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Bayesian phylogeny of Schizorchis based on concatenated rDNA and CYTB sequences.

Details regarding methods of genomic data collection from Schizorchis specimens and phylogenetic analyses.

Arostrilepis beringiensis (Kontrimavichus & Smirnova, 1991) Gulyaev & Chechulin, 1997 (Fig. 8) Syn.: Hymenolepis beringiensis Kontrimavichus & Smirnova, 1991. Hosts in Nearctic: Lemmus trimucronatus (Richardson) and Synaptomys borealis (Richardson). Localities in Nearctic: Alaska- Barrow, Arctic Coastal plain; Brooks Range; eastern Beringia, Yukon Charley Rivers National Preserve. Material examined: Vouchers include 4 specimens in Synaptomys borealis: MSB Para 1227, 1228, 1229 (field numbers AF 49480 / cyt- b sequence and 49480 A in Berlese’s; 49481 / cyt- b sequence , 2 specimens, multiple slides) by H. Henttonen et al., from the Yukon Charley Rivers National Preserve, Alaska across the Yukon River from Glen Creek Cabin (65 o 18 ’ 9 ”N, 142 o02’ 14 ”W), 8 August 2001; MSB 1233, 1234 (AF 61601 B, 61601 C, 2 specimens) by H. Henttonen et al., from Gates of the Arctic National Preserve, Brooks Range, Alaska on unnamed lake off Koyukuk River (67 o 21 ’ 11 ”N, 150 o 51 ’00”W), 23 July 2002. Palearctic specimens: MSB 1235 (LEM 229 a and 229 b, 2 specimens) ex Lemmus sibiricus by V. Fedorov and G. Jarrell on the northwestern Taymyr Peninsula, Russia (ca., 75 o 34 ’N, 94 o 29 ’E), 24–26 June 1994; the specimen from this series (designated as LEM 117 / cyt- b sequence ) from the northwest Taymyr was not available as a voucher. See Appendix 1 for listing of additional identified voucher specimens from the Nearctic and Palearctic. Description: Based on 5 specimens. Fully developed strobila 145–196 mm long, with maximum width at pregravid or gravid proglottides, 1.5–1.8 mm. Scolex slightly compressed dorso-ventrally, 255–285 (270, n = 2) wide, clearly wider than neck. Suckers ovoid in surface view, 160–250 × 110–188 (198 × 149, n = 6), with thick walls, prominent (Fig. 8 A). Neck relatively long and narrow, 160–175 (170, n = 2) wide. Dorsal osmoregulatory canals thin, 1–3 (2.1, n = 8) wide, situated predominantly in same sagittal plane as ventral canals. Ventral osmoregulatory canals 40–65 (54, n = 8) wide. Genital ducts may pass dorsally or between longitudinal osmoregulatory canals within same strobila; intersegmental variation without regularity. Development of proglottides gradual, protandrous. Mature proglottides 160–200 × 825–1120 (174 × 980, n = 12), transversely elongate, trapeziform (Fig. 8 C). Testes usually 3 in number, almost of equal size, 140–195 × 100–140 (168 × 116, n = 15), round or oval, commonly situated in triangle with flat angle or rarely, testes form one row; poral testis separated from 2 antiporal testes by female gonads. Cirrus sac relatively short, 108–127 × 23–32 (117 × 27, n = 10), antiporal part of cirrus-sac commonly does not reach ventral longitudinal canal (Fig. 8 C). Genital atrium simple, cup-shaped, deep, opens laterally about middle of lateral proglottis margin, or slightly more anteriorly. Cirrus small, 36–47 × 9–12 (41 × 10, n = 10), cylindrical; armed along entire length with relatively small (up to 2.5–2.7 long) rosethorn-shaped spines (Fig. 8 B). Internal seminal vesicle, ovoid, 50–73 × 18–26 (63 × 21, n = 10), shorter than half of cirrus sac length (Fig. 8 C). External seminal vesicle 90–135 × 45–65 (111 × 52, n = 8), with size approximately equal to that of seminal receptacle. Ovary 300–420 (365, n = 12) wide, median, fan-shaped, irregularly lobed, slightly overlapping testes (Fig. 8 C). Vitellarium 62–92 × 152–225 (73 × 176, n = 10), postovarian, median, scarcely lobed. Vagina tubular, clearly distinct from seminal receptacle; ventral to cirrus sac. Seminal receptacle relatively small, 87–115 × 30–40 (101 × 36, n = 5). Gravid proglottides 320–430 × 1300–1800 (366 × 1547, n = 8). Fully developed uterus labyrinthine, occupying entire median field and extending bilaterally beyond longitudinal osmoregulatory canals. Eggs 33–37 × 56–62, elliptical, with thin outer coat; oncosphere 12–15 × 18–21 (Fig. 8 D). Embryophore fusiform, 14–19 × 40–46, with straight polar processes. Embryonic hooks small, 7–8 long. Remarks: Results of the present morphological analysis of specimens of A. beringiensis do not indicate a high degree of differentiation between cestodes from the Nearctic and Palearctic currently isolated across the Bering Strait (Makarikov & Kontrimavichus 2011). We observed that in specimens of A. beringiensis from the Nearctic the dimensions of the eggs, embryophores and oncospheres are larger relative to those from the Palearctic. We assume that the differences in egg measurements of the specimens are associated with the methods of specimen preparation rather than with geographical divergence of two populations. Eggs of A. beringiensis from the Palearctic were mostly compressed because these specimens, stained in Ehrlich’s haematoxylin, had been mounted permanently in Canada balsam. In contrast, gravid proglottides of specimens from the Nearctic were mounted in Berlese’s medium and as a consequence the eggs were not influenced by compression. Otherwise specimens we examined representing populations of A. beringiensis in bog lemmings and Nearctic brown lemmings from North America and Siberian brown lemmings from Eurasia do not appear to be differentiated morphologically relative to host species or specific geographic localities (Makarikov & Kontrimavichus 2011). These are the first confirmed records of A. beringiensis in eastern Beringia and the Nearctic. Additionally, cestodes reported as H. horrida in L. trimucronatus (Nearctic brown lemming) from Okpilak River, Alaska (70 o08’N, 143 o 38 ’W) by Haukisalmi and Henttonen (2001) (USNPC 89245) and those from Barrow, Alaska by R.L. Rausch (RLR 29831) are referable to this species. At Siberian localities including Lopatka Peninsula, Taymyr Peninsula, New Siberian Islands, and Wrangel Island, we confirm the presence of A. beringiensis, and redetermine records and specimens (USNPC 89243 and 89244) attributed to H. horrida by Haukisalmi and Henttonen (2001) at these sites. In Eurasia most records refer to cestodes in L. sibiricus, although other species including L. amurensis Vinogradov from eastern Siberia between the Lena and Kolyma Rivers and on the New Siberian Archipelago and L. portenkoi Tchernyavsky on Wrangel Island may be represented as hosts of this species (see Musser & Carleton 2005). Arostrilepis beringiensis appears to be geographically widespread in lemmings (both Synaptomys and Lemmus) at high latitudes in North America and in lemmings of Eurasia, although an association with species of Dicrostonyx Gloger requires confirmation (E.P. Hoberg, K.E. Galbreath, unpublished data; Haukisalmi & Henttonen 2001; Makarikov & Kontrimavichus 2011). Specimens attributed to Hymenolepis horrida have been reported as common parasites in Nearctic collared lemmings (Dicrostonyx groenlandicus (Traill)) from near Barrow, Alaska (Kuns & Rausch 1950; Schiller 1952) and are also known in the Palearctic collared lemming (D. torquatus Pallas) from northern Eurasia (e.g. Ryzhikov et al. 1978); in either case, these specimens were not available for study. Interestingly, Dicrostonyx (tribe Dicrostonychini) is not considered phylogenetically close to the true lemmings (Lemmini) (reviewed in Musser & Carleton 2005), and these arvicolines may be derived from the earliest radiation of the subfamily linking Eurasia and North America and extending to 5–6 MYA (e.g. Conroy & Cook 1999). Such suggests that there is no particular basis to predict that the host distribution for A. beringiensis may extend to species of Dicrostonyx, unless it is present due to host colonization.

Arostrilepis cooki sp. n. (Figs. 4, 5) Type host: Myodes gapperi (Vigors) (Rodentia: Cricetidae: Arvicolinae). Other hosts: Currently unknown. Type locality: Near Meziadin Junction, British Columbia, Canada (56 o 21 ��� 55 ���N, 129 o 16 ��� 28 ���W). Other localities: Taft Creek, British Columbia (56 o 29 ��� 46 ���N, 129 o 25 ��� 31 ���W); near Bell II, British Columbia, south side Deltaic Creek (ca., 56 o 32 ��� 38 ���N, 129 o 32 ��� 39 ���W); Pattee Canyon, Missoula Co., Montana, USA (46 o 48 ���N, 113 o 57 ���W). Type material: Holotype MSB Para 1244 (field number IF 6750 / cyt- b sequence ) from type host and locality by A.M. Runck et al., 9 June 2003. Paratypes from type host species: MSB 1245 (IF 6751 / cyt- b sequence ) by A.M. Runck et al., at type locality, 9 June 2003; MSB 1249���1252 (IF 6830 C 2; 6830 C 3; 6830 C 4; 6830 C 6 / cyt- b sequence ) by A.M. Runck et al., at Taft Creek, British Columbia, 14 June 2003; MSB 1217 (JMK 02- 10), collected by J. M. Kinsella at Pattee Canyon, Montana, 10 October 2002; MSB 1246���1248 (IF 6827 C 1; 6827 C 2; 6827 C 3) by A. Runck et al., at Bell II, British Columbia, 14 June 2003. Symbiotype: Myodes gapperi (IF 6750) at type locality, skull and skeleton in MSB Mammalogy Division. Description: Based on 8 specimens. Fully developed strobila up to 150 mm long, with maximum width at postmature or pregravid gravid proglottides, 1.25���1.4 mm. Strobila flat, consisting of about 850 craspedote proglottides. Scolex slightly compressed dorso-ventrally, 280���372 (324, n = 4) wide, clearly wider than neck. Suckers unarmed, ovoid in surface view, 162���238 �� 124���195 (190 �� 161, n = 8), with thin walls, prominent (Fig. 4 A, B). Rhynchus and rostellar apparatus absent. Neck relatively long and narrow, 160���200 (178, n = 8) wide. Two pairs of osmoregulatory canals, without transverse anastomoses. Dorsal osmoregulatory canals thin, 0.5���2 (1.2, n = 10) wide, situated predominantly in same sagittal plane as ventral canals. Ventral osmoregulatory canals 30���65 (44, n = 15) wide. Position of dorsal osmoregulatory canals not always constant; loops may be situated laterally to ventral canals. Genital pores unilateral, dextral. Genital ducts usually pass dorsally to longitudinal osmoregulatory canals, position of genital ducts between osmoregulatory canals within single strobila appears rarely (Fig. 4 C, D). Development of proglottides gradual, protandrous. Strobilar part containing juvenile proglottides without external segmentation; proglottides become externally distinct at level of premature part of strobila. Mature proglottides 120���275 �� 680���1040 (198 �� 785, n = 12), transversely elongate, trapeziform (Fig. 4 C, D). Testes relatively large, usually three in number, almost of equal size, 115���175 �� 85���125 (135 �� 96, n = 25), round or oval, commonly situated in triangle; poral testis separated from two antiporal testes by female gonads. Arrangement of testes may vary (from triangle with flat angle to linear). Cirrus-sac relatively short, 190���218 �� 35���48 (205 �� 42, n = 15), with well-developed external muscular layers, commonly extends across ventral longitudinal canal (Figs. 4 D, 5 C). Genital atrium simple, infundibular, deep, opens laterally about middle or slightly anterior of lateral proglottis margin. Cirrus 88���109 (98, n = 16) long, conical, with relatively wide basal region, 19���24 (21, n = 16) in diameter, and narrow distal region, 8���14 (11, n = 16) in diameter; armed along entire length with relatively large (up to 3.3���4 long) rosethorn-shaped spines (Fig. 5 A). Internal seminal vesicle with circular musculature, ovoid, 85���120 �� 28���40 (95 �� 33, n = 15), shorter than half of cirrus-sac length (Figs. 4 D, 5 C). External seminal vesicle transversely elongate, 117���171 �� 65���103 (151 �� 78, n = 15), clearly outlined from vas deferens, slightly larger than seminal receptacle. Ovary 305���410 (329, n = 20) wide, median, fan-shaped, irregularly lobed, ventral to male genital organs, occupying substantial part of median field, slightly overlapping testes (Fig. 4 D). Vitellarium 60���117 �� 115���172 (91 �� 153, n = 20), postovarian, median, scarcely lobed. Vagina tubular, clearly distinct from seminal receptacle; ventral to cirrus-sac. Distal part of vagina 92���111 �� 9���19 (100 �� 13, n = 10), thick-walled, covered externally by dense layer of intensely stained cells; proximal part of vagina infundibular (Fig. 5 C). Conductive part of vagina 110���132 �� 10���27 (122 �� 17, n = 10), thin-walled, vastly varying in diameter depending on degree of distention with sperm. Seminal receptacle relatively small, transversely elongate, 80���122 �� 40���77 (100 �� 51, n = 14). Uterus appears as complex of fine-walled anastomosing tubes of varying length and diameter, positioned ventrally to other organs. With development of proglottides, tubular structures increase in width and uterus becomes labyrinthine. Testes remain in postmature and pregravid proglottides; cirrus-sac and vagina persist in gravid proglottides. Gravid proglottides transversely elongate, 185���360 �� 810���1330 (261 �� 1107, n = 10). Fully developed uterus labyrinthine, occupying entire median field, extending bilaterally beyond longitudinal osmoregulatory canals (Fig. 5 D). Uterus contains numerous (up to 1100) eggs. Eggs 31���38 �� 58���72, elliptic, with thin outer coat (Fig. 5 B); oncosphere 13���17 �� 18���23. Embryophore fusiform, 17���20 �� 40���48, with straight polar processes. Embryonic hooks small, 7.5���8.3 long. Etymology: This species has been named in honor of Joseph A. Cook in recognition of contributions in understanding rodent systematics and biogeography, and innovative explorations of host-parasite associations among arvicoline rodents. Remarks: Arostrilepis cooki sp. n. is distinguished from congeners by the length and shape of the cirrus (Table 2). In specimens of A. cooki the cirrus is longer in comparison to A. beringiensis, A. microtis, A. tenuicirrosa, A. gulyaevi, A. mariettavogeae and A. schilleri. The cirrus is armed with relatively large rosethornshaped spines and has a conical form; these features distinguish A. cooki from A. beringiensis, A. intermedia, A. janickii and A. schilleri, which have cylindrical cirri, and from A. microtis, A. tenuicirrosa and A. gulyaevi, in which the cirri have a conical basal region and cylindrical distal region. Compared to A. cooki, the cirrus of A. tenuicirrosa is armed with relatively small needle-shaped spines. The form and the length of the cirrus of A. cooki are most similar to those of A. macrocirrosa, but in specimens of the former the cirrus is narrower in the basal region (Figs. 11, 12). Arostrilepis cooki is characterized by a relatively narrow strobila. The cirrus-sac is shorter than that in A. horrida and A. microtis but larger than in A. beringiensis, A. janickii, A. mariettavogeae and A. schilleri. The ovary is narrower relative to those in A. horrida, A. microtis and A. gulyaevi. The scolex and the suckers are larger in comparison to A. janickii. The egg and oncosphere are large relative to those in A. horrida, A. microtis and A. janickii (see Table 2). The proximal end of the cirrus-sac in hermaphroditic mature proglottides overlaps the ventral longitudinal osmoregulatory canal. This species can be distinguished from A. beringiensis as its testes are arranged in a triangle; in the latter species, the testes form a flat angle or are situated in one row. Similarly, the testes form one row in A. microtis and A. mariettavogeae. Furthermore, the external seminal vesicle is larger than the seminal receptacle, the gravid proglottides are transversely elongate, and the polar processes of the embryophore are straight in A. cooki. This species is a specific parasite of red-backed voles (Myodes) from North America., Published as part of Makarikov, Arseny A., Galbreath, Kurt E. & Hoberg, Eric P., 2013, Parasite diversity at the Holarctic nexus: species of Arostrilepis (Eucestoda: Hymenolepididae) in voles and lemmings (Cricetidae: Arvicolinae) from greater Beringia, pp. 401-439 in Zootaxa 3608 (6) on pages 412-414, DOI: 10.11646/zootaxa.3608.6.1, http://zenodo.org/record/216055

Arostrilepis cooki sp. n. (Figs. 4, 5) Type host: Myodes gapperi (Vigors) (Rodentia: Cricetidae: Arvicolinae). Other hosts: Currently unknown. Type locality: Near Meziadin Junction, British Columbia, Canada (56 o 21 ’ 55 ”N, 129 o 16 ’ 28 ”W). Other localities: Taft Creek, British Columbia (56 o 29 ’ 46 ”N, 129 o 25 ’ 31 ”W); near Bell II, British Columbia, south side Deltaic Creek (ca., 56 o 32 ’ 38 ”N, 129 o 32 ’ 39 ”W); Pattee Canyon, Missoula Co., Montana, USA (46 o 48 ’N, 113 o 57 ’W). Type material: Holotype MSB Para 1244 (field number IF 6750 / cyt- b sequence ) from type host and locality by A.M. Runck et al., 9 June 2003. Paratypes from type host species: MSB 1245 (IF 6751 / cyt- b sequence ) by A.M. Runck et al., at type locality, 9 June 2003; MSB 1249–1252 (IF 6830 C 2; 6830 C 3; 6830 C 4; 6830 C 6 / cyt- b sequence ) by A.M. Runck et al., at Taft Creek, British Columbia, 14 June 2003; MSB 1217 (JMK 02- 10), collected by J. M. Kinsella at Pattee Canyon, Montana, 10 October 2002; MSB 1246–1248 (IF 6827 C 1; 6827 C 2; 6827 C 3) by A. Runck et al., at Bell II, British Columbia, 14 June 2003. Symbiotype: Myodes gapperi (IF 6750) at type locality, skull and skeleton in MSB Mammalogy Division. Description: Based on 8 specimens. Fully developed strobila up to 150 mm long, with maximum width at postmature or pregravid gravid proglottides, 1.25–1.4 mm. Strobila flat, consisting of about 850 craspedote proglottides. Scolex slightly compressed dorso-ventrally, 280–372 (324, n = 4) wide, clearly wider than neck. Suckers unarmed, ovoid in surface view, 162–238 × 124–195 (190 × 161, n = 8), with thin walls, prominent (Fig. 4 A, B). Rhynchus and rostellar apparatus absent. Neck relatively long and narrow, 160–200 (178, n = 8) wide. Two pairs of osmoregulatory canals, without transverse anastomoses. Dorsal osmoregulatory canals thin, 0.5–2 (1.2, n = 10) wide, situated predominantly in same sagittal plane as ventral canals. Ventral osmoregulatory canals 30–65 (44, n = 15) wide. Position of dorsal osmoregulatory canals not always constant; loops may be situated laterally to ventral canals. Genital pores unilateral, dextral. Genital ducts usually pass dorsally to longitudinal osmoregulatory canals, position of genital ducts between osmoregulatory canals within single strobila appears rarely (Fig. 4 C, D). Development of proglottides gradual, protandrous. Strobilar part containing juvenile proglottides without external segmentation; proglottides become externally distinct at level of premature part of strobila. Mature proglottides 120–275 × 680–1040 (198 × 785, n = 12), transversely elongate, trapeziform (Fig. 4 C, D). Testes relatively large, usually three in number, almost of equal size, 115–175 × 85–125 (135 × 96, n = 25), round or oval, commonly situated in triangle; poral testis separated from two antiporal testes by female gonads. Arrangement of testes may vary (from triangle with flat angle to linear). Cirrus-sac relatively short, 190–218 × 35–48 (205 × 42, n = 15), with well-developed external muscular layers, commonly extends across ventral longitudinal canal (Figs. 4 D, 5 C). Genital atrium simple, infundibular, deep, opens laterally about middle or slightly anterior of lateral proglottis margin. Cirrus 88–109 (98, n = 16) long, conical, with relatively wide basal region, 19–24 (21, n = 16) in diameter, and narrow distal region, 8–14 (11, n = 16) in diameter; armed along entire length with relatively large (up to 3.3–4 long) rosethorn-shaped spines (Fig. 5 A). Internal seminal vesicle with circular musculature, ovoid, 85–120 × 28–40 (95 × 33, n = 15), shorter than half of cirrus-sac length (Figs. 4 D, 5 C). External seminal vesicle transversely elongate, 117–171 × 65–103 (151 × 78, n = 15), clearly outlined from vas deferens, slightly larger than seminal receptacle. Ovary 305–410 (329, n = 20) wide, median, fan-shaped, irregularly lobed, ventral to male genital organs, occupying substantial part of median field, slightly overlapping testes (Fig. 4 D). Vitellarium 60–117 × 115–172 (91 × 153, n = 20), postovarian, median, scarcely lobed. Vagina tubular, clearly distinct from seminal receptacle; ventral to cirrus-sac. Distal part of vagina 92–111 × 9–19 (100 × 13, n = 10), thick-walled, covered externally by dense layer of intensely stained cells; proximal part of vagina infundibular (Fig. 5 C). Conductive part of vagina 110–132 × 10–27 (122 × 17, n = 10), thin-walled, vastly varying in diameter depending on degree of distention with sperm. Seminal receptacle relatively small, transversely elongate, 80–122 × 40–77 (100 × 51, n = 14). Uterus appears as complex of fine-walled anastomosing tubes of varying length and diameter, positioned ventrally to other organs. With development of proglottides, tubular structures increase in width and uterus becomes labyrinthine. Testes remain in postmature and pregravid proglottides; cirrus-sac and vagina persist in gravid proglottides. Gravid proglottides transversely elongate, 185–360 × 810–1330 (261 × 1107, n = 10). Fully developed uterus labyrinthine, occupying entire median field, extending bilaterally beyond longitudinal osmoregulatory canals (Fig. 5 D). Uterus contains numerous (up to 1100) eggs. Eggs 31–38 × 58–72, elliptic, with thin outer coat (Fig. 5 B); oncosphere 13–17 × 18–23. Embryophore fusiform, 17–20 × 40–48, with straight polar processes. Embryonic hooks small, 7.5–8.3 long. Etymology: This species has been named in honor of Joseph A. Cook in recognition of contributions in understanding rodent systematics and biogeography, and innovative explorations of host-parasite associations among arvicoline rodents. Remarks: Arostrilepis cooki sp. n. is distinguished from congeners by the length and shape of the cirrus (Table 2). In specimens of A. cooki the cirrus is longer in comparison to A. beringiensis, A. microtis, A. tenuicirrosa, A. gulyaevi, A. mariettavogeae and A. schilleri. The cirrus is armed with relatively large rosethornshaped spines and has a conical form; these features distinguish A. cooki from A. beringiensis, A. intermedia, A. janickii and A. schilleri, which have cylindrical cirri, and from A. microtis, A. tenuicirrosa and A. gulyaevi, in which the cirri have a conical basal region and cylindrical distal region. Compared to A. cooki, the cirrus of A. tenuicirrosa is armed with relatively small needle-shaped spines. The form and the length of the cirrus of A. cooki are most similar to those of A. macrocirrosa, but in specimens of the former the cirrus is narrower in the basal region (Figs. 11, 12). Arostrilepis cooki is characterized by a relatively narrow strobila. The cirrus-sac is shorter than that in A. horrida and A. microtis but larger than in A. beringiensis, A. janickii, A. mariettavogeae and A. schilleri. The ovary is narrower relative to those in A. horrida, A. microtis and A. gulyaevi. The scolex and the suckers are larger in comparison to A. janickii. The egg and oncosphere are large relative to those in A. horrida, A. microtis and A. janickii (see Table 2). The proximal end of the cirrus-sac in hermaphroditic mature proglottides overlaps the ventral longitudinal osmoregulatory canal. This species can be distinguished from A. beringiensis as its testes are arranged in a triangle; in the latter species, the testes form a flat angle or are situated in one row. Similarly, the testes form one row in A. microtis and A. mariettavogeae. Furthermore, the external seminal vesicle is larger than the seminal receptacle, the gravid proglottides are transversely elongate, and the polar processes of the embryophore are straight in A. cooki. This species is a specific parasite of red-backed voles (Myodes) from North America.

Arostrilepis gulyaevi sp. n. (Figs. 2, 3) Type host: Myodes rufocanus (Sundevall) (Rodentia: Cricetidae: Arvicolinae). Other hosts: Rarely Microtus oeconomus Pallas. Type locality: Bol'shekhekhtsirskiy Nature Reserve, Khabarovskiy Kray, Russia (ca., 48 �� 16 ���N, 134 �� 45 ���E). Other localities: Baikal Nature Reserve, Republic of Buryatia, Russia (ca., 51 o 21 ���N, 105 o 17 ���E); Anadyr, Chukotka Autonomous Okrug, Russia, 1 km SE of confluence of Markova and Anadyr Rivers (64 o 40 ��� 57 ���N, 170 o 26 ��� 26 ���E); Buyunda River, Magadanskaya Oblast���, Russia (62 o 20 ���N, 153 o 21 ���E); Chaun Biological Field Station, Chaun River, Chukotka Autonomous Okrug, Russia (69 o00���N, 170 o 50 ���E). Type material: Holotype ISEA No. 18.28. 8.1 from type host and locality by Y. Melnikova, 18 July 2003. Paratypes from type locality and type host species: MSB Para 1262 (ISEA No.18.28.8.4) by Y. Melnikova, 17 July 2003; ISEA No. 18.28. 8.7 by Y. Melnikova, 18 July 2003; No. 18.28. 8.8 by Y. Melnikova, 21 July 2003; and No. 18.28. 8.10 by Y. Melnikova, 21 July 2003. Paratypes from other localities: MSB Para 1263 (field number RLR 43095) in type host species by L. Smirnova at Chaun Biological Field Station, 16 July 1975; MSB 1259, 1261 (IF 5657 / cyt- b sequence ; 5657 C 1) in type host species by A. Lahzuhtkin and K.E. Galbreath at Buyunda River, Russia, 4 July 2002; MSB 1253, 1254 (IF 5079 C 1 / cyt- b sequence ; 5079 C 2) in type host species, by N.E. Dokuchaev at Anadyr, Russia, 23 July 2002; and MSB 1256 (IF 5094 / cyt- b sequence ) in type host species by N.E. Dokuchaev at Anadyr, Russia, 24 July 2002. See Appendix 1 for additional identified vouchers in M. rufocanus and Microtus oeconomus from the Baikal Reserve and Magadanskaya Oblast���. Symbiotype: Type host specimen not deposited in a museum archive. Description: Based on 10 specimens. Fully developed strobila 180���300 mm long, with maximum width at postmature or pregravid gravid proglottides, 1.9���3.4 mm. Strobila flat, consisting of 900���1500 craspedote proglottides. Scolex slightly compressed dorso-ventrally, 250���350 (292, n = 6) wide, clearly wider than neck. Suckers unarmed, ovoid in surface view, 177���253 �� 135���185 (221 �� 153, n = 12), with thin walls, prominent (Fig. 2 A, B). Rhynchus and rostellar apparatus absent. Neck relatively long and narrow, 137���185 (154, n = 8) wide. Two pairs of osmoregulatory canals, without transverse anastomoses. Dorsal osmoregulatory canals thin, 0.5���1.5 (0.9, n = 15) wide, situated predominantly in same sagittal plane as ventral canals. Ventral osmoregulatory canals 60���170 (117, n = 15) wide. Position of dorsal osmoregulatory canals not always constant; loops may be situated laterally to ventral canals. Genital pores unilateral, dextral. Genital ducts may pass dorsally or between longitudinal osmoregulatory canals within single strobila; intersegmental variation not showing regularity (Fig. 2 C, D). Development of proglottides gradual, protandrous. Strobilar part containing juvenile proglottides without external segmentation; proglottides become externally distinct at level of premature part of strobila. Mature proglottides 215���300 �� 1350���2030 (248 �� 1619, n = 10), transversely elongate, trapeziform (Fig. 2 C, D). Testes relatively large, usually three in number, almost of equal size, 173���375 �� 95���216 (238 �� 144, n = 20), oval or pear-shaped, commonly situated in triangle; poral testis separated from two antiporal testes by female gonads. Arrangement of testes may vary (from triangle with flat angle to linear). Cirrus-sac relatively short, 192���235 �� 32���45 (206 �� 39, n = 20), with well-developed external muscular layers (Figs. 2 D, 3 C). Proximal part of cirrus-sac commonly not reaching or rarely overlapping ventral longitudinal canal or rarely overlapping. Genital atrium simple, infundibular, deep, opens laterally about middle or slightly anterior of lateral proglottis margin. Cirrus 53���72 (64, n = 28) long, conical, with relatively wide basal region, 16���24 (19, n = 28) in diameter, and narrow distal region, 9���15 (12, n = 28) wide; armed along entire length with relatively large (up to 4���4.5 long) rosethorn-shaped spines (Fig. 3 A). Internal seminal vesicle with circular musculature, ovoid, 85���120 �� 27���35 (103 �� 31, n = 18), shorter than half of cirrus-sac length (Figs. 2 D, 3 C). External seminal vesicle transversely elongate, 195���390 �� 55���84 (266 �� 69, n = 16), clearly outlined from vas deferens, slightly larger than seminal receptacle or with size approximately equal to that of seminal receptacle. Ovary 575���715 (633, n = 17) wide, median, fan-shaped, irregularly lobed, ventral to male genital organs, occupying a substantial part of median field, slightly overlapping testes (Fig. 2 D). Vitellarium 100���142 �� 215���386 (111 �� 283, n = 17), postovarian, median, scarcely lobed. Vagina tubular, not clearly distinct from seminal receptacle; ventral to cirrus-sac. Distal part of vagina 62���92 �� 7���16 (73 �� 10, n = 15), thick-walled, covered externally by dense layer of intensely stained cells; proximal part of vagina infundibular (Fig. 3 C). Conductive part of vagina 255���320 �� 9���35 (290 �� 19, n = 10), thin-walled, vastly varying in diameter depending on degree of distention with sperm. Seminal receptacle relatively small, transversely elongate, 150���340 �� 30���80 (198 �� 60, n = 14). Uterus appears as complex of fine-walled anastomosing tubes of varying length and diameter, positioned ventrally to other organs (Fig. 3 D). With development of proglottides, tubular structures increase in width and uterus becomes labyrinthine. Uterus may pass dorsally or between longitudinal osmoregulatory canals within same strobila; intersegmental variation does not show any regularity. Testes remain in postmature and pregravid proglottides; cirrus-sac and vagina persist in the gravid proglottides. Gravid proglottides transversely elongate, 340���540 �� 1700���3410 (466 �� 2343, n = 10). Fully developed uterus labyrinthine, occupying entire median field, extending bilaterally beyond longitudinal osmoregulatory canals (Fig. 3 E). Uterus contains numerous (up to 3000) eggs. Eggs 30���37 �� 58���68, elliptic, with thin outer coat (Fig. 3 B); oncosphere 13���15 �� 16���19. Embryophore fusiform, 16���20 �� 40���49, with straight polar processes. Embryonic hooks small, 7.2���8 long. Etymology: The name of this species has been dedicated to the memory of Vladimir D. Gulyaev, in recognition of his critical studies on hymenolepidid cestodes of rodents and faunistic explorations in central Siberia. Remarks: Arostrilepis gulyaevi sp. n. is distinguished from 9 recognized congeners by the length and shape of the cirrus (Table 2). In specimens of A. gulyaevi the cirrus is shorter relative to those in A. horrida, A. macrocirrosa, A. microtis and A. intermedia, but longer in comparison to A. beringiensis and A. mariettavogeae. In A. gulyaevi the length and form of the cirrus is similar to those in A. tenuicirrosa and A. microtis: the cirrus with conical basal region and cylindrical distal region, this species can be distinguished from A. tenuicirrosa as its cirrus is twice as wide as that of A. tenuicirrosa and armed with relatively large rosethorn-shaped spines; in the latter species, the cirrus is armed with relatively small needle-shaped spines (Figs. 11, 12). Arostrilepis gulyaevi is characterized by a relatively wide strobila and ovary (Table 2). The proximal end of the cirrus-sac in hermaphroditic mature proglottides commonly does not reach the ventral longitudinal canal or rarely overlaps it. This species can additionally be distinguished from A. beringiensis as its testes are arranged in a triangle; in the latter species, the testes form a flat angle or are situated in one row. Similarly, the testes form one row in A. microtis and A. mariettavogeae. Furthermore, the gravid proglottides are transversely elongate and the polar processes of the embryophore are straight in A. gulyaevi. This species is a specific parasite of red-backed voles (Myodes) from the eastern Palearctic region., Published as part of Makarikov, Arseny A., Galbreath, Kurt E. & Hoberg, Eric P., 2013, Parasite diversity at the Holarctic nexus: species of Arostrilepis (Eucestoda: Hymenolepididae) in voles and lemmings (Cricetidae: Arvicolinae) from greater Beringia, pp. 401-439 in Zootaxa 3608 (6) on pages 409-412, DOI: 10.11646/zootaxa.3608.6.1, http://zenodo.org/record/216055

Arostrilepis beringiensis (Kontrimavichus & Smirnova, 1991) Gulyaev & Chechulin, 1997 (Fig. 8) Syn.: Hymenolepis beringiensis Kontrimavichus & Smirnova, 1991. Hosts in Nearctic: Lemmus trimucronatus (Richardson) and Synaptomys borealis (Richardson). Localities in Nearctic: Alaska- Barrow, Arctic Coastal plain; Brooks Range; eastern Beringia, Yukon Charley Rivers National Preserve. Material examined: Vouchers include 4 specimens in Synaptomys borealis: MSB Para 1227, 1228, 1229 (field numbers AF 49480 / cyt- b sequence and 49480 A in Berlese���s; 49481 / cyt- b sequence , 2 specimens, multiple slides) by H. Henttonen et al., from the Yukon Charley Rivers National Preserve, Alaska across the Yukon River from Glen Creek Cabin (65 o 18 ��� 9 ���N, 142 o02��� 14 ���W), 8 August 2001; MSB 1233, 1234 (AF 61601 B, 61601 C, 2 specimens) by H. Henttonen et al., from Gates of the Arctic National Preserve, Brooks Range, Alaska on unnamed lake off Koyukuk River (67 o 21 ��� 11 ���N, 150 o 51 ���00���W), 23 July 2002. Palearctic specimens: MSB 1235 (LEM 229 a and 229 b, 2 specimens) ex Lemmus sibiricus by V. Fedorov and G. Jarrell on the northwestern Taymyr Peninsula, Russia (ca., 75 o 34 ���N, 94 o 29 ���E), 24���26 June 1994; the specimen from this series (designated as LEM 117 / cyt- b sequence ) from the northwest Taymyr was not available as a voucher. See Appendix 1 for listing of additional identified voucher specimens from the Nearctic and Palearctic. Description: Based on 5 specimens. Fully developed strobila 145���196 mm long, with maximum width at pregravid or gravid proglottides, 1.5���1.8 mm. Scolex slightly compressed dorso-ventrally, 255���285 (270, n = 2) wide, clearly wider than neck. Suckers ovoid in surface view, 160���250 �� 110���188 (198 �� 149, n = 6), with thick walls, prominent (Fig. 8 A). Neck relatively long and narrow, 160���175 (170, n = 2) wide. Dorsal osmoregulatory canals thin, 1���3 (2.1, n = 8) wide, situated predominantly in same sagittal plane as ventral canals. Ventral osmoregulatory canals 40���65 (54, n = 8) wide. Genital ducts may pass dorsally or between longitudinal osmoregulatory canals within same strobila; intersegmental variation without regularity. Development of proglottides gradual, protandrous. Mature proglottides 160���200 �� 825���1120 (174 �� 980, n = 12), transversely elongate, trapeziform (Fig. 8 C). Testes usually 3 in number, almost of equal size, 140���195 �� 100���140 (168 �� 116, n = 15), round or oval, commonly situated in triangle with flat angle or rarely, testes form one row; poral testis separated from 2 antiporal testes by female gonads. Cirrus sac relatively short, 108���127 �� 23���32 (117 �� 27, n = 10), antiporal part of cirrus-sac commonly does not reach ventral longitudinal canal (Fig. 8 C). Genital atrium simple, cup-shaped, deep, opens laterally about middle of lateral proglottis margin, or slightly more anteriorly. Cirrus small, 36���47 �� 9���12 (41 �� 10, n = 10), cylindrical; armed along entire length with relatively small (up to 2.5���2.7 long) rosethorn-shaped spines (Fig. 8 B). Internal seminal vesicle, ovoid, 50���73 �� 18���26 (63 �� 21, n = 10), shorter than half of cirrus sac length (Fig. 8 C). External seminal vesicle 90���135 �� 45���65 (111 �� 52, n = 8), with size approximately equal to that of seminal receptacle. Ovary 300���420 (365, n = 12) wide, median, fan-shaped, irregularly lobed, slightly overlapping testes (Fig. 8 C). Vitellarium 62���92 �� 152���225 (73 �� 176, n = 10), postovarian, median, scarcely lobed. Vagina tubular, clearly distinct from seminal receptacle; ventral to cirrus sac. Seminal receptacle relatively small, 87���115 �� 30���40 (101 �� 36, n = 5). Gravid proglottides 320���430 �� 1300���1800 (366 �� 1547, n = 8). Fully developed uterus labyrinthine, occupying entire median field and extending bilaterally beyond longitudinal osmoregulatory canals. Eggs 33���37 �� 56���62, elliptical, with thin outer coat; oncosphere 12���15 �� 18���21 (Fig. 8 D). Embryophore fusiform, 14���19 �� 40���46, with straight polar processes. Embryonic hooks small, 7���8 long. Remarks: Results of the present morphological analysis of specimens of A. beringiensis do not indicate a high degree of differentiation between cestodes from the Nearctic and Palearctic currently isolated across the Bering Strait (Makarikov & Kontrimavichus 2011). We observed that in specimens of A. beringiensis from the Nearctic the dimensions of the eggs, embryophores and oncospheres are larger relative to those from the Palearctic. We assume that the differences in egg measurements of the specimens are associated with the methods of specimen preparation rather than with geographical divergence of two populations. Eggs of A. beringiensis from the Palearctic were mostly compressed because these specimens, stained in Ehrlich���s haematoxylin, had been mounted permanently in Canada balsam. In contrast, gravid proglottides of specimens from the Nearctic were mounted in Berlese���s medium and as a consequence the eggs were not influenced by compression. Otherwise specimens we examined representing populations of A. beringiensis in bog lemmings and Nearctic brown lemmings from North America and Siberian brown lemmings from Eurasia do not appear to be differentiated morphologically relative to host species or specific geographic localities (Makarikov & Kontrimavichus 2011). These are the first confirmed records of A. beringiensis in eastern Beringia and the Nearctic. Additionally, cestodes reported as H. horrida in L. trimucronatus (Nearctic brown lemming) from Okpilak River, Alaska (70 o08���N, 143 o 38 ���W) by Haukisalmi and Henttonen (2001) (USNPC 89245) and those from Barrow, Alaska by R.L. Rausch (RLR 29831) are referable to this species. At Siberian localities including Lopatka Peninsula, Taymyr Peninsula, New Siberian Islands, and Wrangel Island, we confirm the presence of A. beringiensis, and redetermine records and specimens (USNPC 89243 and 89244) attributed to H. horrida by Haukisalmi and Henttonen (2001) at these sites. In Eurasia most records refer to cestodes in L. sibiricus, although other species including L. amurensis Vinogradov from eastern Siberia between the Lena and Kolyma Rivers and on the New Siberian Archipelago and L. portenkoi Tchernyavsky on Wrangel Island may be represented as hosts of this species (see Musser & Carleton 2005). Arostrilepis beringiensis appears to be geographically widespread in lemmings (both Synaptomys and Lemmus) at high latitudes in North America and in lemmings of Eurasia, although an association with species of Dicrostonyx Gloger requires confirmation (E.P. Hoberg, K.E. Galbreath, unpublished data; Haukisalmi & Henttonen 2001; Makarikov & Kontrimavichus 2011). Specimens attributed to Hymenolepis horrida have been reported as common parasites in Nearctic collared lemmings (Dicrostonyx groenlandicus (Traill)) from near Barrow, Alaska (Kuns & Rausch 1950; Schiller 1952) and are also known in the Palearctic collared lemming (D. torquatus Pallas) from northern Eurasia (e.g. Ryzhikov et al. 1978); in either case, these specimens were not available for study. Interestingly, Dicrostonyx (tribe Dicrostonychini) is not considered phylogenetically close to the true lemmings (Lemmini) (reviewed in Musser & Carleton 2005), and these arvicolines may be derived from the earliest radiation of the subfamily linking Eurasia and North America and extending to 5���6 MYA (e.g. Conroy & Cook 1999). Such suggests that there is no particular basis to predict that the host distribution for A. beringiensis may extend to species of Dicrostonyx, unless it is present due to host colonization., Published as part of Makarikov, Arseny A., Galbreath, Kurt E. & Hoberg, Eric P., 2013, Parasite diversity at the Holarctic nexus: species of Arostrilepis (Eucestoda: Hymenolepididae) in voles and lemmings (Cricetidae: Arvicolinae) from greater Beringia, pp. 401-439 in Zootaxa 3608 (6) on pages 419-422, DOI: 10.11646/zootaxa.3608.6.1, http://zenodo.org/record/216055

Arostrilepis macrocirrosa Makarikov, Gulyaev & Kontrimavichus, 2011 (Fig. 9) Hosts in Nearctic: Myodes rutilus (Pallas); rarely Microtus xanthognathus (Leach), Microtus pennsylvanicus (Ord) and Tamiasciurus hudsonicus (Erxleben). Localities in Nearctic: Alaska - N Central region, SE region; Seward Peninsula (Bering Landbridge National Preserve); Brooks Range (Kobuk Valley National Park, Noatak National Preserve); Wrangell-St Elias National Preserve; Yukon Charley Rivers National Preserve; and Lake Clark National Park, northern Alaska Peninsula. Material examined: Vouchers include 4 specimens in Myodes rutilus: MSB 1306 (field number- AF 55147, 2 slides/ cyt- b sequence ) by E.P. Hoberg et al., at Braye Lakes in the Wrangell-St. Elias National Preserve, Alaska (62 o01��� 52 ���N, 141 o07��� 46 ���W), 26 July 2001; MSB 1285 (AF 37468, 2 slides) by H. Henttonen near Bonanza Creek Research Station, Alaska (62 o 42 ���N, 148 o 16 ���W), 1 August 2000; MSB 1302, 1303 (AF 49374, 1A and 1 B, 3 slides/ cyt- b sequence ) by H. Henttonen et al., from Yukon Charley Rivers National Preserve, Alaska, NW of Mt. Kathryn on Yukon River, S of Woodchopper (65 o 12 ��� 16 ���N, 143 o 34 ��� 22 ���W), 3 August 2001; MSB 1307 (AF 55196, 2 slides) by E.P. Hoberg et al., at Rex Creek, northwestern slope of Mt. Holmes in the Wrangell-St. Elias National Preserve, Alaska (61 o 18 ��� 37 ���N, 142 o 30 ��� 56 ���W), 30 July 2001; MSB 1304 (AF 49977) ex Tamiasciurus hudsonicus by H. Henttonen et al., from the Yukon Charley Rivers National Preserve, Alaska at Glenn Creek Cabin (65 o 18 ���07���N., 142 o05��� 23 ���W), 12 August 2001; MSB 1351 (RLR 15515, 2 slides) ex T. hudsonicus by R.L. Rausch near Chitina, Alaska (31.6 miles west on highway), 8 October 1955. Palearctic specimens: MSB 1221 (H- 15 / cyt- b sequence ) ex M. rutilus, by A. Lavikainen, on the Tunguska River, Irkutsk Oblast���, Russia (59 o06��� 36 ���N, 108 o 23 ��� 54 ���E), 8 August 2003. See Appendix 1 for listing of additional identified voucher specimens from the Nearctic and Palearctic. Description: Based on 4 specimens. Fully developed strobila 145���196 mm long, with maximum width at pregravid or gravid proglottides, 0.9���1.3 mm. Scolex slightly compressed dorso-ventrally, 275���385 (321, n = 3) wide, clearly wider than neck. Suckers ovoid in surface view, 162���210 �� 130���191 (182 �� 162, n = 8), with thick walls, prominent (Fig. 9 A). Neck relatively long and narrow, 130���185 (157, n = 3) wide. Dorsal osmoregulatory canals thin, 1���2.5 (1.7, n = 10) wide, situated predominantly in same sagittal plane as ventral canals. Ventral osmoregulatory canals 35���70 (53, n = 10) wide. Genital ducts may pass dorsally or between longitudinal osmoregulatory canals within same strobila; intersegmental variation without regularity. Development of proglottides gradual, protandrous. Mature proglottides 167���240 �� 670���980 (205 �� 825, n = 15), transversely elongate, trapeziform (Fig. 9 C). Testes usually 3 in number, almost of equal size, 125���210 �� 90���132 (161 �� 107, n = 15), round or oval, commonly situated in triangle; poral testis separated from 2 antiporal testes by female gonads. Cirrus sac relatively large, 208���245 �� 39���48 (229 �� 43, n = 15), commonly overlapping ventral longitudinal canal (Fig. 9 C). Genital atrium simple, cup-shaped, deep, opens laterally about middle of lateral proglottis margin. Cirrus large, 95���123 (106, n = 20) long, conical, with relatively wide basal region, 27���34 (30, n = 20) in diameter, and narrow distal region, 17���24 (19, n = 20) wide; armed along entire length with relatively small (up to 4 long) rosethorn-shaped spines (Fig. 9 B). Internal seminal vesicle, ovoid, 86���113 �� 30���40 (101 �� 36, n = 15), shorter than half of cirrus sac length (Fig. 9 C). External seminal vesicle 88���145 �� 35���72 (115 �� 53, n = 8), with size approximately equal to that of seminal receptacle. Ovary 270���395 (342, n = 10) wide, median, fan-shaped, irregularly lobed, slightly overlapping testes (Fig. 9 C). Vitellarium 70���115 �� 140���195 (92 �� 167, n = 8), postovarian, median, scarcely lobed. Vagina tubular, clearly distinct from seminal receptacle; ventral to cirrus sac. Distal part of vagina 105���112 �� 15���25 (107 �� 19, n = 8), thick-walled. Seminal receptacle relatively small, 135���155 �� 18���33 (147 �� 72, n = 8). Gravid proglottides 490���611 �� 815���1240 (552 �� 987, n = 10). Fully developed uterus labyrinthine, occupying entire median field and extending bilaterally beyond longitudinal osmoregulatory canals. Eggs 23���26 �� 38���43, elliptical, with thin outer coat; oncosphere 11���13 �� 14���15 (Fig. 9 D). Embryophore fusiform, 12���15 �� 23���26, with straight polar processes. Embryonic hooks small, 7.5���8.2 long. Remarks: Results of the present morphological analysis of specimens of A. macrocirrosa do not indicate a high degree of differentiation between cestode populations from the Nearctic and the Palearctic now isolated by the Bering Strait. Similar to observations in A. beringiensis, we noted differences in egg dimensions between conspecific cestodes in the Nearctic and Palearctic (Makarikov et al. 2011). We attribute these minor differences to methods of specimen preparation and mounting medium. Otherwise, specimens we examined representing populations of A. macrocirrosa in red backed voles and limited numbers of cestodes in red squirrels across the Holarctic do not appear to be differentiated morphologically relative to specific geographic localities (Makarikov et al. 2011). These constitute the first confirmed geographic records for A. macrocirrosa from eastern Beringia and the Nearctic. Arostrilepis macrocirrosa is a dominant cestode of Myodes voles at high latitudes across the Holarctic. Occurrence in other arvicolines and sciurids appear to represent incidental infections; A. macrocirrosa in red squirrels from Alaska is known based on multiple hosts and specimens collected at the Yukon Charley Rivers National Preserve, Lake Clark National Park and near Chitina (Appendix 1). Records in Myodes voles are currently limited to M. rutilus from North America, and further collections will be necessary to determine if there is a broader geographic range extending to temperate latitudes in the Nearctic. It is not known if A. macrocirrosa and A. cooki are parapatric and restricted to different species of Myodes, or whether populations of these cestodes occur in sympatry., Published as part of Makarikov, Arseny A., Galbreath, Kurt E. & Hoberg, Eric P., 2013, Parasite diversity at the Holarctic nexus: species of Arostrilepis (Eucestoda: Hymenolepididae) in voles and lemmings (Cricetidae: Arvicolinae) from greater Beringia, pp. 401-439 in Zootaxa 3608 (6) on pages 422-423, DOI: 10.11646/zootaxa.3608.6.1, http://zenodo.org/record/216055

Arostrilepis rauschorum sp. n. (Figs. 6, 7) Type host: Microtus oeconomus Pallas (Rodentia: Cricetidae: Arvicolinae). Other hosts: Microtus longicaudus (Merriam), M. pennsylvanicus (Ord), M. miurus Osgood and M. xanthognathus (Leach). Type locality: Adjacent toToolik Lake, Brooks Range, Alaska, near US Department of Energy research site (ca., 68 o 38 ���N, 149 o 36 ���W). Other localities: North-central interior, Alaska, near Bonanza Creek Research Station (62 o 42 ���N, 148 o 16 ���W); Gates of Arctic National Preserve, Brooks Range, Alaska, SE side of Walker Lake (67 o06���N, 154 o 16 ���W); Yukon Charley Rivers National Preserve, Alaska, across Yukon River from Glenn Creek Cabin (65 o 30 ���N, 142 o03���W); Kobuk Valley National Park, Alaska, Baird Mountains, Salmon River (67 o 36 ��� 11 ���N, 159 o 47 ��� 20 ���W); and Pattee Canyon, Missoula Co., Montana (46 o 48 ���N, 113 o 57 ���W, and 46 o 49 ���N, 113 o 58 ���W). Type material: Holotype MSB Para 1208 (field number FIN 4072484) from type host and locality by H. Henttonen and G. Batzli, 24 July 1984. Paratypes MSB1360, 1362 (AF 37462 C 1 / cyt- b sequence ; 37462 C 3) ex M. pennsylvanicus, by H. Henttonen at Bonanza Creek, 1 August 2000; MSB 1204 (FIN 2070784) from type host species and locality by H. Henttonen and G. Batzli, 7 July 1984; MSB 1211 (FIN 5220884) from type host species and locality by H. Henttonen and G. Batzli, 22 August 1984; MSB 1205, 1206 (FIN 3120884 -1, 2 slides; 3120884 - 2) from type host species and locality by H. Henttonen and G. Batzli, 12 August 1984; MSB 1363 (AF 42531 / cytb sequence ) from type host and locality by H. Henttonen, 8 August 2000; MSB 1365 (AF 42657) ex M. oeconomus by H. Henttonen et al., near Toolik Lake, 8 August 2000; MSB 1215 (JMK 02-04) ex M. longicaudus, by J.M. Kinsella at Pattee Canyon, Montana (46 o 48 ���N, 113 o 57 ���W), 8 October 2002; MSB 1369 (AF 49499 / cyt- b sequence ) ex M. longicaudus by H. Henttonen et al., from Yukon Charley, 8 August 2001; MSB 1370, 1371 (AF 59099 C3, 2 slides; 59099 C4, 2 slides) ex M. xanthognathus by A. M. Runck et al., from Gates of the Arctic National Preserve, 6 August 2002; and MSB 1216 (JMK 2009, 2 slides) ex M. pennsylvanicus, by J.M. Kinsella at Pattee Canyon, Montana (46 o 49 ���N, 113 o 58 ���W), 20 August 2009. See Appendix 1 for listing of additional identified voucher specimens. Symbiotype: Host specimen not deposited in a museum archive. Description: Based on 13 specimens. Fully developed strobila 120���185 mm long, with maximum width at pregravid or gravid proglottides, 2.4���3.8 mm. Strobila flat, consisting of 750���950 craspedote proglottides. Scolex slightly compressed dorso-ventrally, 240���300 (266, n = 7) wide, clearly wider than neck. Suckers unarmed, ovoid in surface view, relatively small, 130���190 �� 120���155 (166 �� 137, n = 15), with thin walls (Fig. 6 A, B). Rhynchus and rostellar apparatus absent. Neck relatively long and narrow, 125���190 (152, n = 10) wide. Two pairs of osmoregulatory canals, without transverse anastomoses. Dorsal osmoregulatory canals thin, 2���3.5 (2.6, n = 10) wide, situated predominantly in same sagittal plane as ventral canals. Ventral osmoregulatory canals 30���58 (42, n = 10) wide. Position of dorsal osmoregulatory canals not always constant; loops may be situated laterally to ventral canals. Genital pores unilateral, dextral. Genital ducts usually pass dorsally to longitudinal osmoregulatory canals, position of genital ducts between osmoregulatory canals within same strobila appears rarely (for no more than 10 % proglottides) (Fig. 6 C, D). Development of proglottides gradual, protandrous. Strobilar part containing juvenile proglottides without external segmentation; proglottides become externally distinct at level of premature part of strobila. Mature proglottides 170���230 �� 1330���1700 (202 �� 1485, n = 16), transversely elongate, trapeziform (Fig. 6 C, D). Testes relatively large, usually three in number, almost of equal size, 130���252 �� 110���194 (217 �� 164, n = 35), oval or pear-shaped, commonly situated in one row; poral testis separated from two antiporal testes by female gonads. Arrangement of testes may vary (triangle or triangle with flat angle). Cirrus-sac relatively large, 210���242 �� 31���42 (225 �� 37, n = 23), with well-developed external muscular layers. Antiporal part of cirrus-sac commonly not reaching or rarely overlapping ventral longitudinal canal (Figs. 6 D, 7 C). Genital atrium simple, cup-shaped, deep, opens laterally about middle or slightly anterior of lateral proglottis margin. Cirrus 77���92 (83, n = 18) long, conical, with relatively wide basal region, 18���23 (19, n = 18) in diameter, and narrow distal region, 12���15 (13, n = 18) in diameter; armed along entire length with relatively large (up to 3.5���4 long) rosethorn-shaped spines (Fig. 7 A). Internal seminal vesicle with circular musculature, ovoid, 87���122 �� 25���38 (102 �� 30, n = 23), shorter than half of cirrus-sac length (Figs. 6 D, 7 C). External seminal vesicle transversely elongate, 165���270 �� 55���87 (218 �� 70, n = 18), clearly outlined from vas deferens, with size approximately equal to seminal receptacle. Ovary 455���585 (537, n = 25) wide, median, fan-shaped, irregularly lobed, ventral to male genital organs, occupying substantial part of median field, slightly overlapping testes (Fig. 6 D). Vitellarium 75���123 �� 145���240 (96 �� 193, n = 25), postovarian, median, scarcely lobed. Vagina tubular, clearly distinct from seminal receptacle; ventral to cirrus-sac. Distal part of vagina 96���120 �� 8���18 (107 �� 13, n = 12), thick-walled, covered externally by dense layer of intensely stained cells; poral part of vagina infundibular (Fig. 7 C). Conductive part of vagina 170���230 �� 9���30 (210 �� 19, n = 10), thin-walled, vastly varying in diameter depending on degree of distention with sperm. Seminal receptacle relatively small, transversely elongate, 165���280 �� 50���92 (220 �� 68, n = 18). Uterus appears as complex of fine-walled anastomosing tubes of varying length and diameter, positioned ventrally to other organs. With development of proglottides, tubular structures increase in width and uterus becomes labyrinthine. Testes remain in postmature and pregravid proglottides; cirrus-sac and vagina persist in gravid proglottides. Gravid proglottides transversely elongate, 300���500 �� 1750���3800 (373 �� 2600, n = 16). Fully developed uterus labyrinthine, occupying entire median field and extending bilaterally beyond longitudinal osmoregulatory canals (Fig. 7 D). Uterus contains numerous (up to 2100) eggs. Eggs 22���35 �� 50���68, elliptical, with thin outer coat (up to 0.5); oncosphere 11���17 �� 15���22 (Fig. 7 B). Embryophore fusiform, 14���20 �� 38���47, with straight polar processes. Embryonic hooks small, 7.5���8.3 long. Etymology: Arostrilepis rauschorum sp. n. is named in honor of Robert L. Rausch and Virginia R. Rausch in recognition of their seminal and critical studies of parasites of arvicoline rodents, rodent systematics and biogeography at high latitudes of the Holarctic, and insights about the historical development of the Beringian fauna. Further, with the passing of Robert Rausch on 6 October 2012, this species and our recent studies across Beringia are dedicated to his memory and the legacy established by an extraordinary pioneer of parasitology and mammalogy in the north. Remarks: Arostrilepis rauschorum sp. n. is distinguished from congeners by the length and shape of the cirrus (Table 2). In A. rauschorum the cirrus is longer relative to those in A. beringiensis, A. tenuicirrosa, A. mariettavogeae, A. schilleri and A. gulyaevi, but smaller in comparison to A. macrocirrosa and A. cooki (Figs. 11, 12). The cirrus is armed with relatively large rosethorn-shaped spines and has a conical form; these features distinguish A. rauschorum from A. beringiensis, A. intermedia, A. janickii and A. schilleri (cylindrical cirrus), A. microtis and A. gulyaevi (cirrus with wide conical basal region and a cylindrical distal region) and A. tenuicirrosa (cirrus armed with relatively small needle-shaped spines and having a conical basal region and a very narrow cylindrical distal region). Arostrilepis rauschorum is characterized by a relatively wide strobila and ovary and a large seminal receptacle. The cirrus-sac is shorter than in A. horrida, but longer than in A. beringiensis, A. intermedia, A. janickii, A. mariettavogeae and A. schilleri. The egg and oncosphere are large relative to those in A. janickii, A. mariettavogeae and A. schilleri (see Table 2). The proximal end of the cirrus-sac in hermaphroditic mature proglottides commonly does not reach the ventral longitudinal canal or rarely overlaps it. Specimens of A. rauschorum are distinguished from A. horrida, A. macrocirrosa, A. tenuicirrosa, A. intermedia, A. schilleri, A. gulyaevi and A. cooki as its testes form one row; in the latter species, the testes are arranged in a triangle. Furthermore, the gravid proglottides are transversely elongate and the polar processes of the embryophore are straight in A. rauschorum. This species is a specific parasite of voles of the genus Microtus from North America., Published as part of Makarikov, Arseny A., Galbreath, Kurt E. & Hoberg, Eric P., 2013, Parasite diversity at the Holarctic nexus: species of Arostrilepis (Eucestoda: Hymenolepididae) in voles and lemmings (Cricetidae: Arvicolinae) from greater Beringia, pp. 401-439 in Zootaxa 3608 (6) on pages 416-419, DOI: 10.11646/zootaxa.3608.6.1, http://zenodo.org/record/216055

Makarikov, Arseny A., Galbreath, Kurt E., Hoberg, Eric P. (2013): Parasite diversity at the Holarctic nexus: species of Arostrilepis (Eucestoda: Hymenolepididae) in voles and lemmings (Cricetidae: Arvicolinae) from greater Beringia. Zootaxa 3608 (6): 401-439, DOI: http://dx.doi.org/10.11646/zootaxa.3608.6.1

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 C 2) by A.M. Runck et al. near Nome, Alaska, Skookum River (64 o 43 ��� 11 ���N, 163 o 58 ��� 35 ���W), 20 July 2000. MSB 1268, 1269 (AF 36738 C 2, C 3) by A.M. Runck et al., on Seward Peninsula, Alaska, Pilgrim Hot Spring Road (65 o05���09���N, 164 o 54 ���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., Published as part of Makarikov, Arseny A., Galbreath, Kurt E. & Hoberg, Eric P., 2013, Parasite diversity at the Holarctic nexus: species of Arostrilepis (Eucestoda: Hymenolepididae) in voles and lemmings (Cricetidae: Arvicolinae) from greater Beringia, pp. 401-439 in Zootaxa 3608 (6) on page 424, DOI: 10.11646/zootaxa.3608.6.1, http://zenodo.org/record/216055

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 C 2) by A.M. Runck et al. near Nome, Alaska, Skookum River (64 o 43 ’ 11 ”N, 163 o 58 ’ 35 ”W), 20 July 2000. MSB 1268, 1269 (AF 36738 C 2, C 3) by A.M. Runck et al., on Seward Peninsula, Alaska, Pilgrim Hot Spring Road (65 o05’09”N, 164 o 54 ’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.

Arostrilepis macrocirrosa Makarikov, Gulyaev & Kontrimavichus, 2011 (Fig. 9) Hosts in Nearctic: Myodes rutilus (Pallas); rarely Microtus xanthognathus (Leach), Microtus pennsylvanicus (Ord) and Tamiasciurus hudsonicus (Erxleben). Localities in Nearctic: Alaska - N Central region, SE region; Seward Peninsula (Bering Landbridge National Preserve); Brooks Range (Kobuk Valley National Park, Noatak National Preserve); Wrangell-St Elias National Preserve; Yukon Charley Rivers National Preserve; and Lake Clark National Park, northern Alaska Peninsula. Material examined: Vouchers include 4 specimens in Myodes rutilus: MSB 1306 (field number- AF 55147, 2 slides/ cyt- b sequence ) by E.P. Hoberg et al., at Braye Lakes in the Wrangell-St. Elias National Preserve, Alaska (62 o01’ 52 ”N, 141 o07’ 46 ”W), 26 July 2001; MSB 1285 (AF 37468, 2 slides) by H. Henttonen near Bonanza Creek Research Station, Alaska (62 o 42 ’N, 148 o 16 ’W), 1 August 2000; MSB 1302, 1303 (AF 49374, 1A and 1 B, 3 slides/ cyt- b sequence ) by H. Henttonen et al., from Yukon Charley Rivers National Preserve, Alaska, NW of Mt. Kathryn on Yukon River, S of Woodchopper (65 o 12 ’ 16 ”N, 143 o 34 ’ 22 ”W), 3 August 2001; MSB 1307 (AF 55196, 2 slides) by E.P. Hoberg et al., at Rex Creek, northwestern slope of Mt. Holmes in the Wrangell-St. Elias National Preserve, Alaska (61 o 18 ’ 37 ”N, 142 o 30 ’ 56 ”W), 30 July 2001; MSB 1304 (AF 49977) ex Tamiasciurus hudsonicus by H. Henttonen et al., from the Yukon Charley Rivers National Preserve, Alaska at Glenn Creek Cabin (65 o 18 ’07”N., 142 o05’ 23 ”W), 12 August 2001; MSB 1351 (RLR 15515, 2 slides) ex T. hudsonicus by R.L. Rausch near Chitina, Alaska (31.6 miles west on highway), 8 October 1955. Palearctic specimens: MSB 1221 (H- 15 / cyt- b sequence ) ex M. rutilus, by A. Lavikainen, on the Tunguska River, Irkutsk Oblast’, Russia (59 o06’ 36 ”N, 108 o 23 ’ 54 ”E), 8 August 2003. See Appendix 1 for listing of additional identified voucher specimens from the Nearctic and Palearctic. Description: Based on 4 specimens. Fully developed strobila 145–196 mm long, with maximum width at pregravid or gravid proglottides, 0.9–1.3 mm. Scolex slightly compressed dorso-ventrally, 275–385 (321, n = 3) wide, clearly wider than neck. Suckers ovoid in surface view, 162–210 × 130–191 (182 × 162, n = 8), with thick walls, prominent (Fig. 9 A). Neck relatively long and narrow, 130–185 (157, n = 3) wide. Dorsal osmoregulatory canals thin, 1–2.5 (1.7, n = 10) wide, situated predominantly in same sagittal plane as ventral canals. Ventral osmoregulatory canals 35–70 (53, n = 10) wide. Genital ducts may pass dorsally or between longitudinal osmoregulatory canals within same strobila; intersegmental variation without regularity. Development of proglottides gradual, protandrous. Mature proglottides 167–240 × 670–980 (205 × 825, n = 15), transversely elongate, trapeziform (Fig. 9 C). Testes usually 3 in number, almost of equal size, 125–210 × 90–132 (161 × 107, n = 15), round or oval, commonly situated in triangle; poral testis separated from 2 antiporal testes by female gonads. Cirrus sac relatively large, 208–245 × 39–48 (229 × 43, n = 15), commonly overlapping ventral longitudinal canal (Fig. 9 C). Genital atrium simple, cup-shaped, deep, opens laterally about middle of lateral proglottis margin. Cirrus large, 95–123 (106, n = 20) long, conical, with relatively wide basal region, 27–34 (30, n = 20) in diameter, and narrow distal region, 17–24 (19, n = 20) wide; armed along entire length with relatively small (up to 4 long) rosethorn-shaped spines (Fig. 9 B). Internal seminal vesicle, ovoid, 86–113 × 30–40 (101 × 36, n = 15), shorter than half of cirrus sac length (Fig. 9 C). External seminal vesicle 88–145 × 35–72 (115 × 53, n = 8), with size approximately equal to that of seminal receptacle. Ovary 270–395 (342, n = 10) wide, median, fan-shaped, irregularly lobed, slightly overlapping testes (Fig. 9 C). Vitellarium 70–115 × 140–195 (92 × 167, n = 8), postovarian, median, scarcely lobed. Vagina tubular, clearly distinct from seminal receptacle; ventral to cirrus sac. Distal part of vagina 105–112 × 15–25 (107 × 19, n = 8), thick-walled. Seminal receptacle relatively small, 135–155 × 18–33 (147 × 72, n = 8). Gravid proglottides 490–611 × 815–1240 (552 × 987, n = 10). Fully developed uterus labyrinthine, occupying entire median field and extending bilaterally beyond longitudinal osmoregulatory canals. Eggs 23–26 × 38–43, elliptical, with thin outer coat; oncosphere 11–13 × 14–15 (Fig. 9 D). Embryophore fusiform, 12–15 × 23–26, with straight polar processes. Embryonic hooks small, 7.5–8.2 long. Remarks: Results of the present morphological analysis of specimens of A. macrocirrosa do not indicate a high degree of differentiation between cestode populations from the Nearctic and the Palearctic now isolated by the Bering Strait. Similar to observations in A. beringiensis, we noted differences in egg dimensions between conspecific cestodes in the Nearctic and Palearctic (Makarikov et al. 2011). We attribute these minor differences to methods of specimen preparation and mounting medium. Otherwise, specimens we examined representing populations of A. macrocirrosa in red backed voles and limited numbers of cestodes in red squirrels across the Holarctic do not appear to be differentiated morphologically relative to specific geographic localities (Makarikov et al. 2011). These constitute the first confirmed geographic records for A. macrocirrosa from eastern Beringia and the Nearctic. Arostrilepis macrocirrosa is a dominant cestode of Myodes voles at high latitudes across the Holarctic. Occurrence in other arvicolines and sciurids appear to represent incidental infections; A. macrocirrosa in red squirrels from Alaska is known based on multiple hosts and specimens collected at the Yukon Charley Rivers National Preserve, Lake Clark National Park and near Chitina (Appendix 1). Records in Myodes voles are currently limited to M. rutilus from North America, and further collections will be necessary to determine if there is a broader geographic range extending to temperate latitudes in the Nearctic. It is not known if A. macrocirrosa and A. cooki are parapatric and restricted to different species of Myodes, or whether populations of these cestodes occur in sympatry.