Beringitaenia

Beringitaenia n. g.

(Fig. 11)

Etymology. The name of the new genus refers to Beringia. Microtus miurus, the host of B. nanushukensis n. sp., is endemic to eastern Beringia (i.e. Alaska and adjacent regions in north-western North America). “ Beringitaenia ” is feminine.

Diagnosis. Strobila short. Scolex of intermediate dimensions. Suckers embedded within scolex, directed antero-laterally. Strobila distinctly craspedote. Proglottids prominently elongated transversely; length/width ratio ca. 0.11. Neck short and wide. Genital pores unilateral, opening at middle of lateral margin in mature proglottids. Genital ducts running between ventral and dorsal longitudinal osmoregulatory canals in holotype. Longitudinal osmoregulatory canals strongly arched. Testes distributed as single antiporal group; multiple testes extending across antiporal longitudinal canals. Median testes reach antiporal margin of vitellarium, overlapping ovary. Cirrus sac extending across longitudinal canals. Cirrus armed densely with prominent spines. Ovary transversely elongated, median, filling practically whole space between longitudinal canals. Vitellarium distinctly poral. Vagina shorter than cirrus sac. Seminal receptacle initially spherical, later subspherical or ovoid. Uterus appears as fine reticulum in anterior part of mature proglottids, extending beyond longitudinal canals ventrally. Fully developed (pregravid) uterus with irregular sacculations and internal trabeculae. In the singing vole, Microtus miurus (Cricetidae: Arvicolinae), in north-western North America (Alaska). Type species: B. nanushukensis n. sp.

Remarks. Beringitaenia (nanushukensis) is unique among Paranoplocephala -like cestodes because of its short body, distinctly poral vitellarium and prominently spined cirrus. The position of the genital ducts (between dorsal and ventral longitudinal canals) in also unique among Paranoplocephala spp. (dorsal to longitudinal canals in other species), but since this feature was based on a single specimen of B. nanushukensis (the holotype, with canals poorly visible in the paratype), it cannot be ruled out that it represents an aberrant condition. For morphological differences between Beringitaenia and related “wide-necked” genera, see the Remarks sections for Parandrya, Chionocestus and Microticola (above).

Beringitaenia (nanushukensis) had a divergent basal position in the strongly supported clade that also includes Diandrya composita (present only in the cox1 data) and Douthittia spp.