Sperchon (Palpisperchon) nikkoensis Imamura, 1976

Zhang, Xu & Jin, Dao-Chao, 2011, New records of water mites of the family Sperchontidae Thor, 1900 from China (Acari, Hydrachnidia), with descriptions of two new species, ZooKeys 158, pp. 89-109 : 91-93

Sperchon (Palpisperchon) nikkoensis Imamura, 1976 Figures 110

Material examined.

2 females, Hainan Province, Bawangling National Nature Reserve, an unnamed stream (19°07'16"N, 109°04'58"E), 15 August 2005, coll. Xu Zhang; 1 male and 2 females, Guizhou Province, Leigongshan National Nature Reserve, an unnamed stream (26°21'06"N, 108°12'39"E), 3 October 2005, coll. Xu Zhang; 2 males and 2 females, Anhui Province, Jinzhai city, Shuanghe country, an unnamed stream (31°36'37"N, 115°41'30"E), 19 July 2010, coll. Xu Zhang; 1 female, Anhui Province, Anqing city, Mingtangshan scenic area, Hulu River (30°51'19"N, 116°06'06"E), 20 August 2010, coll. Xu Zhang.

Description.

Male (n = 3): Idiosoma flat, 730 (730-768) in length, 583 (583-616) in width, color yellow-brown. Cuticle soft and covered with small flat papillae and fine striations in various form and size (Fig. 3). Dorsum without chitinous plate, only two pair of muscular sigillae faintlyvisible. Each glandularia on dorsum and venter encircled by a plate and raised conically as nipples. The anterior dorsal area before A1 protruded dorsally forward and leaf-shaped with a vein-like line in dorsal view. Coxae in four groups, surface of coxae reticulated. ACG 210 (210-218) in length, close to each other but not fused, posterior apodeme indistinct. E2 laterally between ACG and PCG; PCG 213 (213-230) in length, widely separated. Glandularia absent from CxIII. Distance between anterior end of ACG and posterior end of PCG 438 (438-451). Genital field between CxIV of PCG with a small and rounded platelet in front. Genital valves not covering the genital acetabula, 143 (143-152) in length, 135 (135-140) in width. Three pairs of acetabula, the anterior two elliptic and the posterior more or less rounded. Cuticle with fine striations between the genital organ and coxal groups. V1 without accompanying glandularia but on small sclerites. Excretory pore surrounded by a sclerotized ring and close to the line of V2.

Infracapitulum with a short rostrum, length 292 (292-236). Chelicera total length 352 (352-387), basal segment length 283(283-308), claw length 69 (69-79), basal segment/claw length ratio 4.1 (3.9-4.1). Palp short and thick. Dorsal lengths of the palpal segments: P-I, 35 (35-37); P-II, 114 (114-121); P-III, 48 (48-53); P-IV, 89 (89-98); P-V, 52 (52-59). P-I stout and without seta. P-II thick with a long ventro-distal projection, bearing three setae, one of which nearly at the base of the projection and slightly longer than projection, the other two relatively short located approximately on the middle of projection. Nine seta on the dorsal and lateral side of the P-II. P-III shorter than P-II, with a long and thin ventrodistal seta and three short dorsal setae. P-IV with two greatly enlarged ventral peg-like setae, close to each other.

Dorsal lengths of leg I: I-L-1, 39 (39-48); I-L-2, 72 (72-81); I-L-3, 83 (83-97); I-L-4, 137 (137-151); I-L-5, 156 (156-171); I-L-6, 127 (127-141). Dorsal lengths of leg IV: IV-L-1, 88 (88-97); IV-L-2, 95 (95-110); IV-L-3, 129 (129-145); IV-L-4, 237 (237-255); IV-L-5, 220 (220-236); IV-L-6, 192 (192-208). Ambulacrum with two claws. Claws with well protruded claw-blade and two clawets, a long dorsal and a shorter ventral one (Fig. 8).

Female (n = 3): Similar to male except for the morphology of genital field and the size of idiosoma. Idiosoma 816 (792-857) in length, 688 (643-712) in width. ACG 310 (302-317) in length, PCG 319 (308-336) in length. Distance between anterior end of ACG and posterior end of PCG 606 (587-624). Genital field 234 (226-242) in length, 215 (208-229) in width. Pregenital sclerite crescent-shaped, and more developed than the postgenital sclerite. Infracapitulum length 301 (290-316). Chelicera total length 381 (364-409), basal segment length 308 (293-328), claw length 73 (71-80), basal segment/claw length ratio 4.2 (4.1-4.2). Dorsal lengths of the palpal segments: P-I, 41 (40-47); P-II, 123 (119-128); P-III, 57 (55-62); P-IV, 94 (89-99); P-V, 57 (55-64). Dorsal lengths of the first leg: I-L-1, 54 (52-62); I-L-2, 80 (78-92); I-L-3, 103 (99-116); I-L-4, 157 (149-176); I-L-5, 179 (168-194); I-L-6, 111 (106-120). Dorsal lengths of the fourth leg: IV-L-1, 72 (70-88); IV-L-2, 123 (117-138); IV-L-3, 149 (138-162); IV-L-4, 268 (257-285); IV-L-5, 266 (259-281); IV-L-6, 208 (200-217).

Remarks.

At present, only fivespecies of the subgenus Palpisperchon Lundblad, 1941 are known: Sperchon crassipalpis Marshall, 1933, Sperchon distans Scheffler, 1972, Sperchon mirabilis Lundblad, 1941, Sperchon nikkoensis Imamura, 1976 and Sperchon skopetsi Tuzovskij, 1982.

Due to the shape of cuticle, E4 absent from CxIII, P-II with a very long ventro-distal projection, and P-IV with two greatly enlarged ventral peg-like setae, the spec imens from China show a general conformity with Sperchon (Palpisperchon) nikkoensis , a species previously known only from the female sex from Japan ( Imamura 1976). However, the absence of pregenital sclerite and the presence of a round platelet in front of the genital field (as reported in the original illustration, see Imamura 1976), are typical characters of the male sex ( Di Sabatino et al. 2010). Therefore, the specimen described by Imamura should be a male instead of female. This is the first description of the opposite sex to that in original description ( Imamura 1976), and first record of this species from China.

Distribution.

China (present study); Japan ( Imamura 1976).