Hygrobates longipalpis ( Hermann, 1804 )

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 : 1920-1924

Hygrobates longipalpis ( Hermann, 1804)

( Figures 13 , 14 )

Hydrarachna longipalpis Hermann 1804, p 55 , Table 3, Figure 1.

Hygrobates longipalpis: Uchida 1931, p 262 –264, Abb. 1, 2; 1936b, p 313–314, Figures 3 , 4; Imamura 1950, p 74 –78, Figures 1–7.

Hygrobates japonicus: Uchida 1936a, p 178 –179.

Hygrobates (s. str.) longipalpis: Imamura 1954, p 79 –82, Figures 46, 47; 1955, p 188.

Hygrobates (Hygrobates) longipalpis: Imamura 1980, p 348 –349, Figure 162C.

Material examined

More than 20 adult females and males from Bibi-gawa River, Bibi, Chitose , 10 May 2003 ; one adult female from a pond at Hokkaido University, Sapporo , 15 August 2003 ; more than 20 adult females and adult males from a pond at Shiokari, Wassamu , 5 August 2003 ; more than 10 adult females and adult males from a spring at Turui, Akan-gun , 12 February 2001 ; more than 10 adult females and adult males from a spring at Turui, Akan-gun , 19 February 2002 ; two adult females and two adult males from Shira-kawa River, Mori , 27 May 2002 ; one adult female from Oboro-gawa River, Akkeshi , 13 June 2002 . Uchida’s collection: three adult females (ZIHU-2343, 2345, 1247) from Sapporo , 9 May 1932 ; one adult female (ZIHU-2344) from Sapporo , July 1932 ; one adult female ( ZIHU 2346 ) from Sapporo , 16 May 1932 ; one adult female (ZIHU-2348) from Sapporo , 26 May 1935 ; three adult females (ZIHU-2389, 2390, 2391) and six adult males (ZIHU-2383, 2384, 2385, 2386, 2387, 2388) from Kunashiri Island, Kurile Islands , 2 September 1934 .

Description of male

Cuticular features. Integument soft, very finely striated, spacing of striae 0.8. Coxoglandularia II ( Figure 13D ) without secondary sclerotization. Antenniform setae ( Figure 13E ) thickened and located on small, irregularly shaped bases, length 37 (32–39, n 54). Without dorsalia.

Chelicera ( Figure 13C ). Total length 405 (350–454, n 54), basal segment 292 (259–324, n 54), claw 126 (104–156, n 54), maximum height 90 (75–97, n 54), length/height ratio 4.5 (4.2–4.7, n 54), basal segment/claw ratio 2.3 (2.0–2.6, n 54).

Palps ( Figure 13B ). Length/height, P-1 52/62 (45–65/58–71, n 55), P-2 176/108 (168–194/ 91–123, n 55), P-3 128/80 (117–136/65–91, n 55), P-4 229/55 (207–253/45–65, n 55), P- 5 78/28 (58–107/23–32, n 55). P-2 with low, rounded conical projection having 29 (28–32, n 55) denticles distributed to base. Ventral side of P-3 somewhat swollen distally, with a patch of 28 (20–41, n 55) denticles occupying less than half the ventral segment length, positioned near distal end. P-4 with two ventral setae and nine (6–12, n 55) setae on lateral and dorsal sides. P-4 setae ratio 0.4 (0.4–0.5, n 55). P-5 with three setae.

Capitulum ( Figure 13A ). Broadly fused with the first coxae, width 159 (130–207, n 55). Anterior portion of each half of capitulum with a shallow, rounded notch.

Coxae ( Figure 13A ). Length/width anterior coxal group 390/452 (376–441/369–544, n 55). Length/width posterior coxal groups 399/368 (347–454/324–408, n 55). Posterior end of anterior coxal group rounded; posterolateral apodemes extending beyond sclerotization, 193 (149–220, 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 complete, extending to near gland of Cx4. Medial border of Cx4 angular, without angle apodemes. Legs ( Figure 14A–D ). Swimming hairs absent, claws with a ventral clawlet. Seta to tibia ratio, I-L/IV-L 0.4/0.4 (0.3–0.4/0.4–0.5, n 55).

Genital field ( Figure 13G ). Genital plate length/width 211/281 (168–233/249–318, n 55), with irregularly crenate outer border; anterior end with a squared median notch; posterior end depressed in middle, with a short, rounded median projection; apodemes lacking. Genital plate with 29 (28–30, n 55) setae on right side and 29 (28–32, n 55) on left. Three genital acetabula on each side arranged in an obtuse triangle. Distance between Ac1 and Ac2, and Ac2 and Ac3, less than width of Ac1. Length/width Ac1 86/51 (75–91/49–55, n 55), Ac2 82/48 (71–91/45–52, n 55), Ac3 89/52 (68–97/42–65, n 55).

Description of female

Characters as given for male, except for genital field. Antenniform setae length 38 (32–42, n 53).

Chelicera. Total length 503 (447–551, n 53), basal segment 365 (330–389, n 53), claw 151 (130–175, n 53), maximum height 110 (97–123, n 53), length/height ratio 4.6 (3.6–5.3), basal segment/claw ratio 2.4 (2.2–2.6).

Palp. Length/height P-1 51/62 (39–58/52–71, n 55), P-2 193/113 (156–220/97–136, n 55), P-3 131/79 (110–156/65–104, n 55), P-4 248/56 (207–285/49–71, n 55), P-5 70/27 (45–84/19–32, n 55). P-2 with 30 (20–36, n 55) denticles. P-3 with 27 (17–44, n 55) denticles. P-4 with two ventral setae and 10 (9–12, n 55) setae on lateral and dorsal sides. P-4 setae ratio 0.03 (0.03–0.03, n 55). P-5 with three setae.

Capitulum. Width 191 (123–233, n 55).

Coxae. Length/width anterior coxal group 395/477 (311–467/402–570, n 55). Length/ width posterior coxal group 404/384 (350–454/337–424, n 55). Posterolateral apodemes of anterior coxal group 189 (130–227, n 55) from tip to tip.

Legs. Seta to tibia ratio, I-L/IV-L 0.4/0.5 (0.4–0.4/0.5–0.5, n 55).

Genital field ( Figure 13F ). Entire genital field 321 (285–369, n 55) in width, with irregularly crenate outer border. Length/width genital plates 225/111 (191–259/91–130, n 55); 27 (24–31, n 55) setae on right plate and 25 (21–28, n 55) on left. No setae on membranous integument near genital plate. Three genital acetabula on each side, arranged in an obtuse triangle. Distance between Ac1 and Ac2, and Ac2 and Ac3, less than width of Ac1. Length/width Ac1 82/40 (65–91/32–52, n 55), Ac2 74/41 (65–94/32–55, n 55), Ac3 71/50 (58–78/39–71). Pre- and postgenital sclerites with medially protruded apodemes. No setae on pregenital sclerite. Pregenital sclerite located posterior to the anterior ends of genital plates. Postgenital sclerite located anterior to the posterior ends of genital plates. Genital opening between pre- and postgenital sclerites 185 (136–246, n 55) in length.

Localities

Turui, Akan, Akkeshi, Tomakomai, Chitose, Sapporo, Mori, and Wassamu, all on Hokkaido; Kunashiri, Kurile Islands.

Distribution

Holarctic region : America, Europe, Russia, Japan (Shizuoka, Kyushu, Tokyo, Hokkaido) .

Remarks

There are several previous records of H. longipalpis from Hokkaido ( Uchida 1936b; Imamura 1950, 1954). Among the eight species from Hokkaido, this species is most similar to H. foreli , H. japonicus (see Remarks section for that species) and H. longiporus which shares nine of 18 characters (Table II). H. longipalpis and H. longiporus exclusively share one coxal and two genital features: a complete suture line between the Cx3 and Cx4, a notched anterior border of the male genital plate, and the pregenital sclerite located posterior to the anterior ends of the female genital plates. This species was common in ponds, and in slowly flowing rivers close downstream from springs. It co-occurred with H. bibi sp. nov. in the Bibi-gawa River, Bibi, Chitose.

Figures

Figure 3. Hygrobates bibi sp. nov. Female, holotype (ZIHU-3106). (A) First leg; (B) second leg; (C) third leg; (D) fourth leg. Scale bar: 100 mm.

Figure 13. Hygrobates (Hygrobates) longipalpis. (A–E, G) Male. (A) Ventral side, scale 1; (B) palp, scale 3; (C) chelicera, scale 2; (D) coxoglandularium II, scale 4; (E) antenniform seta, scale 4; (G) genital field, scale 3. (F) Female, genital field, scale 3. Scale bars: 1, 2, 35100 mm; 4550 mm.

Figure 14. Hygrobates (Hygrobates) longipalpis, male. (A) First leg; (B) second leg; (C) third leg; (D) fourth leg. Scale bar5100 mm.