Catenotaenia henttoneni Haukisalmi & Tenora, 1993

Haukisalmi, Voitto, Hardman, Lotta M. & Henttonen, Heikki, 2010, Taxonomic review of cestodes of the genus Catenotaenia Janicki, 1904 in Eurasia and molecular phylogeny of the Catenotaeniidae (Cyclophyllidea), Zootaxa 2489, pp. 1-33 : 10-13

Catenotaenia henttoneni Haukisalmi & Tenora, 1993

(Figs 4 & 5)

Material examined: 21 gravid specimens from the bank vole Myodes glareolus (Schreber) and 20 specimens from the red vole Myodes rutilus (Pallas) ( Cricetidae , Arvicolinae ) from northern Finland (Lapland). For the prevalence and ecology of C. henttoneni (as Catenotaenia sp.), see Haukisalmi & Henttonen (1990, 1993a, b).

Site: Usually the middle third of the small intestine (jejunum).

Deposited voucher specimens: USNPC 102583 and 102585 from M. glareolus from Pallasjärvi, Finland (68.02528o N, 24.15944 o E), USNPC 102584 and 102588 from M. rutilus from Pallasjärvi, Finland, USNPC 102586 and 102587 from M. rutilus from Kilpisjärvi, Finland (69.05222o N, 20.78639o E), USNPC 102582 from M. glareolus from Monte Bondone, Trentino, Italy (46o04' N, 11 o08' E).

Description: Length of fully gravid specimens 62–136 mm (91 mm, n=14); maximum width 1.0– 1.7 mm (1.30 mm, n=22), usually attained in pregravid proglottids. Number of proglottids 58–76 (68.6, n=14). Scolex small, 240–300 (274, n=9) wide, flattened dorso-ventrally, usually separated from neck by slight constriction. Scolex usually with more or less distinct apical cone or bulge. Neck 0.5–0.9 mm (0.63 mm, n=8) long, usually of roughly uniform width, 175–260 (229, n=8) wide immediately posterior to scolex. Suckers 105–138 (119, n=9) in diameter, directed laterally or antero-laterally, embedded within scolex.

Proglottids slightly craspedote or "pseudocraspedote"; velum very short or absent. All proglottids widest in posteriormost part, which widens rather abruptly. Mature proglottids roughly as long as wide. Length and length/width ratio of proglottids increase posteriad; immature proglottids 290–720 (506, n=34) long, with length/width ratio of 0.50–1.09 (0.76, n=34); mature proglottids 800–1470 (1174, n=52) long, with length/ width ratio of 0.71–1.72 (1.12, n=52); fully gravid proglottids 2.7–5.1 mm (3.66 mm, n=19) long with length/ width ratio of 2.42–5.10 (3.42, n=19).

Genital pores irregularly and frequently alternating, with average of 46.2 changes per 100 proglottids or 2.2 (1–11) proglottids per unilateral set. Genital pores positioned roughly at border between anterior and middle thirds of proglottid margin; relative anterior distance of genital pore 0.29–0.39 (0.351, n=14). Genital pore marked by slight bulge on proglottid margin.

Ventral longitudinal osmoregulatory canals 25–85 (50.0, n=30) wide; transverse connecting canals present in posterior margin of proglottid. Dorsal longitudinal osmoregulatory canals not observed. Terminal genital ducts pass longitudinal canal dorsally.

Number of testes 103–137 (127, n=8), diameter of testes 45–100 (67.3, n=22). Testes situated in single compact group posterior to female glands, confined by longitudinal canals, dorso-ventrally in 2–3 layers. Longitudinal division of testicular field absent. Testes usually slightly overlapping ovary, antiporal testes sometimes reaching level of mid-vitellarium. Testicular field covering 33–51% (43.3%, n=14) of proglottid length. Cirrus sac elongate or pyriform with muscular wall; length in mature proglottids 150–210 (n=4).

FIGURE. 4. Catenotaenia henttoneni from Myodes glareolus . A, scolex and neck (scale bar 0.20 mm). B, immature proglottids (scale bar 1.0 mm). C, mature proglottids (scale bar 1.0 mm). D, gravid proglottids (scale bar 1.0 mm). E, F, uterus in pregravid proglottid (scale bars 0.50 mm). G, eggs (scale bar 0.020 mm).

FIGURE. 5. Catenotaenia henttoneni from Myodes rutilus (A) and M. glareolus (B). A, B, mature proglottid (scale bars 0.30 mm).

When cirrus withdrawn, cirrus sac usually overlaps longitudinal canal but does not extend across it. Internal seminal vesicle absent, although slightly expanded reservoir may be present in proximal cirrus sac. Distal vas deferens slightly twisted/looped, covered by thick continuous cell layer. Proximal vas deferens curved posteriad, sometimes slightly looped, not covered by cell layer. Ductus cirri usually provided with short spines; no armature observed on everted cirri.

Ovary lobulated, asymmetrical, confined by longitudinal canals. Short free space (0–60, mean 25, n=14) may separate ovary from anterior margin of proglottid. Length of ovary 640–980 (816, n=14), maximum width (in anterior part) 490–740 (611, n=14). Ovary usually extends slightly more posteriad than posterior edge of vitellarium, sometimes at same level with it. Posterior part of ovary may partly surround vitellarium. Ovary covers 58–76% (67%, n=14) of proglottid length. Vitellarium sparsely lobulated and irregularly shaped, slightly longer than wide in fully expanded proglottids, shorter than wide in more contracted proglottids; length 200–440 (283, n=14), width 270–430 (339, n=14). Midpoint of vitellarium usually slightly posterior to midline of proglottid; relative longitudinal position 0.48–0.58 (0.538, n=14). Mehlis' gland ovoid, 115–180 (143, n=8) in diameter, median or slightly antiporal with respect to mid-line of vitellarium. Vagina opens posterior or postero-ventral to male pore. Proximal vagina strongly curved posteriad, merging seminal receptacle anteriorly or antero-medially. Vagina covered by thick cell layer. Length of vagina 220–330 (263, n=8). Maximum width of vagina 55–90 (68, n=5) and maximum width of lumen 25–35 (n=3). Vaginal lumen with long delicate setae pointing distally. Seminal receptacle ovoid or round; maximum diameter 100–180 (133, n=21), attained in pregravid or gravid proglottids. Uterus in pregravid proglottids with 16–28 (21.8, n=61) irregular primary branches on each side; secondary branches frequent. Anterior uterus usually forms distinct unbranched pocket. Branches disintegrate partly or totally in fully gravid proglottids. Eggs (outer membrane) ovoid or slightly elongate, 20–31 (24.8, n=75) long. Embryophore ovoid, 12–18 (14.2, n=75) long.

Remarks: Catenotaenia henttoneni is a widespread and relatively common parasite of the bank vole Myodes glareolus in Europe ( Haukisalmi & Tenora 1993, Haukisalmi & Henttonen 2000, Milazzo et al. 2003, Bajer et al. 2005). It also occurs, sometimes abundantly, in the red vole Myodes rutilus in Northern Europe, even where the distributions of the red vole and bank vole do not overlap (e.g., at Kilpisjärvi in northern Finland, H. Henttonen, unpublished data). The present phylogenetic analysis confirms the monophyly and probable conspecificity of C. henttoneni -like cestodes from northern Finland (including the type locality Pallasjärvi), northern Italy and Croatia. The phylogenetic data also confirm the conspecificity of cestodes from the red vole and bank vole. However, C. henttoneni is practically absent in the grey-sided vole Myodes rufocanus (Sundevall) (which also has a northern distribution in Europe) and all other arvicoline rodents, even when sympatric with the bank vole or red vole. This pattern indicates phylogenetically determined hostspecificity, since M. glareolus and M. rutilus are probable sister species that have undergone introgression ( Tegelström 1987, Abramson et al. 2009) and still hybridize ( Osipova & Soktin 2008). Myodes rufocanus represents a separate phylogenetic lineage ( Cook et al. 2004).

In the original description ( Haukisalmi & Tenora 1993), C. henttoneni was compared with C. cricetorum , C. peromysci Smith, 1954 , C. afghana Tenora, 1977 , C. pusilla and C. kirgizica . It was differentiated from them by the "markedly craspedote strobila" (all species except C. cricetorum ), external dimensions and egg length ( C. cricetorum ), number of uterine branches ( C. peromysci , C. afghana , C. pusilla ) and number of testes ( C. kirgizica ).

The most characteristic feature of C. henttoneni is that all proglottids are widest in the pronounced posterior region (“velum”), which widens abruptly. However, the proglottids of C. henttoneni are not truly craspedote, because the “velum” does not overhang the subsequent proglottid, except when heavily contracted (thus the term “pseudocraspedote”). In the shape of proglottids and number of uterine branches, C. henttoneni resembles most C. cricetorum . However, according to the illustrations of Kirshenblat (1949), C. cricetorum has longer and more elongate mature proglottids than C. henttoneni and its pregravid/gravid proglottids are of rather uniform width or widest at genital pore. In addition, its maximum body and scolex dimensions exceed markedly those of C. henttoneni . Neither reports nor descriptions of Catenotaenia species from the type host of C. cricetorum [ Mesocricetus brandti (Nehring) ] have been published since Kirshenblat (1949).