Paranoplocephala alaskensis, Haukisalmi, Voitto & Henttonen, Heikki, 2007

Haukisalmi, Voitto & Henttonen, Heikki, 2007, A taxonomic revision of the Paranoplocephala primordialis (Douthitt) complex (Cestoda: Anoplocephalidae) in voles and squirrels, Zootaxa 1548, pp. 51-68 : 62-64

Paranoplocephala alaskensis n. sp.

( Fig. 5 )

Type host: Microtus miurus, Myomorpha , the singing vole.

Type locality: Fortress Mountain, Gates of the Arctic National Park and Preserve ( GAAR), northern Alaska, U.S.A., 68o34'19.7"N, 152o57'20.9"W.

Site: Small intestine (duodenumn or jejunum).

Deposited specimens: Holotype: MSB Endo 14 (field code AF 61775), from Microtus miurus ( UAM 78448), collected on 30th July 2002 at Fortress Mountain, Gates of the Arctic National Park and Preserve ( GAAR), northern Alaska, U.S.A. (68o34'19.7"N, 152o57'20.9"W). Collectors: H. Henttonen, K. Hildebrandt, J. Laakkonen and J. Niemimaa. Paratype: MSB Endo 15 (AF 61754), from Mi. miurus ( UAM 78403), collected on 29th July 2002 at Fortress Mountain, GAAR, Alaska (68o34'48.4"N, 152o57'35.6"W). Collectors as for the holotype. Voucher specimens (all from Mi. miurus from Alaska): i) MSB Endo 17 (AF 58231, UAM 82045), Easter Creek near Lake Tulilik, GAAR, ii) MSB Endo 19 (AF 58239, UAM 82046), Lake Tulilik, GAAR, iii) MSB Endo 21 (AF 61903, UAM 79023), Nanushuk River, GAAR, iv) MSB Endo 20 (AF 61881, UAM 79018), Nanushuk River, GAAR, v) MSB Endo 16 (AF 48382, UAM 56607), Copter Peak, Noatak National Preserve.

Description: Based on 12 specimens from Mi. miurus from various localities in Alaska, primarily from the GAAR ( Tables 1 and 3). Fully gravid strobila 49–75 (62, n=7) long; maximum width (1.29–2.14, 1.75, n=9) attained in pregravid or gravid proglottids. Number of proglottids ca. 200 (n=2). Proglottids craspedote, but velum short or absent in well-relaxed specimens. Length/width ratio of mature proglottids 0.22–0.45 (0.36, n=16), of gravid proglottids marginally higher, 0.25–0.59 (0.38, n=29). Scolex simple, slightly rounded apically; width 0.42–0.55 (0.47, n=11). Suckers 0.15–0.22 (0.17, n=36) in diameter, directed antero-laterally, embedded in scolex. Neck 0.35–0.70 (0.57, n=9) long, not clearly distinct from scolex, tapering posteriorly, minimum width (0.20–0.30, 0.24, n=10) attained in region where segmentation first visible.

Genital pores usually unilateral (10/11), once with four alternations per strobila, opening in posterior third of proglottids margin in mature proglottids.

Ventral longitudinal osmoregulatory canals 0.02–0.08 (0.040, n=24) wide, transverse commissures of ventral canals poorly visible. Dorsal longitudinal osmoregulatory canals 0.010–0.015 wide, lateral to ventral longitudinal canals. Genital ducts passing dorsally to longitudinal osmoregulatory canals.

Number of testes 15–27 (22.4, n=16), distributed in single group antiporally and anteriorly to ovary. Poral testes reach level of middle or poral margin of vitellarium, rarely in contact with longitudinal ventral canal. From 0 to 9 (3.1, n=15) testes positioned lateral to antiporal longitudinal ventral canal. Testes overlap anterior and antiporal margins of ovary, being sometimes in contact with antiporal lobe of vitellarium. Diameter of testes 0.06–0.10, large relative to proglottid size. Cirrus sac 0.18–0.29 (0.23, n=17) long in mature proglottids or 23–32% (27%, n=17) of proglottid width, overlapping or extending across longitudinal ventral canal. Maximum length of cirrus sac 0.20–0.33 (0.27, n=11) in postmature proglottids. Muscle layers of cirrus sac thin. Ductus cirri armed densely with minute spines in its distal part. Internal seminal vesicle initially rounded, occupying up to 1/3 of cirrus sac length when filled with sperm. External seminal vesicle pedunculated or irregularly shaped, distinctly set off from vas deferens, covered by large, poorly-stained cells.

Ovary coarsely lobed, large, 0.24–0.59 (0.38, n=17) wide and 0.18–0.32 (0.23, n=16) long in mature proglottids or 36–53% (44%, n=17) of proglottid width, covering whole space between ventral longitudinal canals and sometimes overlapping them slightly. Vitellarium asymmetrically bilobed or irregularly shaped, positioned slightly porally with respect to midline of ovary and proglottid (index of asymmetry 0.39–0.51, 0.46, n=17), overlapping markedly posterior part of ovary. Mehlis' gland positioned between lobes of vitellarium or anterior to it. Vagina 0.11–0.23 (0.17, n=16) long and 0.04–0.06 (0.049, n=10) wide, usually shorter than cirrus sac (61–104%, 75%, n=16), slightly curved, running posteriorly or postero-ventrally to cirrus sac, distinctly set off from seminal receptacle. Internally, vagina formed by distinct, thin-walled tube, lumen of which widens distally. Internal surface of vagina probably lined with delicate hairs. Vaginal tube covered by layer of large cells; this layer merges with cell layer surrounding genital atrium. Seminal receptacle ovoid, 0.10–0.28 (0.16, n=17) in diameter in mature proglottids. Seminal receptacle retaining its shape when filled with sperm, reaching maximum size of 0.15–0.29 (0.23, n=11) in postmature proglottids. Uterus appears in early mature proglottids as loose, delicate reticulum ventral to testes and other organs and extending across longitudinal osmoregulatory canals bilaterally. Lateral margins of early uterus usually wider than middle part. Uterus in pregravid proglottids filling most of medulla with few irregular anterior, posterior and lateral sacculations or diverticula and few internal trabeculae. Genital ducts, sacculations and trabeculae disappear in fully gravid proglottids. Eggs 0.046–0.061 (0.0515, n=54) long, spherical in surface view, ovoid in side view. Pyriform apparatus present.

Remarks. Paranoplocephala alaskensis n. sp. differs from P. primordialis by its relatively smaller suckers, longer cirrus sac (including maximum length) and larger seminal receptacle (maximum diameter). There may also be a difference in the egg length (smaller in P. alaskensis n. sp.) (Table 2).

Paranoplocephala alaskensis n. sp. may be separated externally from P. nearctica n. sp. by its wider and shorter body and less elongated gravid proglottids. Other statistically significant differences concern the absolute and relative width of the suckers, relative width of the vitellarium and the position of the vitellarium (index of asymmetry; all smaller in P. alaskensis n. sp.) (Table 2).

Paranoplocephala alaskensis n. sp. differs from P. bairdi , P. fellmani , P. arctica and P. nordenskioeldi basically in the same way as P. n e a rc t i c a n. sp. (see above). In addition, P. bairdi has a longer body, more elongate gravid proglottids and smaller eggs, P. a rc t i c a has larger eggs, P. fellmani has smaller eggs, and P. nordenskioeldi a longer body than P. alaskensis n. sp.

Figures

FIGURE 5. Paranoplocephala alaskensis n. sp. from Microtus miurus, Alaska. A. Scolex. B, C. Mature proglottids. D. Early uterus. E. Pregravid uterus. F. Gravid proglottids. Scale-bars in mm.