Catenotaenia microti, 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 : 21-22

Catenotaenia microti n. sp.

(Fig 9 & 10)

Material examined: Thirteen gravid specimens from the social vole Microtus socialis (Pallas) ( Cricetidae , Arvicolinae ) from Kazakhstan.

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

FIGURE. 10. Catenotaenia microti n. sp. from Microtus socialis . A, B, mature proglottid (scale bars 0.30 mm).

Deposited specimens: Holotype, USNPC 102599 from M. socialis from Bakanas, Kazakhstan (44.80851o N, 76.265720o E). Paratypes (3 slides), USNPC 102600, other information as in the holotype. Voucher specimens, USNPC 102601 – 102604, other information as in the holotype.

Description: Length of fully gravid specimens 56–106 mm (74 mm, n=5); maximum width 1.10–1.58 mm (1.29 mm, n=10), attained in postmature, pregravid or gravid proglottids. Number of proglottids 41–54 (n=4). Scolex small, 245–265 (n=4) wide, flattened dorso-ventrally, sometimes with slight apical cone. Neck 370–760 (n=4) long, of roughly uniform width, 175–250 (n=4) wide immediately posterior to scolex. Suckers 110–140 (n=4) in diameter, directed laterally or antero-laterally, embedded within scolex.

Proglottids craspedote or "pseudocraspedote"; velum very short or absent. Mature proglottids usually longer than wide; usually widest in posteriormost part (at velum), rarely at genital pore. Posterior margin usually widens gradually, sometimes abruptly. Gravid proglottids of roughly uniform width, usually widest in mid-region. Last gravid proglottids sometimes strongly contracted (short with very convex margins). Length and length/width ratio of proglottids increase posteriad: immature proglottids 300–750 (461, n=15) long, with length/width ratio of 0.54–1.18 (0.83, n=15); mature proglottids 0.92–1.95 mm (1.37 mm, n=26) long, with length/width ratio of 0.81–2.18 (1.48, n=26); fully gravid proglottids 2.5–3.6 mm (3.19, n=9) long, with length/width ratio of 2.08–3.33 (2.69, n=9).

Genital pores irregularly and frequently alternating, with average of 53.7 changes per 100 proglottids or 1.8 (1–5) proglottids per unilateral set. Genital pores usually positioned slightly anterior to border between anterior and middle thirds of proglottid margin; relative anterior distance of genital pore 0.23–0.36 (0.304, n=9). Genital pore marked by slight bulge on proglottid margin.

Ventral longitudinal osmoregulatory canals 25–48 (37, n=16) 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 88–110 (n=3), their diameter 70–128 (88, n=16). 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 34–48% (43%, n=9) of proglottid length. Cirrus sac pyriform with well-developed muscle layers; length in mature proglottids 183–270 (215, n=7). When cirrus withdrawn, cirrus sac overlaps longitudinal canal or extends across it. 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 provided with short spines; everted cirrus unarmed.

Ovary lobulated, asymmetrical, confined by longitudinal canals. Antero-poral lobe of ovary poorly developed, consisting of few short lobules. Free space separating ovary from anterior margin of proglottid of variable length, usually short (0–135, mean 75, n=9). Length of ovary 630–900 (757, n=9); its maximum width (in anterior part) 310–700 (512, n=9). Ovary extends to posterior edge of vitellarium or slightly short of it. Ovary covers 45–69% (57%, n=9) of proglottid length. Vitellarium sparsely lobulated and irregularly shaped; roughly as long as wide; length 155–350 (278, n=9) and width 190–290 (262, n=9). Vitellarium positioned slightly posterior to middle of proglottid; relative position 0.51–0.58 (0.53, n=9). Mehlis' gland ovoid or spherical, 140–160 (149, n=7) 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 250–340 (296, n=8). Maximum width of vagina 60–90 (68, n=6), maximum width of lumen 30–60 (n=5). Vaginal lumen with long delicate setae pointing distally. Seminal receptacle ovoid or round, with maximum diameter 150–230 (187, n=10) attained in postmature, pregravid or gravid proglottids. Uterus in pregravid proglottids with 21–27 (24.7, n=6) 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 pointed tail-like appendage attached to embryophore (opposite to pole bearing oncospheral hooks). Total egg length 31–46 (37.0, n=20). Embryophore ovoid, 14–19 (17.1, n=20) long.

Remarks: Catenotaenia microti is the first Catenotaenia species described from voles of the genus Microtus . In the Kazakhstan material, it was restricted to M. socialis and did not occur in the sympatric Microtus arvalis (Pallas) and Apodemus uralensis (H. Henttonen et al., unpublished data).

In its egg morphology ("caudate"), C. microti differs fundamentally from other congeneric species except C. cricetuli n. sp. For morphological differences between C. microti and C. cricetuli , see Table 2 and the remarks for the latter species. The independent status of C. microti and C. cricetuli is confirmed by the present sequence data. If egg morphology can not be compared, C. microti differs in the shape of the ovary (poorly developed antero-poral lobe) from all congeneric species.

From other species with posteriorly wide mature proglottids, C. microti differs also in the shape of the gravid proglottids ( C. henttoneni ), diameter of the scolex ( C. cricetorum , C. cricetuli , C. gracilae , C. neotomae , C. peromysci , C. reggiae , C. rhombomydis ) and number of uterine branches ( C. cricetuli , C. laguri , C. reggiae ).