Litarachna enigmatica Pešić, Durucan & Chatterjee, 2018

Durucan, Furkan, Chatterjee, Tapas & Pešić, Vladimir, 2018, Two new species of the marine water mite family Pontarachnidae (Acari: Hydrachnidia) from the Gulf of Antalya, Turkey, Zootaxa 4531 (2), pp. 271-278 : 272-273

Litarachna enigmatica Pešić, Durucan & Chatterjee sp. nov.

( Figs. 1 A–D)

Type series. Holotype female, dissected and mounted in Hoyer, Turkey, Antalya, Hamit Bey Plaji , 36.87555556°N, 30.70722222°E, 30.vii.2017 leg. Durucan.

Diagnosis (Male unknown): Suture lines Cx-II/III and Cx-III/IV complete; medial posterior apodemes of Cx- IV absent; postgenital sclerite with a pair of wheel-like acetabula; P-2 with a anteroventral tubercle; P-4 ventral margin with a peg-like seta.

Description. Female (holotype): Idiosoma elongated L/W 347/241; coxal field L/W 138/188; Cx-I separated medially; suture lines Cx-II/III and Cx-III/IV complete; posterior margin of Cx-IV without medial apodemes, lateral apodemes shortened and broad ( Fig. 1A ). Genital field L/W 67/34, gonopore elongated, pregenital sclerite small (W 27), postgenital sclerite bowed, with a pair of wheel-like acetabula ( Fig. 1A ). A pair of small platelets with coxoglandularia 4 and associated setae free in the integument posterior to postero-lateral apodemes of Cx-IV. Posterior to the genital field three pairs of probably wheel-like acetabula sensu Cook (1996); excretory pore unsclerotized.

Gnathosoma with a short rostrum, vL 66; chelicera two-segmented, typically claw-like in form, total L 95; palp total L 222, dL/H ratio: P-1, 16/16, 1.0; P-2, 69/34, 2.0; P-3, 38/31, 1.2; P-4, 72/22, 3.3; P-5, 27/13, 2.0; dL P-2/P- 4 ratio 0.96; P-2 with an anteroventral tubercle; P-4 ventral margin with a well developed peg-like seta, dividing the segment into two parts, the proximal one longer than the distal one, both with a concave ventral margin, ventral hair-like setae at the level of peg-like seta insertion ( Fig. 1D ).

Legs: dL of I-L ( Fig. 1B ): 33, 36, 38, 48, 59, 69; I-L-6 H 18, I-L-6 dL/H ratio 3.9; dL of IV-L ( Fig. 1C ): 52, 32, 38, 59, 76, 64; IV-L-5 with one short swimming seta.

Male: Unknown.

Etymology. enigmaticu s—an adjective from Latin origin meaning “mysterious”; refers to the elusive features of the new species.

Remarks. The new species resembles Litarachna gracilis Pešić, 2013 due to the absence of medial apodemes of Cx-IV, the presence of a ventral projection on P-2 and the peg-like seta on P-4. The latter species, described from South Korea (Pešić 2013a), is a characteristic inhabitant of marine interstitial (as indicated by the absence of eye pigment) and can be distinguished by a number of features: suture lines Cx-II/III and Cx-III/IV incomplete, gonopore more elongated, a different arrangement of wheel-like acetabula with the the anterior pair positioned on the level of postgenital sclerite, and two posterior pairs almost touching each other, and P-4 ventral setae approached to the distoventral edge of the segment (Pešić 2013a).

Litarachna enigmatica also resembles to L. smiti Pešić, Chatterjee & Ahmed Abada, 2008 from the Red Sea ( Pešić et al. 2008a, b), L. bartschae Smit, 2003 from Australia and Brunei ( Smit 2003, Pešić et al. 2013b) and L. madagascariensis Pešić, 2013 from Madagascar (Pešić 2013b) in having a ventral projection on P-2 and the peg- like seta on P-4. However, the new species can be easily distinguished from them by the lack of a setal tubercle on P-4 and completely reduced medial apodemes of Cx-IV.

Moreover, the new species is unique within the genus Litarachna in the postgenital sclerite having a pair of wheel-like acetabula, a character found only in the females of Pontarachna . As pointed out by Cook (1996), in males of Pontarachna and both sexes of Litarachna no wheel-like acetabula are present associated with the genital sclerites. Anyhow it is worth to mention that the structure of the so-called wheel-like acetabula associated with the postgenital sclerite should be determined under scanning electron microscope (SEM). Unfortunately, with the single specimen of our study this was not possible.

Distribution. Turkey; known only from the type locality.

Figures

FIGURE 1A–E. Litarachna enigmatica sp. nov., female, Antalya, Hamit Bey Plaji: A = idiosoma, ventral view; B = Leg I; C = Leg IV; D = palps; E = gnathosoma and chelicerae. Scale bars = 100 µm.