Microcephaloides Haukisalmi, Hardman, Hardman, Rausch & Henttonen, 2008

Haukisalmi, Voitto, 2009, A taxonomic revision of the genus Anoplocephaloides Baer, 1923 sensu Rausch (1976), with the description of four new genera (Cestoda: Anoplocephalidae), Zootaxa 2057, pp. 1-31 : 9-10

Microcephaloides Haukisalmi, Hardman, Hardman, Rausch & Henttonen, 2008

(Fig. 2)

FIGURE. 2. Microcephaloides spp. A. Strobila of M. cf. variabilis from Microtus agrestis (scale-bar 5.0 mm). B. Scolex of M. cf. variabilis from Microtus agrestis (scale-bar 0.20 mm). C. Mature proglottis of M. cf. variabilis from M. oeconomus (scale-bar 0.30 mm). D, E. Development of uterus in M. variabilis from Thomomys talpoides (scale-bars 0.30 mm). F. Genital ducts and early uterus of M. variabilis from T. talpoides (scale-bar 0.10 mm).

Diagnosis: Strobila fairly short and slender. Scolex small. Suckers embedded in scolex, directed laterally or antero-laterally. Neck (unsegmented region) present. Proglottides craspedote, much wider than long. Velum straight or arched anteriorly. Genitalia single. Genital pores unilateral, positioned in middle of proglottis margin or slightly posteriorly. Genital atrium weak; genital papilla absent. Genital ducts cross osmoregulatory canals dorsally. Internal and external seminal vesicles present. Cirrus sac short, overlapping or barely extending across ventral longitudinal canal. Retractor muscle of cirrus sac absent. Testes arranged in single transverse group in antiporal part of proglottis, extending beyond antiporal ventral longitudinal canal. Ovary very large relative to proglottis size, more or less poral, sparsely lobed. Vagina short, not extending across ventral longitudinal canal; enters genital atrium ventral or postero-ventral to cirrus-sac. Early uterus transverse tube in anterior part of proglottis, with or without fenestrated extremities, ventral to testes, crossing longitudinal osmoregulatory canals ventrally and bilaterally; poral end terminates anterior to cirrus sac and external seminal vesicle or partly overlaps them. Fully developed (pregravid) uterus usually sparsely sacculated with wide anterior and posterior sacculi that are usually pressed against adjacent sacculi throughout their development; distinct transverse trunk absent. Female reproductive organs mature simultaneously with or slightly earlier than male organs; testes persist after resorption of female glands overlapping developing uterus. Pyriform apparatus present. Parasitic in geomyid (type hosts), cricetid ( Arvicolinae ) and spalacid rodents. Type-species: M. variabilis ( Douthitt, 1915) Haukisalmi, Hardman, Hardman, Rausch & Henttonen, 2008 ; cotypes USNPC 7375, 7408, 7410 and 49524–49531 from Geomys bursarius . Other species: M. neofibrinus (Rausch, 1952) n. comb. (syn. Paranoplocephala neofibrinus Rausch, 1952 ), M. mascomai ( Murai, Tenora & Rocamora, 1980) n. comb. (syn. Paranoplocephala mascomai Murai, Tenora & Rocamora, 1980 ), M. tenoramuraiae ( Genov & Georgiev, 1988) Haukisalmi, Hardman, Hardman, Rausch & Henttonen, 2008 (syn. Anoplocephaloides tenoramuraiae Genov & Georgiev, 1984 ), M. nevoi ( Fair, Schmidt & Wertheim, 1990) n. comb. (syn. Paranoplocephala nevoi Fair, Schmidt & Wertheim, 1990 ) and M. krebsi ( Haukisalmi, Wickström, Hantula & Henttonen, 2001) Haukisalmi, Hardman, Hardman, Rausch & Henttonen, 2008 (syn. Paranoplocephala krebsi Haukisalmi, Wickström, Hantula & Henttonen, 2001 ). Notice that M. variabilis -like cestodes include at least 6 more or less cryptic species, as determined by molecular methods ( Haukisalmi et al. 2008b).

Remarks. Microcephaloides differs unequivocally from all the other genera considered here with respect to the transverse, longitudinal and/or dorso-ventral position of the early uterus, except Anoplocephaloides , Paranoplocephaloides, Hokkaidocephala and Gallegoides (Table 2; see also Haukisalmi et al. 2008b). The differences between Microcephaloides and Anoplocephaloides have been evaluated above. Microcephaloides differs from Paranoplocephaloides by its wider body, laterally or antero-laterally directed suckers and unilateral genital pores. Microcephaloides differs from Hokkaidocephala primarily by the unique uterine development in the latter genus, but also by the smaller scolex and presence of a neck in the former genus. Gallegoides may be differentiated unambiguously from Microcephaloides by the distribution of the testes and alternation of the genital pores.

Microcephaloides neofibrinus differs from the congeneric species by its slightly larger scolex, slightly longer vagina and, perhaps, different type of fully developed (pregravid) uterus (approaching the “arborescent” type in M. neofibrinus ; cf. Figs. 8–11). However, none of these differences is striking, and because only a single, partly contracted specimen (the holotype) was available, M. neofibrinus is not separated as an independent genus. Microcephaloides nevoi differs from the congeneric species by having testes positioned antiporal and anterior to ovary (only antiporal to ovary in the other congeneric species), but this difference is not considered significant at the generic level (see below).

The monophyly of several M. variabilis -like species from Microtus -voles and M. krebsi from collared lemmings ( Dicrostonyx spp.) was confirmed by Haukisalmi et al. (2008b), However, there are yet no phylogenetic data for M. variabilis from the type host ( Geomys Rafinesque ), M. neofibrinus , M. tenoramuraiae , M. nevoi and M. mascomai .

Microcephaloides spp. inhabit the anterior small intestine (duodenum).