Nayoro, Otofuke, and Obihiro. The 28S rDNA sequence of the isolate JA317 has already been reported ( Haukisalmi et al. 2017). The following description was made based on one specimen ( Fig. 6D–F ): Scolex unarmed, 0.23 in maximum width. Suckers spherical, four in number, 0.11–0.13 in diameter. Mature proglottids much longer in length than width, 1.30–1.50 long by 0.85–0.10 wide. Genital pore positioned on anterior half of lateral margin. Testes mini-spherical, 0.42–0.60 in diameter, 80–96 in number, assembled in a cluster behind female glands. Ovary lobed, asymmetrical, widely occupies anterior space of proglottid. Vitellarium lobed, positioned posterior to genital pore. Gravid proglottids widest in middle, 2.83–2.96 long by 0.82–0.95 wide. Uterine brunches 34–52 in number.

The cox1 sequences of all the isolates were almost identical to one another (mean pairwise divergence=0.011). A BLAST homology search could not detect any sequences similar to them. In contrast, the 28S rDNA sequences of related species ( Haukisalmi et al. 2017) allowed us to construct a phylogenetic tree. The resultant tree ( Fig. 8 ) clearly showed that our isolates (AMU, JA212, and JA317) are distinct from Catenotaenia henttoneni Haukisalmi and Tenora, 1993 , C. microti Haukisalmi, Hardman, and Henttonen, 2010 , C. cricetuli Haukisalmi, Hardman, and Henttonen, 2010 , C. apodemi Haukisalmi, Hardman, and Henttonen, 2010 , and C. kirgizica (Tokobaev, 1959) .

Members of Catenotaenia are known as parasites of voles ( Haukisalmi et al. 2010b). In Japan, Catenotaenia pusilla (Goeze, 1782) was reported from My. rufocanus , My. rutilus , and Mu. musculus in Hokkaido and Honshu ( Yamaguti 1935; Asakawa et al. 1983), while Catenotaenia gracilae Asakawa, Tenora, Kamiya, Harada, and Borkovcova, 1992 was described from Eo. andersoni and Eo. smithii in Honshu ( Asakawa et al. 1992b). In addition, unidentified species of Catenotaenia have been recorded from Ap. argenteus , My. rufocanus , My. rutilus , Eo. smithii , and Mi. montebelli , without their detailed morphological information ( Asakawa and Ohbayashi 1986; Asakawa and Tomonari 1988; Asakawa 1989; Asakawa et al. 1992b; Asakawa 1993; Ito and Itagaki 2003). The morphological classification of Catenotaenia is usually based on the number of uterine branches and the shape of proglottids. However, the diagnosis is challenging because the scolex lacks a rostellum and hooks, and other organs are generally uniform ( Asakawa et al. 1992b; Haukisalmi et al. 2010b). Catenotaenia sp. found in this study is similar to C. pusilla and C. gracilae from the views of the size and shape of proglottids and the amount of anterior free space in mature proglottids. However, Catenotaenia sp. has a greater number of uterine branches (34–52) than those of C. pusilla (9–17), and a fewer number of testes (80– 96) than those of C. gracilae (about 150). The present morphological and molecular information is still insufficient for the description of a new species.

Figures

Fig. 6. Adult tapeworms of Paranoplocephala kalelai, Catenotaenia sp., and Raillietina sp. A, Scolex of P. kalelai; B, mature proglottid of P. kalelai; C, gravid proglottid of P. kalelai; D, scolex of Catenotaenia sp.; E, mature proglottid Catenotaenia sp.; F, gravid proglottids of Catenotaenia sp.; G, scolex of Raillietina sp.; H, mature proglottids of Raillietina sp. Scale bars: A–C, E, H, 500µm; D, G, 200µm; F, 1mm.

Fig. 8. A maximum-likelihood phylogenetic tree of the genus Catenotaenia. The tree was made with 28S rDNA sequences (1208 nucleotide sites) under the substitutional model GTR+G. The isolates of this study (AMU, JA212, and JA317) are shown in bold face. The DNA accession number of each taxon is shown in parenthesis. Hymenolepis diminuta (accession no. AY157181) was used as an outgroup taxon.