Semicerura draconis Potapov & Sun, 2020

Potapov, Mikhail, Xie, Zhijing, Kuprin, Alexander & Sun, Xin, 2020, The genus Semicerura (Collembola; Isotomidae) in Asia, Zootaxa 4751 (1), pp. 105-118 : 111-115

Semicerura draconis Potapov & Sun , sp. nov.

Figs 2, 18–32, 39

Type material. Holotype, female on slide; Russia, Far East, Primorski Krai, Shkotovski district, Livadiysky Range, Pidan Mt.; 43.067° N, 132.683° E; altitude ca 1000 m, litter under Microbiota and Betula , 20 Sep. 2004; M. Potapov leg. (kept in MSPU).

Paratypes, Russia: 8 paratypes (on slides); the same site and in thick moss under Rhododendron (5 paratypes kept in MSPU and 3—in SMNG) . China: 10 paratypes (4 on slides, 6 in alcohol); Jilin province, Fusong County, Manjiang town forest (foothills of Changbai Mts ); Mar. 2018; D. Wu leg. (kept in IGA) .

Other material. Russia, Far East, Primorski Krai, Shkotovski district, Falaza Mt. ; 43.101° N, 132.789° E; 19 Sep. 2004; L. Deharveng and A. Bedos leg.; below the top, litter. Shkotovski district , Falaza Mount; 43.101° N, 132.789° E; altitude ca 800 m; 02 Oct. 2004; R. Pomorski leg.; soil and humus near the stream. Lazovski district , in mountains nearby Preobrazheniye, Maralovaya River ; altitude ca 600 m; 21 Sep. 2011; M. Potapov leg.; litter in deciduous forest. Khasansky district , near Barabash; 27 Sep. 2004; M. Potapov leg.; litter of oak wood. Terneyski District , Sikhote-Alimski Reserve , Kabani station ; 45.13824° N, 135.88690° E; altitude ca 525 m; 08 Aug. 2017; N. Kuznetsova, A. Geraskina, A. Kuprin leg.; different coniferous woods, litter and rotten wood. Pozharski District , middle part of Bikin River , near inflow of Amba; 46.69949° N, 135.77142° E; 20 Sep. 2009; O. Smirnova leg.; cedar-broadleaved forest. Chuguevski District , Oblachnaya Mt. ; 43.695° N, 134.199° E; altitude ca 1220 m; 19 Sep. 2018; A. Kuprin leg.; spruce forest .

Russia, Far East, Khabarovski Krai. Khekhtsyr Range ( 24 km S Khabarovsk ); 17 Sep. 1988 and 30 Sep. 1988 ; V. Behan and N. Ryabinin leg.; mixed forest. Khekhtsyr Range (ca 25 km S Khabarovsk); 12 Sep. 2000 ; H. Motohiro leg.; litter. ibidem, ca. 10 km N Korfovski , 28 Jun. 2007 ; E. Sokolova leg. ibidem, near Korfovski ; 24 Apr. 2010 ; M. Potapov and E. Sokolova leg.; poplar forest, mixed forest, litter and mosses on tree. Nanaisky District , ~ 15 km N road Khabarovsk-Sov.Gavan, Golaya mount. 49.422° N, 138.298° E; altitude ca 1350 m; 28 Jun. –07 Jul. 2017 ; A. Brinev leg.; massive pass, spruce forest, litter. Nanaisky District , ~ 40 km S road Khabarovsk-Sov.Gavan, Tardoki-Yani Mt.; 48.897° N, 138.053° E; 16–26 Jun. 2017 ; A. Brinev leg.; Betula ermanii forest, litter. Vaninski district , nearby Vysokogorny, valley of Mulinka, altitude about 750 m; 29 Sep. 2011 ; M. Potapov leg.; closed coniferous forest on NE slope. Lazo District , Ko Mt.; 47.124° N, 136.611° E; altitude ca 500 m and 970 m; 01 Jul. 2018 ; A. Brinev leg.; mixed cedar forest (middle part of Katen spring, 500 m alt.) and spruce forest (upper part of Katen spring, 970 m alt.), litter. Lazo District , Arsenyevskiye Granity Range, Arsenyeva Mt.; 46.844° N, 136.703° E; altitude ca 500–600 m and 900 m; 08 Jul. 2019 ; A. Brinev leg.; junction of Malinovy and Maly Katen, mixed cedar forest (500–600 m alt.) and spruce forest (900 m alt.), litter and rotten wood .

China, Jilin province, Huinan county, Triangle longwan forest; 42.37° N, 126.44° E; Mar. 2018; D. Wu leg. ; Laoning province, Huanren county forest; 41.27° N, 125.36° E; Mar. 2018; D. Wu leg.

Description. Body size 1.4–2.2 mm. Body shape as common for the family (Fig. 2). Abd. V and VI fused, without a wrinkle and with unclear break in chaetal cover. Spotty grey (Fig. 39), from rather pale to almost black, especially in large individuals. Legs and antennae paler. Integument smooth, without visible granulation. 6+6 ocelli, with 4 in anterior group and 2 in posterior ( Fig. 21 ), number of ocelli is recognizable after the pigmentation of eye spot, cornea of 2 anterior ocelli marked much better. PAO larger (1.2–1.8) than nearest ocellus, 0.4–0.6 as long as Claw III. Ventral side of Ant. I with 4–7 long s-chaetae and 3–4 short ones in apical position. Ant. III organ with a pair of small blunt rods in a groove. Ant. II with III with few s-chaetae. Ant. IV without thickened s-chaetae, very densely covered with minute chaetae and s-chaetae (contrasting to Ant. III), apical bulb absent, conical process often present (see the Discussion, Figs 26, 27 ). Subapical pin chaeta simple, subapical organite pin-like, on pedicle, or small and simple (see the Discussion). Labrum with 4/554 chaetae, apical edge with 4 broad ridges. Maxillary outer lobe with trifurcate palp and 4 sublobal hairs. Labial palp with all apical papillae (A–E) and 16 guards, e7 present. 5 proximal chaetae (arranged as in Fig. 36 in Ding et al. 2011). Basal fields of labium with 5–6 median and 5 lateral chaetae; 7–10+7–10 postlabial chaetae along ventral line. Capitulum of maxilla with 3 teeth and 6 unmodified lamellae, without long denticles ( Fig. 22 ).

Tibiotarsi with 10 acuminate apical chaetae on all legs in fully grown specimens. Basic number of apical chaetae of tibiotarsi not clear due to polychaetosis. Immature specimens of middle size with 9 chaetae, small 1- st stadia with 8 chaetae on all legs. T2 and T3 chaetae probably absent in all stages. Claws common for the genus, with strong inner and lateral teeth, unguiculus ca. 0.6 as long as inner edge of claw, inner tooth absent ( Fig. 25 ). Base of Leg I with 3 outer chaetae (coxa with 2 chaetae and subcoxa with 1 chaeta, as in S. bryophila ). Ventral tube with 4–6+4–6 anterior, 8–11+8–11 latero-distal and 5–8 posterior chaetae. Posterior side with few chaetae in proximal part and 4 (sometimes with 1–2 additional) chaetae arranged in distal transversal row. Retinaculum with 4+4 teeth and 3–5 chaetae. Ventral chaetae on thorax absent. Ventroapical thickening of manubrium complex and variable, multispinose, with 2 large and several minute teeth ( Figs. 28, 29 ). Anterior side of manubrium with 2+2 medial spine-like chaetae and 3+3 long chaetae in distal group, central group with ca. 17–19 chaetae ( Fig. 28 ). In medial group, chaetae positioned closer to axial line smaller (vary) and sometimes absent on one side resulting in 2+1 pattern. Distal chaetae of lateral row often spine-like. Dens tapering, with annulated posterior side, considerably expanded in area around distal spines ( Figs 18, 19 ). Dens with 25–29 anterior chaetae, with several (up to 4) minute and 1 long chaeta at apex. Posterior side of dens normally with 4 chaetae and 4 spines arranged as: 2 basal chaetae (1 of which much longer than others), 2 shorter chaetae (sometimes spine-like) in more distal position and 2 pairs of spines (distal pair strong) ( Figs 18, 19 , 23 ). Inner side of dens with 4–6 spines, outer side with 3–6 weaker spines ( Figs 18 , 24 ). Mucro tridentate, basal tooth small, mucronal chaeta absent.

Chaetae cover sparse, especially on anterior half of abdomen, and strongly heterochaetotic. Some chaetae in posterior row of tergites subequal to macrochaetae. Axial chaetotaxy for Abd. I–IV as 3, 4(3), 4–6, 4–5 (for half of tergite, without consideration of unpaired chaetae). Asymmetry and many axial unpaired chaetae often make axial chaetotaxy on Abd. III and IV unclear. Macrochaetotaxy on Th. II, III/Abd. I–IV as: 2,2/3,3,3,3 ( Fig. 20 ). Macro- chaetae thick, sparsely serrated on thorax and Abd. I–II, macrochaetae on Abd. III–VI smooth or, more rarely, with 1–2 denticles ( Fig. 31 ). Macrochaetae on Abd. V 2.4–2.9 as long as Claw of Leg III, and ca. twice longer than tergite length. Sensillar chaetotaxy as 4,4/3,3,3,3,6 (s) and 1,1/1,1,1 (ms). Th. II with 2 long accp-s and 2 short al-s, Th. III with 2 long and 1 short accp-s and 1 short al-s. Abd. I–III each with 2 long and 1 short accp-s, Abd. IV with 2 long and 1 short accp-s. Long s-chaetae vary in length but always greatly differ from short lateral s-chaetae. Abd. V with 2 long as-s and 2 accp-s, lateral side with 2 short al-s set together in longitudinal line. In accp-group of Abd. V, accp1 s-chaetae moved to Abd. VI, behind anterior row of macrochaetae, accp2 situated in more lateral position, close to 2 short lateral al-s ( Figs 30–32 ). Accp-s-chaetae in front of p-row on Th. II–Abd. IV. Ms-chaetae well visible, on Abd. I in frontal position, at anterior edge of chaetae cover, on Abd. III placed together with short accp-s ( Fig. 20 ). S-chaetae as long as middle common chaetae and hardly distinguishable. Formula of s-chaetae for Th. II—Abd.V as: 2+2+ms, 2+2+ms/2+1+ms, 2+1+ms, 2+1+ms, 2+1, 4+2 (see also the Discussion). Males present, without sexual dimorphism.

Discussion. The new species resembles S. goryshini described from South Primorye (south of Far East of Russia). It differs in 2 long s-chaetae on Abd. IV (vs. 3 in goryshini ) and 5 ocelli (vs. 4 in S. goryshini ). After the original description, S. goryshini has the inner tooth on inner edge of unguiculus present (vs. absent in S. draconis sp. nov.). In the type specimens and our materials the presence of inner unguicular tooth is a variable character, even in one individual, this tooth is, for example, absent on Leg 1 in holotype of S. goryshini . S. draconis sp. nov. seems to be generally darker than S. goryshini but this difference is taxonomically unreliable because of the high variability of pigmentation in both species.

Dányi et al. (2014) recorded S. goryshini in South Korea and pointed out 6 ocelli, smooth macrochaetae and fused two last abdominal segments, the three characters contradicting the first description of S. goryshini . Six ocelli indicate S. draconis sp. nov., the two other characters are equal in both species S. draconis sp. nov. and S. goryshini (see the Description parts). Hasegawa & Niijima (2012) cited S. goryshini in the list of Japanese Isotomidae while also showing 6 ocelli. This record can belong to S. draconis sp. nov. as well while the posterior chaetotaxy of dens looks different ( Fig. 15b in Hasegawa & Niijima 2012).

In Khehtsyr Range (Khabarovski Krai, Russia) the specimens have fewer long accp-s-chaetae on Th. II–Abd. I (1,1,1–2 vs. 2,2,2). So far we consider them as the members of the new species but further study is needed to make a reliable conclusion. The apical part of Ant. IV shows variation in apical papilla (present/absent) and shape of organite (pin-like or roundish). Intermediate variants were also seen and we consider them as intrapopulation variability of the characters.

Distribution and ecology. The new species is widely distributed in forest litter of East Asia (Primorye and Khabarovsky Krai in Russia, and Jilin Province in China) (Fig. 40). The occurrence in Korea and Japan is probable (as S.goryshini ) although the all records should be verified. The previous records of S. goryshini from Far East of Russia (apart from the type locality) possibly refer to S. draconis sp. nov.

Etymology. The species is named after to the spectacular spines on the dens resembling dragon claws.

Figures

FIGURES 20–27. Semicerura draconis sp. nov.: 20, macro- and s-chaetae on body; 21, ocelli and PAO; 22, maxillary head; 23–24, posterior (21) and anterior (22) sides of proximal part of dens; 25, apical part of tibiotarsus and claw III; 26–27, apex of Ant. IV, different specimens. ms—ms-chaeta, s—s-chaeta of middle size, ss—small s-chaeta.

FIGURES 33–37. Semicerura goryshini: 33, Abd. III–VI; 34, s-chaetae of Abd. IV–V; 35, macro- and s-chaetae on Abd. II–VI; 36, ocelli and PAO; 37, Holotype, Abd. IV–V (dorsal area).

FIGURES 28–32. Semicerura draconis sp. nov.: 28, anterior side of manubrium; 29, manubrial thickening; 30, Abd. IV–V (dorsal area); 31, Abd.III–VI; 32, s-chaetae of Abd. IV–V. ms—ms-chaeta, s—s-chaeta of middle size, ss—small s-chaeta.

FIGURES 16–19. Outer (16, 18) and inner (17, 19) views of dens in Semicerura bryophila sp. nov. (16, 17) and S. draconis sp. nov. (18, 19). So, Spo, Spi, Si—spines of outer, posterior-outer, posterior-inner, and inner rows.

FIGURES 9–15. Semicerura bryophila sp. nov. (9–13) and holotype of S. bishopi (14–15): 9, Abd. III–VI; 10, Abd. IV–V (dorsal area); 11, basal part of Leg I; 12, anterior side of manubrium, central group of chaetae and spine-like chaetae marked; 13, chaetae of central group, another specimen; 14, posterior side of proximal part of dens; 15, anterior side of manubrium. ms—ms-chaeta, s—s-chaeta of middle size, ss—small s-chaeta.