Petalomium crossi Khaustov

Khaustov, Alexander A., 2015, Two new myrmecophilous species of the genus Petalomium (Acari: Pygmephoroidea: Neopygmephoridae), Zootaxa 3999 (4), pp. 549-559 : 550-554

Petalomium crossi Khaustov sp. n.

( Figs. 1–4 )

Description. FEMALE (holotype, Figs. 1–4 ). Body weakly sclerotized. Length of idiosoma 365, width 295. Gnathosoma ( Fig. 2 ). Gnathosomal capsule semioval, slightly longer than its width. Cheliceral setae (cha, chb) smooth and pointed. Setae chb (19) distinctly longer than cha (12). Dorsal median apodeme weakly developed. Pair of needle-like postpalpal setae (pp) situated anteriorly to setae cha. Ventral gnathosoma with 1 pair of smooth, pointed subcapitular setae m (17) and 1 pair of round pits situated posterior to bases of m. Palps freely articulated to gnathosomal capsule, with smooth, pointed setae dFe and dGe dorsolaterally, setae dGe slightly longer than dFe. Ventrally with large accessory setigenous structure (ass) and small solenidion. Palps terminated with a small claw; palptarsus with a tiny peg-like setigenous structure. Pharyngeal pump I small, situated inside gnathosomal capsule; pharyngeal pump II large, about 2 times longer than pharyngeal pump III. Idiosomal dorsum ( Fig. 1 A). Only posterior part of prodorsum covered by anterior margin of tergite C, with 2 pairs of setae (v 2, sc 2), 1 pair of clavate and weakly barbed trichobothria (sc 1) with pointed apex and 1 pair of round stigmata with transverse slit-like openings. All dorsal plates smooth. Setae v 2 smooth, vestigial, other dorsal setae distinctly barbed; setae h 2 densely covered by numerous and thin barbs (pubescent), other dorsal setae sparsely barbed. All dorsal setae pointed. Posterior margin of tergite C distinctly concave; posterior margin of tergite EF deeply concave; Tongue-like elongation not evident on posterior margin of tergite H. Cupules ia on tergite D and ih on tergite H small, round. Lengths of dorsal setae: v 2 3, sc 2 37, c 1 105, c 2 135, d 140, e 56, f 155, h 1 115, h 2 80. Distances between setae: v 2 –v 2 78, sc 2 –sc 2 80, c 1– c 1 94, c 1– c 2 59, d–d 86, e–f 20, f–f 74, h 1– h 1 27, h 1– h 2 16. Idiosomal venter ( Fig. 1 B). All ventral plates smooth. Ventral setae 3 b with swollen basal part and pointed apex, smooth; setae 4 c and ps 3 smooth, other ventral setae barbed. Setae 1 b not bifurcate. Apodemes 1 (ap1) well developed and joined with prosternal apodeme (appr); apodemes 2 (ap2) weakly developed, thin, not joined with appr, prosternal and sejugal (apsej) apodemes well developed; appr with gap in central part; apodemes 3 (ap3) weakly developed, straight, diffuse. Apodemes 4 (ap4) well sclerotized, long and joined with poststernal apodeme (appo), distal end of appo bifurcate; apodemes 5 absent. Posterior margin of posterior sternal plate convex in its middle part. Posterior margin of aggenital plate weakly concave. Anterior genital sclerite (ags) bell-like, posterior genital sclerite (pgs) triangular, median genital sclerite (mgs) weakly sclerotized, small, rounded. Length of ventral setae: 1 a 72, 1 b 45, 2 a 68, 2 b 53, 3 a 40, 3 b 21, 3 c 60, 4 a 52, 4 b 83, 4 c 90, ps 1 60, ps 2 50, ps 3 11. Legs ( Figs. 3 , 4 ). Leg I ( Fig. 3 A) distinctly shorter and thinner than leg II. Setal formula: 1–3–4–16 (4). Tibiotarsus not thickened, with terminal claw situated on distinct pretarsus, tip of its claw thin. Lengths of solenidia ω 1 13> ω 2 8> φ 1 7 = φ 2 7; ω 2 and φ 2 baculiform, φ 1 clavate, ω 1 finger-shaped. Eupathidium tc” situated on short pinnaculum. Setae dFe broadened, slightly curved at the tip. Setae l’Fe bluntended, smooth, other leg setae (except eupathidia) pointed and sparsely barbed. Leg II ( Fig. 3 B). Setal formula: 1– 3–3–4(1)–6(1). Tarsus with sickle-like, padded claws and large flipper-like and longitudinally striated empodium. Solenidion ω (13), finger-shaped, solenidion φ (7) weakly clavate. Setae v”Fe smooth, other leg setae sparsely barbed, pointed. Leg III ( Fig. 4 A) similar in shape and length with leg II. Setal formula: 1–2–2–4(1)–6. Claws and empodium of same shape as on tarsus II. Solenidion φ (7) weakly clavate. All leg setae pointed and sparsely barbed. Leg IV ( Fig. 4 B). Setal formula: 1–2–1–4(1)–6. Tarsus long and thin, pretarsus long, with two small simple claws and small non-striated empodium. Solenidion φ (52) unusually long, uniformly thin. Seta v’Ti slightly thickened and pubescent in distal half, other leg setae pointed and sparsely barbed.

MALE and LARVA unknown.

Type material. Female holotype, slide No. AP 051214 from ant Myrmicaria distincta Santschi, 1925 , ETHIOPIA: Amhara Region, Bahir Dar city, territory of the Bahir Dar Fisheries and other Aquatic Life Research Center, coast of lake Tana, 11º36,70'N, 037º22,36'E, 5 December 2014, coll. A.A. Prokin.

Etymology. The new species is named after the well-known acarologist Dr. Earl Cross to honor his great contributions to the studies about heterostigmatic mites.

Differential diagnosis. The new species is most similar to P. heterotrichus Mahunka, 1970 by pubescent setae h 2, similar relative lengths of pseudanal setae, relatively short pinnaculum of setae tc” on tibiotarsus I and similar shape of trichobothria. It differs from P. heterotrichus by swollen basally setae 3 b (not modified in P. heterotrichus ), thickened and pubescent in distal half setae v’TiIV (not thickened and sparsely barbed in P. heterotrichus ), by setae e shorter than h 2 (e distinctly longer than h 2 in P. heterotrichus ) and by smooth setae 4 c (barbed in P. heterotrichus ).

Figures

FIGURE 1. Petalomium crossi Khaustov sp. nov., female: A—idiosomal dorsum, B—idiosomal venter.

FIGURE 2. Petalomium crossi Khaustov sp. nov., female: A—gnathosoma in dorsal view, B—gnathosoma and pharyngeal pumps in ventral view.

FIGURE 3. Petalomium crossi Khaustov sp. nov., female: A—leg I in dorsal view, B—leg II in dorsal view.

FIGURE 4. Petalomium crossi Khaustov sp. nov., female: A—leg III in dorsal view, B—leg IV in dorsal view.