Entomobrya margaretae Gruia, 1967

Winkler, Daniel, Grujić, Nikola Z. & Fiera, Cristina, 2023, A new species of Entomobrya Rondani, 1861 (Collembola, Entomobryidae, Entomobryinae) from Croatia with the redescription of Entomobrya margaretae Gruia, 1967, Zootaxa 5352 (3), pp. 411-425 : 419-423

Entomobrya margaretae Gruia, 1967

Figs 19–32 , Table 1

Entomobrya margaretae Gruia, 1967: 314–316 (original description); Gruia, 2000: 57; Jordana 2012: 83, 137 (keyed, diagnosis).

Material examined. Five topotypic specimens. Neotype: adult female on slide (Nr. HNHM-coll-906). Three females and one specimen with invisible genital plate on three slides (Nr. HNHM-coll-907 to HNHM-coll-909). Near Băile Herculane , Cerna Valley, Banat, Romania, 358 m a.s.l., N 45°1’9”; E 22°33’22”, from riverine forest litter, 2021.ix.14., leg. A. Erdo.

Other material examined. Two specimens (female) on slide (Nr. HNHM-coll-910), four juveniles in alcohol (Vial WD 181). Near Baške Oštarije, Croatia, 1019 m a.s.l., N 44°32’0”; E 15°8’30”, from dolomite grassland, hand collecting, 20.viii.2022, leg. D. Winkler.

Redescription. Adult body length (excluding antennae) 3.09–4.39 mm (n=7) (type material: 3–3.28 mm after Gruia 1967, neotype 4.16 mm). Body ground colour white, with a broad black band from first third of Th III to posterior part of Abd III (excluding lateral part of the latter segment). Black patches also on the posterior part of Abd IV ( Fig. 19A ). As a rare variation of colour pattern (observed in one specimen only), the broad black band can be missing ( Fig. 19B ).

Head. 8+8 eyes, GH smaller than EF ( Fig. 20 ). Interocular chaetotaxy with five chaetae (s, t, q, r as mic and p as mes). Antennae length 1.93–2.94 mm (n=5), neotype 2.87 mm. Antennal length to head diagonal length ratio 3.57–3.73 (n=5), neotype 3.73. Relation of the antennal joints I–IV as 1: 1.6–1.9: 1.7–1.9: 2.0–2.5 (n=5). Ant IV with bilobed apical bulb. Ant III sensillary organ composed of two sensory rods partially behind a cuticular fold, guarded by three short sensilla. Arrangement of chaetae on the labrum 4/554, prelabral chaetae ciliated, posterior, median and anterior labral chaetae smooth. Labrum with four rounded labral papillae, each with 2–3 spin-like projections ( Fig. 21 ). Outer maxillary palp with two smooth chaetae and three smooth sublobal chaetae. Lateral process on labial papilla E large, extending apex of papilla ( Fig. 22 ). Labium chaetotaxy formed by 5 smooth “ a ” chaetae and, in the basal row, by ciliated chaetae M, R, E, L 1 and L 2 ( Fig. 23 ), with R thinner and slightly reduced (ratio of R/M ~0.7).

Body. Ratio of Abd IV/III length 5.28–7.19 (n=7), neotype 6.36. Trochanteral organ with numerous (up to 80) smooth spiny chaetae (see Gruia 1967: Fig. 1D ). Unguis inner side with sub-equal paired basal teeth at 50–54 % from the inner edge, and with two more unpaired, well-developed teeth at 72–74 % and 84–86 % from inner edge, respectively. Outer side with paired lateral teeth close to the basis of the claw, unpaired dorsal tooth in intermediate position between the paired internal teeth and the claw basis. A small pretarsal chaeta present on both anterior and posterior surfaces. Unguiculus lanceolate, outer lamella serrated ( Fig. 24 ). Tibiotarsus ventrally with number of thick macrochaetae, dorsally with very long, thinner macrochaetae ( Fig. 24 ). Tibiotarsal tenent hair clavate, longer than claw. Ratio of smooth terminal (supraempodial) chaeta / unguiculus 0.9. Ventral tube with 22+22 ciliated chaetae on anterior side (4 of them as well-developed Mac) and 37+37 ciliated chaetae on posterior side ( Fig. 25 ); lateral flap with 13 ciliated and 6 smooth chaetae ( Fig. 26 ). Manubrial plate with 14–15 chaetae and 3 psp ( Fig. 27 ). Length of not ringed terminal dens about four times the length of mucro. Mucro with distal tooth equal to anteapical; mucronal spine reaching tip of anteapical tooth ( Fig. 28 ).

Macrochaetotaxy ( Figs 20 , 29–32 ). Simplified Mac formula: 5-1-0(1)-3-1/11(15)-8(12)/2-4(5)/0-2-1(2)/5(9)-4(5)- (1 0)1(3)-(1 0)3(6)-5(7). Head ( Fig. 20 ): H1 area with five Mac (An 2, An 3a1, An 3a2, An 3, and one additional Mac from the An series); H2 area with one Mac (A 5); H3 area regularly without Mac, but in one specimen Mac S’ 0 present; H4 area with three Mac (S 1, S 3 and S 4i); H5 area with one Mac (Ps 2), Ps 5 present as mes. Mesothorax ( Fig. 29 ): plurichaetotic, area T1 with 11–15 Mac (m 1, m 2, m 2i and m 2i2 and another 7–11 Mac); T2 with 7–12 Mac (a 5 and a 5’; 4–9 Mac in the m 4 group; m 5). Abdomen: Abd II ( Fig. 30 ) area A1 with two Mac (a 2 and a 3); area A2 with 4–5 Mac (m 3, m 3e, m 3ei and m 3ep always present, m 3eai present or absent); Abd III ( Fig. 31 ) area A3 without Mac; area A4 with two Mac (a 2 and a 3), and area A5 with 1–2 Mac (m 3 always present, m 3e present or absent); Abd IV ( Fig. 32 ) area A6 with 5–9 Mac (A 1, A e2, B e2, B e3 and D 1 always present, B 1 and three supplementary Mac of uncertain homology present or absent); area A7 with 4–5 Mac (A 3, B 2, C 1 and E 1 always present; A 2 present or absent); area A8 with unpaired central Mac A 04 present or absent, and 1–3 Mac (A 4 always present, A 4a and A e4 present or absent); area A9 with unpaired central Mac A 05 present or absent, and 3–6 Mac (A 5, A e5p and B 5 always present, A e5, A e5pp and A i1 present or absent); and area A10 with 5–7 Mac (A 6, A e7, A e8, A i2 and B 6 always present, two supplementary Mac of uncertain homology present or absent); sensillar formula from Th II to Abd V: 2,2/1,2,2,8,3; microsensillar formula from Th II. to Abd III: 1,0/1,0,1.

Ecology and distribution. The species was originally found among bare rocks near a cave and on river bank. Topotypic specimens were collected among riverbank rocks where small amounts of forest litter accumulated. Specimens in Croatia were collected at the base of rocky outcrops in a dolomite grassland. Until now, the species was only known from its type localities in Romania ( Gruia 1967, Gruia 2000, Fiera 2007); this is its first occurrence in Croatia. In this same habitat, we found an abundant co-existent Entomobrya species, namely E. atrocincta , also new to the Croatian fauna.

Remarks. The already-known characters are in good accordance with the original description ( Gruia 1967). Among the collected specimens, a different colour form was found and described as an important variation. The essential dorsal macrochaetotaxy shows slight variations (often bilateral) in the specimens examined, mainly in the plurichaetotic areas T1 and T 2 in Th. II, as well as in most of the areas in Abd. IV.

Figures

FIGURE 1. Entomobrya, symbols used for chaetae types and pseudopore.

FIGURE 19. Entomobrya margaretae. A, Regular colour pattern B, Specimen without dark pigmentation on Th III–Abd III. Scale bar: 1 mm (19A–B).

FIGURE 20–28. Entomobrya margaretae. 20, head chaetotaxy; 21, labral papillae; 22, labial papilla E with lateral process (l.p.); 23, labial triangle; 24, empodial complex III and part of tibiotarsus; 25, ventral tube anterior view (right side) and posterior view (left side), dots—ciliated chaetae; 26, ventral tube lateral flap; 27, manubrial plate, dots—ciliated chaetae; 28, mucro. Scale bars: 20 and 25, 0.05 mm; 21 and 24, 0,02 mm; 22, 0,01 mm; 23 and 26–28, 0.03 mm.

FIGURE 29–32. Entomobrya margaretae. 29, Th II dorsal macrochaetotaxy; 30, Abd II dorsal macrochaetotaxy; 31, Abd III dorsal macrochaetotaxy; 32, Abd IV dorsal macrochaetotaxy. Scale bars: 0.05 mm (29–32).