Megarthrusheise Zhang, Cuccodoro, Chen & Liu, 2021

Zhang, Shan, Cuccodoro, Giulio, Chen, Li & Liu, Zhiping, 2021, Megarthrus of China. Part 3. Comments on the occurrence of Megarthrus nitidulus Kraatz, 1857 in China, and description of a new species, with notes on teratology and phoretic acari in the genus (Coleoptera: Staphylinidae: Proteininae), Zootaxa 4920 (4), pp. 554-564 : 555-562

Megarthrusheise Zhang, Cuccodoro, Chen & Liu sp. nov.

( Figs 1–40 )

Type material. Holotype, male, in cSch “ CHINA, Qinghai province, Yunning si [lamasery], 2890 m, 36°45.6’N, 102°10.6’E, 1–2.VII.2005, J. Hájek, D. Král & J. Rüžička leg. [Ch 10]; individually under stones and logs, in excrements and on vegetation in coniferous forest ”.

Paratypes: same data as holotype, 8 males and 5 females in cSch, 4 males and 2 females in MHNG, and 2 males and 2 females in SWUC; “ CHINA, Qinghai province, Yunning Si [lamasery], 2890 m, 36°45.6’N, 102°10.6’E, 1–16.VII.2005, J. Hájek, D. Král & J. Rüžička leg. [Ch 10 & 19], baited pitfall traps (fish meat) withethylene glycol, wet coniferous forest, close valley above the village, M. Schülke ”, 6 males and 6 females in cSch, and 2 males and 2 females in MHNG ; “ CHINA, Qinghai prov., [CH11-16], road from Honggu to Men Yuan , 37°08’46’’N, 102°14’58.7’’E, 2473 m, river valley, forest edge, semi-open pasture, sifted from mushrooms, 3.VII.2011, leg. M. Schülke ”, 4 males and 3 females in cSch, and 1 male and 1 female in MHNG ; “ CHINA, Qinghai prov., [CH11- 09e], Daban Shan , 62 km NNW Honggu creek valley, Picea , Populus , Betula forest, 36°51’5–28’’N, 102°36’34’’– 37’07’’E, 2236–2350 m, creek valley, litter, dead wood & moss sifted, 10.VII.2011, leg. M. Schülke ”, 1 male in cSch; “ CHINA [26], N-Sichuan, N Songpan, 33°15’26’’N, 103°46’03’’E, 2700 m, spruce forest with birch, 12.VIII. 2012, V. Assing ”, 1 female in cAss; “ CHINA, W Sichuan. Kangding, 2800 m. 30°04N, 101°58E, 21.VII.1998, A. Smetana [C88]”, 1 malein MHNG ; “ CHINA, Sichuan province, Kangding (formerly Tatsienlu), 2900 m. 2.VII.1996, 30°03N, 102°02E, A. Smetana [C48]”, 2 males in MHNG ; “ CHINA, W. Sichuan province, Wassuland. Bzk. Sankiangkou , Coll. H. Becker ”, 1 female in SWUC ; “ CHINA, Gansu province, DAGCANGLHAMO (lamaseri) env. , 34°04.6’N, 102°37.7E, 3644 m, J. Hájek, D. Král & J. Rüžička leg. [Ch6], in Marmota himalayana burrow on excrement of carnivore, alpine meadow with shrubs, on upper margin of coniferous forest, M. Schülke ”, 6 males in cSch; “ CHINA, Gansu prov., [CH11-27], Lenglong Ling Mts. , 60 km NNW Honggu, Jin Sha Gorge , mixed forest ( Picea , Populus , Betula ), 36°51’56.9’’N, 102°38’55.3’’E, litter, moss, mushrooms sifted, 12.VII.2011, leg. M. Schülke ”, 5 males and 5 females in cSch, and 2 males and 2 females in MHNG ; “ CHINA, Gansu province, Lazikou valley , 1946 m. 34°06.9′N, 103°53.7′E (GPS), 26–27.VI.2005. J. Hájek, D. Král & J. Růžička leg., [Ch7] baited pitfalltraps (fish meat + cheese) withethylene glycol, mixedforest ( Quercus , Pinus ) onbankof the river ”, 1 male in cSch; “ CHINA, Gansu province, Yonghai cca 20km. SW Yuzhong 2700–2800 m, 9.VIII.1994. A. Smetana [C34]”, 5 males and 5 females in MHNG, and 1 male and 1 female in SWUC ; “ CHINA, SW Gansu province, road YuZhong-Lanzhou/ Aganzhen SW of Yonghai, 2800 m. 8–9.VIII.1994, K.W. Anton ”, 1 malein MHNG ; “ CHINA, Gansu province, Xinglong Shan , cca 70km S Lanzhou, 2225–2380 m, 7.VIII.1994. A. Smetana [C32]”, 2 females in MHNG ; “ CHINA, Gansu province, 120 km. S Lanzhou Guanghe Xian Mai Jia. 2300 m, 8.VII.1994. A. Smetana [C3]”, 7 males and 2 females in MHNG, and 2 males and 1 female in SWUC ; “ CHINA, Shaanxi Daba Shan mtn. Range Npass 22 km NW Zhenping, 32°01’N, 109°21’E, 2850 m, 14. VII. 2001, A. Smetana [C10]”, 1 malein NMPC ; “ CHINA, Shanxi. Wutaishan, leaf litter. 4.–5.VI.1993. G. de Rougemont ”, 6 males and 6 females in MHNG, 1 male and 1 female in SWUC ; “ CHINA, Beijing, Xizolong men , Leaf litter. 28.–29.VI.1993. G. de Rougemont.” 4 males MHNG and 2 males in SWUC ; “ CHINA, Beijing, Xizolong men , Leaf litter. 23.–25.VI.1993. G. de Rougemont.” 1 female in MHNG .

Description. Habitus as in Figs 1–3 . Combined length of head, pronotum and elytra = 1.5–1.7 mm; maximal pronotal width = 0.8–0.9 mm. Body predominantly dark brown, with head and abdomen blackish, and appendages markedly paler. Dorsal pubescence fairly uniform, slightly shorter on abdomen, consisting of setae almost straight, recumbent; pubescence on frons sexually dimorphic, with medial setae directed backward; metaventral setae shorter than proventral setae; pubescence on abdominal tergites IV–VII parallel; sternites IV–VII each with two posteromedial macrosetae; sternites VI–VII with pubescence slightly denser posteromedially. Frons and vertex finely granulate; pronotum and elytra granulo-fossulate; prohypomeron almost smooth; metaventrite smooth in front metacoxae, coarsely punctate elsewhere.

Frons above clypeus forming blunt ridge, the latter not carinate; mesal portion of disc slightly arcuate in lateral view; U–shaped frontal impression shallow. Temples slightly expanded just behind eyes, then abruptly narrowed, finely granulate. Occipital ridge indistinct. Antenna ( Figs 6 , 29 ) with scape fairly conical, not compressed; antennomere 11 ovoid, slightly compressed; pubescence markedly denser on antennomeres 5–11. Maxillary palpus with palpomere 3 about 1.5 timesas long as palpomere 2. Pronotum ( Fig. 26 ) shallowlydepressed along posteriorportion of lateral edges; medial groove shallow, weakly convex in frontal view, almost straight in lateral view; hypomeron lacking transverse ridge. Scutellum triangle, with anterior margin rounded. Elytral disc shallowly depressed along lateral edge, without notable relief.

Male. Frontoclypeal area, protarsomere 5, metaventrite, and abdominal sternites IV–VI unmodified. Pubescence on posterior portion of frons only slightly converging ( Fig. 31 ). Protibia incrassate ( Fig. 30 ). Protarsomere 1 possessing ventral patch of modified adhesive setae. Metatarsomere 1 approximately 1.5 times shorter than combined length of metatarsomeres 2–4. Peg-like setae absent from protrochanter, protibia, profemur and mesofemur ( Figs 13–14 ); arranged in a row on mesotrochanter ( Fig. 14 ); grouped in a field on mesotibia ( Figs 10–11 ); metatrochanter with 2–3 peg-like setae ( Figs 17–19 ); metafemur with upto 2 peg-like setae ( Figs 17–19 ); arranged in 2 rows on metatibia ( Figs 15–16 ). Abdominal tergite VIII as in Figs 12, 21 ; sternite VIII as in Fig. 20 ; hemitergite IX as in Fig 9 . Aedeagus as in Figs 4–5, 7–8 .

Female. Pubescence on posterior portion of frons strongly converging ( Fig. 32 ). Abdominal tergite VIII forming apical projection ( Figs 27–28 ); sternite VIII as in Fig. 25 . Genitalia as in Figs 22–24 ; dorsal part of genital segment ( Fig. 24 ) forming 2 sclerotized arcuate sclerites; gonocoxal plate without dorsal or ventral medial ridges.

Comparisons and diagnostic notes. Megarthrus heise sp. nov. and M. nitidulus are the only members of the genus to have a blackish body in combination with an adventral projection on the male metatibia. They share in common many other features, notably very similar genitalia, and therefore the new species was previously confused with M. nitidulus ( Shen et al 2008). However, the males of M. heise have the metatibial peg-like setae restricted to its apical half except a single peg-like seta near apex of the adventral projection ( Figs 15–16 ), while in M. nitidulus a loose row of 3 peg-like setae extend adventrally on metatibia to its adventral projection ( Cuccodoro and Löbl 1997: Fig. 22d ). In addition, the ventral outline of the aedeagal ventral wall in lateral view is sinuate in M. heise ( Figs 4–5 ), while it is concave in M. nitidulus ( Cuccodoro and Löbl 1997: Fig. 22b ). Females of these two species can be distinguished by the shape of the dorsobasal margin of the gonocoxal plate—extended anterad and arcuate in M. heise ( Figs 22–23 ) while straight in M. nitidulus ( Cuccodoro and Löbl 1997: Figs 23 a–b)—and of their pair of dorsal genital sclerites—arcuate in M. heise ( Fig. 24 ) while semicircular in M. nitidulus ( Cuccodoro and Löbl 1997: Fig. 23c ).

Distribution and natural history. Megarthrus heise sp. nov. is distributed in Qinghai, Sichuan, Gansu, Shaanxi, Shanxi provinces and Beijing of China, at elevations ranging from 1946 to 2900 m a.s.l. It was collected in coniferous or mixed forest ( Betula , Picea , Pinus , Populus , Quercus ), in creek valley, semi-open pasture, and alpine meadow, from samples of sifted leaf litter, mushrooms, mosses, dead wood, excrements of carnivores, at sight under stones and logs, or using baited pitfall traps (fish meat + cheese) with ethylene glycol.

Etymology. The name of the new species means black in Chinese, with reference to its coloration. Noun in apposition.

Note on teratological abdominal tergite VII. One male paratype of M. heise sp. nov. collected together with the holotype has a malformation of the penultimate visible abdominal tergite (i.e. tergite VII), in which the latter is entirely divided transversely in a tergite VII and a tergite VII’ ( Figs 33, 34 ). That teratological specimen was well sclerotized and caught at sight, indicating that the malformation was non-lethal and apparently had little impact on its fitness. It is the first time, such an anormality is documented in the genus. No attempt was made to investigate this malformation further by dissection or clearing of the specimen, which is deposited in MHNG.

Note on phoresy of Acari by Megarthrus . Seven paratypes of the new species collected together with the holotype appeared to bear 1 μm long translucent structures attached to their body. According to us these structures are anal pedicels of deutonymphs of phoretic mites of Uropodina (Acari: Mesostigmata ) ( Bajerlein & Błoszyk 2004, Halliday 2015). Such pedicels were found on specimens of both sexes of M. heise . The species of mite involved has apparently no particular preferences for attaching to a particular body part, as similar pedicels were located on the pronotum ( Fig. 38 ), on the elytra ( Figs 37, 39 ), on the abdomen ( Fig. 37 ) and even on the eyes ( Figs 35–36 ), with one specimen bearing up to 7 pedicels on the elytra (5) and abdomen (2) ( Fig. 37 ). This observation, which is the first report of evidence of phoresy of mites by Megarthrus , indicates that members of M. heise are mobile enough to be used by phoretic mites as dispersal vectors, suggesting that the species particularly appreciates ephemeral microhabitats usually also suitable for the development of Uropodina mites, in particular excrements of mammals.

Figures

FIGURES 1–3. Megarthrus heise sp. nov., habitus, male: dorsal (1), ventral (2), and lateral (3) views. Scale bar = 0.5 mm.

FIGURES 4–9. Megarthrus heise sp. nov., male: aedeagus in lateral (4–5) and ventral (7–8) views. antenna (6); left hemitergite IX (9). Scale bar = 0.1 mm.

FIGURES 10–21. Megarthrus heise sp. nov., male: mesotibia in lateral (10) and ventral (11) views; abdominal tergite VIII in lateral (12) and dorsal (21) views; protrochanter and profemur in lateral view (13); mesotrochanter and mesofemur in lateral view (14); metatrochanter and metafemur in lateral view (17–19); metatibia in lateral (15) and ventral (16) views; abdominal sternite VIII in ventral view (20). Scale bar = 0.1 mm.

FIGURES 22–28. Megarthrus heise sp. nov., female: genital segments, ventral part in dorsal (22) and lateral (23) views, and dorsal part (24) in ventral view; sternite VIII in ventral view (25); outline of pronotum (26); tergite VIII in dorsal (27) and lateral (28) views. Scale bars: a = 0.2 mm; b–c = 0.1 mm.

FIGURES 29–34. Megarthrus heise sp. nov.: antenna (29); male, protibia and protarsus (30); head of male (31) and female (32) in dorsal view; male: apex of abdomen in lateral (33) and dorsal (34) views (T VI = tergite VI, T VII = basal part of abnormal tergite VII, T VII’ = posterior part of abnormal tergite VI, T VIII = tergite VIII. Scale bars: 29–32 = 0.1 mm; 33–34 = 0.2 mm.

FIGURES 35–39. Megarthrus heise sp. nov. with anal pedicels of deutonymphs of Uropodina mites: head and anterior part of pronotum of the same specimen in dorsal (35) and oblique (36) views with pedicel on left eye; elytra and abdomen in dorsal view of specimen with pedicels on elytra and abdomen (37); pronotum in dorsal view of specimen with pedicel on pronotum (38); elytra in latetal view of specimen with pedicel on elytra (39). Scale bar = 0.2 mm; up = 35–36, 38–39; down = 37.

FIGURE 40. Distribution map of Megarthrus heise sp. nov. Scale bar =100 km.