Hygrobates longiporus Thor, 1898

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 : 1924-1928

Hygrobates longiporus Thor, 1898

( Figures 15 , 16 )

Hygrobates (Hygrobates) longiporus Thor 1898, p 272 –273; Imamura 1953a, p 216 –219, Figures 14 , 15 ; 1980, p 348–349, Figure 162D.

Hygrobates (s. str.) longiporus: Imamura 1953b, p 432 ; 1954, p 82.

Material examined

One adult female from Hamamasu, 31 July 2001; one adult female and one adult male from Gosen-gawa River , Horokanai, 7 July 2002 ; three adult females and three adult males from Horonobe , 20 August 2002 ; one adult female from Otoineppu , 7 July 2002 .

Description of female

Cuticular features. Integument soft, very finely striated, spacing of striae 0.9. Coxoglandularia II ( Figure 15D ) with heavy secondary sclerotization. Antenniform setae ( Figure 15E ) very thin and located on small, ovoid bases, length 61 (58–62, n 54). Without dorsalia.

Chelicera ( Figure 15C ). Total length 439 (415–467, n 54), basal segment 319 (305–337, n 54), claw 133 (117–143, n 54), maximum height 92 (78–97, n 54), length/height ratio 4.8 (4.3–5.4, n 54), basal segment/claw ratio 2.4 (2.3–2.7, n 54).

Palp ( Figure 15B ). Length/height, P-1 40/56 (26–45/45–58, n 55), P-2 170/86 (156–181/ 52–110, n 55), P-3 118/71 (104–130/58–84, n 55), P-4 221/47 (214–230/45–52, n 55), P- 5 70/29 (65–71/26–32, n 55). P-2 somewhat swollen distally into a blunt, angular ventral projection; 51 (38–59, n 55) denticles covering two-thirds of ventral segment length, from proximal half of projection to near proximal margin. Ventral side of P-3 flat with 34 (29– 47, n 55) denticles in a patch covering nearly entire ventral length. P-4 with two ventral setae and 10 (8–12, n 55) setae on lateral and dorsal sides. P-4 setae ratio 0.04 (0.03–0.08, n 55). P-5 with three setae.

Capitulum ( Figure 15A ). Broadly fused with the first coxae and 140 (130–149, n 55) in width. Anterior portion of each half of capitulum with a rounded notch.

Coxae ( Figure 15A ). Length/width anterior coxal group 401/490 (350–437/460–531, n 55). Length/width posterior coxal groups 422/369 (395–447/337–421, n 55). Posterior end of anterior coxal group triangular; posterolateral apodemes extending slightly beyond sclerotization, 200 (181–214, n 55) from tip to tip. Suture line between Cx1 and capitulum nearly straight or slightly curved. Coxoglandularium I on Cx2. Suture line between Cx3 and Cx4 complete; glandularium on Cx4 located near suture line. Medial margin of Cx4 evenly rounded, without angle apodemes.

Legs ( Figure 16A–D ). Swimming hairs absent; claws with a ventral clawlet. Seta to tibia ratio, I-L/IV-L 0.2/0.3 (0.2–0.3/0.3–0.3, n 55).

Genital field ( Figure 15F ). Entire genital field 303 (298–337, n 55) in width. Genital plates with smooth outer border. Genital plates with 25 (23–26, n 55) setae on right plate and 24 (19–26, n 55) on left. No setae in the membranous integument near genital plate. Length/ width genital plates 265/135 (246–285/130–139, n 55). Three genital acetabula on each side arranged in an obtuse triangle. Distance between Ac1 and Ac2 greater than width of Ac1; distance between Ac2 and Ac3 less than or equal to width of Ac1. Length/width Ac1 93/29 (84–100/26–39, n 55), Ac2 93–33 (84–104/26–39, n 55), Ac3 80/39 (65–81/32–45, n 55). 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 184 (175–201, n 55) in length.

Description of male

Characters same as for female, except for genital field. Antenniform setae length 52 (42–58, n 53).

Chelicera. Total length 390 (366–408, n 53), basal segment 281 (266–305, n 53), claw 122 (113–136, n 53), maximum height 80 (78–84, n 53), length/height ratio 4.9 (4.7–5.1, n 53), basal segment/claw ratio 2.3 (2.0–2.6, n 53).

Palp. Length/height P-1 38/53 (32–42/49–58, n 54), P-2 151/87 (143–162/75–97, n 54), P-3 104/71 (104–104/65–78, n 54), P-4 194/48 (188–201/42–52, n 54), P-5 62/25 (58–65/ 23–26, n 54). P-2 with 51 (46–55, n 54) denticles. P-3 with 34 (31–39, n 54) denticles. P-4 with two ventral setae and nine (7–10, n 54) setae on lateral and dorsal sides. P-4 setae ratio 0.04 (0.0–0.07, n 54). P-5 with three setae.

Capitulum. Width 113 (104–123, n 54).

Coxae. Length/width anterior coxal group 363/429 (318–402/402–460, n 54). Length/ width posterior coxal group 381/339 (356–415/285–382, n 54). Apodemes of anterior coxal group 147 (110–168, n 54) from tip to tip.

Legs. Seta to tibia ratio, I-L/IV-L 0.2 (0.2–0.3, n 54)/0.3 (0.3–0.3, n 53).

Genital field ( Figure 15G ). Genital plate length/width 232/288 (227–240/272–318, n 54), with smooth, evenly rounded outer border. Anterior border of genital plate deeply notched, with a triangular projection in notch; posterior border with a small, mammiform median projection; apodemes lacking. Genital plate with 25 (24–27, n 54) setae on right side and 25 (23–28, n 54) on left. Three genital acetabula on each side arranged in the manner of an isosceles triangle. Distance between Ac1 and Ac2 approximately equal to width of Ac1; distance between Ac2 and Ac3 less than width of Ac1. Length/width Ac1 84/35 (81–87/26– 32, n 54), Ac2 90/36 (84–97/32–39, n 54), Ac3 104/33 (104–104/26–39, n 54).

Localities

Hamamasu, Horokanai, Horonobe, and Otoineppu, all on Hokkaido.

Distribution

Palaearctic region : Europe, Russia, Japan (Kyushu, Hiroshima, Gifu, Hokkaido). Remarks

Hygrobates longiporus has been previously recorded once from Hokkaido ( Imamura 1954). It is most similar to H. longipalpis (see Remarks section for the latter) sharing nine of 18 characters with each (Table II). Among the eight Japanese species of this subgenus, only H. longiporus and H. sokolowi have the genital plate with the distance between Ac1 and Ac2 greater than the width of Ac 1 in the female, and greater than or equal to the width of Ac 1 in the male. Hygrobates longiporus is easily distinguished from the other seven Hygrobates species by two unique characters: heavy secondary sclerotization of coxoglandularium 2 and the long patch of denticles on P-2 occupying nearly the entire ventral segment length. This species was common among stones on the bottoms of rivers.

Figures

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

Figure 15. Hygrobates (Hygrobates) longiporus. (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 16. Hygrobates (Hygrobates) longiporus, female. (A) First leg; (B) second leg; (C) third leg; (D) fourth leg. Scale bar: 100 mm.