Phthiracarus minutus, Liu & Zhang, 2016

Liu, Dong & Zhang, Zhi-Qiang, 2016, Phthiracarus species (Acari: Oribatida: Phthiracaridae) from New Zealand, with description of a new species, redescription of Phthiracarus pellucidus and a key to 19 described species from the Australian Region, Journal of Natural History (J. Nat. Hist.) 50, pp. 1463-1472 : 1464-1467

Phthiracarus minutus sp. nov.

( Figure 1 )

Diagnosis

Surface of idiosoma densely punctate; median carina and lateral carinae absent; median sigillar fields narrow, longer than laterals; sensilli short, broad proximally and slightly narrow in the distal; other prodorsal, notogastral and ano-adanal setae minute and fine; setae c 1–2 farther away from anterior border, setae c 3 close; vestigial setae f 1 posterior to setae h 1; four pairs of lyrifissures ia, im, ip and ips present; h <h–h; genital plates with oblique lines not reaching inner margin; formula of genital setae: 9(4 + 5): 0; adanal setae situated close to paraxial margin; setae d on femora I situated near distal end of article; setae v’ on femora I absent.

Description

Measurements. Holotype: Prodorsum: length 351, width 235, height 130, setae: ss 50, ro 10, le 10, in 10, ex 20; notogaster: length 598, width 460, height 462; setae: c 1 20, d 1 20, e 1 20, h 1 18, ps 1 18; ventral region: ad 3 15, an 1 7, an 2 7; genito-aggenital plate 102 × 210, ano-adanal plate 126 × 261. Paratype: Prodorsum: length 305, width 206, height 120; notogaster: length 490, width 422, height 405.

Integument. Colour greyish-yellow. Surface of idiosoma densely punctate.

Prodorsum ( Figure 1A–C ). Median carina, lateral carinae and posterior furrows absent; sigillar fields distinct, median region narrow, longer than lateral regions; sensilli short and smooth, broad proximally and slightly narrow in the distal; other prodorsal setae minute and fine; comparative length: ss> ex> in = le = ro; mutual distance: in – in / ro – ro ≈ 4.

Notogaster ( Figure 1A ). 15 pairs of setae present, minute (c 1 <1/5 c 1 – d 1) and fine; setae c 1–2 farther away from anterior border, setae c 3 close; three pairs of elongated insertion prints present on the roots of setae ps 2 – ps 4; vestigial setae f 1 posterior to setae h 1; four pairs of lyrifissures ia, im, ip and ips present.

Venter ( Figure 1A, D–G ). Setae h of mentum shorter than distance between them. Genital plates with oblique lines not reaching inner margin; nine pairs of genital setae present, arranged in two rows with formula: 9(4 + 5): 0; anoadanal plates each with five minute setae; adanal setae situated close to paraxial margin, setae ad 1 closest and ad 3 furthest.

Legs ( Figure 1H–I ). Setal counts for leg segments (without tarsi): I: 1–3–2(2)–5(1); II: 1–3–2(1)–3(1), III: 2–2–1(1)–2(1), IV: 2–1–1–2(1); setae d on femora I situated near distal end of article; setae v’ on femora I absent; setae a” on tarsi I and setae ft” on tarsi II curved distally; setae a” on tarsi II curved distally; setae s and pv’ on tarsi IV present; setae s on tarsi I and II present.

Material examined

Holotype: adult (in alcohol, 72/227), New Zealand: Red I. Mercury Is. Cl., from litter, 24 November 1972, leg. G.W. Ramsay. Paratype: one adult (in alcohol, 72/227), same data as holotype.

Etymology

Named after the minute notogastral setae.

Remarks

This new species is very easily distinguishable from all congeneric species of this genus by the following combination of features: sensilli short and slightly narrow distally; all other setae minute and fine; vestigial setae f 1 posterior to setae h 1; four pairs of lyrifissures ia, im, ip and ips present; formula of genital setae: 9(4 + 5): 0; setae v’ on femora I absent.

Redescription of known species

Figures

Figure 1. Phthiracarus minutus sp. nov.: (A) lateral view of body (legs removed); (B) prodorsum, dorsal view; (C) sensillus, dorsal view; (D) left side of ventral plate; (E) subcapitulum, palpi removed; (F) palp, antiaxial view; (G) chelicera, antiaxial view; (H) femur I; (I) tibia IV. Scale bars: A, B, D = 100 μm; C, E–I = 50 μm.