Arostrilepis janickii Makarikov & Kontrimavichus 2011

Arostrilepis cf. janickii Makarikov & Kontrimavichus, 2011

(Fig. 10)

Host in Nearctic: Microtus oeconomus Pallas.

Material examined: Vouchers include 3 specimens in M. oeconomus: MSB 1267 (field number AF 36025 C2) by A.M. Runck et al. near Nome, Alaska, Skookum River (64o43’11”N, 163o58’35”W), 20 July 2000. MSB 1268, 1269 (AF 36738 C2, C3) by A.M. Runck et al., on Seward Peninsula, Alaska, Pilgrim Hot Spring Road (65o05’09”N, 164o54’05”W), 1 August 2000. Sequence data for cyt- b are not currently available for these specimens from the Nearctic. See Appendix 1 for listing of additional identified voucher specimens from the Palearctic.

Description: Based on 3 specimens. Fully developed strobila about 115 mm long, with maximum width at pregravid or gravid proglottides, up to 1.9 mm. Scolex slightly compressed dorso-ventrally, 273 wide, clearly wider than neck. Suckers ovoid in surface view, 170–190 × 120–150 (184 × 134, n = 4), with thin walls, prominent (Fig. 10 A). Neck relatively long and narrow.

Genital ducts commonly pass dorsally to longitudinal osmoregulatory canals. Development of proglottides gradual, protandrous.

Mature proglottides 160–190 × 870–975 (177 × 913, n = 5), transversely elongate, trapeziform (Fig. 10 C). Testes usually 3 in number, almost of equal size, 113–135 × 70–90 (124 × 78, n = 7), oval or pear-shaped, commonly situated in triangle or rarely, testes form one row; poral testis separated from 2 antiporal testes by female gonads. Cirrus sac relatively short, 157–180 × 29–37 (167 × 32, n = 11), commonly extending across ventral longitudinal canal (Fig. 10 C). Genital atrium simple, cup-shaped, deep, opens laterally about middle of lateral proglottis margin. Cirrus small, 62–81 × 13–15 (69 × 13, n = 13), cylindrical, armed along entire length with relatively small (up to 3.5 long) rosethorn-shaped spines (Fig. 10 B). Internal seminal vesicle ovoid, 70–87 × 24–29 (80 × 25, n = 5), shorter than half of cirrus sac length (Fig. 10 C). External seminal vesicle 104–120 × 26–33 (114 × 29, n = 5), with size approximately equal to that of seminal receptacle.

Ovary 365–450 (405, n = 11) wide, median, fan-shaped, irregularly lobed, overlapping testes (Fig. 10 C). Vitellarium 67–90× 145–186 (77 × 162, n = 7), postovarian, median, scarcely lobed. Vagina tubular, clearly distinct from seminal receptacle; ventral to cirrus sac. Seminal receptacle relatively small, 97–114 × 27–36 (106 × 31, n = 5).

Gravid proglottides 340–390 × 1650–1900 (369 × 1802, n = 6). Fully developed uterus labyrinthine, occupying entire median field and extending bilaterally beyond longitudinal osmoregulatory canals. In present material outer coat of eggs very compressed, elliptical, with thin outer coat; oncosphere 10–11 × 14–16. Embryophore fusiform, 13–14 × 33–41, with straight polar processes. Embryonic hooks small, 6.5–7 long.

Remarks: Specimens attributed to A. cf. janickii are largely consistent with the original description, particularly with respect to the structure, dimensions and spination of the cirrus (based on a partial view), dimensions of the cirrus sac and distribution of the testes (Makarikov & Kontrimavichus 2011). The few available specimens from the western Seward Peninsula, however, could not be completely evaluated, as the cirrus was not fully evaginated in these cestodes, nor was sequence data available; this does not preclude the possibility of another undescribed species being represented. Confirmation will require additional specimens from which these characters may be assessed. Assuming a correct identification, based on the current data, specimens of A. janickii had not been previously reported in arvicolines from the Nearctic and these would be the first confirmed records from eastern Beringia. A minimum geographic distribution in Microtus from the western Seward Peninsula may be established. The species has not been found to the east in the Brooks Range or to the south where A. rauschorum appears to be common.