Arrenurus piersigi, Smit & Pešić, 2023

Smit, Harry & Pešić, Vladimir, 2023, New records of water mites of the family Arrenuridae from the Oriental region, with the description of one new species (Acari: Hydrachnidia), Ecologica Montenegrina 66, pp. 1-10 : 5-6

Arrenurus piersigi n. sp.

https://zoobank.org/ urn:lsid:zoobank.org:act:1030BA9F-6D57-4020-9253-EA5A6BAA4BF7

Figure 2-3

Material examined — Holotype male, Khiri Thaen Reservoir , Chanthaburi Province, Thailand, 12°45.147 N 102°19.443 E, 204 m a.s.l., 14 November 2017, leg H. Smit ( RMNH) . Paratypes: four males, two females, same data as holotype ( RMNH) ; twelve males, five females, pond at Phu Rua, Loei Province, Thailand , 17°26.907 N 101°21.336 E, 618 m a.s.l., 30 Oct. 2017 ( RMNH) .

Other material — Thailand. 1/0/0, Lotus-pond along road 2112, Ubon Ratchathani Province, 15°32.562 N 105°30.952 E, 140 m a.s.l., 8 Nov. 2017 ; 4/6/0, Nong Bua pond, Phu Rua , Loei Province, 17°26.645 N 101°21.213 E, 618 m a.s.l., 30 Oct. 2017 .

Diagnosis (Male) — Idiosoma posteriorly with a large concavity; posterior cauda margin straight with a small median indentation, D1 on large humps, Cx-I and -II laterally with hook-like extensions. Female: D1 and L3 on large humps, idiosoma posteriorly truncated, Cx-I and -II laterally with hook-like extensions (but less distinct than in male).

Description. Male — Idiosoma colour greenish, dorsally 818 (721-802) long and 688 (616-680) wide, ventrally 729 (648-721), the latter measurements very dependent on the position in the slide due to the large humps. Anterior idiosoma margin concave, cauda well set off from idiosoma. Dorsal shield complete, oval, posterior margin with a shallow indentation, 340 (300-340) long and 251 (227-259) wide. D1 on large humps, D3 on small humps. Cauda posteriorly with a large concavity. Cauda 308 wide, posterior margin of cauda straight, with a small median indentation and a slit-like separation. Cx-I and II with hook-like lateral extensions. Suture line Cx-III/IV incomplete. Medial margin of Cx-III longer than medial margin of Cx-IV. Gonopore small, 30 long, not lying between the genital plates. Genital plates relatively wide, extending onto lateral sides. Length of P1-5: 30, 58, 48, 68, 46. P2 medially with three setae. P4 anteroventrally with a broad extension. Length of I-leg-4-6: 132, 124, 130. Length of IV-leg-4-6: 166 (including short spur), 122, 126. Third and fourth legs with numerous swimming setae.

Female — Idiosoma colour greenish, dorsally 883 (834-871) long and 749 (713-761) wide, ventrally 778 (713-786) long. Idiosoma anteriorly concave, D1 and L3 on large humps, idiosoma truncated posteriorly. Dorsal shield 462 (462-502) long and 389 (413-421) wide. Coxal field relatively small, Cx-I not extending to anterior idiosoma margin. Cx-I and Cx-II laterally with hook-like extensions. Suture line CxIII/IV incomplete. Median margin of Cx-III larger than median margin of Cx-IV. Medial distance of Cx-IV smaller than width of gonopore valve. Genital field 486 wide, genital plates relatively wide and bowed, not extending to lateral idiosoma margin. Gonopore without sclerotization, 114 long and 82 wide. Length of P1- 5: 30, 62, 44, 68, 44. Palp as in male. Length of I-leg-4-6: 120, 108, 102. Length of IV-leg-4-6: 160, 150, 126. Third and fourth legs with numerous swimming setae.

Etymology — Named after the German acarologist Richard Piersig (1857-1906).

Discussion — The new species is close to Arrenurus gibberifrons . Differences can be found in the shape of the cauda. The male of the new species has the posterior margin of the cauda with a small indentation, A. gibberifrons has a wide indentation (compare figs 1A and 2A). Moreover, both sexes of the new species have larger D1 humps compared to A. gibberifrons , and the size of the idiosoma is larger (although there is a large overlap). According to Piersig 1906) the male A. gibberifrons is dorsally 675 long and 485 wide which is much less than the holotype of the new species. According to Cook (1967) male specimens of A. gibberifrons from India are 699-714 in length and 517-577 in width. The illustrated male of A. gibberifrons of this study is 672 long and 567 wide. Females of the two species are very similar in shape, but A. gibberifrons is smaller. The illustrated female of A. gibberifrons of this study is dorsally 782 long and 672 wide, other females of A. gibberifrons of this study are dorsally 705-786 long and 592-664 wide.

Figures

Figure 2. Arrenurus piersigi n. sp., holotype male: A = dorsum; B = venter; C = lateral view; D = palp. Scale bars: A- C = 200 µm, D = 50 µm.

Figure 3. Arrenurus piersigi n. sp., paratype female: A = dorsum; B = venter. Scale bar = 200 µm.