Hygrobates foreli ( Lebert, 1874 )

Matsumoto, Noriko, Dick, Matthew H. & Mawatari, Shunsuke F., 2005, Water mites of the genus Hygrobates Koch, 1837 (Acari: Parasitengona: Hygrobatidae) from Hokkaido, northern Japan, Journal of Natural History 39 (21), pp. 1893-1945 : 1910-1914

Hygrobates foreli ( Lebert, 1874)

( Figures 9 , 10 )

Compognatha foreli Lebert 1874, p 645 .

Hygrobates foreli: Uchida 1934, p 92 , Figure 25.

Hygrobates (s. str.) foreli: Imamura 1954, p 75 –77, Figures 43, 44.

Material examined

One female and one male from a stream in Akan , 4 June 2002 ; one male from Iwana-sawa River, Hurano , 4 August 2003 ; more than 20 females and males from Kan-noko-ike Spring, Kiyosato , 12 August 2002 ; more than 20 females and males from Hukidasi-Yusui, Kyogoku , 14 May 2002 ; all on Hokkaido.

Description of female

Cuticular features. Integument soft, finely striated, spacing of striae 1.6. Secondary sclerotization of coxoglandularia II weak ( Figure 9D ). Antenniform setae thin, each on a small, oval base ( Figure 9E ), length 67 (58–78, n 53). Without dorsalia.

Chelicera ( Figure 9C ). Total length 431 (408–447, n 53), basal segment 307 (285–324, n 53), claw 137 (136–139, n 53), maximum height 102 (97–104, n 53), length/height ratio 4.2 (4.2–4.3, n 53), basal segment/claw ratio 2.2 (2.1–2.4, n 53).

Palp ( Figure 9B ). Length/height, P-1 41/49 (36–45/42–52, n 55), P-2 152/83 (130–168/ 71–97 n 55), P-3 132/56 (91–181/52–65, n 55), P-4 203/51 (162–240/36–58, n 55), P-5 64/25 (55–68/16–29, n 55). Ventral projection on P-2 neglible, a slightly raised knob with 16 (9–31, n 55) denticles. Ventral side of P-3 flat with a patch of 14 (12–19, n 55) denticles occupying slightly less than half the ventral length, offset toward distal end. P-4 with two ventral setae and 14 (12–16, n 55) setae on lateral and dorsal sides. P-4 setae ratio 0.05 (0.03–0.07, n 55). P-5 with three setae.

Capitulum ( Figure 9A ). Broadly fused with first coxae, width 142 (123–181, n 55). Anterior portion of each half of capitulum is broadly and shallowly notched.

Coxae ( Figure 9A ). Length/width anterior coxal group 380/478 (324–389/395–505, n 55). Length/width posterior coxal groups 404/375 (305–460/360–405, n 55). Posterior end of anterior coxal group rounded, posterolateral apodemes extending scarcely beyond sclerotization, 228 (194–246, n 55) from tip to tip. Suture line between first coxae and capitulum nearly straight. Coxoglandularium I on Cx2. Suture line between Cx3 and Cx4 incomplete, extending near to gland of Cx4. Medial margins of fourth coxae rounded, slightly angular, without angle apodemes.

Legs ( Figure 10A–D ). Swimming hairs absent. Claws with a ventral clawlet. Seta to tibia ratio, I-L/IV-L 0.3/0.3 (0.3–0.4/0.2–0.3, n 55).

Genital field ( Figure 9F ). Entire genital field 367 (311–434, n 55) in width, with smooth outer border. Length/width genital plates 191/117 (162–220/100–130, n 55). Right genital plate with 20 (16–25, n 55) setae, left with 19 (17–21, n 55). No setae on membranous integument near genital plate. Three genital acetabula on each side arranged in an acute triangle. Distance between Ac1 and Ac2, and Ac2 and Ac3, less than width of Ac1. Length/ width in Ac1 67/45 (55–84/32–58, n 55), Ac2 80/32 (65–97/26–39, n 55), Ac3 93/44 (78– 104/29–58, n 55). Pre- and postgenital sclerites with apodemes medially. Pregenital sclerite located anterior to the anterior ends of genital plates, setae lacking. Postgenital sclerite extends slightly posterior to posterior ends of genital plates. Genital opening between pre- and postgenital sclerites 189 (175–207, n 55) in length.

Description of male

Characters as given for female, except for genital field. Antenniform setae length 70 (65– 78, n 54).

Chelicera. Total length 394 (363–454, n 53), basal segment 279 (253–324, n 53), claw 129 (117–143, n 53), maximum height 97 (97–97, n 53), length/height ratio 4.1 (3.7–4.7, n 53), basal segment/claw ratio 2.2 (2.0–2.3, n 53), length/height P-1 39/41 (29–45/39–45, n 55), P-2 137/82 (130–156/71–97, n 55), P-3 99/54 (75–123/45–65, n 55), P-4 179/44 (156–201/42–49, n 55), P-5 62/21 (55–65/19–23, n 55). P-2 with 14 (9–21, n 55) denticles. P-3 with 15 (12–16, n 55) denticles. P-4 with two ventral setae and 13 (11–16, n 55) setae on lateral and dorsal sides. P-4 setae ratio 0.03 (0.0–0.08, n 55). P-5 with three setae.

Capitulum. Width 124 (84–143, n 55). Coxae. Length/width anterior coxal group 352/456 (337–382/389–518, n 55). Length/ width posterior coxal group 395/343 (376–434/292–395, n 55). Posterolateral apodemes of anterior coxal group 202 (181–214, n 55) from tip to tip.

Legs. Seta to tibia ratio, I-L/IV-L 0.3/0.3 (0.3–0.4/0.2–0.4, n 55).

Genital field ( Figure 9G ). Genital plate length/width 196/255 (165–233/220–292, n 55), with smooth, evenly curved outer border. Anterior end of genital plate with a low, broad, rounded median projection; posterior end depressed, with a mammiform median projection; apodemes lacking. Genital plate with 22 (21–23, n 55) setae on right side and 20 (18–22, n 55) on left. Three genital acetabula on each side arranged in an acute triangle. Distance between Ac1 and Ac2, and Ac2 and Ac3, less than width of Ac1. Acetabulum length/width Ac1 67/44 (62–71/42–52, n 55), Ac2 80/35 (71–91/29–42, n 55), Ac3 88/55 (78–97/42–71, n 55).

Localities

Akan, Hurano, Kiyosato, and Kyogoku, on Hokkaido.

Distribution

Palaearctic region: Europe, Russia, Japan (Hokkaido).

Remarks

Hygrobates foreli has previously been reported twice from Hokkaido ( Uchida 1934; Imamura 1954). This species and H. longipalpis are both larger in overall body size than the other species treated. However, H. foreli is most similar to H. nigromaculatus ; the two share 14 of 18 characters (Table II) and, among the species treated, are the only ones with rounded medial projections on both the anterior and posterior borders of the male genital plate. Next most similar to H. foreli is H. calliger and H. longipalpis , sharing nine of 18 characters.

Figures

Figure 9. Hygrobates (Hygrobates) foreli. (A–F) Female. (A) Ventral side, scale 1; (B) palp, scale 3; (C) chelicera, scale 2; (D) coxoglandularium II, scale 3; (E) antenniform seta, scale 3; (F) genital field, scale 3. (G) Male, genital field, scale 3. Scale bars: 1, 2, 3 (B, F, G)5100 mm; 3 (D, E)550 mm.

Figure 10. Hygrobates (Hygrobates) foreli, female. (A) First leg; (B) second leg; (C) third leg; (D) fourth leg. Scale bar: 100 mm.