Eylais (Meteylais) hamata Koenike, 1897

Li, Hai-Tao, Jin, Dao-Chao, Yi, Tian-Ci & Guo, Jian-Jun, 2022, Contributions to the knowledge of Eylaoidea (Acari: Hydrachnidiae) from China, European Journal of Taxonomy 787 (1), pp. 53-70 : 55-59

Eylais (Meteylais) hamata Koenike, 1897

Figs 1–5

Diagnosis

Eye-plate relatively long; eye bridge almost uniform-in-width, straight or slightly curved; longer than eye capsules; O 2 inserted into a pair of sclerotic loops on eye bridge; excretory pore with a sclerotized ring; E

4

behind the middle of Cx-IV.

Material examined

CHINA • 3 ♂♂, 2 ♀♀; Qinghai Province, Qinghaihu National Nature Reserve ; 36°36′23″ N, 100°46′35″ E; 3209 m a.s.l.; 7 Aug. 2020; Dong-Dong Li & Hai-Tao Li leg.; water depth 20–40 cm, located in a prairie, with many aquatic plants on the bottom; GUGC, slides No. QH-EY-20200801 to 20200805 .

Description

Male (n = 3) BODY. Dull red color. Idiosoma extremely soft and oval; integument with fingerprint-like striae. No sclerites except eye-plate in dorsal view ( Fig. 1A ). Eye-plate relatively long; eye bridge almost uniformin-width, straight or slightly curved; O 2 inserted into a pair of sclerotic loops on eye bridge; a pair of humps existed sometimes ( Figs 1B , 2A–B ).

COXAE. The apical angles of Cx-I–IV with 2–4 setae, line of setae on each coxa; all coxae striated, like elephant skin ( Fig. 1E ).

GENITALIA. Genital field with numerous tapered setae; a pair of sclerotic genital flaps with many fine setae and two small and narrow transverse genital sclerites surrounding gonopore ( Fig. 2C ); V 1 free and close to rear side of ACG; acetabula rounded and stalked, occupying all over the integument; excretory pore with a sclerotized ring; E 4 behind the middle of Cx-IV and at the level of the excretory pore ( Fig. 1E ).

GNATHOSOMA. Cuticle porous; basal segments of chelicera large, cheliceral claws short and blunt, projecting through the center of the filled wheel-like membrane; pharynx with a pair of bulges at the lateral bottom, two strongly sclerotized rings on pharynx ( Figs 1C , 2D ).

PALP. Five-segmented; P-I with 1–2 dorsal setae, apical setae feathered or smooth; P-II with three setae on dorsum, three lateral setae in a line (feathered or not) on outer side, and 4–5 distal setae (feathered or not) and 1–2 lateral setae on inner side; P-III with six ventrodistal feathered setae on inner side, 5–6 setae in a line (feathered or not) and one anteroventral seta (feathered or not) on outer side; P-IV relatively long, with one seta at about ⅓ of the total length of the segment on outer side, and numerous setae on inner side; P-V with two dorsal and 3–4 lateral setae, and 1–2 heavy setae on outer side, 2–3 setae on inner side, and with a six-toothed claw at distal end ( Figs 3C–D , 4A–B ).

Female (n = 2)

Bright red color; similar to male; gonopore without sclerotized genital flaps; excretory pore relatively round ( Fig. 1D ); P-IV as broad as in the male but shorter, P-V hook-like ( Fig. 3A–B ).

Measurements

Male (n = 3)

Idiosoma 1859–2539 in length, 1427–2138 in width; ACG length 695–792 (from apex of Cx-I to Cx- II base angle); PCG length 699–855 (from apex of Cx-III to Cx-IV base angle); eye plate 393–464 in length, eye bridge length 158–197, eye capsules 151–176 in length, 114–133 in width; capitulum

length 596–691 (from chelicera peak to pharynx bottom), mouth opening 173–199 in diameter, pharynx 282–334 in length; gonopore length 238–282; sclerotization of excretory pore 76–79 in diameter; dorsal lengths of palp segments: P-I 114–142, P-II 157–180, P-III 154–210, P-IV 304–364, P-V 173–199; P-IV 81–97 in width; dorsal lengths of leg segments: I-L-2 340–355, I-L-3 309–324, I-L-4 382–391, I-L- 5 378–385, I-L-6 384–397. II-L-2 374–389, II-L-3 362–368, II-L-4 422–431, II-L-5 489–492, II-L-6 383–389. III-L-2 450–454, III-L-3 418–427, III-L-4 450-459, III-L-5 502–506, III-L-6 431–434. IV-L-2 453–462, IV-L-3 496–501, IV-L-4 551–557, IV-L-5 585–591, IV-L-6 448–454.

Female (n = 2)

Idiosoma 1725–1814 in length, 1412–1468 in width; ACG length 529–540; PCG length 540-561; eye plate 343–365 in length, eye bridge length 168–184, eye capsules 123–130 in length, 88–89 in width; capitulum length 501, mouth opening 127–152 in diameter, pharynx 254–256 in length; gonopore length 253–259; sclerotization of excretory pore 45–48 in diameter; dorsal lengths of palp segments: P-I 95– 110, P-II 130–135, P-III 136–148, P-IV 246–256, P-V 156 (147–156), P-IV 87 (87–95) in width; dorsal lengths of leg segments: I-L-2 233–238, I-L-3 204–210, I-L-4 239–240, I-L-5 289–296, I-L-6 285–296. II-L-2 262–265, II-L-3 233–241, II-L-4 274–278, II-L-5 328–334, II-L-6 316–321. III-L-2 320–322, III-L-3 270–274, III-L-4 324–326, III-L-5 337–347, III-L-6 345–352. IV-L-2 228–231, IV-L-3 269– 274, IV-L-4 331–338, IV-L-5 383–391, IV-L-6 369–380.

Remarks

Eylais (M.) hamata is widely distributed all over the world ( Piersig 1897 –1900; Halbert 1903; Sezek & Özkan 2000). Lundblad (1936) had reported this species from Northwest China, while the previous descriptions were relatively simple ( Uchida & Imamura 1951). Current specimens, which were also collected from Northwest China (Qinghaihu National Nature Reserve), are similar with the description mentioned above, especially their eye plate, which is considered as the most distinguishing feature. The only difference with the Turkish population is the body size: males ranging from 1859 to 2539, females ranging from 1725 to 1824 in our specimens, but with the Turkish population, 2250 for the male and 4200 for the female ( Sezek & Özkan 2000). This problem can be interpreted by Lanciani (1969, 1970) that the size of newly emerged eylaid mites could increase continuously in both sexes, even during their adult stages, and the gravid females could grow twice as long. In summary, we attribute our specimens to E. (M.) hamata .

Figures

Fig. 1. Eylais (Meteylais) hamata Koenike, 1897. A–C, E. ♂ (GUGC QH-EY-20200801). D. ♀ (GUGC QH-EY-20200804). A. Idiosoma, dorsal view. B. Eye plate (with a pair of humps). C. Gnathosoma. D–E. Idiosoma, ventral view. Scale bars = 200 μm.

Fig. 2. Eylais (Meteylais) hamata Koenike, 1897, SEM photographs, ♂. A. GUGC QH-EY-20200802. B–D. GUGC QH-EY-20200803. A. Eye plate (curved). B. Eye plate (straight). C. Genital field (cuticle crumpled). D. Gnathosoma.

Fig. 3. Eylais (Meteylais) hamata Koenike, 1897. A–B. ♀ (GUGC QH-EY-20200804). C–D. ♂ (GUGC QH-EY-20200801). A. Palp, inner side. B. Palp, outer side. C. Palp, inner side. D. Palp, outer side. Scale bar = 200 μm.

Fig. 4. Eylais (Meteylais) hamata Koenike, 1897, SEM photographs, ♂ (GUGC QH-EY-20200803). A. Palp-2–5. B. Palp-5, terminal.

Fig. 5. Eylais (Meteylais) hamata Koenike, 1897, ♀ (GUGC QH-EY-20200804). A. I-L-1–6. B. II-L- 1–6. C. III-L-1–6. D. IV-L-1–6. Scale bar = 200 μm.