| abstract | The genus Myonyssus Tiraboschi, contains at present 9 species, including the new species herein described. The geographical distribution of this genus seems to be quite wide. In this country there are two species, namely, M. shibatai and the new species, namely, M. ochotonae described in the present paper.
Bregetova considered M. shibatai Asanuma as synonymous with M. dubinini Bregetova, but Strandtmann & Wharton regarded them as separate species. As we have examined a large number of specimens of both sexes of M. shibatai from Microtus maximoviczii Schrenck, Clethrionomys rutilus Pallas and C. rufocanus Sundevall in the province of Heilungkiang and the Inner Mongolia, and compared carefully with the classical descriptions of both M. shibatai and M. dubinini and found that in M. dubinini Bregetova, the enlarged portion of the genitoventral plate is broadly rounded and its setae are arranged irregularly, while in M. shibatai Asanuma, it is rectangular in shape and the setae are regularly arranged. All of the dorsal setae in the male of M. dubinini Bregetova appear minute but in M. shibatai Asanuma, basing upon our specimens, the 7th and 8th pairs of dorsal setae are long, especially those of the latter pair. Based upon the above mentioned characteristics, the two species can easily be distinguished one from each other. We therefore agree that they represent two distinct species.
Myonyssus ochotonae, sp. nov.
Female (figs. 1-3): Idiosoma 761-800µ long, 450-480µ wide, oval, with distinct shoulders. Dorsal plate bearing 38 pairs of setae, of which 11 pairs are marginal. In some specimens, the sixth marginal pair often wanting and also the fourth marginal pair unsymmetrical on either side. The third pair of intermedial setae (I3) wanting. Four pairs of sensory rounded spots on the plate.
Sternal plate broad and strong, convex between the first pair of sternal setae (St1), hind margin slightly concave; with three pairs of sternal setae (St1-St3) subequa1 in length and three pairs of slit-like pores, the third one being outside of the plate. Genito-ventral plate flask-shaped, expanded far behind coxae IV, bearing seven pairs of setae and a single seta at the center. Anal plate broad and large, concave anteriorly, about 124µ long, 156µ wide lateral and posterior margins convex. Adanal setae long, reaching to the end of anal plate and situated at a little in front of the horizontal level of center of anus. Postanal seta long, and thick. Metapodal plate usually elliptical in form but variable. Peritremal plate reaching anteriorly usually to the front of coxae I; peritremalia connected with stigma on the basal end and produced posteriorly to the inner margin of coxae IV, with its tip expanded and with a slit-like pore at the center of the latter. Naked portion of venter usually with 15-17 pairs of linear setae.
Legs stout and strong. On the anterior margin of femur I bears two long setae and with a prominent dorsal spur on coxa II.
Gnathosoma broad, about 102.5µ in width. Chelae narrow, tapering apically, the movable chela much broader than the fixed one.
Male (figs. 4-5): Idiosoma 650-690µ long, 430-450µ wide. Dorsal plate also bearing setae as those in female, but usually much longer and thicker.
Holoventral plate complete and narrow. Genital opening rounded and located at the center of convex anterior margin, flanked by the first anterior sternal setae; the plate bearing 14 pairs, plus one postanal and one median unpaired setae, first five anterior pairs of setae long and subequal in length, others being shorter, except the postanal; the lateral margins of holoventral plate slightly expanded and mildly tapering posteriorly. Adanal setae long, often reaching beyond the posterior end; approximately 15-18 pairs of setae on the naked portion of the venter. Metapodal plate elliptical in form. Peritremal plate reaching forward in front of coxae I; peritremalia around over the hind margin of coxae IV and reaching to the lateral side of the holoventral plate.
Legs gross and strong. Tarsus II & III bearing a highly chitinized process on apices.
The base of gnathosoma about 92.5µ in width. Chelae narrow, and long, the movable chela broad at base and graduall tapering anteriorly, the fixed chela narrow and pointed apically.
Holotype (♀), allotype(♂) and paratypes (1♂ 15♀♀), all collected from Ochotona thibetana Milne-Edwards from May to August, 1960, from Hupeh Province, China.
The type specimens are preserved in the Institute of Epidemiology and Microbiology, the Chinese Academy of Medical Sciences, Peking.
This species is very closely related to M. montanus Furman & Tipton but differs from the latter by possessing a different form of anal plate in the female, in the length of adanal setae and in the form of the holoventral plate in the male. |