Entomobrya arenaria Winkler, Florian & Danyi, 2023

Winkler, Daniel, Sternalski, Jakub, Onodi, Gabor, Szigeti, Nora, Florian, Norbert & Danyi, Laszlo, 2023, Investigation on the true identity of Entomobrya nigriventris Stach, 1929 (Collembola, Entomobryidae) with the description of a new species, ZooKeys 1185, pp. 321-353 : 321

Entomobrya arenaria Winkler, Florian & Danyi sp. nov.

Figs 2 , 3 , 4

Type material.

Holotype: ♂ on slide (slide number HNHM-collpr-911), Hungary, Bács-Kiskun county, Fülöpháza, 106 m a.s.l., 46°52'16"N, 19°25'14"E, D-vac sample, 12 Jun. 2020, leg. D. Winkler and G. Ónodi. Paratypes: ♀ on slide (slide number HNHM-collpr-912) and six ♂♂ on slide (slide numbers HNHM-collpr-913 to HNHM-collpr-914; WD-coll-141 to WD-coll-144, respectively); same data as holotype. The holotype and three paratypes are deposited at HNHM. Four paratypes are preserved at SOE in the first author’s collection.

Diagnosis.

Body orange-yellow, with thin dark dorsal centreline, dark transverse stripes anteriorly on Th II-Abd IV and Abd VI, and dorsomedial rectangular patch posteriorly on Abd IV. Ventral body entirely dark in adults. Ant IV with trilobed apical bulb. Labral papillae with spine-like projection. Lateral process on labial papilla E not reaching apex of papilla. Claw with four inner teeth. Paired lateral teeth and dorsal tooth intermediate. The exact identification of the species can be made by using the abbreviated macrochaetotaxy formula (sensu Jordana and Baquero 2005) of the head (H1-5 areas), Th II (T1-2 areas), Abd II (A1-2 areas), Abd III (A3-5 areas), and Abd IV (A6-10 areas) as: 5(6)-1(2)-0-3-2/4-5(6)/2-5(6)/0-2-2/0-4(6)-10(0)4-10(0)3(5)-2.

Description.

Habitus. Adult body length (excluding antennae) 2.79-3.41 mm (n = 8), holotype 3.41 mm. Adult body ground colour orange-yellow (Fig. 2A, B ), juveniles and subadults pale yellow (Fig. 2C, D ). Pattern with a thin dark longitudinal line along dorsal centreline of Th II-Abd IV, widened towards end of Abd IV segment (in juvenile specimens, thin middle dorsal line purple and from Th II to Abd III only). Dark narrow, continuous, or occasionally interrupted transverse stripes on anterior margins of Th II-Abd IV and Abd VI. In juveniles, transverse stripes either very thin or missing. Posteriorly on Abd IV, a dorsomedial dark rectangular patch always present, both in adult and juvenile specimens. Antenna base black, black spot between bases of antennae. Dark violet pigment on antennae with increasing intensity from base to apex of segments. Lateral parts of abdominal segments and ventral body entirely dark in adult specimens. Ventral side in juveniles with no dark pigmentation, appearing first between legs in later developmental stages (Fig. 2D ). In adults, dark pigmentation also on coxae and manubrial base.

Head. 8+8 eyes, GH smaller than EF (Fig. 3A ). Interocular chaetotaxy with five chaetae (s, t, p, q, r). Antennae length 1.41-1.73 mm (n = 8), holotype 1.73 mm. Antennal length to head diagonal length ratio 2.50-2.77 (n = 8), holotype 2.50. Relation of antennal joints I-IV as 1: 1.8-2.3: 1.4-2.0: 1.8-2.3 (n = 7). Ant IV with trilobed apical bulb (Fig. 3B ). Ant III sensillary organ composed of two sensory rods partially behind a cuticular fold, guarded by three short sensilla (Fig. 3C ). Arrangement of chaetae on labrum 4/554, prelabral chaetae ciliated, posterior, median and anterior labral chaetae smooth (Fig. 3D ). Labrum with four rounded labral papillae with strong, armed spine-like projection (Fig. 3D ). Outer maxillary palp with two smooth chaetae and three smooth sublobal chaetae. Lateral process (sensu Fjellberg 1999) on labial papilla E not reaching apex of papilla (Fig. 3E ). Labium chaetotaxy formed by five smooth “a” chaetae and, in the basal row, by ciliated chaetae M1, M2, R, E, L1 and L2 (Fig. 3F ); M2 thinner and shorter than M1, R reduced. Chaeta M2 present in four of eight type specimens, bilaterally present in two specimens, and absent in two specimens.

Body. Ratios of Abd IV/III length 3.57-4.47 (n = 8), holotype 4.23. No differentiated chaetae on tibiotarsus III, with exception of smooth terminal chaeta opposite to tenent hair. Trochanteral organ with up to 29 spine-like chaetae (Fig. 4A ). Unguis and unguiculus of claw III as in Fig. 4B . Unguis inner side with sub-equal paired basal teeth at 54% from inner edge, and with two more unpaired teeth at 71% and 86% from inner edge, respectively. Paired lateral teeth intermediate, at level slightly below the paired internal teeth. Unpaired dorsal tooth located approximately at 35-45% of distance from base. A small pretarsal chaeta present on both anterior and posterior surfaces. Unguiculus lanceolate, outer lamella serrated. Tibiotarsal tenent hair clavate, as long as claw. Ratio of smooth terminal chaeta / unguiculus around 1. Ventral tube with 19+19 ciliated chaetae on anterior side and 9+9 ciliated chaetae on posterior side (Fig. 4C ); lateral flap with nine ciliated and seven smooth chaetae (Fig. 4D ). Manubrial plate with eight or nine chaetae, including two larger inner chaetae and six or seven chaetae outer two psp (Fig. 4E ). Length of not ringed terminal dens ~ 2 × the length of mucro. Mucro with distal tooth larger than anteapical one; basal spine just reaching tip of anteapical tooth (Fig. 4F ).

Macrochaetotaxy (Figs 3A , 5A-D ). Simplified Mac formula: 5(6)-1(2)-0-3-2/4-5(6)/2-5(6)/0-2-2/0-4(6)-10(0)4-10(0)3(5)-2. Head (Fig. 3A ): H1 area with five Mac (An2, An3a1, An3a2, An3 and one additional Mac from the An series); H2 area regularly with one Mac (A5) and occasionally (and always bilaterally) also with A6 as Mac; H3 area without Mac; H4 area with three Mac (S1, S3 and S4i); H5 area with two Mac (Ps2 and Ps5). Mesothorax (Fig. 5A ): area T1 with four Mac (m1, m2, m2i and m2i2); T2 with 5-6 Mac (a5, m4, m4i, m4p always present, m4pi present or absent). Abdomen: Abd II (Fig. 5B ) area A1 with two Mac (a2 and a3); area A2 with 5-6 Mac (m3, m3e, m3ep, m3ei and m3ea always present, m3eai present or absent); Abd III (Fig. 5C ) area A3 without Mac; area A4 with two Mac (a2 and a3), and area A5 with two Mac (m3 and m3e); Abd IV (Fig. 5D ) area A6 without Mac; area A7 with 4-6 Mac (A3, B2, C1 and E1 always present; Ae3 present in half of the studied specimens while B3 in a quarter); area A8 with unpaired central Mac A04 present or absent, and four Mac (A4a, Ae4, B4 and C2a); area A9 with unpaired central Mac A05 present or absent, and 3-5 Mac (A5, B5 and one Mac of uncertain homology always present, Ae5 and Ae5pp present or absent); and area A10 with two Mac (A6 and B6); sensillar formula from Th II to Abd V: 2,2/1,2,2,12,3; microsensillar formula from Th II to Abd III: 1,0/1,0,1.

Ecology and distribution.

The habitat of the type locality is extremely xerophilic. It belongs to the Pannonic sand steppes, where the vegetation is a partly opened grass dominated by Festuca vaginata and Stipa borysthenica (Fig. 6 ).

Etymology.

The name of the new species refers to the habitat, Pannonic open sand steppes, where E. arenaria is one of the most dominant epigeic Collembola species.

Remarks.

Based on the colour pattern, E. arenaria sp. nov. is very close to E. violaceolineata Stach, 1963, with the difference that, in the case of the latter, neither the original description ( Stach 1963) nor other descriptions ( Jordana 2012) mention the presence of a dark ventral side, which is a key character of the new species. Stach (1963) only notes that, similarly to E. schoetti Stach, 1922, the dark-pigmented body side often appears also in individuals of E. violaceolineata . Entomobrya arenaria sp. nov. differs from E. violaceolineata by the morphology of the labral papillae (rounded with one strong-armed spine-like projection in the new species while truncate and bearing three short setulae in E. violaceolineata ). There is a further difference regarding the apical bulb of the fourth antennal segment, trilobed in the new species, while simple (sensu Stach 1963) or bilobed (sensu Jordana 2012) in E. violaceolineata . The shape of unguiculus is also different, as its external edge is serrate in the new species while smooth in E. violaceolineata . The Abd IV/III ratio of E. arenaria sp. nov. is above 4, while Abd IV of E. violaceolineata is relatively short, resulting in a smaller (~3) Abd IV/III ratio. Based on specimens collected in Spain, Jordana (2012) was the first to provide the complete macrochaetotaxy for E. violaceolineata , compared to which marked differences in the number of macrochaetae can be observed in most areas, including head H1, H4, and H5; Th II T2; Abd II A2; Abd III A3 and A5; Abd IV A6, A7, and A8, respectively (Table 1 ). Regarding habitat characteristics, E. arenaria sp. nov. inhabits xerophilic open grasslands, while E. violaceolineata has been found under dead leaves and litter in parks, pine and riparian forest litter, and belts of meadows along river banks ( Stach 1963; Jordana 2012; Buşmachiu et al. 2017).

Upon further investigation, ten species share the same or very similar macrochaetotaxy of Abd II-III (Table 1 ), namely E. armeniensis Jordana, Potapov & Baquero, 2011; E. cheni Baquero, Arbea & Jordana, 2010; E. handschini Stach, 1922; E. hirsutothorax Jordana & Baquero, 2021 (in Baquero et al. 2021); E. kuznetsovae Jordana, Potapov & Baquero, 2011; E. murreensis Yosii & Ashraf, 1965; E. nigriventris ; E. pazaristei Denis, 1933; E. strigata Stach, 1963; E. taigicola Jordana, Potapov & Baquero, 2011; respectively. While the colour pattern of the new species is quite different from the abovementioned species, there are differences also in chaetotaxy and other characters (Table 1 ). Entomobrya armeniensis is characterised by a slightly different formula for the head and has an additional Mac (S4p) absent in the new species, fewer Mac on the T1 area of Th II, A8-A9 area of Abd IV. Entomobrya cheni bears significantly more Mac on Abd IV areas A7, A8, and A10, respectively, and fewer chaetae on the manubrial plate compared with E. arenaria sp. nov. The dorsal macrochaetotaxy scheme of E. handschini is very close to that of the new species, with the only difference involving the area H1 on the head with fewer Mac (3 or 4); in addition, the smaller number of chaetae on the manubrial plate can be mentioned when compared to the new species. In the case of E. kuznetsovae , the simple apical bulb (trilobed in the new species) and the presence of macrochaetae in the A6 area in Abd IV (without Mac in the new species) can be highlighted as differential characters. Entomobrya murreensis differs from E. arenaria sp. nov., most notably by the macrochaetae formula of Th II and by the presence of macrochaetae in the A6 area in Abd IV. The dorsal macrochaetotaxy scheme of E. nigriventris and E. strigata is very close to that of the new species. In E. strigata , differences include fewer Mac in the area H1 on the head, T1 area of Th II, and A7-A9 areas of Abd IV. Entomobrya nigriventris has only one Mac in the area H5 of the head and, similarly to E. strigata , has a significantly smaller number of chaetae on the manubrial plate. The cave-dwelling species E. pazaristei differs from the new species by the different Mac formula for the head, the higher number of Mac in the area T1 in Th II, and the presence of macrochaetae in the A6 area of Abd IV. Entomobrya taigicola mainly differs from the new species by the higher number of Mac (3) in the area H2 on the head, the fewer number (1) of Mac in the area A8 of Abd IV, and fewer chaetae on the manubrial plate.

Figures

Figure 2. Entomobrya arenaria sp. nov. Habitus A adult specimen, dorsolateral view B same adult specimen ventral view C subadult specimen, dorsolateral view D same subadult specimen, dorsoventral view. Scale bars: 1 mm.

Figure 3. Entomobrya arenaria sp. nov. A head chaetotaxy B apex of Ant IV C Ant III sensillar organ D labrum with labral papillae, maxillary palp and sublobal plate E labial papilla E with lateral process (l. p.) F labial triangle, arrow indicates M 2 chaeta present or absent. Abbreviations: Ant = antennal segment. Scale bars: 0.05 mm (A); 0.02 mm (B, D); 0.03 mm (C, F); 0.01 mm (E).

Figure 4. Entomobrya arenaria sp. nov. A trochanteral organ B unguis and unguiculus of leg III C ventral tube anterior view (right side) and posterior view (left side), circles indicate ciliated chaetae D ventral tube lateral flap E manubrial plate F mucro. Scale bars: 0.05 mm (A, C); 0.03 mm (B, D, E-F).

Figure 5. Entomobrya arenaria sp. nov. A Th II dorsal macrochaetotaxy B Abd II dorsal macrochaetotaxy C Abd III dorsal macrochaetotaxy D Abd IV dorsal macrochaetotaxy. Abbreviations: Abd = abdominal tergite; Th = thoracic tergite. Scale bar: 0.05 mm.

Figure 6. Entomobrya arenaria sp. nov. Type locality in Pannonic sand steppe grassland (Fueloephaza, Hungary).