Oribotritia gigas Bayoumi & Mahunka, 1979

Liu, Dong, 2015, Review of Oribotritia (Acari, Oribatida, Oribotritiidae) with a world checklist and description of a new species from China, Zootaxa 4007 (2), pp. 217-241 : 226-229

Oribotritia gigas Bayoumi & Mahunka, 1979

( Figs 5–6 )

Oribotritia nepalensis Niedbała, 2000 syn. nov.

Measurements of specimen from Sichuan. Prodorsum: length 706, width 546, height 250, setae: ss 240, ro 230, in 410, le 190, ex 100, mutual distance: in–in 185, le–le 438, ro–ro 100; notogaster: length 1200, width 1170; c 1 146, c 2 175, c 3 120, c p 130, d 2 120, e 1 125, e 2 115, h 1 134, ps 2 160, ps 3 150, mutual distance: c 1– d 1 145, d 1– e 1 265, e 1– h 1 145; genito-aggenital plate 321×200, ano-adanal plate 765×155.

Measurements of specimen from Jilin. Prodorsum: length 560–609, width 400–580, height 160–170, setae: ss 200, ro 180, in 244, le 100, ex 135, mutual distance: in–in 145, le–le 380, ro–ro 115; notogaster: length 1050– 1233, width 790–885, height 768–810; c 1 190, c 2 174, c 3 150, c p 170, d 1 164, d 2 150, e 1 174, e 2 152, h 1 190, h 2 170, h 3 130, ps 1 190, ps 2 146, ps 3 140, mutual distance: c 1– d 1 280, d 1– e 1 472, e 1– h 1 315, h 1– ps 1 250; genito-aggenital plate 320×170, ano-adanal plate 570×140.

Description of Specimen from Sichuan ( Figs 5 A–C): Colour brown. Prodorsum with one pair of long and simple lateral carinae; sensilli setiform, smooth and tapering; interlamellar and rostral setae long, thick erect, and sparsely barbed; other prodorsal setae fine and smooth; comparative lengths: in> ss> ro>le> ex, in–in / ro–ro≈ 1.9. Notogastral setae similar in shape to interlamellar setae (c 1/ c 1– d 1 ≈ 1). Setae h of mentum longer than distance between them; setation of palps: 0-3-0-3-9(1); epimeral setal formula: 3-0-3-3. Eight pairs of minute genital setae present, including three pairs inserted on progenital area; two pairs of aggenital, one or two pairs of anal (left side with one pair, right side with two pairs in one specimen, and both sides with two pairs in another one) and three pairs of adanal setae present, all minute; setae ad 3 situated between setae an 1 and an 2; lyrifissures iad placed at level between setae ad 2 and ad 3. Setal counts for leg segments: I: 1-4-5(2)-5(1)-22(3); II: 1-4-4(1)-4(1)-18(2), III: 3-2- 3(1)-3(1)-15, IV: 3-2-2(1)-3(1)-14; femora I slightly thicken at distal end.

Description of specimen from Jilin ( Figs 6 A–G): Colour brown to dark brown, anterior part of prodorsum with distinct striations. Prodorsum with one pair of long and simple lateral carinae; sensilli rough and setiform; interlamellar and rostral setae stout, erect and densely barbed in distal half, thicker than sensilli; lamellar and exobothridial setae smooth and fine; comparative lengths: in> ss> ro>ex> le, in–in / ro–ro≈ 1.3. Notogastral setae fairly short (c 1/ c 1– d 1 ≈ 0.7), densely barbed as interlamellar setae. Setae h of mentum considerably longer than distance between them; setation of palps: 0-3-0-3-9(1); epimeral setal formula: 3-0-2-2 or 3-0-2-3. Eight pairs of genital setae arranged with formula: 6:2; two or three pairs of minute aggenital setae located longitudinally; two pairs of anal and three pairs of adanal setae present, all minute; setae ad 3 situated between setae an 1 and an 2; lyrifissures iad placed at level of setae ad 3. Setal counts for leg segments: I: 1-4-5(2)-5(1)-22(3); II: 1-4-4(1)-4(1)- 19(2), III: 3-2-3(1)-4(1)-16, IV: 3-2-2(1)-3(1)-14; femora I slightly thicken at distal end.

Material examined. ZMCAS: China: Sichuan Province: 2 adults (in alcohol, W-90-19), Nanping, Jiuzhaigou, Wucaihu, 2800 m a.s.l., from soil, 5 Jul. 1990, leg. Fu-Sheng Huang. ZMCAS: China: Jilin Province: 1 adult (in alcohol, CB-C-7), Changbai Mt., from leaves under shrub, 23 Jul. 1980, leg. Hui-Fu Wang and Yun-Qi Cui. 10 adults (in alcohol, CB-C-29), Changbai Mt., Hanconggou, 750 m a.s.l., from litter, 31 Jul. 1980, leg. Hui-Fu Wang and Yun-Qi Cui; 4 adults (in alcohol, CB-C-35), Changbai Mt., from moss under Betula sp., 28 Jul. 1980, leg. Hui- Fu Wang and Yun-Qi Cui; 2 adults (in alcohol, CB-C-44), Changbai Mt., Yihaodi, 750 m a.s.l., from leaves, 2 Aug. 1980, leg. Hui-Fu Wang and Yun-Qi Cui. NIGA: China: Jilin Province: 2 adults (in alcohol, CB-12-005), Changbai Mt., Xiaotianchi, 710 m a.s.l., from litter, 28 May 2012, leg. Dong Liu, Xin Sun and Donghui Wu; 1 adult (in alcohol, CB-12-006), same data as CB-12-005; 1 adult (in alcohol, CB-12-007), same data as CB-12-005; 3 adults (in alcohol, CB-12-010), Changbai Mt., Beipo, 960 m a.s.l., from litter under mixed forest, 28 May 2012, leg. Dong Liu, Xin Sun and Donghui Wu; 1 adult (in alcohol, CB-12-013), same data as CB-12-010; 1 adult (in alcohol, CB- 12-015), same data as CB-12-010; 3 adults (in alcohol, CB-12-016), same data as CB-12-010.

Remarks. Compared with the original description of holotype and redescription of specimens from Nepal, some characters vary in this species: 1) length of prodorsal setae: e.g. length of exobothridial setae (ex> le in Jilin Province, but ex <le in Sichuan Province and Nepal); length of sensilli (longest in Sichuan, shortest in Nepal). 2) number of barbules of setae (densely barbed in Jilin, sparsely barbed in others); 3) length of notogastral setae (c 1 ≈c 1– d 1 in Sichuan, others c 1 <c 1– d 1); 4) epimeral setal (3-0-2-2 or 3-0-2- 3 in Jilin); 5) number of aggenital setae (two or three pairs in Jilin); 6) number of anal setae (one or two pairs in Sichuan); 7) setal counts of legs.

The genus Oribotritia is not easy to deal with as there are few reliable morphological features. This species is very similar to O. asiatica . As mentioned above (see remarks on O. asiatica ), the number of genital setae of O. asiatica varied (eight pairs in Chinese specimens versus nine pairs in type specimen), so they are distinguished only by the number of anal setae (one or two pairs in O. gigas versus three pairs in O. asiatica ). Although the character “one or two pairs anal setae versus three pairs of anal setae” may be a reliable difference, molecular methods may be needed to help resolve the issue.

The species O. gigas and O. nepalensi s, both recorded in Nepal, have nearly the same shape and size, and are similar in other morphological characters; they differ only in setation of epimera and palps. Niedbała (2000) inferred that they may have same origin and may have been subjected to relatively recent adaptative radiation. In my opinion, setation of epimera and palps are difficult traits to study, especially in Oribotritia species, because they usually have a dark cuticule and tightly bundled legs which make setation of epimera and palps very hard to be observed and counted. Many descriptions of Oribotritia species actually did not include or inaccurately include these data. In addition, I have found some examples of the varied setation of epimera and palps in some species or even between sides of a single specimen (see example in Jilin Province and remarks on O. chichijimensis ). Therefore, Oribotritia nepalensis Niedbała, 2000 is probably conspecific with O. gigas .

Figures

FIGURE 5. Oribotritia gigas Bayoumi & Mahunka, 1979 (damaged specimen from Sichuan): A, lateral view of body (part); B, prodorsum, dorsal view; C, ventral region and part of notogaster. Scale bars: 200 Μm.

FIGURE 6. Oribotritia gigas Bayoumi & Mahunka, 1979 (specimen from Jilin): A, lateral view of body (legs removed); B, prodorsum, dorsal view; C, right side of ano-genital region; D – F, trochanter, femur, genu and tibia: D, leg I; E, leg II; F, leg III; G, femur, genu and tibia of leg IV. Scale bars: 200 Μm.