Endonura reticulata Axelson 1905

Endonura reticulata (Axelson, 1905)

Figs 22–34, Tab. 3

Neanura reticulata Axelson, 1905: 790

Neanura (Endonura) tundricola Fjellberg, 1985: 120

Material examined. 2 males and 3 juveniles on slides: Russia: North Karelia, Sedlovataya Island, tundra vegetation, mosses and flood debris, 25.ix.1992, leg. R. J. Pomorski. 1 male, 1 female and juvenile on slides: Russia: North Karelia, Lebyazh’ya Inlet, sea shore, under rooting logs, 25.ix.1992, leg. R. J. Pomorski, D. Skarżyński. 1 female on slide: Russia: North Karelia, Bolshoye Cherlivoye Lake, sea shore, mosses on rocks, 25.ix.1992, leg. R. J. Pomorski. 1 juvenile (I instar) on slide: Russia: North Karelia, Sredniy Island, sea shore, lichens on rocks, 26.ix.1992, leg. M. Wożny. 1 juvenile on slide: Russia: South of Taimyr Peninsula, upper current of Nizhnaya Agapa river, Ladannakh lake, R139/99, under bark of deciduous tree, 11.viii.1999, leg. A. Babenko. 1 female and male on slide: Russia: Putorana plateau, Dynkenda Mts., Yt-kyuel (Sobach’e) lake, R53/97, forest belt 80 m a.s.l., cover of lichens and mosses on stones, 22.vii.1997, leg. A. Babenko. 1 male on slide: Russia: Northwestern part of Yamal Peninsula, Martyusha river, peat hillock of dead Sphagnum, 22–23.viii.1994, leg. A. Babenko. 1 female on slide: Russia: delta of Indigirka river, peat hillock in sedge/moss bog, 14–15.vii.1994, leg. A. Babenko. 10 females on slides: Russia: Arkhangelsk province, Pechora bay, Kuznetskoe Lake, Tussock tundra, under logs, 25–26. viii.1994, leg. A. Babenko. 1 juvenile on slide: Russia: Krasnoyarskii Kray, mouth of Nizhnaya Tunguska River, vicinity of Turukhansk, birch forest, 8.viii.2003, leg. A. Babenko. 4 females and 3 juvenile on slides: Russia: Primorskyi Kray, Shkotovsky area, Livadiysky Range, Anisimovka, mixed forest and dry river’s bed, under bark of trees and stones, ix.2004. leg. R. J. Pomorski. 21 specimens juveniles to subadult (2 on slide): Russia: Primorskyi Kray, Kraskino, Devil’s Hill, Quercus forest, litter, 28.ix.2004, leg. L. Deharveng & A. Bedos (sample RU-115).

Diagnosis. Habitus typical of the genus Endonura. Dorsal tubercles present and well developed, sometimes tubercles Di on th. I absent. 2+2 eyes dark-pigmented. Buccal cone rather short. Head with chaetae A, B, C, D and E. Chaeta O present. Tubercles Dl and (L+So) on head with 6 and 10 chaetae respectively. Tubercles De on th. II and III with 3 and 4 chaetae respectively. Tubercles L on abd. III and IV with 4 and 6–9 chaetae respectively. Abd. IV and V with 8 and 3 tubercles respectively. Claw without inner tooth. Tibiotarsi with chaetae B4 and B5 short.

Redescription. Habitus typical of the genus. Body length (without antennae): 0.6–2.30 mm. Colour of the body spotted bluish grey, sometimes very pale. 2+2 medium dark pigmented eyes (Fig. 22).

Types of dorsal ordinary chaetae. Macrochaetae Ml thickened, relatively long, arc-like or straight, narrowly sheathed, feebly serrated, apically rounded or rarely pointed (Figs 22, 24, 32–34); macrochaetae Mc and Mcc thickened, straight and not pointed; mesochaetae and microchaetae short, thin and pointed.

Head. Buccal cone short. Labrum rounded, with ventral sclerifications as in Fig. 25. Labrum chaetotaxy 4/2, 4. Labium with four basal, three distal and four lateral chaetae, papillae x absent. Maxilla styliform (Fig. 28), mandible thin with two basal and two apical teeth (Fig. 29). Chaetotaxy of antennae as in Tab. 3 c and in Figs 26–27.

Apical vesicle distinct and variable, from unilobed to trilobed (Fig. 26). S–chaetae of ant.IV of medium length and moderately thickened (Fig. 27). Chaetotaxy of head as in Tab. 3 a, b, and Fig. 22. Tubercles Cl and Af separate (Fig. 22). Chaeta O present. Chaetae D and E free. Tubercle Dl with 6 chaetae, chaeta Dl3 present (Fig. 22). Tubercle (L+So) with 10 chaetae, chaetae So3 and L3 present (Fig. 22). Elementary tubercle BE absent. Chaeta A shorter than B.

Thorax, abdomen, legs. Body s-chaetae fine and smooth, shorter than nearby macrochaetae (Fig. 24). Chaetotaxy of th. and abd. as in Tab. 3 d and in Figs 24, 30–34. Tubercles Di on th.I differentiated or not. Chaetae De3 on th. III and abd. I–III as Mc, Mcc or mi. Chaetae De2 on th. II–III and De3 on th. III free. Chaetae De3 on abd. I–III free (Fig. 24). The line of chaetae De1–chaeta s not perpendicular to the dorsomedian line on abd. I–IV. Tubercle L on abd. III with 4 chaetae. Tubercle L on abd. IV sometimes divided (Fig. 30), with 6–9 chaetae and without free chaetae (Figs 30–31). Furca rudimentary without microchaetae (Fig. 30).Tubercles Di on abd. V fused, with chaetae Di2 as Mc and Di3 as Mcc or mi (Figs 32–34). Chaetae L' and Vl on abd. V present (Fig. 30). No cryptopygy. Chaetotaxy of legs as in Tab. 3 d. Tibiotarsi with rather long chaetae B4 and B5. Claw without inner tooth (Fig. 23).

Discussion. See: Discussion of E. asiatica.

a) Cephalic chaetotaxy––dorsal side b) Cephalic chaetotaxy––ventral side

Group Number of chaetae Vi 6 Vea 4 Vem 3 Vep 4 labium 11, 0x

c) Chaetotaxy of antennae

Segment, Group Number of chaetae Segment, Group Number of chaetae I 7 IV Adult First instar II 12 or, 8 S, i, 12 mou, 6 brs, 2 iv or, 2 S, i, 6 mou, 1 brs, 2

iv III 5 sensilla AO III

5 ap 8 bs, 5 miA 8 bs, 5 miA ve

vc 4 ca 2 bs, 3 miA 2 bs, 3 miA vi 4 cm 3 bs, 1 miA 3 bs, 1 miA d 5 cp 8 miA, 1 brs 8 miA

d) Postcephalic chaetotaxy

Terga Legs

Di De Dl L Scx2 Cx Tr Fe T th. I 1 2 1 - 0 3 6 13 19 th. II 3 2+s 3+s+ms 3 2 7 6 12 19 th. III 3 3+s 3+ s 3 2 8 6 11 18

Sterna

abd. I 2 3+ s 2 3 VT: 4

abd. II 2 3+ s 2 3 Ve: 5–6 Ve1 - present

abd. III 2 3+ s 2 4 Vel: 5 Fu: 4–6 me 0 mi abd. IV 2 2+ s 3 6 –9 Vel: 4 Vec: 2 Vei: 2 Vl: 4 abd. V (3+3) 7–8+s Ag: 3 Vl: 1 L': 1 abd. VI 7 Ve: 13–14 An: 2mi Remarks. The species was described by Axelson (1905) from Russian Karelia. However, since the original description was very insufficient, Gisin (1960) in his “Collembolenfauna Europas” considered “ Neanura reticulata ” as species dubiae. Lately Fjellberg (1998) in his “ Collembola of Fennoscandia and Denmark “ studied syntypes from Russian Karelia and described the species more precisely; nevertheless, the author did not fully resolve its taxonomical position. Analysis of new reach materials, including specimens from North Karelia (see: Material examined), and taxonomical uncertainties mentioned by Fjellberg (1998) led us to propose a thorough redescription to establish and clarify its identity. Unfortunately, Axelson’s syntypes has been lost during the removal of the museum collections a few years ago (dr. Pekka Vilkamaa, Curator of Zoological Museum, University of Helsinki, pers. comm.).

The species is actually Holarctic and circumboreal, occurring in North Europe, northern Asia and North America. Western Palearctic records reach 56o N (Öland, Sweden, Fjellberg 1998), but further east E. reticulata reaches more southerly latitudes (43o N, Russian Far East, Nachodka). At first, the North American population was thought to represent an undescribed species that Fjellberg (1985) described as E. tundricola, but later this species was considered as a possible synonym of E. reticulata by Fjellberg (1998), a suggestion that was finally accepted by Babenko and Fjellberg (2006). A juvenile specimen of Endonura cf. tetrophtalma from Polish Carpathians led Fjellberg (1998) to suggest a possible synonymy with E. reticulata. More recent work (Smolis 2008) have shown that the mentioned specimen represents E. tatricola (Stach, 1951), distinct and well defined taxon from the Carpathians.

E. reticulata is an eurytopic species with preferences to wet sites, found both in vegetation of sea and lakes shores, tundra, arctic meadows, willow/birch/alder thickets, boreal and temperate forests (Fjellberg 1989, 1998; Pomorski & Skarżyński 1995).