Litarachna enigmatica Durucan & Chatterjee & Pešić 2018, sp. nov.
Creators: name: Durucan, Furkan
name: Chatterjee, Tapas
name: Pešić, Vladimir
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Trombidiformes
Pontarachnidae
Litarachna
Litarachna enigmatica

description: 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.
description: Published as part of 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, pp. 271-278 in Zootaxa 4531 (2) on pages 272-273, DOI: 10.11646/zootaxa.4531.2.8, http://zenodo.org/record/2614636