Cookiella n. g.

(Fig. 21)

Etymology. The name of the new genus refers to Joseph A. Cook, an expert in the phylogeny and historical biogeography of mammals. “ Cookiella ” is feminine.

Diagnosis. Strobila relatively long and wide. Scolex globular, distinctly demarcated from neck. Suckers embedded within scolex, directed antero-laterally. Neck long and narrow. Length/width ratio of mature proglottids ca. 28%. Proglottids craspedote, but velum short. Genital pores infrequently (and irregularly) alternating. Genital ducts pass dorsal to longitudinal osmoregulatory canals. Testes antiporal, anterior and slightly antero-poral to ovary, sometimes overlapping ventral longitudinal canals, but not extending beyond them on either side of proglottids. Testes mostly not overlapping ovary. Cirrus sac short and wide, not usually extending to ventral longitudinal canal. Vagina very short, less than half of cirrus sac length; covered by a prominent cell layer. Seminal receptacle long, elongated, with narrow distal “neck”. Ovary median, not extending to longitudinal canals. Vitellarium median with respect to ovary. Early uterus extensive, densely reticulated, overlapping ovary. In arvicoline rodents ( Cricetidae) of the genera Ondatra and Microtus in North America.

Type species: C. ondatrae (Rausch, 1948) n. comb.

Andrya ondatrae Rausch, 1948

Paranoplocephala ondatrae (Rausch, 1948) Tenora, Murai & Vaucher, 1985

Holotype of C. ondatrae: USNPC 46326.

Remarks. Cookiella ( ondatrae) is morphologically closely related to Rodentocestus, from which it differs mainly in the distribution of lateral testes (not extending beyond the ventral longitudinal canals in Cookiella). For morphological differences between Cookiella and Tenoraia, see the Remarks section for the latter genus.

Cookiella ondatrae was originally described (as Andrya ondatrae) from the muskrat ( Ondatra zibethicus) in Ohio, USA (Rausch 1948), based on a single cestode specimen. Haukisalmi et al. (2002) compared the holotype of A. ondatrae with morphologically related cestodes from Microtus spp. from North America, and concluded that they are probably conspecific. Because A. ondatrae has evidently not been found from the muskrat after Rausch (1948), it is probably a parasite of Microtus -voles, being able to infect sporadically also other arvicoline rodents. Cookiella ondatrae had an unresolved basal phylogenetic position in all sequence data sets.