Agrenia bidenticulata (Tullberg, 1876) sensu

Potapov, Mikhail, Gulgenova, Ayuna & Babykina, Marina, 2016, Isotomidae (Collembola) of Buryat Republic. III. The genera Vertagopus and Agrenia, with a note on ' Claw index', Zootaxa 4088 (1), pp. 112-128 : 124

Agrenia bidenticulata (Tullberg, 1876) sensu lato

Figs 30–37

Material examined. Russia: Buryat Republic: NW Buryatia, northern shore of Baikal Lake, Baikalsky Range, ~ 600 m alt., under stones along bank of Goudjekit River, 16.viii.2013, coll. A.G. and M.P. (together with A.riparia ); Ibidem, nearby Goudjekit, 700–900 m alt., mosses along bank of Akulikan Stream, 15.viii.2013, coll. A.G. and M.P.; NW Buryatia, Barguzinsky Range, ca. 5 km W Barguzin, middle flow of Gremyachaya Brook, forest belt, moistened mosses along brook, 17.viii.2008, coll. M.P. and A.G.

Russia: Irkutskaya Region: W Khamar-Daban Range, Slyudyanka River, taiga belt, in moistened mosses on stones in river, from 800 to 1300 m alt., 28–29.viii.2008, coll. M.P.; W Khamar-Daban Range, near Cherskogo Peak, Serdtse Lake, in wet mosses near water edge, ~ 1800 m alt., 26.viii.2008. coll. V. Kadnikov

For quantitative analysis the individuals from the following localities were studied:

Arctic: Russia: Graham Bell Isl. (Franz Josef Land, 5 ex., coll. V.B.); Kheysa Isl. (Franz Josef Land, 34 ex., coll. V.B.); Franz Josef Land (an island not precised, 23 ex., coll. V. B.); Uboynaua River (Taimyr Peninsula, 2 ex., coll. A.B.); Pyasina River (Taimyr Peninsula, 1 ex., coll. A.B.); Bol'shevik Isl. (Severnaya Zemlya Archipelago, 1 ex., coll. V.B.); mouth of Olenek River (N Yakutia, 2 ex., coll. A.B.); Stolbovoy Isl. (Novosibirskiye Isls, 4 ex., coll. V.B.); Zemlya Bunge (Novosibirskiye Isls, 4 ex., coll. V.B.); Canada: Devon Isl., two localities (Nunavat province), 11 ex., coll. A.B.).

Subarctic: Zelentsy (Kolsky Peninsula, northern coast, 3 ex., coll. A.B.); Khibin Mts (Kolsky Peninsula, 6 ex., coll. A.B. and M.P.); Dynkengda Mts. (Putorana Plateau, 10 ex., coll. A.B.); Lavrentiy Bay (E Chukotka, 3 ex., coll. A.B.)

Mountains of boreal zone: Komi Republic (Middle Ural Mts, Pechora River, 2 ex., coll. M.P.); Bol'shoy On River (Khakasiya, W Sayan, 1 ex., coll. S.Bugrov); Goudjekit River (NW Buryatia, 16 ex., coll. M.P. and A.G.); Gremyachaya Brook (NW Buryatia, Barguzin Range, 2 ex., coll. M.P. and A.G.); Slyudyanka River and Serdtse Lake (Irkutskaya Region, W Khamar-Daban Range, 9 ex., coll. M.P. and V.Kadnikov); Ola River (Magadan Region, 1 ex., coll. A.B.).

Description of populations from Buryatia and Irkutskaya Region. Ground colour yellowish or greenish. Dorsum much darker, pigmentation more developed on thorax and anterior half of abdomen. Antennae 1.4–2.4 (mostly 1.6–2.1) as long as head diagonal. Frontoclypeal field without a distinct "moustache", chaetae stronger over labral base. Chaetae of body subequal, short and fine. Ventral tube with more than 20 posterior chaetae, 11– 18+11–18 lateral, and 3–8+3–8 frontal chaetae. Tenaculum with more than 20 chaetae. Claw index 2.5–3.8 (see below). Furca 2.0–2.7 as long as head diagonal. Dens 1.6–2.1 as long as manubrium. Mucro with lateral chaeta, apical and subapical teeth subequal. Proportions of body limbs, chaetae covering and integument are not affected by maturity and sex. Morphology of winter form unknown.

Distribution and ecology. A. bidenticulata is a transholarctic species (Babenko & Fjellberg 2006, Fjellberg & Bernard 2009). Typical form is a common component of Arctic desert and wet tundra. In more southern parts of Asia the species comprises the closely related populations/species of unclear status and is very common along water streams both in alpine and forest zone. In Nearctic the species probably occurs only in high latitudes being absent in southern areas (Fjellberg & Bernard 2009).

A. bidenticulata sensu lato is common all over the Buryatian mountains. In Scandinavia A. riparia tends to replace A. bidenticulata in the forest belt (Fjellberg & Bernard 2009). We did not find such regularity in Buryatia so far but the current material along latitudinal gradients is not sufficient to make a final conclusion.

Figures

FIGURES 30 – 36. Claw index in populations of Agrenia bidenticulata complex: 30 – 32, distal half of Leg III in specimens from S Buryatia (Boreal zone of East Siberia) (30), Putorana Plateau (Subarctic zone of East Siberia) (31), and Franz Josef Land (High Arctic) (32), 33, relationship of Claw index, ratio Tibiotarsus length / outer edge of claw, and size of animal, plotted for 141 individuals, open circles—Baikal populations, plain circles—other populations, diameter of a circle is representative of Tibiotarsus length (smaller circles: juveniles, large circles: adults or large juveniles); 34 – 36, plots of Claw index against length of tibiotarsus 3 in individuals from all localities under study (34), in Arctic (35), and Boreal mountain populations (36). In figs 35 and 36 only the specimens with the length of tibiotarsi 3> 0.2 mm are plotted. tun—tunica.

FIGURE 37. Average values of Claw index against latitude in populations of Agrenia bidenticulata complex. Locations are marked according to zonal division, only the specimens with the length of tibiotarsi 3> 0.2 mm were used to average. Habitus of an individual with long claws (Khamar Daban Mts) is shown.