Hygrobates bibi, Matsumoto & Dick & Mawatari, 2005
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publication ID |
https://doi.org/ 10.1080/00222930400023727 |
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persistent identifier |
https://treatment.plazi.org/id/415ED655-971F-FF8A-9BF0-30455181FA37 |
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treatment provided by |
Felipe |
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scientific name |
Hygrobates bibi |
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Subgenus Hygrobates Koch, 1837 View in CoL
Hygrobates bibi sp. nov.
( Figures 2 View Figure 2 , 3 View Figure 3 ) Hygrobates (s. str.) japonicus Imamura 1953b, p 429 –432, Figure 12 View Figure 12 ; 1955, p 188. Hygrobates (Hygrobates) japonicus: Imamura 1980, p 348 –349, Figure 162A.
Type locality
Bibi River, Bibi, Chitose, Hokkaido, Japan.
Etymology
The species name refers to the type locality.
Material examined
Holotype: adult female (ZIHU-3106), dissected and mounted in polyvinyl alcohol, from type locality, 10 May 2003. Allotype: adult male (ZIHU-3107), dissected and mounted in polyvinyl alcohol, from type locality, 10 May 2003. Paratypes: four adult males (ZIHU- 3112, 3113, 3114, 3115), dissected and mounted in polyvinyl alcohol; four adult females (ZIHU-3108, 3109, 3110, 3111), dissected and mounted in polyvinyl alcohol, from type locality, 10 May 2003.
Additional specimens. Two males from Akkeshi, Hokkaido, 12 June 2003; three males from Hamanaka, Hokkaido, 13 June 2003 . Uchida’s collection: one female (ZIHU-2334) and two males (ZIHU-2338, 2339) from Sapporo , Hokkaido, July 1932 ; two females (ZIHU- 2335, 2336) and one male (ZIHU-2337) from Sapporo , Hokkaido, 16 May 1932 ; one female (ZIHU-2340) from Shakujii , Tokyo, 24 July 1935 ; one female (ZIHU-2341) from Shakujii , Tokyo, May 1934 ; one female (ZIHU-2342) from Myoshoji , Tokyo, 19 July 1935 . Imamura’s collection: one female (collection number 940) and one male (collection number 938) from Toba River , Gifu, 20 October 1951 ; one male (collection number 1266) from Rakuju-en , Shizuoka, 15 May 1953 .
Description of female
Cuticular features. Body spherical. Integument soft, finely striated, spacing of striae 2.7. Secondary sclerotization of coxoglandularia II weak ( Figure 2D View Figure 2 ). Antenniform setae thickened, each located on a small, rounded base ( Figure 2E View Figure 2 ), 45 in length. Without dorsalia.
Chelicera ( Figure 2C View Figure 2 ). Total length 340, basal segment 233, claw 97, maximum height 65, length/height ratio 6, basal segment/claw ratio 2.
Palp ( Figure 2B View Figure 2 ). Length/height: P-1 36/45, P-2 136/78, P-3 97/55, P-4 159/42, P-5 52/16. P-2 with prominent, rounded-conical projection having 38 denticles distributed all over the ventral surface. Ventral margin of P-3 swollen, evenly convex in outline, with 22 denticles in a central patch occupying about half the ventral length. P-4 with two setae on ventral side and 10 setae on lateral and dorsal sides; distance between two ventral setae 10; P-4 setae ratio 0.06. P-5 with two setae.
Capitulum ( Figure 2A View Figure 2 ). Broadly fused with the first coxae, 139 in width; anterior margin of each half of capitulum with a rounded notch.
Coxae ( Figure 2A View Figure 2 ). Length/width anterior coxal group 337/395. Length/width posterior coxal groups 318/272. Posterior end of anterior coxal group rounded-triangular; posterolateral apodemes extending slightly beyond sclerotization, 156 from tip to tip. Suture line between Cx1 and capitulum irregular, not curved. Coxoglandularium I on Cx2. Suture line between Cx3 and Cx4 nearly straight, incomplete, extending to near glandularium of Cx4. Medial margin of Cx4 rounded; angle apodemes lacking.
Legs ( Figure 3A–D View Figure 3 ). Swimming hairs absent. Claws with a ventral clawlet. Lengths of leg segments I-L-1 to I-L-6, 75/91/143/201/181/175; II-L-1 to II-L-6, 71/117/130/194/201/ 188; III-L-1 to III-L-6, 78/110/156/240/253/220; IV-L-1 to IV-L-6, 162/152/201/292/305/ 253. Seta to tibia ratio, I-L to IV-L, 0.36/0.32/0.23/0.26.
Genital field ( Figure 2F View Figure 2 ). Entire genital field 230 wide. Genital plates with smooth, rounded-angular border. Right genital plates with 22 setae, left with 16. Setae lacking on membranous integument near genital plate. Length/width genital plates 149/75. 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 52/32, Ac2 52/32, Ac3 52/29. Pre- and postgenital sclerites with medially protruded apodemes. No setae on pregenital sclerite. Genital opening between pre- and postgenital sclerites 130 in length.
Description of male
Characters as given for female, except for genital field. Antenniform setae length 42.
Chelicera. Total length 201, basal segment 194, claw 91, maximum height 65, length/ height ratio 6, basal segment/claw ratio 2.
Palp. Length/height P-1 32/39, P-2 117/78, P-3 87/58, P-4 143/39, P-5 55/19. P-2 with 30 denticles. P-3 with 31 denticles. P-4 with two setae on ventral side and 10 setae on lateral and dorsal sides; distance between two ventral setae 10; P-4 setae ratio 0.07. P-5 with two setae.
Capitulum. Width 123.
Coxae. Length/width anterior coxal groups 311/369. Length/width of posterior coxal group 305/262. Posterolateral apodemes of anterior coxal group 149 from tip to tip.
Legs. Lengths of leg segments I-L-1 to I-L-6, 81/110/123/175/165/156; II-L-1 to II-L-6, 71/104/123/175/181/175; III-L-1 to III-L-6, 71/104/136/214/227/214; IV-L-1 to IV-L-6, 162/143/188/272/279/240. Seta to tibia ratio, I-L to IV-L, 0.35/0.32/0.24/0.21.
Genital field ( Figure 2G View Figure 2 ). Genital plate length/width 149/194. Genital plate with smooth, even border; anterior margin depressed, with a slight median projection; posterior margin deeply notched with a large, rounded median projection; apodemes lacking. Genital plate with 23 setae on right side and 25 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 45/23, Ac2 55/26, Ac3 52/32.
Variation in measurements, female
Antenniform setae length 49 (42–58, n 54).
Chelicera. Total length 327 (317–337, n 54), basal segment 225 (220–227, n 54), claw 102 (97–104, n 54), maximum height 65 (65–65, n 54), length/height ratio 6, basal segment/ claw ratio 2.
Palp. Length/height P-1 32/44 (32–32/42–45, n 54), P-2 128/84 (123–130/81–88, n 54), P-3 99/60 (91–104/52–65, n 54), P-4 158/43 (156–162/39–45, n 54), P-5 57/19 (52–65/ 19–19, n 54). P-2 with 30 (26–38, n 54) denticles. P-3 with 27 (22–30, n 54) denticles. P4 with two ventral setae and 11 (10–12, n 54) setae on lateral and dorsal sides; P-4 setae ratio 0.07 (0.04–0.10, n 54). P-5 with two (2–2, n 54) setae.
Capitulum. Width 133 (123–143, n 54).
Coxae. Length/width anterior coxal group 323/374 (321–324/324–402, n 54). Length/ width posterior coxal group 306/264 (292–311/259–266, n 54). Posterolateral apodemes of anterior coxal group 152 (130–162, n 54) from tip to tip.
Legs. Lengths of leg segments I-L-1 to I-L-6, 71/91/118/179/177/166 (65–79/91–91/113– 123/175–181/168–188/162–175, n 53); II-L-1 to II-L-6, 69/96/125/184/191/181 (65–75/ 84–104/123–130/175–194/181–201/175–188, n 54); III-L-1 to III-L-6, 71/97/144/220/233/ 214 (65–78/91–104/136–156/214–227/227–246/207–227, n 54); IV-L-1 to IV-L-6, 147/147/ 188/267/293/251 (130–162/143–162/168–207/233–292/285–311/240–266, n 54). Seta to tibia ratio, I-L to IV-L, 0.37/0.32/0.24/0.24 (0.35–0.39/0.30–0.33/0.20–0.28/0.22–0.26, n 54).
Genital field. Width of entire genital field 228 (217–240, n 54). Right genital plate with 19 (18–20, n 54) setae, left with 19 (17–22, n 54). Length/width genital plates 143/83 (143– 146/78–88, n 54). Length/width of Ac1 50/32 (45–55/29–32, n 54), Ac2 52/27 (39–64/23– 32, n 54), Ac3 49/33 (45–52/29–39, n 54). Length of genital opening between pre- and post- genital sclerites 120 (97–149, n 54).
Variation in measurements, male
Antenniform setae length 47 (45–49, n 54).
Chelicera. Total length 287 (259–305, n 54), basal segment 198 (175–214, n 54), claw 89 (84–94, n 54), maximum height 65 (65–65, n 54), length/height ratio 6, basal segment/claw ratio 2 (2–2, n 54).
Palp. Length/height P-1 31/40 (26–32/39–45, n 54), P-2 109/72 (104–120/65–78, n 54), P-3 83/51 (78–91/45–52, n 54), P-4 140/38 (136–146/36–42, n 54), P-5 52/17 (49–55/16– 19, n 54). P-2 with 28 (25–30, n 54) denticles. P-3 with 28 (25–30, n 54) denticles. P4 with two ventral setae and 10 (10–10, n 54) setae on lateral and dorsal sides. P-4 setae ratio 0.07 (0.04–0.09, n 54). P-5 with two setae.
Capitulum. Width 127 (110–143, n 54).
Coxae. Length/width anterior coxal group 151/241 (130–188/181–311, n 54). Length/ width posterior coxal group 297/251 (272–314/220–266, n 54). Posterolateral apodemes of anterior coxal group 147 (130–159, n 54) from tip to tip.
Legs. Lengths of leg segments I-L-1 to I-L-6, 61/89/105/160/159/154 (52–68/84–91/104– 110/156–168/149–168/149–156, n 54); II-L-1 to II-L-6, 59/97/113/168/175/170 (55–58/84– 104/104–123/162–175/168–181/162–175, n 54); III-L-1 to III-L-6, 70/100/128/203/207/196 (58–78/97–104/123–130/201–207/201–214/188–207, n 54); IV-L-1 to IV-L-6, 133/139/173/ 248/272/231 (123–149/130–143/162–188/220–272/259–285/220–240, n 54). Seta to tibia ratio, I-L to IV-L, 0.38/0.34/0.26/0.23 (0.35–0.42/0.24–0.42/0.23–0.35/0.22–0.34, n 54).
Genital field. Length/width 139/188 (130–149/181–201, n 54). Genital plate with 23 (22– 24, n 54) setae on right side and 23 (20–27, n 54) setae on left. Length/width Ac1 41/28 (39–45/26–32, n 54), Ac2 52/23 (45–58/19–32, n 54), Ac3 47/32 (45–49/29–32, n 54).
Localities
Akkeshi, Hamanaka, Sapporo, and Tomakomai on Hokkaido; Tokyo, Gifu, Shizuoka.
Distribution
Hokkaido, Gifu, Shizuoka; northern and middle Japan .
Remarks
Hygrobates bibi sp. nov. is most similar to H. calliger , but differs from the latter in four of 18 characters (Table II). Hygrobates bibi has a rounded projection on P-2, the ventral margin of P-3 convex, the pair of ventral setae on P-4 very close together, and an integument pattern of fine striation. In contrast, H. calliger has a sharper, triangular P-2 projection, the ventral side of P-3 flat, the pair of ventral setae on P-4 farther apart, and an integument pattern of strong lineation.
Examination of the old collections revealed that the new species had already been collected from Japan prior to our study. Three of about 20 specimens labelled H. japonicus in Uchida’s collection and both specimens labelled H. japonicus in Imamura’s collection proved to be H. bibi . Imamura (1954) noted some differences in the morphology of P-3 between his specimens and the original description of H. japonicus ( Uchida, 1931) , but concluded that these differences were due to the immaturity of his specimens. Examination of more than 20 specimens newly collected from Hokkaido has revealed that P-3 morphology is diagnostic between H. japonicus and the new species. The character state Uchida (1931, p 266) described for H. japonicus as ‘‘Der gezackte Höcker auf den Beugeseite des dritten Gliedes ist niedrig, aber ziemlich breit’’ (serrated knob on the ventral side of P-3 is low, but relatively broad; our translation) is separable into ‘‘ventral side of P-3 with a low knob in the middle’’ ( Figure 11B View Figure 11 ) in H. japonicus and ‘‘ventral side of P-3 convex without a distinct knob’’ ( Figure 2B View Figure 2 ) in H. bibi , without any transitional states.
Other characters previously used to distinguish species of Hygrobates include the morphologies of P-2 and the genital plates, and the distribution of the ventral setae on P4. Uchida (1931, p 265) mentioned for H. japonicus , ‘‘auf den Beugeseite des zweiten Palpengliedes befindet sich ein mit Spitzen besetzter stumpfer Zapfen’’ (on the ventral side of P-2 is a blunt projection occupied by points; our translation), but provided a poor illustration. Once again, the character state described by Uchida can be separated into two states: ‘‘projection narrow, with a truncated end’’ ( Figure 11B View Figure 11 ) for H. japonicus and ‘‘projection broad, with a round end’’ ( Figure 2B View Figure 2 ) for H. bibi , also without any transitional states.
A comparison of character states between H. bibi sp. nov. and H. japonicus is summarized in Table II. The two species differ in 10 of the 18 characters compared, including the morphology of the P-2 projection and the ventral side of P-3, the P-4 setae ratio, the ratio of the longest terminal seta on IV-L-5 to length of IV-L-5, the shape of the male genital plate, and secondary sclerotization of the coxoglandularia.
Uchida (1931) noted that H. japonicus has the two setae on ventral side of P-4 widely separate ( Figure 11B View Figure 11 ). However, his specimens labelled H. japonicus include specimens of H. bibi that have these setae close together ( Figure 2B View Figure 2 ). The ratio of the distance between the two setae to P-4 length does not overlap between H. japonicus and H. bibi , and the means are significantly different (Figure 4). Finally, as a novel taxonomic character for distinguishing species of water mites, we propose here the ratio of the longest terminal seta on IV-L-5 to the length of IV-L-5. This ratio does not overlap between H. japonicus and H. bibi , and the means are significantly different (Figure 5, also compare Figures 3D View Figure 3 and 12D View Figure 12 ).
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