Catenotaenia cricetuli, Haukisalmi, Voitto, Hardman, Lotta M. & Henttonen, Heikki, 2010

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 : 15-20

Catenotaenia cricetuli n. sp.

(Figs 7 & 8)

Material examined: Nine gravid specimens from the grey dwarf hamster Cricetulus barabensis (Pallas) ( Cricetidae , Cricetinae ) from the Republic of Buryatia ( Russian Federation). For the distribution and prevalence of C. cricetuli (as Catenotaenia sp. 1) in Buryatia, see Haukisalmi et al. (2009).

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

Deposited specimens: Holotype, USNPC 102595 from C. barabensis from Ganzurinov, Buryatia (51.30745o N, 107.09544o E). Paratypes (2 slides), USNPC 102596, other information as in the holotype. Voucher specimens, USNPC 102597 and 102598 from C. barabensis from Sharaldai, Buryatia (51.03750o N, 107.34620o E) and MSB Endo 157 from C. barabensis from Ganzurinov, Buryatia.

FIGURE. 7. Catenotaenia cricetuli n. sp. from Cricetulus barabensis . A, scolex and neck (scale bar 0.20 mm). B, immature proglottids (scale bar 1.0 mm). C, early mature proglottids (scale bar 1.0 mm). D, late mature proglottids (scale bar 1.0 mm). E, F, uterus in pregravid proglottid (scale bars 1.0 mm). G, eggs (scale bar 0.020 mm).

FIGURE. 8. Catenotaenia cricetuli n. sp. from Cricetulus barabensis . A, B, mature proglottid (scale bars 0.30 mm).

Description: Length of fully gravid specimens 81–208 mm (109 mm, n=8); maximum width 0.98–1.55 mm (1.20 mm, n=8), attained in pregravid or gravid proglottids. Number of proglottids 63–95 (71.6, n=8). Scolex 320–385 (n=4) wide, slightly flattened dorso-ventrally, usually separated from neck by slight constriction. Scolex sometimes with slight apical bulge. Neck ca. 1.1 mm (n=2) long, of roughly uniform width, 260–340 (n=3) wide immediately posterior to scolex. Suckers 160–170 (n=4) in diameter, directed laterally or antero-laterally, embedded within scolex.

Proglottids craspedote, velum short. Mature proglottids always longer than wide; widest in posteriormost part (at velum), which widens gradually. Gravid proglottids of roughly uniform width; widest posteriorly, middle or at genital pore. Length and length/width ratio of proglottids increase posteriad: immature proglottids 350– 690 (511, n=14) long, with length/width ratio of 0.55–0.90 (0.72, n=14), mature proglottids 1.22–1.98 mm (1.64 mm, n=15) long, with length/width ratio of 1.24–2.18 (1.63, n=15); fully gravid proglottids 4.40–7.03 mm (5.30, n=5) long, with length/width ratio of 3.97–6.39 (5.06, n=5).

Genital pores irregularly and frequently alternating, with average of 54.8 changes per 100 proglottids or 1.8 (1–6) proglottids per unilateral set. Genital pores positioned at border between anterior and middle thirds of proglottid margin; relative anterior distance of genital pore 0.29–0.35 (0.330, n=8). Genital pore marked by slight bulge on proglottid margin.

Ventral longitudinal osmoregulatory canals 35–90 (54, n=14) wide; transverse connecting canals present in posterior margin of proglottid. Dorsal longitudinal osmoregulatory canals absent. Terminal genital ducts pass longitudinal canal dorsally.

Number of testes 130–166 (146, n=5), their diameter 60–115 (86, n=14). Testes situated in single compact group posterior to female glands, confined by longitudinal canals, dorso-ventrally in 2–3 layers. Anterior part of testicular field may be divided longitudinally. Testes may slightly overlap ovary, antiporal testes sometimes reaching level of mid-vitellarium. Testicular field covers 40–51% (47%, n=8) of proglottid length. Cirrus sac usually pyriform, with rather poorly developed muscle layers; length in mature proglottids 170–250 (210, n=6). When cirrus withdrawn, cirrus sac usually overlaps longitudinal canal or extends across it slightly. Internal seminal vesicle absent, although slightly expanded reservoir may be present in proximal cirrus sac. Distal vas deferens slightly twisted or 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; everted cirrus always unarmed.

Ovary lobulated, asymmetrical, confined by longitudinal canals. Free space separating ovary from anterior margin of proglottid distinct, 140–245 (186, n=8) long. Length of ovary 710–1090 (881, n=8), its maximum width (in anterior part) 420–530 (484, n=8). Ovary usually extends slightly more posteriad than posterior edge of vitellarium, sometimes in same level with it. Ovary covers 43–54% (48%, n=8) of proglottid length. Vitellarium sparsely lobulated and irregularly shaped, usually roughly as long as wide, sometimes shorter; length 235–430 (338, n=7), width 300–365 (328, n=7). Vitellarium positioned slightly anterior to middle of proglottid; relative position 0.45–0.50 (0.48, n=7). Mehlis' gland ovoid, 120–150 (133, n=5) in diameter, antiporal with respect to mid-line of vitellarium. Vagina opens posterior or postero-ventral to male pore. Proximal vagina strongly curved posteriad, usually merging seminal receptacle antero-medially. Vagina covered by thick cell layer. Length of vagina 250–320 (297, n=6). Maximum width of vagina 55–80 (69, n=6), maximum width of lumen 22–45 (n=4). Vaginal lumen with long delicate setae pointing distally. Seminal receptacle ovoid or round; maximum diameter 170–220 (198, n=6), attained in pregravid proglottids. Uterus in pregravid proglottids with 27–43 (33.9, n=14) irregular primary branches on each side; secondary branches few. Anterior part of uterus usually without unbranched pocket. Branches disintegrate partly or totally in fully gravid proglottids. Outer egg membrane forms rather wide tail-like appendage attached to embryophore (opposite to pole bearing oncospheral hooks). Total egg length 37–55 (47.2, n=30). Embryophore ovoid or subspherical, 17.0–22.5 (18.9, n=30) long.

Remarks: Despite an examination of ca. 500 Buryatian cricetid and murid rodents representing 6 species, C. cricetuli was only found from C. barabensis ( Haukisalmi et al. 2009) , suggesting a high level of host specificity.

In its egg morphology ("caudate"), C. cricetuli differs unequivocally from other congeneric species except C. microti n. sp. (the caudate eggs of C. asiatica Tenora & Murai, 1975 have only a rudimentary "cap"; see Tenora & Murai 1975). Besides molecular differences, C. cricetuli and C. microti differ in the diameter of the scolex, length of the "free space" anterior to the ovary, number of uterine branches, egg length (all higher in C. cricetuli ) and shape of the gravid proglottids (more uniform in C. cricetuli ). If egg morphology cannot be compared, C. cricetuli is distinguished by its long anterior "free space" from C. asiatica , C. californica Dowell, 1953 , C. cricetorum , C. gracilae , C. henttoneni , C. pusilla and C. rhombomydis Shulz & Landa, 1934 . Additional interspecific differences include the scolex width ( C. asiatica , C. californica , C. gracilae , C. henttoneni ), shape of the proglottids ( C. asiatica , C. californica , C. cricetorum , C. henttoneni , C. pusilla and C. rhombomydis ) and the number of uterine branches ( C. asiatica , C. cricetorum , C. gracilae , C. henttoneni , C. pusilla and C. rhombomydis ). From the species with a long or intermediate "free space", C. cricetuli differs by its proglottid shape ( C. dendritica , C. linsdalei , C. peromysci and C. reggiae Rausch, 1951 ) and width of the scolex ( C. laguri Smith, 1954 and C. neotomae Babero & Cattan, 1983 ).

Tenora & Murai (1975) described C. asiatica from C. barabensis , the type host of C. cricetuli , from Mongolia. Catenotaenia cricetuli and C. asiatica differ, however, for most of the characters listed in Table 2, including the shape of the proglottids, length of the anterior free space and number of uterine branches.

Catenotaenia afghana was described from Cricetulus migratorius (Pallas) and Alticola roylei (Gray) ( Cricetidae , Arvicolinae ) from Afghanistan ( Tenora 1977). The description is very brief and unillustrated, and it was not stated which is the type host (no type specimens were deposited). As C. afghana cannot be plausibly compared with other species, it is treated here as a species inquirenda. Ganzorig et al. (1999) later redescribed C. afghana from Lasiopodomys brandtii (Radde) ( Cricetidae , Arvicolinae ) from Mongolia. However, considering the generally high host specificity of Catenotaenia spp., C. afghana sensu Ganzorig et al. (1999) probably includes more than one species.

FIGURE. 9. Catenotaenia microti n. sp. from Microtus socialis . A, scolex and neck (scale bar 0.20 mm). B, scolex, apical view. C, immature proglottids (scale bar 1.0 mm). D, mature proglottids (scale bar 1.0 mm). E, F, gravid proglottids (scale bars 1.0 mm). G, H, uterus in pregravid proglottid (scale bars 1.0 mm). I, eggs (scale bar 0.010 mm).