Litarachna lukai, Pešić, Vladimir, 2013

Pešić, Vladimir, 2013, Pontarachnid mites from marine interstitial, with a description of three new species from South Korea (Acari: Hydrachnidia: Pontarachnidae), Zootaxa 3701 (1), pp. 83-92 : 85-87

Genus Litarachna Walter, 1925

Litarachna lukai sp. nov. ( Figs. 2D , 3A–G )

Type series. Holotype male (NIBRIV0000268888), dissected and slide mounted in Hoyer's fluid, South Korea, Yellow Sea, Wido Island, beach, 35º35.089' N, 126º 15.196' E, interstitial, 12.iv.2013 Karanović. Paratypes: one male, one female, same locality and data as holotype, female dissected and slide mounted (NIBRIV0000268889).

Diagnosis: Ocular pigment absent; P-2 with ventrodistal extension; P-2 and P-4 almost equal in length; P-4 stout, with a ventral setal tubercle. Male: Medial apodemes of Cx-IV not extending to anterior margin of genital field; nine pairs of perigenital setae around genital field.

Description. Male: Integument soft, ocular pigment absent ( Fig. 2D ). Idiosoma L/W 316/191. Coxal field: L/ W 105/152; Cx-I separated medially; suture lines Cx-II/III and Cx-III/IV incomplete; posterior margin of Cx-IV strongly concave, with two pairs of apodemes of moderate length, the medial ones not extending to anterior margin of genital field ( Fig. 3A ). Genital field L/W 28/28, consisting of a sclerotized ring with three pairs of setae; nine pairs of perigenital setae free in integument around genital field. Between the posterior apodemes of the fourth coxal plates a pair of glandularia-like structures and a pair of small platelets with coxoglandularia 4 and associated setae. Posterior to the genital field a pair of platelets with three pores and three pairs of wheel-like acetabula (sensu Cook 1996). Two of these wheel-like structures large with many radiating spokes, the most posterior ones small with relatively few radiating spokes. Excretory pore unsclerotized, near posterior end of idiosoma. Gnathosoma L 95; chelicera total L 122, claw L 34, basal segment L 90, L ratio basal segment/claw 2.65. Palp ( Fig. 3C ): total L 201, dL/H, L/H ratio: P-1, 14/22, 0.65; P-2, 60/32, 1.86; P-3, 34/29, 1.16; P-4, 59/20, 2.9; P-5, 34/12, 3.0; dL P-2/ P-4 ratio 1.03; P-2 with ventrodistal extension, ventral margin concave, dorsal margin convexly bowed; P-3 ventrally slightly concave; P-4 stout, ventral margin with a setal tubercle, dividing segment in two parts, distal patr slightly longer than proximal part, both parts with a slightly concave margin. Legs: dL of I-L-4–6 ( Fig. 3E ): 38, 57, 68; I-L-6 H 22, I-L-6 dL/H ratio 3.04, I-L-6 ventral margin convex; dL of IV-L-4–6 ( Fig. 3F ): 62–64, 72, 69–73; III-L-5 with one swimming seta; IV-Leg-5 with one swimming setae.

Female: Similar to male, except for the shape of the genital field and postgenital area ( Fig. 3B ). Idiosoma L/W 354/212. Coxal field: L/W 111/166, medial posterior apodemes of Cx-IV reaching lateral margins of the pregenital slerite. Genital field L/W 55/29, pregenital and postgenital sclerite bowed, postgenital sclerite L 26. Posterior to the genital field a pair of platelets with three pores and four pairs of wheel-like acetabula; three of these wheel-like structures large with many radiating spokes, the most posterior of the wheel-like structures small with fewer radiating spokes. Gnathosoma L 108; chelicera ( Fig. 3G ) total L 139, claw L 35, basal segment L 108, L ratio basal segment/claw 3.1. Palp ( Fig. 3D ): total L 221, dL/H, L/H ratio: P-1, 14/22, 0.65; P-2, 68/35, 2.0; P-3, 34/32, 1.05; P-4, 66/23, 2.86; P-5, 39/14, 2.8; dL P-2/P-4 ratio 1.02; palp as in male. Legs: dL of I-L: 36, 29, 41, 42, 62, 70; I-L- 6 H 26, I-L-6 dL/H ratio 2.67; dL of IV-L-3-6: 43, 62, 75, 77; number of swimming setae as in the male.

Etymology. The species is named after Luka Pešić, the three-year old son of the author.

Remarks. The new species belongs to the L. duboscqi species group (see Pešić et al. 2008b). Due to the glandularium-like structur posterior to Cx-IV, not fused with adjoining coxoglandularia 4, and the similar number of perigenital setae (about ten pairs) in the male, the new species resembles Litarachna hongkongensis Smit, 2002 , a species described by Smit (2002) from Starfish Bay, Hong Kong. The new species can easily be distinguished from the latter species and other members of the duboscqi -species group by the reduced ocular pigment and ventrodistal edge of P-2 ending in a pointed extension. Moreover, L. hongkongensis has much longer medial posterior apodemes of Cx-IV in the both sexes (see Smit 2002).

Distribution. South Korea (Yellow Sea); known only from the type locality.

Figures

FIGURE 2 A – H. Photographs of the dorsum. A – C Pontarachna ivonae sp. nov.: A – B – specimens from Wido Island, interstitial; C – specimen from Yeondeok, littoral. D Litarachna lukai sp. nov., holotype. E – F Litarachna gracilis sp. nov., female holotype. G – H Litarachna cf. denhami (Lohmann, 1909), female, Gupyeong-ri, South Korea, littoral.

FIGURE 3 A – G. Litarachna lukai sp. nov. (A, C, F – G = male holotype, B, D, G = female): A – B = idiosoma, ventral view; C = palp; D = palp (P- 1 missing); E = I-L- 4 – 6; F = IV-L- 4 – 6; G = chelicera. Scale bars = 100 µm.