Hygrobates pilosus, Goldschmidt & Nishikawa & Hiruta & Shimano, 2020

Goldschmidt, Tom, Nishikawa, Kanto, Hiruta, Shimpei F. & Shimano, Satoshi, 2020, Description of three new water mite species of Hygrobates Koch, 1837 (Lurchibates Goldschmidt & Fu, 2011) (Acari, Hydrachnidia, Hygrobatidae), parasitic in newts of the genera Paramesotriton and Pachytriton (Amphibia, Caudata, Salamandridae) from China, Zootaxa 4768 (1), pp. 25-42 : 36-41

Hygrobates pilosus sp. nov. Goldschmidt, Nishikawa & Shimano

Material examined: Holotype male, slide mounted in glycerine jelly, preparation no. CIB INV 0008, parasitic on Paramesotriton yunwuensis ( Amphibia, Caudata , Salamandridae ): newt from pet shop, preserved in 99% Ethanol; mite was attached to the waist of the newt ( KUHE 49342).

Paratypes: three females CIB INV 0009, CIB INV 0010, CIB INV 0011, five males CIB INV 0012, CIB INV 0013, CIB INV 0014, CIB INV 0015, CIB INV 0016 from head, lateral body, or groin of the newt ( KUHE 49340)—same data as holotype, but fixed by freezing (-80°C) [therefore the mites were in poor conditions and could only partly be measured and illustrated].

Distribution: All specimens of H. pilosus sp. nov. have been collected from Paramesotriton yunwuensis . The new species is probably limited to the same distribution as its host, which was described from Yunwu Mountains, Luoding, Guangdong Province, China, and is only known from there.

Derivatio nominis: pilosus lat. hairy—referring to the many long setae at the margin of the male genital plate.

Diagnosis: Characters of the subgenus; coxal field relatively slender (compared to other species of the subgenus), anterior coxal group triangular, posteriorly narrow, elongated, posterior margin rounded; male genital field broad-oval, bearing many long setae; female genital plates crescent-shaped, anteriorly narrow, rounded; P-4 relatively slender, proximo-ventral extension of P-5 large, triangularly pointed; cheliceral claw relatively straight, long and slender.

Description, Male (n = 6): Idiosoma rounded-oval, L/W ratio 1.42 (1.36–1.39), L/W 888 (816–864)/624 (588–636); fused anterior coxae of both sides elongated, triangular (Cx-I + II L/W 312 (330–336)/442 (456–492)), medio-posterior margin extended by secondary sclerotization (posteriorly convex, curved tips of lateral extension reaching under medial margin of Cx-III), Cx-I basal width 136 (120–136); gnathosoma relatively long and slender, anteriorly only very slightly projecting, lateral margin with Cx-I posteriorly clearly converging, at fusion with the posterior part of the Cx-I relatively narrow ( Fig. 39 ); anterior and posterior coxal groups laterally very close (but not overlapping), medially slightly diverging (the clear lateral separation at one side given in Fig. 39 , is an artifact, as the integument of the respective side is broken between Cx-II and -III); posterior coxae very close to each other, triangular, medial edges smoothly rounded, formed by Cx-IV only, Cx-IV nearly rectangular, posterior margin transverse, slightly undulating, lateral margin straight, parallel to longitudinal axis of idiosoma ( Fig. 39 ), posterior coxal groups (Cx-III + Cx-IV of one side) L/W 276 (270–288)/241 (269–288); genital plate very broad oval to wing-like, acetabular plates smoothly fused with strongly sclerotized pre- and postgenitale, genital opening broad egg-shaped, anteriorly obtuse-angled, genital field L/W 174 (198–216)/366 (354–390); acetabula relatively far distant from each other (about the width of an acetabulum), Ac-1 and -2 irregularly oval, Ac-3 triangularly rounded, L/W Ac-1 76 (63–82)/33 (36–40), Ac-2 70 (63–72)/43 (36–46), Ac-3 63 (61–80)/55 (57–63), 38–47 setae on each side of the plate (see Fig. 39 ) mainly arranged at the margins, lateral setae longer than anterior and posterior ones ( Fig. 39 ); genital skeleton typical for the subgenus, large, L/W 277 (287–306)/181 (193–202) and slender, L/W ratio 1.53 (1.49–1.51), brachia distalia strong, laterally curved, oblique antero-medially to postero-laterally, brachia proximalia strong, distally broadened, parallel to longitudinal axis (left side slightly distorted in the illustrated specimen) ( Fig. 40 ); all legs slender, bearing many heavy setae ( Figs. 41–44 ); measurements (L/H) of distal leg segments: I-leg-5, 264 (264)/52 (48), I-leg-6, 218 (216)/54 (48); II-leg-5, 276 (276)/54 (54), II-leg-6, 234 (228)/54 (54); III-leg-5, 306 (318)/56 (56), III-leg-6, 252 (258)/54 (48); IV-leg-3, 174 (174)/72 (70), IV-leg-5, 324 (342)/54 (53), IV-leg-6, 294 (313)/52 (42); chelicerae strong, relatively slender; cheliceral claws very large, distally straight, sharply pointed, dorsal margin in the distal third with strong serration that continues proximally in a lateral serration, medially and laterally striated ( Figs. 45, 46 ); palps strong ( Figs. 47, 48 ), ventral margin of P-2 straight, anteroventral corner with very few denticles, P-3 ventrally straight with few denticles in distal half, P-4 relatively long, straight, distally slightly curved, with a pair of ventral setae in the distal third; P-5 with a well developed, coneshaped ventro-proximal projection, dorso-distally with a compact, denticle-like distal claw and ventro-distally a pair of large, strong, ventrally-directed curved claws similar to each other; mouthpart measurements: chelicera total L 420 (414–456), maximum H 102 (110–115), L/H ratio 4.1 (3.7–4.0), basal segment L 257 (240–273), claw L 197 (180–197), basal segment/claw ratio 1.3 (1.4–1.5); curvation of cheliceral claw 21°, palp total L 536 (530–543), L/H P-1, 52 (49–52)/68 (69–75), P-2, 146 (139–146)/94 (87), P-3, 103 (103–118)/82 (80–82), P-4, 186 (181–188)/63 (59–61), P-5, 49 (47–51)/49 (49–52).

Description, Female (n = 3): Idiosoma similar to male, much larger, L/W 1800–1908 /1536–1440, and more rounded (L/W ratio 1.17–1.33); unpaired anterior coxal group wider and relatively shorter than in males, L/W 390–438/576–601, medio- and latero-posterior margin extended by secondary sclerotization as in males, but lateroposterior apodemes of Cx-I not reaching under Cx-III, basal width Cx-I 208–237; gnathosoma relatively wider and shorter than in males, lateral margins posteriorly clearly converging, broadly fused with the posterior part of the first coxae ( Fig. 49 ); paired posterior coxal groups more distanced from each other and from the anterior coxal group than in males, roughly triangular in shape with medial edges formed by Cx-IV only, medial margin undulating, Cx-IV trapezoid, L/W 354–360/336–342 ( Fig. 49 ); genital field rounded (exact position of strongly sclerotized pre- and postgenitale not clear as all females in poor conditions due to fixation technique, see above), genital plates slender kidney-shaped, total genital field L/W 186/318; acetabula irregularly-oval to triangular ( Fig. 49 ), L/W Ac-1, 70–75/33–39, Ac-2, 86–89/34–45, Ac-3, 75–96/51–57; 21–24 setae arranged mainly at the anterior, posterior and lateral margins of the genital plates, none to one setae anterior to genital plates ( Fig. 49 ); measurements of distal leg segments: L/H I-leg-5, 319/-, I-leg-6, 264/-; II-leg-5, 336–366/54–60, II-leg-6, 282–288/54; III-leg-5, 402–410/55– 66, III-leg-6, 330–348/54; IV-leg-3, 252–258/72, IV-leg-5, 376–438/56–66, IV-leg-6, 336–378/54–48 (legs not illustrated due to poor conditions); chelicerae similar to males, slightly stronger ( Figs. 50, 51 ); palps similar to males ( Fig. 52 ); mouthpart measurements: chelicera total L 541–600, maximum H 144–156, L/H ratio 3.5–3.9, basal segment L 354–362, claw L 271–275, basal segment/claw ratio 1.3; cheliceral claw curve 20–22°; palp total L 632–658, L/H P-1, 61–68/89–108, P-2, 172–181/108, P-3, 118–125/90–99, P-4, 221–230/71–73, P-5, 56/61–63.

Remarks: The new species Hygrobates intermedius sp. nov. from Jiangxi Province, China is most similar to H. robustipalpis sp. nov. —males of both species are characterized by a slightly dumbbell-shaped genital field. However, in H. intermedius sp. nov. the outline of the male genital field is rather regularly oval, whereas in H. robustipalpis sp. nov. the outline is apple-shaped. Furthermore, in the latter the anterior coxal group is posteriorly wider (Cx-I basal width/Cx-I+II width: robustipalpis male 0.36–0.37, female 0.40; intermedius male 0.34–0.35, female 0.36); the palps (especially P-4) are more compact: P-4 L/H 2.5–2.7 ( robustipalpis male), 2.5–2.6 ( robustipalpis female); 3.0–3.1 ( intermedius male) 3.1 ( intermedius female). Hygrobates robustipalpis sp. nov. (especially the male) is the smallest Lurchibates species so far described: idiosoma L/W 640–670/560–600 ( robustipalpis male); 760–920/580–720 (other species of Lurchibates males). The female of H. intermedius sp. nov. is similar to H. aloisii , especially in the shape of the genital field, as in both species the genital plates are flanking the posterior 2/3 of the genital opening; however, in the latter species the genital plates are anterior more pointed. In H. salamandrarum the genital plates are in the same position as in the two species mentioned before, but this species is characterized by a very broad gnathosoma and a very short P-4: L/H 2.1 ( H. salamandrarum , female); 3.0 ( intermedius sp. nov., female); 3.0–3.2 ( H. aloisii , female).

As mentioned before, H. robustipalpis sp. nov., the smallest species described so far, is characterized by the combination of it’s dumbbell-shaped genital field, relatively compact palps and a dense, rather large denticle field ventrally at P-3 (as well as relatively many denticles ventrally at P-2); the female is separated from those of the other species of the subgenus mainly by it’s typical palp (similar to the male—compact P-4 (L/H 2.5–2.6), large strong claws and large pointed basal cone at P-5, dense field of denticles at P-3) and relatively large, broad genital plates larger than the genital opening.

Hygrobates pilosus sp. nov. is mainly characterized by the very characteristic male genital field—it’s wing-like shape and large number of setae is clearly separating the species from all other so far described ones; the anterior coxal group (with the pointed, narrow posterior margin) is slightly similar to H. forcipifer , however it’s rectangular Cx-IV, and especially the shape of the genital field, are clearly separating H. pilosus sp. nov. from the latter.

There are also obvious differences in the shape of the genital skeleton, with regard to the poor conditions of this structure in most preparations so far these are not used systematically in the separation of the species.

Figures

FIGURE 39. Hygrobates pilosus sp. nov., holotype male, ventral view of idiosoma; scale bar = 100 μm.

FIGURES 40–48. Hygrobates pilosus sp. nov., holotype male, Fig. 40. genital skeleton in anterior view, Fig. 41. I-leg, left, Fig. 42. II-leg, left, Fig. 43. III-leg, left, Fig. 44. IV-leg, left, Fig. 45. right chelicera in lateral view, Fig. 46. left chelicera in medial view, Fig. 47. left palp in medial view, Fig. 48. right palp in lateral view; scale bar = 100 μm.

FIGURES 49–52. Hygrobates pilosus sp. nov., paratype female, Fig. 49. ventral view of idiosoma (integument between coxal field and genital field broken, therefore glandularia and setae normally surrounding genital field lost), Fig. 50. left chelicera in medial view, Fig. 51. right chelicera in lateral view, Fig. 52. left palp in lateral view (most setae missing due to poor condition of specimen), scale bar = 100 μm.