Eremulus spindleformis, Ermilov & Hugo-Coetzee, 2012

Ermilov, Sergey G. & Hugo-Coetzee, Elizabeth A., 2012, Oribatid mites of the genus Eremulus Berlese, 1908 (Acari: Oribatida: Eremulidae) from South Africa, African Invertebrates 53 (2), pp. 559-559 : 560-562

Genus Eremulus Berlese, 1908 Eremulus spindleformis sp. n.

Figs 1–3

Etymology: Named in reference to the spindle-form sensilli.

Diagnosis: This species is distinguished from other species of the genus by the following combination of characteristics: body size 397–448×224–265; rostrum weakly protruding anteriorly; transcostula absent; prodorsal setae smooth; interlamellar setae shorter than rostral and lamellar setae; sensilli spindle-form, ciliate; 11 pairs of notogastral setae, medium-sized, setiform and smooth; aggenital setae branched; adanal setae ad 1 longer than ad 2 and ad 3; epimeral setae 1c long and setiform.

Description:

Measurements. Body length 409 (holotype, female), 397–448 (mean 424, 14 paratypes); body width 243 (holotype, female), 224–265 (mean 240, 14 paratypes).

Integument ( Fig. 1A, B ). Body yellow-grey-brownish. Body and legs covered by secretion granules (diameter up to 1 µm). Posterior part of prodorsum with foveolae, which are absent between costulae. Foveolate band on notogaster and anterior to genital plates distinct. A small concave region present between rows of notogastral setae c and la.

Prodorsum ( Figs 1A ; 2A ). Rostrum weakly protruding anteriorly. Costulae long, narrow, almost straight. Transcostula absent, but the rudimentary sites present. Rostral (49–57), lamellar (49–57), interlamellar (32–41) and exobothridial (20–24) setae setiform, smooth, inserted on tubercles. Rostral setae inserted in lateral position on prodorsum. Sensilli (110–118) spindle­form, covered by short cilia, with long stalk (45–53), welldeveloped oblong head (16) and long, flagelliform distal part (49–53). Bothridial margins with teeth (visible under high magnification).

Notogaster ( Figs 1A ; 2B ). Anterior border straight. One pair of humeral condyles indistinctly visible and cristae present. Eleven pairs of notogastral setae (p 3 inserted in marginal position) medium in size, approximately similar in length (45–57; only p 2 and p 3 shorter, 28–36), setiform, smooth, covered by thin, colourless cerotegument. Opisthonotal gland opening and lyrifissures located in arrangement typical for genus, but poorly visible.

Anogenital region ( Fig. 1B ). Six pairs of genital (g 1 – g 6) and three pairs of aggenital (ag) setae with two to four branches. Setae g 1 setiform, not branched or with one short cilium. Two pairs of anal (an 1, an 2, 16–20) and three pairs of adanal (ad 1, 41–45; ad 2 and ad 3, 28–32) smooth, setiform setae. Adanal setae ad 3 inserted close to anal plates. Lyrifissures iad located in arrangement typical for genus.

Epimeral region ( Figs 1B ; 2C, D ). Apodemes 1, 2, sejugal apodeme and short apodeme 3 present. Shape of apodemes and epimeral borders typical for the genus. Epimeral setal formula 3–1–3–3. Setae 1c long (57–65), setiform, smooth or with one short cilium on basal part; all the others shorter, with two to four branches. Two pairs of strongly developed tubercles Sa and Sp present on epimeral region.

Gnathosoma ( Fig. 2E–G ). Subcapitulum longer than wide: 90–98×61–69. Hypostomal setae of different morphology: h branched, longest branch 36–41; m (36–41) setiform, curved in basal part, slightly barbed; a (20–24) setiform and smooth. Adoral setae absent on lips. Palp (length 49–57) with setation 0–2–1–3–8(+1ω). Palpal setae (except tarsus) slightly barbed; solenidion thickened, pressed to palptarsus. Chelicera (90–94) with small tooth on dorsal side. Cheliceral setae long, setiform and barbed; cha (24–26) slightly longer than chb (16–20). Tragardh’s organ long, narrow, with thin distal part, blunt-ended.

Legs ( Fig. 3A–D ). Legs with one simple claw. Formulae of leg setation and solenidia: I (1–5–3–4–20) [1–2–2], II (1–5–3–4–16) [1–1–2], III (2–3–1–3–15) [1–1–0], IV (1–3–2–4–12) [0–1–0]; homology of setae and solenidia indicated in Table 1. Setae smooth or slightly barbed unilaterally. Famulus short, setiform, inserted very close to solenidion ω 2.

Holotype: ♀ SOUTH AFRICA: KwaZulu­Natal: Ladysmith District , 28°28'S 29°51'E, in humid soil and decomposed plant material under indigenous trees, 27.i.1982, C.M. Engelbrecht ( NMBA 1888.12.1).

Paratypes: 14, same data as for holotype (5 NMBA, 5 SZMN, 4 PC) .

Remarks: The new species is clearly distinguishable from the majority of its congeners by the morphology of sensilli. In having spindle-form sensilli, E. spindleformis sp. n. is similar only to E. jyotsnai Sarkar, 1991 from India and E. spinosus Ermilov & Anichkin, 2011 from Vietnam. However, the new species is unlike E. jyotsnai in that it has long, setiform, distal parts of sensilli (short in E. jyotsnai ), setiform notogastral setae (lanceolate in E. jyotsnai ), interlamellar setae of medium size (very short in E. jyotsnai ), genital and aggenital setae branched (setiform in E. jyotsnai ), and setiform epimeral setae 1c (branched in E. jyotsnai ). E. spindleformis sp. n. can be differentiated from E. spinosus by the larger body size (282–315× 157–166 in E. spinosus), sensilli with short cilia (with strong spines in E. spinosus), and the medium size of the interlamellar setae (short in E. spinosus).

Figures

Fig. 1. Eremulus spindleformis sp. n.: (A) dorsal view, legs not shown; (B) ventral view, legs not shown (except trochanters). Scale bar = 100 μm.

Fig. 2. Eremulus spindleformis sp. n.: (A) medial part of sensillus; (B) notogastral setae h2; (C) epimeral tubercles and seta 3c; (D) epimeral seta 1c; (E) subcapitulum, right half; (F) palp; (G) chelicera, anterior part. Scale bars A–D, F, G = 10 μm; E = 20 μm.

Fig. 3. Eremulus spindleformis sp. n.: (A) leg I, right, antiaxial view; (B) tarsus, tibia and genu of leg II, right, antiaxial view; (C) tibia and genu of leg III, left, paraxial view; (D) leg IV, right, antiaxial view. Scale bar = 20 μm.