Entomobrya unostrigata Stach, 1930

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 unostrigata Stach, 1930

Figs 14 , 15

Material.

Four ♂♂ and four ♀♀ on three slides (slide numbers as HNHM-collpr-923 to HNHM-collpr-924; and WD-coll-150), ~ 80 specimens in 96% ethyl alcohol (Vial WD180). Hungary, Budapest, 307 m asl, 47°29'14"N, 18°59'23"E, D-vac sample, 14 Mar. 2023, leg. D. Winkler. Two slides are preserved at HNHM, one slide and the specimens in alcohol are stored at SOE .

Description.

Habitus. Adult body length up to 3.91 mm excluding antennae. Colour polymorphic. Ground colour usually pale yellow (Fig. 14A ). Transitional form (Fig. 14B, C ) with yellow head and Th II, and dark purple from Th III-Abd IV and dark ventral side not rare. Completely dark form (Fig. 14D ) occasional, with head and body dorsally and ventrally dark purplish black, dark shades also on ventral tube and manubrium. Pattern typically with narrow medial longitudinal stripe extending from Th II to posterior margin of Abd IV. Broad transverse stripe on posterior margin of Abd II, occasionally also with thin transverse stripes on posterior margins of Th II-Abd I and Abd III-IV. Posteriorly on Th II-Abd III, often with irregular or trapezoidal patches along centreline, usually broadest on Abd III. Pattern on darker specimens barely detectable.

Head. 8+8 eyes, GH smaller than EF, Interocular chaetotaxy with six chaetae (s, t, p, q, r, v) (Fig. 15A ). Antennae length 1.80-2.27 mm (n = 7). Antennal length to head diagonal length ratio 2.56-3.20 (n = 7). Relation of antennal joints I-IV as 1: 2.1-2.3: 1.8-2.1: 2.4-3.0 (n = 7). 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 labral papillae with 1-3 setulae expansion (Fig. 15B ). Outer maxillary palp with two smooth chaetae and three smooth sublobal chaetae. Lateral process on labial papilla E barely reaching or slightly beyond apex of papilla. Labium chaetotaxy formed by 5 smooth “a” chaetae and, in the basal row, by ciliated chaetae M, R, E, L1 and L2 with R smaller than other chaetae (ratio of R/M~0.6).

Body. Ratio of Abd IV/III length 4.04-5.57 (n = 8). No differentiated chaetae on tibiotarsus III, with exception of the smooth terminal chaeta opposite to tenent hair. Trochanteral organ with up to 33 spine-like chaetae forming a +/- V-shaped pattern. Unguis with sub-equal paired basal teeth at 47% from the inner edge, and with two more unpaired teeth at 74% and 87% from inner edge, respectively. Unpaired dorsal and paired lateral teeth intermediate, at a level below the paired internal teeth. A small pretarsal chaeta present on both anterior and posterior surfaces. Unguiculus lanceolate, outer lamella smooth or serrate (Fig. 15C ). Tibiotarsal tenent hair clavate, ~0.8 as long as claw. Ratio of smooth terminal chaeta/unguiculus 0.9. Ventral tube with 30+30 ciliated chaetae on anterior side and 19+19 ciliated chaetae on posterior side; lateral flap with 12 chaetae. Manubrial plate with three chaetae and two psp. Length of not ringed terminal dens ~ 2.5 × the length of mucro. Mucro with anteapical tooth markedly smaller than apical; basal spine just reaching tip of anteapical tooth (Fig. 15D ).

Macrochaetotaxy (Fig. 15E-H ). The studied population can be described by the following abbreviated formula: 3(4)-1(2)-0-3-2/1-4/2-4(5)/1-0-1/4(5)-104(5)-102-102-2.

Head (Fig. 15A ): H1 area with 3-4 Mac, An2, An3a1, and An3 always present, An3a2 present or absent. H2 area with 1-2 Mac, A5 always present, A6 present or absent; H3 area without Mac; H4 area with three Mac (S1, S3, S4i); H5 area with two Mac (Ps2 and Ps5). Mesothorax (Fig. 15E ): area T1 with one Mac (m2i2); T2 with four Mac (a5, m4, m4i, m5). Abdomen: Abd II (Fig. 15F ) area A1 with two Mac (a2 and a3); area A2 with 4-5 Mac (m3, m3e, m3ep, m3ea always present, m3ei present or absent); Abd III (Fig. 15G ) area A3 with one Mac (a1); area A4 without Mac, and area A5 with one Mac (m3); Abd IV (Fig. 15H ) area A6 with 4-5 Mac (A1, B1, Be3, D1 always present, one Mac of uncertain homology present or absent; area A7 with unpaired central Mac A03, and with 4-5 Mac (A2, B2, C1, E1 always present; B3 present or absent); area A8 with unpaired central Mac A04, and two Mac (A4 and B4); area A9 with unpaired central Mac A05, and two Mac (A5 and B5); and area A10 with two Mac (A6 and B6); sensillar formula from Th II to Abd V: 2,2/1,2,2,14,3; microsensillar formula from Th II to Abd III: 1,0/1,0,1.

Ecology.

The species was found in an urban park (grass habitat) in considerable abundance.

Remarks.

Originally described from the Spanish mainland ( Stach 1930), E. unostrigata has since been detected mainly from southern European countries, such as Italy ( Simon 1965), France ( Renaud et al. 2004), and Bulgaria ( Tsonev and Kazandzhieva 1991), as well as introduced to North America and Australia ( Christiansen 1956; Greenslade 1995). In Hungary, this is the first record of the species. The fact that it was found in the capital, where it proved to be extremely abundant, but not anywhere else, despite the extensive Collembola collections that have taken place in the country in the past decades, raises the idea that the species was also introduced in Hungary.

The specimens collected show great variability in terms of pattern and colour form. In the original ( Stach 1930) and later descriptions ( Stach 1963), the author distinguished three forms based on the colour pattern. Apart from the typical principal form, a slightly different pattern was described as var. Entomobrya unostrigata dorsosignata , as well as a pale-coloured form (ab. Entomobrya astrigata ) without any pattern but a small dot between the antennae. Further variations in colour pattern and pigmentation have been documented by, e.g., Wray (1953), Christiansen (1958), Simón (1976), Christiansen and Bellinger (1980), Greenslade (1995), and more recently by Katz et al. (2015), Baquero and Jordana (2018), and Jordana and Greenslade (2020). Dark lateral pigmentation on the edges of certain tergites has already been noted (e.g., Stach 1963; Simón 1976; Katz et al. 2015), and darker pigmented specimens have also been presented in some papers ( Greenslade 1995). Nevertheless, specimens with dark ventral sides or completely dark specimens with hardly visible patterns (as in Fig. 14C, D ) we found in the sampled Hungarian population have not been described yet.

Large individuals are not uncommon in the studied Hungarian material; the maximum length (without antennae and furca) almost reaches 4 mm, while, according to the data published so far, the species is smaller: specimens up to 2 mm from the Spanish mainland ( Stach 1963), up to 2.5 mm from the United States ( Christiansen and Bellinger 1980), up to 2.62 mm from the Canary Islands ( Baquero and Jordana 2018), and up to 2.35 from Australia ( Jordana and Greenslade 2020), respectively. Similarly to European and Australian specimens, the eyes G and H are smaller compared to C and F, while they are similar in size in the case of specimens from the USA ( Katz et al. 2015).

Slight variations in the macrochaetotaxy of some areas can also be detected compared to previous descriptions ( Katz et al. 2015; Baquero and Jordana 2018; Jordana and Greenslade 2020). Larger specimens often have four Mac in the H1 area of the head. In some specimens, there is one more additional Mac also in the H2 area. Similarly to the specimens from North America, we found four or five Mac in area A2 of Abd II, while individuals from Australia and other European regions bear three or four macrochaetae in this area. On Abd IV, the unpaired macrochaetae A03-A05 are present in the Hungarian individuals (the absence of these macrochaetae has only been documented in North American individuals ( Katz et al. 2015)). The number and homology of macrochaetae in the areas A6-A10 roughly correspond to those documented in previous redescriptions ( Katz et al. 2015; Baquero and Jordana 2018; Jordana and Greenslade 2020). Considering all these variations, the species E. unostrigata can be characterised by the following simplified formula: 3(4)-1(2)-0-3-2(3)/1-4/2-4(3-5)/1-0-1/4(2-5)-10(0)4(5)-10(0)1(2)-10(0)2(1-3)-2(3).

Figures

Figure 13. Entomobrya cf. quinquelineata A head chaetotaxy B labral papillae C trochanteral organ D unguis and unguiculus of leg III E Th II dorsal macrochaetotaxy F Abd II dorsal macrochaetotaxy G Abd III dorsal macrochaetotaxy H Abd IV dorsal macrochaetotaxy. Abbreviations: Abd = abdominal tergite; Th = thoracic tergite. Scale bars: 0.03 mm (A-C); 0.02 mm (D); 0.05 mm (E-H).

Figure 14. Entomobrya unostrigata. Habitus A typical colour pattern (dorsal view) B intermediate semi-dark colour form (dorsolateral view) C intermediate semi-dark colour form (ventrolateral view - same specimen as Fig. 13 B) D dark colour form (ventrolateral view). Scale bars: 0.5 mm.

Figure 15. Entomobrya unostrigata A head chaetotaxy B labral papillae C claw III (unguiculus with two different morphologies: outer edge smooth or serrate) D mucro E Th II dorsal macrochaetotaxy F Abd II dorsal macrochaetotaxy G Abd III dorsal macrochaetotaxy H Abd IV dorsal macrochaetotaxy. Abbreviations: Abd = abdominal tergite; Th = thoracic tergite. Scale bars: 0.03 mm (A, C); 0.02 mm (B, D); 0.05 mm (E-H).