Ephemerotoma buryatica Potapov, Huang & Gulgenova, 2020

Potapov, Mikhail, Huang, Cheng-Wang, Gulgenova, Ayuna & Luan, Yun-Xia, 2020, New and little known Isotomidae (Collembola) from the shore of Lake Baikal and saline lakes of continental Asia, ZooKeys 935, pp. 1-24 : 1

Ephemerotoma buryatica Potapov, Huang & Gulgenova sp. nov. Figures 19-26 , 27-31

Type material.

Holotype: female. Russia, south-western part of Buryat Republic, Gusinoozerskaya Basin, 0.5 km SW from Tokhoy, 51.356417°N, 106.558733°E, 590 m alt., southern shore of Sul’phatnoye (= Selenginskoye) Lake, grassland with Caragana sp., Achnatherum splendens , Atriplex sp., Leymus sp., 18.X.2015, coll. M. Potapov and A. Gulgenova. 24 paratypes (sub-adult and adult males and females) from the same place. Holotype and 10 paratypes deposited in MSPU, 4 in BSU, 5 in SMNG, 5 in SEM.

Other material.

From the type locality dated 02.V.2015 and 25.VII.2015.

Description.

Size 0.6-0.9 mm. Body as common for Anurophorinae with short furca (Fig. 27 ). Pigmentation grey, as in Proisotoma minuta (Tullberg, 1871). Cuticle finely reticulated, size of largest polygons smaller than bases of setae. Ocelli 8+8, G and H smaller (Fig. 23 ), all ocelli usually look subequal by pigmentation. PAO with three guard setae along posterior margin, elliptical, not constricted, as long as 0.4-0.6 of Ant.1 width and 0.7-1.1 as long as U3 (Fig. 23 ). Maxillary outer lobe with simple maxillary palp and four sublobal hairs. Labral formula as 2/554. Labium with all papillae (A-E), papillae A-D with normal number of guards (1,4,0,4), E with four guards (Fig. 21 ). Main part of labium with three proximal, four basomedian and five basolateral setae. Ventral side of head with 4+4 postlabial setae. Ant.1 with two basal, ventral and dorsal, bms, two ventro-lateral s, and eleven setae, without p-setae (Fig. 23 ). Ant.2 with three bms and one laterodistal s. Ant.3 without bms and with five distal s (including one lateral spine-like), inner s of AO small (Fig. 22 ). All s-setae on Ant.1-3 very short. S-setae on Ant.4 weakly differentiated, subapical organite small. Apex of Ant.4 with bilobed bulb (Figs 24-26 ), well visible in dorsal view (Fig. 25 ). In fully grown animals the bulb can look trilobed due to slight secondary division of one of the lobes (Fig. 26 ).

Body with smooth and rather short setae. Dorsal axial setal pattern of Th.II-Abd.IV: 7-8,6-7/5,5,5,7-8. Th.I and II without ventral setae, Th.III with 3-5+3-5 (usually 4+4) ventral axial setae (Fig. 31 ). Abd.II with a pair of mid-ventral setae (Fig. 31 ). Macrosetae weakly differentiated, medial macrosetae on Abd.V as long as 0.25-0.35 of tergal midline (Fig. 20 ). S-setae on tergites very short (Fig. 20 ). S-formula as 3,3/2,2,2,2,4 (s) and 1,1/1,1,1 (ms). In al-group of Th.II and III front s-seta and ms-seta set close to each other (notated as ‘ms+s’ in Fig. 21 ). S-setae on Th.II-Abd.V set in front of p-row of setae (Fig. 1 ). On Abd.V s-setae arranged in one transverse row, lateral pair very short (Fig. 2 ).

Unguis of unusual shape, expanded at the middle, without teeth. Empodial appendage slender, without lamellae. Ti.1 and Ti.2 without additional setae (21), Ti.3 usually with 25 setae. B-row of setae on Ti.1-2 complete (B4 and B5 present). Male spurs (x and B5 on Ti.3) in adult males thin, stick-like. Tibiotarsal tenent setae pointed (Fig. 30 ). Ventral tube with 4+4 distal and four posterior setae arranged in one transversal row (Fig. 31 ). Tenaculum with 3+3 teeth and one seta. Anterior furcal subcoxae with 10-13 setae, posterior subcoxae with five or six setae (Fig. 28 ). Anterior side of manubrium with a pair of distal setae (Fig. 28 ), posterior side with 9-10+9-10 setae on main part, lateral edges without setae (Fig. 29 ), laterobasal lobes with 3+3 setae. Dens short, about half as along as Ti.3. Anterior side of dens with three setae in subapical position (Figs 28 , 29 ). Posterior side of dens usually with large subapical hump, more proximal part without clear modifications. Dens with four posterior setae, three in basal half, one subapical. Mucro with two teeth, subapical tooth largest. Ratio of manubrium: dens: mucro = 5.5-6.5: 2.4-3.3: 1.0. Males present.

Affinity.

The species belongs to recently described genus Ephemerotoma Potapov, Kahrarian, Deharveng & Shayanmehr, 2015 due to simple maxillary palp, reduced number (four) of guards on labial papilla E, two prelabral setae, complete set of ms-setae on tergites (11/111), and tergal s-setae on abdomen set in front of p-row. Ephemerotoma buryatica sp. nov. does not share a significant character of the genus, the "two transverse rows" pattern of s-setae on Abd.V. The sexual dimorphism common for the genus Ephemerotoma [ E. porcella (Ellis, 1976), E. skarzynskii Potapov, Kahrarian, Deharveng & Shayanmehr, 2015, E. huadongensis (Chen, 1985)] is not observed in the new species. Small and rather slender body, short furca, shape of unguis, and absence of sexual dimorphism indicate a preference for deeper edaphic habitat than in its congeners.

Regarding all genera of the Proisotoma complex, a peculiarity of the new species is the bilobed apical bulb on Ant.4, which is otherwise known only in Proisotoma bulba Christiansen & Bellinger, 1980 (California, U.S.A.). The generic position of P. bulba is obscure because of lack of information on mouth parts and s-setae on body. In other characters, E. buryatica sp. nov. differs from P. bulba by fewer setae on dens (3/4 vs. 4-5/5-6), shorter dens (dens: mucro = 9: 1 in bulba ), teeth on tenaculum (3+3 vs. 4+4) and characters of unguis and tibiotarsi ( bulba has inner tooth on unguis and a clavate tenent hair). In Proisotoma complex, a similar furca is shown, for example, for Weberacantha echinodermata Potapov, Babenko & Fjellberg, 2006 and Scutisotoma robustodens Huang & Potapov, 2012, which belong to other genera. Mouth parts (two prelabral setae, simple maxillary palp and reduced number of e-guards) of E. buryatica sp. nov. resemble the " asiatica " group of the genus Subisotoma but several other characters of great value are different (e.g., presence/absence of anterior setae on manubrium).

Distribution and ecology.

Known only from one locality in SW Buryatia where it inhabits soil of dry steppe at upper part of a salt-lake catena. The species probably occurs in all seasons since it was recorded in May, July and October in the type locality. It was highly aggregated in October which that suggests a resemblance to the “ephemeral” species of the genus Ephemerotoma .

Name derivation.

It is named after the type locality.

Figures

Figures 19 - 26. Ephemerotoma buryatica sp. nov. 19 s-, ms-setae, macrosetae, and p-rows of setae on body tergites 20 chaetotaxy of Abd. III-VI 21 labial papilla E 22 Ant. 3, dorso-lateral view 23 ommatidia and Ant. 1 24 - 26 apex of Ant. 4, lateral (24), dorsal (25), and ventro-lateral (26) views. Abbreviations: bms-basal micro s-seta, ab-apical bulb, ms-micro s-seta, org-organite, s-s-seta, is, ls, os-inner, lateral, and outer s-setae of antennal organ.

Figures 27 - 31. Ephemerotoma buryatica sp. nov. 27 appearance 28 furcal area, lateral view 29 furca, posterior view 30 tibiotarsus of Leg 3, outer view 31 ventral side of Th. II and Abd. I and II. Abbreviations: vmc-ventro-medial setae.

Figures 1 - 5. Pseudanurophorus barathrum sp. nov. 1 appearance of dark coloured specimen 2 labrum, maxillary outer lobe and hypostomal setae, lateral view 3 labrum and maxillary outer lobe, fronto-ventral and ventral views 4 labium, ventral view 5 maxillary head. Abbreviations: A, B, C, D, E-papillae of labial palp, H, h 1, h 2 - hypostomal setae, mo, m 1, m 2, p 1, p 2, p 3 - setae of m - and p-row of labrum, mx. ol-maxillary outer lobe, cap., 1 - 6 - capitulum and lamellae 1 - 6 of maxillary head, a 1, b 1, b 2, b 3, b 4, e 7 - labial guards, l. p. - lateral processes. Characters of greater value encircled.