Hygrobates calliger Piersig, 1896

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 : 1903-1910

publication ID	https://doi.org/ 10.1080/00222930400023727
persistent identifier	https://treatment.plazi.org/id/415ED655-9715-FF95-9B8A-31E651B4FB4B
treatment provided by	Felipe
scientific name	Hygrobates calliger Piersig, 1896
status

Treatment

( Figures 6 View Figure 6 , 7 View Figure 7 ) Hygrobates calliger Piersig 1896, p 439 ; Enami 1940, p 230–233, Text figures 23–25; Imamura 1953a, p 220–222, Figure 16 View Figure 16 . Hygrobates (s. str.) calliger: Imamura 1953b, p 428 –429, Figure 11 View Figure 11 ; 1954, p 75; 1955, p 188.

Figure Hygrobates 4. Comparison bibi (n 519) and of the H. ratio japonicus of the (n 5distance 6). (O, between Z) Mean P- values 4 ventral; (•) setae value to of the holotype segment of H length. japonicus of P-. 4 Bars for indicate ranges. Mann–Whitney U test; P,0.001.

Hygrobates calliger calliger: Imamura 1960, p 41 ; 1980, p 348–349, Figure 162B. Hygrobates heteropalpis Imamura 1954, p 77 –79, Figure 45.

Material examined

Five females and five males from Nanashi-gawa River , Niseko, 13 May 2002 ; one female from Urahoro-gawa River , Obihiro, 30 June 2002 ; one female from Koetoi , Wakkanai, 19 August 2002 ; one female and two males collected from Koetoi, Wakkanai, 5 August 2003; all from Hokkaido. From Imamura’s collection, holotype (female, collection number 1247) and one paratype (female, collection number 1248) of H. heteropalpis from Ebeotsu, Hokkaido, 19 June 1947 .

Description of female

Cuticular features. Integument soft, strongly lineated, line spacing 2.0. Secondary sclerotization of coxoglandularia II weak ( Figure 6D View Figure 6 ). Antenniform setae ( Figure 6E View Figure 6 ) thin, located on small, rounded bases, length 58 (52–65, n 54). Without dorsalia.

Chelicera ( Figure 6C View Figure 6 ). Total length 330 (298–363, n 55), basal segment 242 (227–266, n 55), claw 101 (94–120, n 55), maximum height 66 (58–71, n 55), length/height ratio 5.0 (4.9–5.1, n 55), basal segment/claw ratio 2.4 (2.1–2.7, n 55).

Palp ( Figure 6B View Figure 6 ). Length/height, P-1 33/45 (29–36/39–52, n 55), P-2 133/91 (117–156/ 75–110, n 55), P-3 111/64 (91–130/52–84, n 55), P-4 167/41 (149–194/36–45, n 55), P-5 56/18 (52–62/16–19, n 55). P-2 with truncated projection. P-2 with a tapering,

Figure 5. Comparison of the ratio of the length of the longest terminal seta to the segment length of IV-L-5 for Hygrobates bibi (n 519) and H. japonicus (n, 56). (O, Z) Mean values; (•) value of holotype of H. japonicus . Bars indicate ranges. Mann–Whitney U test; P 0.001.

blunt-triangular ventral projection having 26 (21–30, n 55) denticles distributed all over the surface. Ventral side of P-3 flat, with a patch of 27 (22–31, n 55) denticles occupying more than half the ventral length of segment, closer to distal end. P-4 with two ventral setae and 10 (9–11, n 55) setae on lateral and dorsal sides. P-4 setae ratio 0.1 (0.1–0.2, n 55). P-5 with three setae.

Capitulum ( Figure 6A View Figure 6 ). Broadly fused with the first coxae, 152 (143–168, n 55) in width. Anterior portion of each half of capitulum deeply notched.

Coxae ( Figure 6A View Figure 6 ). Length/width anterior coxal group 318/395 (285–337/369–421, n 55). Length/width posterior coxal groups 293/253 (279–305/240–272, n 55). Posterior end of anterior coxal group triangular, posterolateral apodemes extending slightly beyond sclerotization, 158 (143–175, n 55) from tip to tip. Suture line between Cx1 and capitulum nearly straight to irregular, not curved. Coxoglandularium I on Cx2. Suture line between Cx3 and Cx4 incomplete, extending to near glandularia on Cx4. Medial margins of Cx4 acutely rounded, without angle apodemes.

Legs ( Figure 7A–D View Figure 7 ). Swimming hairs absent, claws with a ventral clawlet. Seta to tibia ratio, I-L/IV-L 0.3/0.2 (0.2–0.4/0.2–0.2, n 55).

Genital field ( Figure 6F View Figure 6 ). Entire genital field 232 (227–240, n 55) in width. Genital plates with smooth outer border. Right genital plate with 15 (13–16, n 55) setae, left with 14 (12– 15, n 55). No setae on membranous integument near genital plate. Length/width genital plates 135/77 (130–143/71–84, n 55). 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 of Ac1 45/29 (39–49/19–32, n 55), Ac2 51/27 (42–58/23–29, n 55), Ac3 50/ 32 (39–58/32–36, n 55). Pre- and postgenital sclerites with medially protruded apodemes. Pregenital sclerite anterior to the anterior ends of genital plates, lacks setae. Postgenital sclerite anterior to the posterior ends of genital plates. Genital opening between pre- and post-genital sclerites 123 (97–149) in length.

Description of male

Characters as given for female, except for genital field. Antenniform setae length 51 (49– 58, n 55).

Chelicera. Total length 330 (298–363, n 55), basal segment 203 (181–227, n 55), claw 87 (81–97, n 55), maximum height 57 (49–65, n 55), length/height ratio 4.9 (4.3–5.4, n 55), basal segment/claw ratio 2.3 (2.2–2.5, n 55).

Palp. Length/height P-1 30/41 (26–32/39–45, n 55), P-2 109/73 (97–130/65–97, n 55), P- 3 84/48 (78–97/42–65, n 55), P-4 136/36 (130–162/32–39, n 55), P-5 51/17 (49–52/16– 19, n 55). P-2 with 28 (24–33, n 55) denticles. P-3 with 25 (22–28, n 55) denticles. P-4 with two ventral setae and 11 (10–12, n 55) setae on lateral and dorsal sides. P-4 setae ratio 0.1 (0.1–0.1, n 55). P-5 with three setae.

Capitulum. Width 119 (110–136, n 55).

Coxae. Length/width anterior coxal group 187/351 (266–314/324–369, n 55). Length/ width posterior coxal group 275/231 (259–305/207–266, n 55). Posterolateral apodemes of anterior coxal group 135 (123–149, n 55) from tip to tip.

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

Genital field ( Figure 6G View Figure 6 ). Genital plate length/width 142/184 (139–143/175–194, n 55), anterior end flat, outer border smooth, posterior end deeply notched with a drop-shaped median projection; apodemes lacking. Genital plate with 20 (17–23, n 55) setae on right side and 20 (15–24, n 55) on left. Three genital acetabula arranged in an obtuse triangle on each side. Distance between Ac1 and Ac2, and Ac2 and Ac3, less than width of Ac1. Length/width Ac1 40/29 (32–45/26–32, n 55), Ac2 51/25 (45–55/19–26, n 55), Ac3 50/32 (45–52/29–39, n 55).

Localities

Ebeotsu, Niseko, Obihiro, and Wakkanai on Hokkaido.

Distribution

Palaearctic region: Europe, Russia, Central Asia (Samarkand), Japan (southern Honshu, Hokkaido).

Remarks

Imamura (1954) described Hygrobates heteropalpis from Hokkaido as very similar to H. calliger , noting that the former has a longer ventral projection on P-2 compared to the latter. Two P-2 projections in the original illustration of H. heteropalpis ( Imamura 1954, p 78, Figure 45b, c) certainly seem to be longer than those of H. calliger calliger illustrated by Imamura (1953a). However, the P-2 projections of three subspecies of H. calliger ( H. calliger calliger , H. calliger obtusipalpis , and H. calliger latilaminata ) illustrated by Viets (1930, p 378, Figures 13–15 View Figure 13 View Figure 14 View Figure 15 ) do not seem to be shorter than those of H. heteropalpis . We addressed this problem by examining the shape variation of the P-2 projection among 11 specimens of the two species, including the holotype and paratype of H. heteropalpis , three specimens of H. calliger from Sicily and North Tuscany, Italy, and six specimens from a population at Nanashi-gawa river, Niseko, southern Hokkaido. As is clearly shown in Figure 8 View Figure 8 , there are no diagnostic differences in the P-2 projection between the two nominal species. Both the length and shape of the projection in the types of H. heteropalpis fall within the range of variation of the Hokkaido population of H. calliger . The P-2 projection of the European specimens of H. calliger tends to be broader than that of either H. calliger or H. heteropalpis from Japan, but again the character overlaps (e.g. compare Figure 8B View Figure 8 with 8E). Except for uncertainty regarding the male characters of H. heteropalpis (the male has not been described), H. heteropalpis and H. calliger overlap completely in P-2 morphology and other characters examined (Table II). With little doubt, H. heteropalpis Imamura, 1954 is a junior synonym of H. calliger Piersig, 1896 .

Hygrobates calliger is most similar to H. bibi sp. nov. but differs from the latter in four of 18 characters (Table II). The former has a narrow, spike-like P-2 projection, the flat ventral side of P-3 flat, and a strongly lineated integument, whereas the latter has a broad, rounded P-2 projection, the ventral side of P-3 convex (compare Figures 6B View Figure 6 and 2B View Figure 2 ), and a finely striated integument. The P-4 setae ratio is somewhat greater in H. calliger than in H. bibi .