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Research Article
Phylogenetic analysis of Endonura Cassagnau, 1979 (Collembola, Neanuridae, Neanurinae), including descriptions of four new species
expand article infoAdrian Smolis‡, Nataliya Kuznetsova§, Grzegorz Paśnik|
‡ University of Wrocław, Wrocław, Poland
§ Moscow State Pedagogical University, Moscow, Russia
| Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Kraków, Poland

Corresponding author: Grzegorz Paśnik ( pasnik@isez.pan.krakow.pl )

Academic editor: Michael Schmitt
© 2024 Adrian Smolis, Nataliya Kuznetsova, Grzegorz Paśnik.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
ZooBank: urn:lsid:zoobank.org:pub:88A70CAC-692F-48EA-99E3-73D4DAEB15FD
Open Access

Abstract

With 54 described species, Endonura is one of the most species-rich genera of the Neanurinae. The taxon is characterised by the presence of 0–2 ocelli, separate tubercles Di and De with the non-crossed type of chaetotaxy on the head, and two or three tubercles on the fifth abdominal tergite. Four new species from the Crimea and the Caucasian region have been described based on adult specimens: Endonura armeniaca sp. nov., E. cochlearifera sp. nov., E. crimica sp. nov., and E. duplex sp. nov. A phylogenetic analysis of the genus Endonura using 70 characters of adult external morphology is presented. Two methods were chosen to examine different approaches to the reconstruction of evolutionary relationships: Maximum Parsimony (MP) and Bayesian Inference (BI). Besides supporting Endonura monophyly both analyses failed to resolve any of the deeper relationships within the genus. All known species within the genus are grouped into two main clades, A and D. Both of these clades have members distributed throughout Europe, the Caucasus and the western part of Central Asia. Endonura crimica sp. nov. can be considered as an intermediate between these two clades.

Keywords

Cladistic analysis, Bayesian inference, Springtails, taxonomy

1. Introduction

Springtails belonging to the subfamily Neanurinae are an example of evolutionary success, with over 800 currently described taxa, representing almost one tenth of all the known Collembola (Bellinger et al. 2023). Members of the subfamily differ significantly from other Collembola in terms of morphology and behaviour. Firstly, they have completely lost the jumping organ (furca or furcula) and their movement can be defined as exceptionally slow compared to the majority of springtails. Another striking difference between members of this subfamily and other Collembola is that the integument surface has prominent tubercles. In addition, unlike other Collembola, the chaetae that cover the body of Neanurinae are well developed, elongated, widened and covered with numerous teeth.

The evolutionary success of this subfamily is probably due to a number of factors. The first is the presence of body tubercles and well-developed chaetae, which in turn provides an important mechanical barrier for potential predators. The second is protection of toxic volatile chemicals, e.g. phenols (Messer et al. 2000). The third is an apparently narrow feeding specialisation, often on slime moulds, which has recently been observed and experimentally demonstrated (Smolis 2009; Hoskins et al. 2015; Deharveng et al. 2017; Smolis and Greenslade 2020). Slime moulds are cosmopolitan and mostly associated with terrestrial habitats with high humidity. Such habitats are also preferred by Neanurinae, which are almost exclusively springtails of forest ecosystems, with an exceptional diversity of species found in the temperate and tropical forests (e.g. Cassagnau 1988, 1993; Deharveng and Weiner 1984; Deharveng 1989a; Greenslade and Deharveng 1991; Deharveng and Bedos 2000; Simón Benito and Palacios-Vargas 2008; Smolis and Bernard 2017).

The genus Endonura Cassagnau, 1979 is one of the most thoroughly studied and the largest genera within Neanuridae, with 54 valid species currently (Bellinger et al. 2023). Endonura is a Holarctic genus, with the highest concentration of taxa in some regions of the Western Palearctic, e.g. the Iberian Peninsula, the Caucasus, the Crimea, the Carpathians and northwestern Iran (e.g., Deharveng 1979; Jordana et al. 1997; Smolis et al. 2007; Smolis 2008; Smolis and Kuznetsova 2016; Smolis and Skarżyński 2020). A recent phylogenetic analysis, although based on a very small representation of the genus, showed that Endonura is poorly defined and probably consists of not very closely related taxa (Smolis and Paśnik 2020). The objectives of our study were: (1) to analyse and describe the morphology of new, unique taxa; (2) to analyse the phylogenetic relationships among species within the genus Endonura based on morphology, and to determine the phylogenetic position of the new taxa; and (3) to evaluate the usefulness of chaetotaxy in resolving relationships within Endonura.

2. Materials and methods

2.1. Taxonomic analysis

Material for taxonomic descriptions was collected during field trips to the Crimea (by Alexander Sharikov and Dmitry Shitikov; February 2015 and 2016) and the Caucasus (by: Boris Efeikin, Alexander Kremenitsa, Ivan Kuchiev, Nataliya Kuznetsova and Mikhail Potapov; September 1980, July 2015 and May 2016). Samples were taken from soil, litter and moss and extracted using a Berlese-Tullgren apparatus. After extraction, the specimens were preserved in alcohol. For detailed morphological analysis, they were cleared in Nesbitt’s fluid, mounted in Swan’s medium and examined using a Nikon Eclipse E600 phase-contrast microscope. Figures were drawn using a camera lucida and prepared for publication using Adobe Photoshop CS3.

Abbreviations used. General morphology: Abd. – abdomen; Ant. – antenna; AOIII – sensory organ of antennal segment III; Cx – coxa; Fe – femur; Scx2 – subcoxa 2; T – tibiotarsus; Th. – thorax; Tr – trochanter; VT – ventral tube. Groups of chaetae: Ag – antegenital; An – chaetae of anal lobes; ap – apical; ca – centroapical; cm – centromedial; cp – centroposterior; d – dorsal; Fu – furcal; vc – ventrocentral; Ve or ve – ventroexternal; Vea – ventroexternoanterior; Vem – ventroexternomedial; Vep – ventroexteroposterior; Vel – ventroexternolateral; Vec – ventroexternocentral; Vei – ventroexternointernal; Vi or vi – ventrointernal; Vl – ventrolateral. Tubercles: Af – antenno–frontal; Cl – clypeal; De – dorsoexternal; Di – dorsointernal; Dl – dorsolateral; L – lateral; Oc – ocular; So – subocular. Types of chaetae: Ml – long macrochaeta; Mc – short macrochaeta; me – mesochaeta; mi – microchaeta; ms – s–microchaeta; S or s – chaeta s; bs – s–chaeta on Ant. IV; miA – microchaetae on Ant. IV; iv – ordinary chaetae on ventral Ant. IV; or – organite of Ant. IV; brs – border s–chaeta on Ant. IV; i – ordinary chaeta on Ant. IV; mou – cylindrical s–chaetae on Ant. IV („soies mousses”); x – labial papilla x; L’ – ordinary lateral chaeta on Abd. V; B4, B5 – ordinary chaetae on tibiotarsi.

Terminology. Terminology and layout of the tables used in the paper follow Deharveng (1983), Deharveng and Weiner (1984), Smolis and Deharveng (2006) and Smolis (2008).

Depositories. Department of Invertebrate Biology, Evolution and Conservation, University of Wrocław, Poland (DIBEC); Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Kraków, Poland (ISEZ); Moscow State Pedagogical University, Moscow, Russia (MSPU); Muséum d’histoire naturelle, Geneva, Switzerland (MHNG); Muséum national d’Histoire naturelle, Paris, France (MNHN); Oregon State Arthropod Collection, Zoology Department, Oregon State University, Corvallis, U.S.A. (OSAC); Senckenberg Museum of Natural History, Görlitz, Germany (SMNG); State Museum of Natural History, Ukrainian National Academy of Sciences, L’viv, Ukraine (SMNHL); Zoological Museum of University of Amsterdam, Amsterdam, Netherlands (ZMA); U.S. National Museum of Natural History, Washington, D.C. U.S.A (NMNH).

2.2. Phylogenetic analysis

To investigate the phylogenetic relationships between species of the genus Endonura, 43 of the 54 known species were selected for analyses (Table 1). Because of the unavailability of specimens for examination and insufficient descriptions, the following species were not included in the analyses: E. caeca (Gisin, 1963), E. granulata (Cassagnau, Delamare & Deboutteville, 1955), E. ichnusae Dallai, 1983, E. immaculata Deharveng, 1980, E. ludovicae (Denis, 1947), E. occidentalis Deharveng, 1979, E. pejai Deharveng, 1980, E. poinsotae Deharveng, 1980, E. tartaginensis (Deharveng, 1980), E. tetrophthalma (Stach, 1929) and E. tyrrhenica Dallai, 1983.

Table 1.
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List of examined material.

Species Number of examined specimens Status of examined types Collections Other sources of data e.g. literature
Endonura agnieskae 24 Holotype, Paratypes MHNG —
E. aibgai 12 Holotype, Paratypes DIBEC, MSPU —
E. annae 22 Holotype, Paratypes MHNG —
E. alavensis — — — Pozo and Simon 1982
E. alticola 1 Holotype ISEZ —
E. arbasensis — — — Deharveng 1979
E. asiatica 11 Holotype, Paratypes MNHN, DIBEC —
E. baculifer — — — Deharveng 1979
E. cantabrica — — — Deharveng 1979
E. carpatica 8 Holotype, Paratypes DIBEC —
E. centaurea 3 Syntypes MNHN —
E. ceratolabralis 7 Holotype, Paratypes DIBEC —
E. colorata — — — Jordana et al. 1997
E. cretensis 7 Holotype ZMA, DIBEC, SMNHL —
E. cryptopyga 4 Holotype MSPU —
E. dalensi — — — Deharveng 1979
E. dentifera 7 Holotype, Paratypes DIBEC, SMNHL —
E. deharvengi 2 Syntypes MNHN —
E. dichaeta 14 Holotype, Paratypes DIBEC —
E. diminutichaeta 11 Holotype, Paratypes MSPU, DIBEC —
E. dobrolyubovae 8 Holotype, Paratypes MSPU, DIBEC —
E. dudichi 40 — DIBEC —
E. gracilirostris 5 Holotype, Paratypes DIBEC, SMNHL —
E. gladiirostra 1 Holotype DIBEC —
E. gladiolifer — — — Jordana et al. 1997
E. incolorata 26 Lectotype, Paralectotype ISEZ, DIBEC —
E. kremenitsai 11 Holotype, Paratypes MSPU, DIBEC —
E. levantica 2 Holotype, Paratype DIBEC, SMNHL —
E. longirostris 4 Holotype, Paratypes DIBEC —
E. lusatica 38 Holotype, Paratype SMNG —
E. ossetica 2 Holotype, Paratype MSPU, DIBEC —
E. paracantabrica 5 Holotype, Paratypes MSPU, DIBEC —
E. paracentaurea 4 Holotype, Paratypes DIBEC —
E. persica 14 Holotype, Paratypes DIBEC —
E. reticulata 52 — DIBEC, MNHN —
E. saleri — — — Fanciulli and Dallai 2008
E. schwendingeri 9 Holotype, Paratypes MHNG —
E. tatricola 162 Lectotype ISEZ, DIBEC —
E. taurica 11 Holotype, Paratypes ISEZ, DIBEC —
E. transcaucasica 1 Lectotype ISEZ —
E. turkmenica 2 Holotype, Paratype DIBEC —
E. quadriseta 17 Holotype, Paratype MNHN, DIBEC —
E. urotuberculata 2 Holotype, Paratype MNHN, DIBEC —
Neanura muscorum 177 — DIBEC —
Kalanura babenkoi 34 Holotype, Paratypes DIBEC, MSPU —
Xylanura oregonensis 47 Holotype, Paratypes NMNH, OSAC, DIBEC —

The four new species described in this paper were included in the phylogenetic analysis. Forty-seven species were analysed out of 58. The trees were rooted using Neanura muscorum (Templeton, 1836), Kalanura babenkoi Smolis, 2007 and Xylanura oregonensis Smolis 2011 as outgroup taxa.

Species were selected based on specimen availability, with a preference for the type-specimens. Most characters were based on personal observations of specimens. These observations were supplemented by previous taxonomic/phylogenetic studies (Deharveng 1983; Deharveng and Weiner 1984; Greenslade and Deharveng 1990; Smolis and Deharveng 2006; Smolis 2008).

A total of 70 characters were scored for the study taxa, including 61 binary characters and 9 multistate characters. Missing data were coded as ‘?’ in the matrix (Table 2). All characters were treated as unordered (Fitch 1971) and equally weighted (Wilkinson 1992), thus making no assumptions about character evolution. The character matrix was constructed and characters mapped with WinClada ver. 1.00.08 (Nixon 2002) to observe character state transformation on a tree.

Table 2.
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Morphological data matrix used in the analyses.

Taxon Characters Characters
11111111112222222222333333
12345678901234567890123456789012345		 33334444444444555555555566666666667
67890123456789012345678901234567890
N. muscorum 00010100000110001000000010100010100 01010000010100101100000001001101100
K. babenkoi 00010000000110001000000010000010100 01100000000000001100000001000011110
X. oregonensis 00011011110010001030100010000010121 1110010101010110000101?001001011000
E. agnieskae 10011000000110001000000000010110100 01111110000100101110000001101111110
E. aibgai 10011000000111121001?00010010110100 01001111000100101110000001111010110
E. alavensis 100110011001100110201000100101102?? ?1001?1???0????0??100010?00??011111
E. alticola 10011000000110001000000010010110210 011011110001001111100000??111?11111
E. annae 10011001000110021100110000011200000 0100101001010100001101?001101010110
E. arbasensis 111?100000011000100000001001111???? ?1001111000000?0??100010?000?011111
E. armeniaca 10011001000112121101?001?1?10100200 000011111?111?10111101?0?1111111111
E. asiatica 10001000000110001000000010010110100 00001111000100101110101000111011111
E. baculifer 10011001100111111121?1001001110???? ?0001010010101?0111010100110?0111??
E. cantabrica 10011001000110011001?0001001011???? ?1001111000100?0??100000?100?0111??
E. carpatica 111?1000100110021121?10000011111100 00001010010101001110000001101011111
E. centaurea 11011001001110011101?00000011110110 000010100101010011100010?0101011110
E. ceratolabralis 10011001000110011100100000010110221 111010100101010011100010?0101011111
E. cochlearifera 10011000000110011000000000010110200 00001111000100101110100001001111110
E. colorata 10011001110110001021?0000001011???? ??001?1???0????0??101000?100?011110
E. cretensis 10011000100012121020000010010111210 011111111?111?10221101?101000111111
E. crimica 10011001000100011001?00000010110100 010010100001001011100000?1000011110
E. cryptopyga 10011000000111121101?00010010100200 010111110001001011100000?1001110010
E. dalensi 1001100000001001100000001001111???? ?1001111000000?0??100010?100?011111
E. deharvengi 10011000000111121000000010011?10110 00001010010101001110100001100011111
E. dentifera 10011000000110001100000000010110100 00001111000100101110100001001110001
E. dichaeta 11011001100111121121?00000011?10210 00001010010101001111000000101011111
E. diminutichaeta 10011001000111101000100010010?00200 01101111000100102210001001001111010
E. dobrolyubovae 10011001000111121101?00000010?00100 00001111000100101110100011001?10110
E. dudichi 11011001000110000101?00000011?10100 01001010010101011110000000100111110
E. duplex 10011000000110001000000000010110100 01001111000100101110100001000011110
E. gladiirostra 10011011110110011130100010010200221 111110100101010000100010?1101?11110
E. gladiolifer 10011000100110001021?000?001010???? ?11110100111???0111011?0?000?010111
E. gracilirostris 10011000100100011020000000010?10220 00001111000100101110001001101?11010
E. incolorata 11011000000110000101?00000011110100 00001010??0101001120001000100011111
E. kremenitsai 10011000000111101000000010010110100 01101111000100101110000011001111110
E. levantica 10011000000110021000000000011110120 000110100101010011100000?0101011111
E. longirostris 10011000000112121101?00010011110220 000011110000001012100010?1100011111
E. lusatica 10011000000111011000000000010110200 00001111000100101110100001001010010
E. ossetica 10011001010110021110100010011100200 011010100001011010101010?1001011111
E. paracantabrica 10011000000110001001?00010010110100 01101111000100101110000001001011010
E. paracentaurea 10011001000110021101?00000011110120 010010100101010011100000?0101011111
E. persica 10011000000111121100000010010200100 01001111000100100010000001001010010
E. quadriseta 10011000100110011020000010010110100 00001111000100101110001011000011111
E. reticulata 10011000000110001000000000010110100 00001111000000001110100001000011110
E. saleri 10011000000111111111?00000011111120 000010100001000011100000?1001111111
E. schwendingeri 10011001000111121101?001?1?10100100 00001111000100101110001011111110110
E. tatricola 11011001000110000101?00000011110100 00001010010101001110000000100011111
E. taurica 10011001100100011120100010010110000 00001111000100101110000001001110011
E. transcaucasica 10011001000110021100111000011110210 010010100101010011100010?1101011111
E. turkmenica 10011000000110021100000000010110220 00001010010101001110000001101011110
E. urotuberculata 111?1000000010011100000000011110100 00001111000000101110001100101011111

The morphological dataset was analysed using both Maximum Parsimony (MP) and Bayesian Inference (BI).

Parsimony analyses utilized New Technology heuristic searches implemented in the program TNT v. 1.5 (Goloboff and Catalano 2016). New Technology searches (Goloboff 1999) consisted of Tree Fusion, Ratchet, Tree Drifting and Sectorial searches performed, with default parameters applied, until the most-parsimonious tree was found 10 times. All characters were treated as unordered and equally weighted.

Some argue (e.g. Goloboff 1993; Goloboff et al. 2008) that results based on correctly weighted characters are preferable to those where all characters have the same weight. Implied weighting is a commonly used method for assigning different weights during tree searches. It’s a good choice because it’s independent of previous analyses and weights. The strength against homoplasy under implied weighting is related to a constant k. A lower value of k indicates a higher strength against homoplasy. This value represents the ratio of single extra step to the cost of the most homoplasious character. The value of k was calculated using the TNT script setk.run, written by Salvador Arias (Instituto Miguel Lillo in San Miguel de Tucuman, Argentina), which returned a value of 9.687500 for our dataset.

Clade supports were assessed based on Bremer support (BS) (Bremer 1994) and symmetric resampling (Goloboff et al. 2003). The Bremer support value was calculated by searching suboptimal trees up to 10 steps longer than the shortest one using TBR swapping on the shortest trees. Up to 10,000 suboptimal trees were retained during each turn.

The Symmetric Resampling (SR) support calculated the differences in the frequencies of a given group and its most frequent contradictory group (GC). The analyses were run in TNT with the traditional search, using 10,000 replications, change probability of 0.33, two initial Wagner trees, and holding three trees per replicate.

The following values were applied to support the clades: weak (SR<50%, BS 1–2), moderate (SR 51–75%, BS 3–6), good (SR 76–90%, BS 7–8), and strong (SR>90%, BS 9–10).

The synapomorphies were mapped in WinClada onto the most parsimonious tree using an option showing unambiguous changes only.

Bayesian inferences were performed in MrBayes v3.2.7 (Ronquist et al. 2012) using two simultaneous Markov Chain Monte Carlo runs, with 4 chains of 10 million generations each, sampling trees every 1,000th generation. In this analysis, the dataset was treated as a single partition and analysed under gamma-distribution variation, considering all state frequencies (change rates) set equal, all topologies with equal probabilities, and with unconstrained branch length.

In tree resulting from Bayesian inference, Posterior Probability (PP) was interpreted as statistical support values.

3. Results

3.1. Taxonomic descriptions

Endonura Cassagnau, 1979

Neanura (Endonura) Cassagnau, 1979: 192.

Type species

Achorutes tetrophtalmus Stach, 1929: 282.

Diagnosis

0–2 + 0–2 eyes, pigmented or not. Colour of body blue, purple brown, white, never yellow or red. Dorsal tubercles present, well developed. Mouthparts feebly developed, maxilla styliform, mandible slender or rarely strong. Labral chaetotaxy: 4/2, 4; sometimes prelabral or labral chaetae reduced. Sensilla S on Ant. IV of similar size. Head with 10 or 12 tubercles. Tubercles Af and Cl separate or fused. Tubercles Di and De on head separate, sometimes Di not differentiated. Arrangement of chaetae Di and De on head of the „non-croisé” type (Deharveng 1983). Tubercles L and So on head fused. S-chaetae present in typical arrangement and number; 22/11111 on each half tergite from th. II to abd. V. Abdomen IV with 8 tubercles: 2 Di, 2 De, 2 Dl and 2 L, or 5 tubercles: (Di+Di), 2 (De+Dl) and 2 L. Abdomen V with 3 tubercles: 2 (De+Dl+L) and (Di+Di) or 2 tubercles: 2 (Di+De+Dl+L). Tubercles Di on abd. V fused or separate. Tibiotarsal chaetotaxy 19, 19, 18. Claw with inner tooth or untoothed.

Endonura armeniaca sp. nov.

https://zoobank.org/554E1A9B-F28D-4ED2-8C7B-4B72DC48CE68
Figs 1–15, Tables 3a–c, 4

Type material

Holotype: adult female on slide, Armenia, road to Agveran village (40°29´32.6´´ N; 44° 35´35.1´´ E), mountain oak forest, litter and soil, 24.V.2016, leg. B. Efeikin (DIBEC). Paratype: adult female on slide, same data as holotype.

Diagnosis

2+2 pigmented eyes. Buccal cone long, labrum ogival. Head with chaetae B, C and D. Chaetae A, O, Ocp and E absent. Tubercles Cl and Af separate. Tubercles Dl and (L+So) on head with 4 and 7 chaetae respectively. Tubercles Di on Th. I absent. Tubercles De on Th. II and III with 3 chaetae. Tubercles L on Abd. III and IV with 3 and 5 chaetae respectively. Abd. IV and V with 8 and 3 tubercles respectively. Claw without inner tooth. Tibiotarsi with chaetae B4 and B5 short.

Description

Body length : 1.1 to 1.2 mm (without antennae) (holotype: 1.2 mm). — Colour: pale bluish grey (alive and in alcohol). 2+2 black eyes, in a typical arrangement for the genus (one anterior, one posterior, Fig. 1). — Chaetal morphology: Dorsal ordinary chaetae of five types: long macrochaetae (Ml), short macrochaetae (Mc), mesochaetae and microchaetae. Long macrochaetae thick, slightly arched or straight, narrowly sheathed, feebly serrated, apically rounded (Figs 1, 10, 14). Macrochaetae Mc morphologically similar to long macrochaetae, but much shorter. Mesochaetae similar to ventral chaetae, thin, smooth and pointed. Microchaetae similar to mesochaetae, but shorter. S–chaetae of tergites thin, smooth and short, notably shorter than nearby macrochaetae (Figs 1, 10, 13). — Antennae: Dorsal chaetotaxy of Ant. as in Table 3b. S–chaetae of Ant. IV of medium length and moderately thickened (Fig. 3), sensillum sgd long and thickened (Fig. 8). Apical vesicle distinct, trilobed (Figs 4, 5). Ventral chaetotaxy of Ant. III with 14 ordinary chaetae, sense organ AOIII with long sensillum sgv and short peg (Fig. 9). — Mouthparts: Buccal cone long with labral sclerifications ogival (Fig. 11). Labrum chaetotaxy: 4/2, 4 (Fig. 12). Labium with four basal, three distal and four lateral chaetae, papillae x absent. Maxilla styliform (Fig. 3), mandible thin with two basal and two apical teeth (Fig. 2). — Dorsal chaetotaxy and tubercles: Chaetotaxy of head reduced, chaetae A, E, O, Ocp, Dl3, Dl6, So2, L2 and L3 absent (Figs 1, 6; Table 3a). Tubercles Di on Th. I not differentiated (Fig. 1). Thorax with chaetae De2 free (Fig. 1). On Abd. I–III, the line of chaetae De1–chaeta s not perpendicular to the dorsomedian line. On Abd. V tubercle (Di+Di) with 2+2 chaetae (Fig. 10). Abd. VI partially visible from above (Fig. 10). — Ventral chaetotaxy: On head, groups Vea, Vem and Vep with 2, 2, 4 chaetae, respectively (Fig. 6). Group Vi on head with 6 chaetae. On Abd. IV, furca rudimentary without microchaetae. On Abd. IV, tubercle L with 5 chaetae (Fig. 15). On Abd. V, chaetae Vl present and chaetae L’ absent. Legs: Chaetotaxy of legs as in Table 3c. Claw without internal tooth. On tibiotarsi, chaeta M present, chaetae B4 and B5 relatively short and pointed.

Table 3a.
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Chaetotaxy of Endonura armeniaca sp. nov.: cephalic chaetotaxy–dorsal side.

Tubercle Number of chaetae Types of chaetae Names of chaetae
Cl 4 Ml F
Mc G
Af 6 Ml B
Mc C, D
Oc 2 Ml Ocm
mi Oca
Di 2 Ml Di1
Mc Di2
De 2 Ml De1
Mc De2
Dl 4 Ml Dl5, Dl1
Mc Dl4
mi Dl2
(L+So) 7 Ml L1, L4, So1
me So3–6
Table 3b.
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Chaetotaxy of Endonura armeniaca sp. nov.: antennae.

Segment, Group Number of chaetae Segment, Group Number of chaetae adult
I 7 IV or, 8 S, i, 12 mou, 6 brs, 2 iv
II 11
III 5 sensilla AO III
ve 5 ap 8 bs, 5 miA
vc 4 ca 2 bs, 3 miA
vi 4 cm 3 bs, 1 miA
d 5 cp 8 miA, 1 brs
Table 3c.
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Chaetotaxy of Endonura armeniaca sp. nov.: postcephalic chaetotaxy.

Terga Legs
Di De Dl L Scx2 Cx Tr Fe T
Th. I 1 2 1 — 0 3 6 13 19
Th. II 3 2+s 3+s+ms 3 2 7 6 12 19
Th. III 3 2+s 3+s 3 2 8 6 11 18
Sterna
Abd. I 2 2+s 2 2 VT: 4
Abd. II 2 2+s 2 2 Ve: 3–6; chaeta Ve1 present
Abd. III 2 2+s 2 3 Vel: 3–5; Fu: 5 me, 0 mi
Abd. IV 2 1+s 3 5 Vel: 4; Vec: 1–2; Vei: 2; Vl: 4
Abd. V (2+2) 4+s Ag: 3; Vl: 1
Abd. VI 7 Ve: 10–11; An: 2mi
Figure 1–15. 

Endonura armeniaca sp. nov.: 1 dorsal chaetotaxy of head and Th. I–II; 2 mandible; 3 maxilla; 4 apical bulb, ventral view; 5 apical bulb, dorsal view; 6 ventral chaetotaxy of head; 7 S– chaeta of Ant. IV; 8 sensillum sgd; 9 ventral chaetotaxy of Ant. III; 10 dorsal chaetotaxy of Abd. III–VI; 11 ventral sclerifications of labrum; 12 chaetotaxy of labrum; 13 sensillum of Abd. V; 14 chaeta Di1 of Abd. V; 15 tubercle L of Abd. IV.

Etymology

The name armeniaca is derived from Armenia, the country where the species was found.

Remarks

Among the known members of the genus, E. armeniaca sp. nov. is distinguished by an extraordinary reduction of dorsal cephalic chaetotaxy. This includes the absence of chaetae A, O, E, Ocp, Dl3, L2, L3 and So2, as well as the presence of an ogival labrum and the absence of an internal tooth on the claws. Morphologically, the new species appears to be most similar to E. schwendingeri Smolis and Skarżyński, 2020, a species recently described from northwestern Iran (Smolis and Skarżyński 2020). For instance, both species are identified by the absence of chaetae A and Ocp. However, they differ in several aspects, such as the shape of the labrum (ogival in armeniaca, not ogival in schwendingeri), the number of chaetae Dl on the head (four in armeniaca, five in schwendingeri), the number of ordinary chaetae De on Th. III (two in armeniaca, three in schwendingeri), the number of ordinary chaetae De on Abd. I–III (two in armeniaca, three in schwendingeri), the number of chaetae L on Abd. III and IV (three and five in armeniaca and two and four in schwendingeri, respectively), the number of chaetae Di on the penultimate abdominal segment, with armeniaca having 2+2 and schwendingeri having 3+3. Additionally, schwendingeri has an internal tooth on its claws, which is absent in armeniaca.

E. armeniaca sp. nov. is also similar to E. cretensis (Ellis, 1976) and E. quadriseta Cassagnau and Peja, 1979, which were described from Greece and recently redescribed (Smolis et al. 2007, Smolis and Kaprus’ 2009). The differences between E. armeniaca sp. nov. and the related species mentioned above are summarised in Table 4.

Table 4.
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Morphological differences between E. armeniaca sp. nov., E. schwendingeri, E. cretensis and E. quadriseta.

Characters E. armeniaca sp. nov. E. schwendingeri E. cretensis E. quadriseta
Shape of labrum ogival not ogival ogival not ogival
No. of labial chaetae 11 11 8 11
No. of prelabral chaetae 4 4 2 4
Cephalic chaetae A, E and O absent absent present present
No. of cephalic chaetae Dl 4 5 3 6
No. of cephalic chaetae (L+So) 7 7 7 9
No. of cephalic chaetae Oc 2 2 3 3
Tubercle Di on Th. I absent absent present absent
No. of chaetae De on Th. III 2+s 3+s 2+s 3+s
No. of chaetae De on Abd. I–III 2+s 3+s 2+s 3+s
No. of chaetae L on Abd. III and IV 3 and 5 2 and 4 4 and 7 4 and 6–8
No. of chaetae Di on Abd. V 2+2 3+3 2+2 3+3
Cauliflower-like tubercles on Abd. IV–VI absent absent present absent
Male ventral organ unknown present absent present
Internal tooth on claws absent present absent absent

Endonura cochlearifera sp. nov.

https://zoobank.org/839FDE20-6D6E-4117-8B61-5E9D374603E8
Figs 16–25, Tables 5a–c, 6

Type material

Holotype: adult female on slide, Russia, Caucasus, Northern Ossetia, North Ossetia Nature Reserve, surroundings of the village Tsey, green moss pine forest, in mosses, 23.IX.1980, leg. I. Kuchiev (DIBEC). Paratypes: 4 adult females, subadult male and 2 juveniles on slides, same data as holotype (DIBEC and MSPU).

Diagnosis

2+2 pigmented eyes. Buccal cone long, labrum ogival. Head with chaetae A, B, C, D, E and O. Tubercles Cl and Af separate. Tubercles Dl and (L+So) on head with 6 and 9 chaetae respectively. Tuberles Di on Th. I absent. Tubercles De on Th. II and III with 3 and 4 chaetae respectively. Tubercles L on Abd. III and IV with 4 and 6–7 chaetae respectively. Abd. IV and V with 8 and 3 tubercles respectively. Claw without inner tooth. Tibiotarsi with chaetae B4 and B5 short.

Description

Body length : 0.55 (juvenile) to 1.45 mm (without antennae) (holotype: 1.45 mm). — Colour: body pale bluish grey (alive and in alcohol). 2+2 black eyes, in a typical arrangement for the genus (Fig. 16). — Chaetal morphology: Dorsal ordinary chaetae of five types: long macrochaetae (Ml), short macrochaetae (Mc), mesochaetae and microchaetae. Long macrochaetae thick, slightly arched or straight, narrowly sheathed, feebly serrated, apically rounded or pointed (Figs 16, 21, 25). Macrochaetae Mc morphologically similar to long macrochaetae, but shorter. Mesochaetae similar to ventral chaetae, thin, smooth and pointed. Microchaetae similar to mesochaetae, but shorter. S–chaetae of tergites thin, smooth and short, notably shorter than nearby macrochaetae (Figs 16, 21, 24). — Antennae: Dorsal chaetotaxy of Ant. III–IV as in Fig. 17 and Table 5b. S–chaetae of Ant. IV of medium length and moderately thickened (Fig. 17). Apical vesicle distinct, trilobed. Ventral chaetotaxy of Ant. III with 14 ordinary chaetae, sense organ AOIII with long sensillum sgv and short peg (Fig. 18, Table 5b). — Mouthparts: Buccal cone long with labral sclerifications ogival and spoon-like (Figs 16, 22). Labral chaetotaxy: 4/2, 4 (Fig. 23). Labium with four basal, three distal and four lateral chaetae, papillae x absent. Maxilla relatively thick and styliform (Fig. 20). Mandible thin with two basal and two apical teeth (Fig. 19). — Dorsal chaetotaxy and tubercles: Head without chaetae L3 (Fig. 16, Table 5a). Tubercles Di on Th. I not differentiated. Thorax with chaetae De2 and De3 free (Fig. 16). On Abd. I–III, the line of chaetae De1–chaeta s non perpendicular to the dorsomedian line. Abd. I–III with chaetae De3 free (Fig. 21). On Abd. V tubercle (Di+Di) with 3+3 chaetae. Abd. VI well visible from above (Fig. 21). — Ventral chaetotaxy: On head, groups Vea, Vem and Vep with 3, 4, 4 chaetae respectively. Group Vi on head with 6 chaetae. On Abd. IV, furca rudimentary without microchaetae. On Abd. V, chaetae Vl present and chaetae L’ absent. Legs: Chaetotaxy of legs as in Table 5c. Claw without internal tooth. On tibiotarsi, chaeta M present and chaetae B4 and B5 relatively short and pointed.

Table 5a.
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Chaetotaxy of Endonura cochlearifera sp. nov.: cephalic chaetotaxy-dorsal side.

Tubercle Number of chaetae Types of chaetae Names of chaetae
Cl 4 Ml F
Mc G
Af 11 Ml B
Mc A, C, D, E, O
Oc 3 Ml Ocm
Mc Ocp
mi Oca
Di 2 Ml Di1
Mc Di2
De 2 Ml De1
Mc De2
Dl 6 Ml Dl5, Dl1
Mc Dl2, Dl3, Dl4, Dl6
(L+So) 9 Ml L1, L4, So1
Mc L2
mi So2
me So3–6
Table 5b.
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Chaetotaxy of Endonura cochlearifera sp. nov.: antennae.

Segment, Group Number of chaetae Segment, Group Number of chaetae adult
I 7 IV or, 8 S, i, 12 mou, 6 brs, 2 iv
II 12
III 5 sensilla AO III
ve 5 ap 8 bs, 5 miA
vc 4 ca 2 bs, 3 miA
vi 4 cm 3 bs, 1 miA
d 5 cp 8 miA, 1 brs
Table 5c.
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Chaetotaxy of Endonura cochlearifera sp. nov.: postcephalic chaetotaxy.

Terga Legs
Di De Dl L Scx2 Cx Tr Fe T
Th. I 1 2 1 — 0 3 6 13 19
Th. II 3 2+s 3+s+ms 3 2 7 6 12 19
Th. III 3 3+s 3+s 3 2 8 6 11 18
Sterna
Abd. I 2 3+s 2 3 VT: 4
Abd. II 2 3+s 2 3 Ve: 5; chaeta Ve1 present
Abd. III 2 3+s 2 4 Vel:5–6; Fu: 5–7 me, 0 mi
Abd. IV 2 2+s 3 6–7 Vel: 4; Vec: 2; Vei: 2; Vl: 4
Abd. V (3+3) 8–9 +s Ag: 3; Vl: 1
Abd. VI 7 Ve: 14; An: 2mi
Figure 16–25. 

Endonura cochlearifera sp. nov.: 16 dorsal chaetotaxy of head and Th.; 17 dorsal chaetotaxy of Ant. III–IV; 18 ventral chaetotaxy of Ant. III; 19 mandible; 20 maxilla; 21 dorsal chaetotaxy of Abd. III–VI; 22 ventral sclerifications of labrum; 23 chaetotaxy of labrum; 24 sensillum of Abd. V; 25 chaeta Di1 of Abd. V.

Etymology

The name cochlearifera refers to the spoon-like shape of the labral sclerifications of this species.

Remarks

E. cochlearifera sp. nov. is unique and differs from other species of the genus by the spoon-like shape of the apical labral sclerifications. In general appearance (e.g. dorsal chaetotaxy of head and thorax) the new species strongly resembles E. annae Smolis & Skarżyński, 2020, E. dentifera Smolis et al., 2007 and E. lusatica (Dunger, 1979). However, they can be easily distinguished by the following characters: number of chaetae Dl on the head (six in cochlearifera, annae and dentifera, five in lusatica), number of chaetae (L+So) on the head (eight in annae, nine in cochlearifera and lusatica, 10 in dentifera), number of ordinary chaetae (De+Dl+L) on Abd. V (8–9 in cochlearifera, 5 in annae, 7 in lusatica, 8 in dentifera), presence of chaetae L’ on Abd. V (absent in cochlearifera and dentifera, present in annae and lusatica), length and shape of chaetae B4 and B5 on tibiotarsi (short and acute in cochlearifera and annae, elongate and clavate in lusatica and dentifera) and presence of internal tooth on claw (absent in cochlearifera, present in lusatica and dentifera). All differences between E. cochlearifera sp. nov. and the related species mentioned above are summarised in Table 6.

Table 6.
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Morphological differences between E. cochlearifera sp. nov., E. lusatica, E. dentifera and E. annae.

Characters E. cochlearifera sp. nov. E. lusatica E. dentifera E. annae
Shape of apical labral sclerifications spoon-like ogival not ogival not ogival
Shape of labrum elongated and narrow elongated and narrow rather long and narrow short and wide
Cephalic chaeta O present present absent absent
Cephalic chaetae C present present present absent
No. of cephalic chaetae Dl 6 5 6 6
No. of cephalic chaetae (L+So) 9 9 10 8
No. of chaetae L on Abd. IV 6–7 7 8–9 6
No. of chaetae Di on Abd. V 3+3 3+3 3+3 2+2
No. of ordinary chaetae (De+Dl+L) on Abd. V 8–9 7 8 5
Chaeta L’ on Abd. V absent present absent present
Length and shape of tibiotarsal chaetae B4 and B5 short and pointed elongated and clavate elongated and clavate short and pointed
Internal tooth on claws absent present present present

Endonura crimica sp. nov.

https://zoobank.org/B2C84D73-4B5A-467A-B206-9B7064B04234
Figs 26–36, Tables 7a–c, 8

Type material

Holotype: adult female on slide, Crimea, Jaltynskyi Nature Reserve (34 24.344 N; 44 55.137 E), 570 m alt., mixed forest (pine, beech), 3.II.2016, leg. D. Shitikov, A. Szarikov (DIBEC). Paratype: subadult male on slide, Crimea, Ajudag near Gurzuf, 450 m alt., oak forest, 6.II.2015, leg. D. Shitikov, A. Szarikov (MSPU).

Diagnosis

2+2 pigmented eyes. Buccal cone relatively short and narrow, labrum not ogival. Head with chaetae A, B, C, D and O. Tubercles Cl and Af separate. Tubercles Dl and (L+So) on head with 6 and 9 chaetae respectively. Tuberles Di on Th. I present. Tubercles De on Th. II and III with 3 and 4 chaetae respectively. Tubercles L on Abd. III and IV with 4 and 6–7 chaetae respectively. Abd. IV and V with 8 and 3 tubercles respectively. Claw without inner tooth. Tibiotarsi with chaetae B4 and B5 short.

Description

Body length : 1.05 (subadult male) to 1.15 mm (holotype) (without antennae). — Colour: body pale bluish grey (alive and in alcohol). 2+2 black eyes, in a typical arrangement for the genus (Fig. 28). — Chaetal morphology: Dorsal ordinary chaetae of five types: long macrochaetae (Ml), short macrochaetae (Mc), mesochaetae and microchaetae. Long macrochaetae thick, slightly arched or straight, narrowly sheathed, feebly serrated, apically rounded or pointed (Figs 28, 29, 34). Macrochaetae Mc morphologically similar to long macrochaetae, but shorter. Mesochaetae similar to ventral chaetae, thin, smooth and pointed. Microchaetae similar to mesochaetae, but shorter. S–chaetae of tergites thin, smooth and short, notably shorter than nearby macrochaetae (Figs 28, 30, 34). — Antennae: Dorsal chaetotaxy of Ant. III–IV as Fig. 26 and Table 7b. S–chaetae of Ant. IV of medium length and moderately thickened (Fig. 26), sensillum sgd notably short. Apical vesicle distinct, trilobed. Ventral chaetotaxy of Ant. III with 14 ordinary chaetae, sense organ AOIII with long sensillum sgv and short peg (Fig. 27, Table 7b). — Mouthparts: Buccal cone relatively short with labral sclerifications not ogival (Fig. 33). Labral chaetotaxy: 4/2, 4 (Fig. 33). Labium with four basal, three distal and four lateral chaetae, papillae x absent. Maxilla styliform (Fig. 31), mandible thin and tridentate (Fig. 32). — Dorsal chaetotaxy and tubercles: Head without chaetae E and L3 (Fig. 28, Table 7a). Tubercles Di on Th. I developed. Th. III with chaetae De3 free (Fig. 28). On Abd. I–III, the line of chaetae De1–chaeta s non perpendicular to the dorsomedian line. Abd. I–III with chaetae De3 free (Fig. 34). On Abd. V tubercle (Di+Di) with 3+3 chaetae. Abd. VI partially visible from above (Fig. 34). — Ventral chaetotaxy: On head, groups Vea, Vem and Vep with 3, 4, 4 chaetae respectively. Group Vi on head with 6 chaetae. On Abd. IV, furca rudimentary without microchaetae. One chaeta L on Abd. IV free (Fig. 35). On Abd. V, chaetae Vl and chaetae L’ present. Legs: Chaetotaxy of legs as in Fig. 36 and Table 7c. Claw without internal tooth (Fig. 36). On tibiotarsi, chaeta M present and chaetae B4 and B5 relatively short and pointed.

Table 7a.
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Chaetotaxy of Endonura crimica sp. nov.: cephalic chaetotaxy–dorsal side.

Tubercle Number of chaetae Types of chaetae Names of chaetae
Cl 4 Ml F
Mc G
Af 9
 Ml B
Mc A, C, D, O
Oc 3 Ml Ocm
Mc Ocp
mi Oca
Di
2 Ml Di1
Mc Di2
De 2 Ml De1
Mc De2
Dl 6 Ml Dl5, Dl1
Mc Dl3, Dl4
mi Dl2, Dl6
(L+So) 9 Ml L1, L4, So1
Mc L2
mi So2
me So3–6
Table 7b.
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Chaetotaxy of Endonura crimica sp. nov.: antennae.

Segment, Group Number of chaetae Segment, Group Number of chaetae adult
I 7 IV or, 8 S, i, 12 mou, 6 brs, 2 iv
II 12
III 5 sensilla AO III
ve 5 ap 8 bs, 5 miA
vc 4 ca 2 bs, 3 miA
vi 4 cm 3 bs, 1 miA
d 5 cp 8 miA, 1 brs
Table 7c.
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Chaetotaxy of Endonura crimica sp. nov.: postcephalic chaetotaxy.

Terga Legs
Di De Dl L Scx2 Cx Tr Fe T
Th. I 1 2 1 — 0 3 6 13 19
Th. II 3 2+s 3+s+ms 3 2 7 6 12 19
Th. III 3 3+s 3+s 3 2 8 6 11 18
Sterna
Abd. I 2 3+s 2 3 VT: 4
Abd. II 2 3+s 2 3 Ve: 5; chaeta Ve1 present
Abd. III 2 3+s 2 4 Vel: 4–5; Fu: 5–7 me, 0 mi
Abd. IV 2 2+s 3 6–7 Vel: 4; Vec: 2; Vei: 2; Vl: 4
Abd. V (3+3) 7+s Ag: 2–3; Vl: 1 L‘: 1
Abd. VI 7 Ve: 14; An: 2mi
Figure 26–36. 

Endonura crimica sp. nov.: 26 dorsal chaetotaxy of Ant. III–IV; 27 ventral chaetotaxy of Ant. III; 28 dorsal chaetotaxy of head and Th.; 29 chaeta Di1 of Abd. V; 30 sensillum of Abd. V; 31 maxilla; 32 mandible; 33 chaetotaxy and ventral sclerifications of labrum; 34 dorsal chaetotaxy of Abd. III–VI; 35 tubercle L of Abd. IV; 36 tibiotarsus and claw of leg III, lateral view.

Etymology

The name crimica refers to the geographic area of its collecting.

Remarks

E. crimica sp. nov. belongs to a very small group of Endonura characterised by a broad and short (equal to or shorter than tubercle Oc) cephalic tubercle Af. In addition to the new species, this group includes E. taurica (Stach, 1951) and E. gracilirostris Smolis et al., 2007. E. crimica sp. nov. can be reliably distinguished from these Crimean species by the following characters: presence/absence of cephalic chaetae E (present in crimica, absent in taurica and gracilirostris), presence/absence of cephalic chaeta O (present in crimica and gracilirostris, absent in taurica), shape of labrum (not ogival in crimica and taurica, ogival in gracilirostris), presence/absence of tubercle Di on Th. I (present in crimica, absent in taurica and gracilirostris), position of chaetae De2 on Th. II and III (within tubercle in crimica, free in taurica and gracilirostris), and length and shape of tibiotarsal chaeta B4 (short and acute in crimica, elongated and clavate in taurica and gracilirostris). Morphologically, E. crimica sp. nov. also closely resembles E. colorata (Gama, 1964), a species known only from Portugal (Jordana et al. 1997). However, these species differ in several crucial characters: position of cephalic chaetae D (free in crimica, located inside tubercle Cl in colorata), number of me chaetae on furca rudimentary (5–7 chaetae in crimica, 8–9 chaetae in colorata), number of ordinary chaetae (De+Dl+L) on Abd. V (7 in crimica, 6 in colorata). Furthermore, the ratio Di1/Di2/Di3 on Abd. V is 50:21:3 in crimica and 40:22:10 in colorata. A summary of the differences between these species is given in Table 8.

Table 8.
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Morphological differences between E. crimica sp. nov., E. taurica, E. gracilirostris and E. colorata.

Characters E. crimica sp. nov. E. taurica E. gracilirostris E. colorata
Shape of labrum not ogival not ogival ogival not ogival
Prelabral chaetae present present absent present
Shape of manible thin thick thin thin
Shape of cephalic tubercle AF wide wide wide narrow
Length of cephalic tubercle AF equal or shorter than tubercle Oc equal or shorter than tubercle Oc equal or shorter than tubercle Oc longer than tubercle Oc
Cephalic chaetae E present absent absent present
Cephalic chaeta O present absent present present
Position of cephalic chaetae D free located within tubercle Cl located within tubercle Cl located within tubercle Cl
Tubercle Di on Th. I present absent absent present
Position of chaetae De2 on Th. II–III located within tubercle De free free located within tubercle De
No. of ordinary chaetae (De+Dl+L) on Abd. V 7 8 8 6
Ratio Di1/Di2/Di3 on Abd. V 50:21:3 48:18:2 46:11:2 40:22:10
No. of mesochaetae on furca rudimentary 5‒7 5 5‒6 8‒9
Length and shape of tibiotarsal chaeta B4 short and pointed elongated and clavate elongated and clavate short and pointed

Endonura duplex sp. nov.

https://zoobank.org/EF8EDEA5-F506-440B-A958-32624FFD6AE8
Figs 37–47, Tables 9a–c, 10

Type material

Holotype: adult female on slide, Russia, NW Caucasus, Adygeya, Caucasus Nature Reserve, ‘Kamennoye More’ ridge, southern slope, 1850 m. alt., mixed forest (pine, birch), coniferous litter, 21.VII.2015, leg. M. Potapov, N. Kuznetsova, A. Kremenitsa, L.Vanyavina (DIBEC). Paratype: subadult male and 2 juveniles on slides, same data as holotype (DIBEC and MSPU).

Diagnosis

2+2 pigmented eyes. Buccal cone short, labrum not ogival. Head with chaetae A, B, C, D and E. Two chaetae O present. Tubercles Cl and Af separate. Tubercles Dl and (L+So) on head with 6 and 10 chaetae respectively. Tuberles Di on Th. I present. Tubercles De on Th. II and III with 3 and 4 chaetae respectively. Tubercles L on Abd. III and IV with 4 and 7 chaetae respectively. Abd. IV and V with 8 and 3 tubercles respectively. Claw without inner tooth. Tibiotarsi with chaetae B4 and B5 short.

Description

Body length : 0.55 (juvenile) to 1.55 mm (holotype) (without antennae). — Colour: body pale bluish grey (alive and in alcohol). 2+2 black eyes, in a typical arrangement for the genus (Fig. 38). — Chaetal morphology: Dorsal ordinary chaetae of five types: long macrochaetae (Ml), short macrochaetae (Mc), mesochaetae and microchaetae. Long macrochaetae thick, slightly arc-like or straight, narrowly sheathed, feebly serrated, apically rounded or pointed (Figs 38, 43, 47). Macrochaetae Mc morphologically similar to long macrochaetae, but shorter. Mesochaetae similar to ventral chaetae, thin, smooth and pointed. Microchaetae similar to mesochaetae, but shorter. S–chaetae of tergites thin, smooth and short, notably shorter than nearby macrochaetae (Figs 38, 43, 46). — Antennae: Dorsal chaetotaxy of Ant. III–IV as Fig. 41 and Table 9b. S–chaetae of Ant. IV of medium length and moderately thickened (Fig. 41), sensillum sgd relatively long. Apical vesicle distinct, trilobed (Figs 39, 40). Ventral chaetotaxy of Ant. III with 14 ordinary chaetae, sense organ AOIII with long sensillum sgv and short peg (Fig. 42, Table 9b). — Mouthparts: Buccal cone short with labral sclerifications not ogival (Fig. 44). Labral chaetotaxy: 4/2, 4 (Fig. 45). Labium with four basal, three distal and four lateral chaetae, papillae x absent. Maxilla styliform, mandible thin and tridentate. — Dorsal chaetotaxy and tubercles: Head with two chaetae O (Fig. 38, Table 9a). Tubercles Di on Th. I developed. Th. II–III with chaetae De2 and De3 free (Fig. 38). On Abd. I–III, the line of chaetae De1–chaeta s not perpendicular to the dorsomedian line. Abd. I–III with chaetae De3 free (Fig. 43). On Abd. V tubercle (Di+Di) with 3+3 chaetae. Abd. VI well visible from above (Fig. 43). — Ventral chaetotaxy: On head, groups Vea, Vem and Vep with 3, 4, 4 chaetae respectively. Group Vi on head with 6 chaetae. On Abd. IV, furca rudimentary without microchaetae. One chaeta L on Abd. IV free (Fig. 37). On Abd. V, chaetae Vl and chaetae L’ present. Legs: Chaetotaxy of legs as in Table 9c. Claw without internal tooth. On tibiotarsi, chaeta M present and chaetae B4 and B5 relatively short and pointed.

Table 9a.
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Chaetotaxy of Endonura duplex sp. nov.: cephalic chaetotaxy–dorsal side.

Tubercle Number of chaetae Types of chaetae Names of chaetae
Cl 4 Ml F
Mc G
Af 12 Ml B
Mc A, C, D, E, O
Oc 3 Ml Ocm
Mc Ocp
mi Oca
Di 2 Ml Di1
Mc Di2
De 2 Mc De1, De2
Dl 6 Ml Dl5, Dl1
Mc Dl2, Dl3, Dl4, Dl6
(L+So) 10 Ml L1, L4, So1
Mc L2, L3, So2
me So3–6
Table 9b.
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Chaetotaxy of Endonura duplex sp. nov.: antennae.

Segment, Group Number of chaetae Segment, Group Number of chaetae adult
I 7 IV or, 8 S, i, 12 mou, 6 brs, 2 iv
II 12
III 5 sensilla AO III
ve 5 ap 8 bs, 5 miA
vc 4 ca 2 bs, 3 miA
vi 4 cm 3 bs, 1 miA
d 5 cp 8 miA, 1 brs
Table 9c.
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Chaetotaxy of Endonura duplex sp. nov.: postcephalic chaetotaxy.

Terga Legs
Di De Dl L Scx2 Cx Tr Fe T
Th. I 1 2 1 — 0 3 6 13 19
Th. II 3 2+s 3+s+ms 3 2 7 6 12 19
Th. III 3 3+s 3+s 3 2 8 6 11 18
Sterna
Abd. I 2 3+s 2 2–3 VT: 4
Abd. II 2 3+s 2 3 Ve: 5; chaeta Ve1 present
Abd. III 2 3+s 2 4 Vel: 5; Fu: 5 me, 0 mi
Abd. IV 2 2+s 3 7 Vel: 4; Vec: 2; Vei: 2; Vl: 4
Abd. V (3+3) 7+s Ag: 3; Vl: 1 L‘: 1
Abd. VI 7 Ve: 14; An: 2mi
Figure 37–47. 

Endonura duplex sp. nov.: 37 tubercle L of Abd. IV; 38 dorsal chaetotaxy of head and Th.; 39 apical bulb, ventral view; 40 apical bulb, dorsal view; 41 dorsal chaetotaxy of Ant. III–IV; 42 ventral chaetotaxy of Ant. III; 43 dorsal chaetotaxy of Abd. III–VI; 44 ventral sclerifications of labrum; 45 chaetotaxy of labrum; 46 sensillum of Abd. V; 47 chaeta Di1 of Abd. V.

Etymology

The name duplex is derived from the presence of two chaetae O on head.

Remarks

E. duplex sp. nov. differs from all other Endonura by the presence of two cephalic chaetae O. Besides this character, the new species strongly resembles E. agnieskae Smolis & Skarżyński, 2020, E. alticola (Stach, 1951) and E. reticulata (Axelson, 1905). However, the differences between the new species and the outlined taxa include a number of characters: Shape of labrum (ogival in alticola, not ogival in others), number of prelabral chaetae (two in alticola, four in others), number of lateral labial chaetae (three in agnieskae, four in others), length of cephalic chaetae A and Ocp (chaeta A longer than Ocp in duplex and alticola, chaeta A shorter than Ocp in reticulata, equal in agnieskae), presence of tubercle Di on Th. I (present in duplex, present and fused with tubercle De in agnieskae and alticola, usually absent in reticulata), position of chaeta Di3 on Th. II–III (within tubercle Di in alticola, free in others), position of chaeta De2 on Abd. I–III (free in reticulata, within tubercle De in others), position of chaeta s on Abd. I–III (line of chaeta De1-chaeta s not parallel to dorsomedial line in reticulata, parallel in others), fusion of tubercles Di on Abd. IV (present in alticola, absent in others) and presence of free chaeta L on Abd. IV (present in duplex, absent in others). The differences between the species mentioned in the remarks are summarised in Table 10.

Table 10.
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Morphological differences between E. duplex sp. nov., E. agnieskae, E. alticola and E. reticulata.

Characters E. duplex sp. nov. E. agnieskae E. alticola E. reticulata
Shape of labrum not ogival not ogival ogival not ogival
No. of prelabral chaetae 4 4 2 4
No. of lateral labial chaetae 4 3 4 4
No. of cephalic chaetae O 2 1 1 1
Length of cephalic chaetae A and Ocp chaeta A longer than Ocp equal in lenght chaeta A longer than Ocp chaeta A shorter than Ocp
Tubercle Di on Th. I present and not fused with De present and fused with De present and fused with De usually absent
Position of chaetae Di3 on Th. II–III free free located within tubercle Di free
Position of chaeta De2 on Abd. I–III located within tubercle De located within tubercle De located within tubercle De free
Position of chaeta De2 on Abd. I–III line of chaeta De1–chaeta s parallel to dorsomedial line line of chaeta De1–chaeta s parallel to dorsomedial line line of chaeta De1–chaeta s parallel to dorsomedial line line of chaeta De1–chaeta s not parallel to dorsomedial line
Fusion of tubercles Di on Abd. IV absent absent present absent
Number of chaetae Lon Abd. III and IV 4 and 7 3 and 5‒6 4 and 6 4 and 6‒9
Free chaeta L on Abd. IV present absent absent absent

3.2. Phylogeny

List of morphological characters

Head eyes

1. Number of eyes on each side of head: (0) 3 eyes present; (1) 0–2 eyes present.

2. Pigmentation of eyes: (0) present; (1) absent.

3. Presence of anterior eyes: (0) present (Fig. 1); (1) absent.

4. Position of anterior eyes: (0) outside tubercle Oc (Fig. 2, Smolis 2011); (1) within tubercle Oc (Fig. 1).

Head tuberculation

5. Tubercle L: (0) separate (Fig. 5, Smolis 2007); (1) fused with tubercle So (Fig. 28).

6. Tubercle Dl: (0) separate (Fig. 16); (1) fused with tubercle L (Fig. 5E, Smolis and Deharveng 2017).

7. Tubercle Af: (0) separate (Fig. 16); (1) fused with tubercle Cl (Fig. 5, Smolis and Kaprus’ 2003).

8. Elementary tubercles BE: (0) absent; (1) present (Fig. 5, Smolis et al. 2015).

9. Elementary tubercles DF: (0) absent; (1) present (Fig. 1, Smolis et al. 2015).

10. Elementary tubercles DE: (0) absent; (1) present (Fig. 5, Smolis and Kaprus’ 2003).

11. Non-reticulate area within tubercle Af: (0) absent; (1) present (Fig. 9, Smolis 2016).

12. Tubercles Di: (0) tubercles absent; (1) tubercles present (Fig. 1).

13. Length of tubercle Af: (0) longer than tubercle Oc (Fig. 1); (1) equal or shorter than tubercle Oc (Fig. 20, Smolis et al. 2007).

Head chaetotaxy

14. Number of chaetae Dl (on half of head): (0) 6 chaetae present (Fig. 5, Smolis 2007); (1) 5 chaetae present (Fig. 13, Smolis 2016); (2) 4 or fewer chaetae present (Fig. 1).

15. Chaeta Dl3: (0) present (Fig. 5, Smolis 2007); (1) absent.

16. Number of chaetae L+So (on half of head): (0) 10 chaetae present (Fig. 5, Smolis 2007); (1) 9 chaetae present (Fig. 16); (2) 8 or fewer chaetae present (Fig. 1).

17. Position of chaeta L4: (0) included within tubercle L+So (Fig. 37, Smolis 2008); (1) free.

18. Chaeta O: (0) present (Fig. 16); (1) absent.

19. Chaetae D: (0) free (not included in tubercle Af or Cl) (Fig. 1); (1) included in tubercle Af (Fig. 58, Smolis and Kuznetsova 2016); (3) included in tubercle Cl (Fig. 1, Smolis et al. 2015); (4) included in tubercle Af+Cl (Fig. 5, Smolis & Kaprus’ 2003).

20. Chaetae E: (0) present (Fig. 5, Smolis 2007); (1) absent.

21. Position of chaetae E: (0) free, not included in tubercle Af (Fig. 5, Smolis 2007); (1) included in tubercle Af (Fig. 58, Smolis and Kuznetsova 2016).

22. Chaetae C: (0) present (Fig. 1); (1) absent.

23. Chaetae Oca: (0) present (Fig. 1); (1) absent.

24. Chaetae Ocp: (0) present (Fig. 16); (1) absent.

25. Length of chaetae Ocp: (0) longer than chaeta A (Fig. 9, Smolis 2016); (1) shorter than chaeta A (Fig. 38).

26. Chaetae A: (0) present (Fig. 28); (1) absent.

27. Length of chaetae A: (0) shorter than chaetae B (Fig. 28); (1) equal to chaetae B (Fig. 1B, Smolis and Deharveng 2017).

28. Arrangement of chaetae Di2 and De2: (0) “croisée” (line between chaetae Di 2 and De2 crosses line between Di1 and De1, Deharveng 1983) (Fig. 5, Smolis 2007); (1) “non croisée” (line between chaetae Di 2 and De2 does not cross line between Di1 and De1) (Fig. 1).

Body

29. Color in alive: (0) blue, bluish grey or purple brown; (1) white.

30. Placement of the longest macrochaetae: (0) Abd. VI (Fig. 7, Smolis 2007); (1) Abd. V (Fig. 1); (2) Abd. IV (Fig. 1, Smolis and Kaprus’ 2003).

31. Cryptopygy: (0) present (Fig. 1, Smolis and Kaprus’ 2003); (1) absent.

Mouthparts

32. Labial chaeta f: (0) present (Fig. 14, Smolis 2008); (1) absent.

33. Shape of labial apex: (0) truncate (Fig. 2, Smolis et al. 2007); (1) rounded (Fig. 33); (2) ogival (Fig. 12).

34. Number of prelabral chaetae: (0) 4 chaetae present (Fig. 12); (1) 2 chaetae present (Fig. 2, Smolis and Kaprus’ 2009); (2) chaetae absent.

35. Number of labral chaetae: (0) 6 chaetae present (Fig. 1); (1) 4 chaetae present (Fig. 3, Smolis and Kaprus’ 2003).

36. Number of apical labral chaetae: (0) 4 chaetae present (Fig. 1); (1) 2 chaetae present (Fig. 3, Smolis and Kaprus’ 2003).

Thorax

37. Tubercles Di on the first tergite: (0) absent; (1) present (Fig. 28).

38. Tubercles Di and De on the first tergite: (0) separate (Fig. 28); (1) fused (Fig. 1, Smolis and Kaprus’ 2003).

39. Position of chaetae Di3 on the second and third tergites: (0) free (Fig. 1); (1) included in tubercle Di (Fig. 1, Smolis and Kaprus’ 2003).

40. Number of ordinary chaetae De on the second tergite (on half of tergite): (0) 3 chaetae present (Fig. 5, Smolis 2007); (1) 2 chaetae present (Fig. 1).

41. Position of chaeta De2 on the second tergite: (0) free (Fig. 1); (1) included in tubercle De (Fig. 28).

42. Number of ordinary chaetae De on the third tergite (on half of tergite): (0) 4 chaetae present (Fig. 6, Smolis 2007); (1) 3 or fewer chaetae present (Fig. 16).

43. Position of chaeta De2 on the third tergite: (0) free (Fig. 6, Smolis 2007); (1) included in tubercle De (Fig. 28).

44. Presence of chaeta De3 on the third tergite: (0) present (Fig. 6, Smolis 2007); (1) absent.

45. Position of chaeta De3 on the third tergite: (0) free (Fig. 6, Smolis 2007); (1) included in tubercle De (Fig. 8, Smolis 2016).

Abdomen dorsal

46. Number of ordinary chaetae De on tergites I–III: (on half of tergite): (0) 3 chaetae present (Fig. 21); (1) 2 chaetae present (Fig. 10).

47. Position of chaeta De2 on tergites I–III: (0) free (Fig. 13, Smolis 2011); (1) included in tubercle De (Fig. 10).

48. Presence of chaeta De3 on tergites I–III: (0) present (Fig. 21); (1) absent.

49. Position of chaeta De3 on tergites I–III: (0) free (Fig. 21); (1) included in tubercle De (Fig. 66, Smolis and Kuznetsova 2016).

50. Line of chaetae De1 and s-chaeta on each of tergites I–III: (0) perpendicular to midline (Figs 31, 33; Fig. 5, Smolis 2008); (1) parallel to midline (Figs 16, 17; Smolis 2008).

51. Number of tubercles on tergite IV (excluding tubercles L): (0) 5 or fewer tubercles present (Fig. 5, Smolis and Kuznetsova 2016); (2) 6 tubercles present (Fig. 21).

52. Length of chaeta Di1 on tergite III: (0) longer than chaeta Di1 on tergite V (Fig. 1, Smolis and Kaprus’ 2003); (1) slightly shorter than chaeta Di1 on tergite V (Fig. 1, Smolis 2007); (2) no more than half the length of chaeta Di1 on tergite V (Fig. 1, Smolis and Kaprus’ 2009).

53. Length of chaeta Di1 on tergite IV: (0) longer than chaeta Di1 on tergite V (Fig. 1, Smolis and Kaprus’ 2003); (1) slightly shorter than chaeta Di1 on tergite V (Fig. 10); (2) no more than half the length of chaeta Di1 on tergite V (Fig. 1, Smolis and Kaprus’ 2009).

54. Number of tubercles on tergite V: (0) 4 tubercles present (Fig. 7, Smolis 2007); (1) 3 tubercles present (Fig. 10); (2) 2 tubercles present (Fig. 57, Smolis 2008).

55. Number of chaetae Di on tergite V (on half of tergite): (0) 3 chaetae present (Fig. 21); (1) 2 or fewer chaetae present (Fig. 10).

56. Length of chaeta Di2 on tergite V: (0) less than half the length of chaeta Di1 on tergite V (Fig. 10); (1) half the length of chaeta Di1 on tergite V (Fig. 21).

57. Presence of chaeta Di3 on tergite V: (0) present (Fig. 21); (1) absent.

58. Length of chaeta Di3 on tergite V: (0) more than twice shorter than chaeta Di2 on tergite V (Fig. 21); (1) maximum twice shorter than chaeta Di2 on tergite V (Fig. 12, Smolis 2011).

59. Shape of tubercles on two last segments: (0) normal (Fig. 10); (1) cauliflower-like (Fig. 6, Smolis and Kaprus’ 2009).

Abdomen ventral

60. Male ventral organ (secretory structure composed of modified chaetae, Simiczyjew et al. 2018): (0) absent; (1) present (Fig. 34, Smolis and Kuznetsova 2016).

61. Microchaetae on furcal remnant: (0) present (Fig. 38, Smolis 2008); (1) absent.

62. Number of chaetae L on segment III: (0) more than 3 chaetae present (Fig. 12, Smolis 2011); (1) fewer than 3 chaetae present.

63. Number of chaetae L on segment IV: (0) more than 5 chaetae present (Fig. 4, Smolis 2007); (1) 5 or fewer chaetae present (Fig. 15).

64. Position of chaetae L on segment IV: (0) at least 1 chaeta free (Fig. 4, Smolis 2007); (1) all chaetae included in tubercle L (Fig. 15).

65. Chaeta L’: (0) present (Fig. 4, Smolis 2007); (1) absent.

66. Number of chaetae Vei: (0) 6 chaetae (Fig. 6D, Smolis and Deharveng 2017); (1) 4 or fewer chaetae (Fig. 21, Smolis 2008).

Legs

67. Tooth on claw: (0) present (Fig. 13, Smolis 2008); (1) absent.

68. Clavate chaetae B4 and B5 on tibiotarsus: (0) present (Fig. 13, Smolis 2008); (1) absent.

Antennae

69. Number of chaetae on antennal segment I: (0) 8 chaetae (Fig. 1F, Deharveng 1981); (1) 7 chaetae (Fig. 1D, Deharveng 1981).

70. Number of chaetae on antennal segment II: (0) 12 chaetae (Fig. 2, Wang et al. 2016) 11 chaetae (Fig. 2, Ji-Gang Jiang et al. 2018).

3.3. Phylogenetic analysis

Phylogenetic analysis with TNT under an equal weighting scheme produced nineteen most parsimonious trees, with a length of 310 steps, consistency index of 36, and a retention index of 69.

Implied character weighting analyses resulted in a single most parsimonious cladogram with k = 9.687500 (Best score: 14.85760, tree length: 319, total fit: 49.14240) (Fig. 48). The phylogenetic topology obtained through Bayesian inference is presented in Figure 49. The trees resulting from both Bayesian and maximum parsimony analyses produced a similar topology. Both analyses supported Endonura monophyly, but failed to resolve deeper relationships within the genus. The resulting trees showed two main clades containing the same species, but with different internal relationships between them.

Figure 48. 

Single cladogram obtained in the analysis of morphology under implied weights k = 9.687500 (Length = 319; Fit = 49.14240). Node values indicate the frequency of GC groups derived from Bremer support (above) and symmetric resampling (below). The main clades are indicated with capital letters (A–H) on branches.

Figure 49. 

Bayesian consensus phylogram of Endonura. Numbers below branches are Bayesian posterior probability (PP) values (>50%). The main clades are indicated with capital letters on branches and correspond to this of Fig. 48.

We use the most parsimonious tree obtained under implied weighting as a hypothetical reconstruction to discuss character transformations and relationships within the ingroup (Fig. 50). For arguments on the benefits of character weighting in morphological data sets, see Goloboff et al. (2008).

Figure 50. 

Unambiguous morphological character optimization obtained from analysis of the data (Table 1) under implied weights. The numbers above and below circles on the branches indicate character numbers and states, respectively. White and black circles represent homoplasious and nonhomoplasious character state transformations, respectively.

In the analyses, the species of Endonura have been classified into two primary clades (A and D). Both contains several different subclades (B–C and E–H respectively). (Fig. 48).

Clade A includes nineteen species, and it is supported by four character state but none of them represent synapomorphy (Fig. 50): the head with 9 chaetae L+So (character 16:1), the body colour white in alive (character 29:1), the prelabral chaetae absent (character 34:2) and the antennal segment II with 11 chaetae (character 70:1). The E. saleri is placed in the basal position within the clade, but this grouping has very low support. The remaining species are grouped into two subclades.

Subclade B includes 8 species and is supported only by one character: the labial apex ogival in shape (character 33:2, ambiguous). The remaining species form subclade C and this grouping is supported by the presence of microchaetae on furcal remnant (character 61:0, ambiguous).

Clade D comprises twenty eight remaining species, and it is supported by three character state: the head chaeta ‘O’ present (character 18:0, ambiguous), the presence of tubercle ‘Di’ on first thoracic tergite (character 37:1, ambiguous) and by the line of chaetae De1 and s-chaeta on abdominal tergites I–III parallel to midline (character 50:1, ambiguous).

The phylogenetic position and affiliation of the two species, Endonura colorata and E. crimica within this clade are obscure, despite their basal positions. It is uncertain whether they belong to clade D. These species exhibit the position of ‘De3’ chaetae on the third tergite of the thorax (character 45) and of ‘De1’ chaetae on thoracic tergites I–II (character 50), similar to taxa of this clade. However, they also share the same position of ‘De2’ chaetae on the thorax (characters 41 and 43) as species belonging to clade A. The Endonura agnieskae is placed in the basal position to the remaining species of this clade, but it shares certain characters with species of clade A, as do the two species mentioned above and this grouping has very low support.

The remaining species constitute a distinct group (clade E), which is characterized by the one character: thoracic chaeta ‘De2’ included in tubercle ‘De’ (character 43:1, ambiguous). This group forms 3 separate subclades. The species of subclade F are supported by the following characters: the absence of tubercles ‘Di’ on first thoracic tergite (character 37:0) and the chaeta ‘Di2’ on fifth abdominal tergite shorter than chaeta ‘Di1’ (character 56:1). This group comprises two newly described species. Endonura duplex was clustered with E. reticulata, while E. cochlearifera was placed as a similar species to E. dentifera and E. lusatica.

Subclade G includes ten species, and it is supported by one character state: the presence of chaeta L’ on ventral abdominal sternites (character 65: 0).

Subclade H comprises 10 species that share two common characters: the presence of 5 chaetae ‘Dl’ on head (character 14:1) and the absence of chaeta ‘Dl3’ on the head (character 15:1). The group comprises a newly described species, E. armeniaca, which has been clustered with E. schwendingeri.

4. Discussion

In terms of species richness, Endonura is the third most abundant genus in the subfamily. Only two other genera, Deutonura Cassagnau, 1979 and Pronura Dellamare Deboutteville, 1953 contain more taxa, 62 and 58 species, respectively (Bellinger et al. 2023).

It is common taxonomic practice in large genera to create informal groups of species within them, as opposed to subdividing them into subgenera. The formation and naming of these groups are usually on the basis of both geographical and morphological features. Deutonura, the genus referred to above, has five such groups, fodinarum, alticola, centralis, conjuncta and phlegrea (Deharveng 1982). It should be noted, however, that further cladistic analysis of the genus has failed to confirm that such morphological groups exist (Deharveng 1989b).

The genus Endonura has not yet been phylogenetically analysed. The obtained results indicate Endonura to be non-homogeneous genus and all considered species can be grouped into two major clades, A and D (Fig. 48). While distinct species groups are apparent within each clade, their low support precludes their formal designation.

In most Collembola groups, including the subfamily Neanurinae to which the analysed genus belongs, chaetotaxy is the main source of characters used in taxonomic and phylogenetic analyses at different levels of classification, as demonstrated by several studies (e.g. Deharveng 1983, 1986; Bedos and Deharveng 1998; Palacios-Vargas et al. 2010; Smolis and Paśnik 2020), and in the present analysis chaetotaxy-based characters account for almost two thirds of the characters used (see List of characters). As chaetae primarily function as sensory organs, usually as mechanoreceptors (Crouau et al. 1987) or less commonly, with glandular function (Simiczyjew et al. 2018), their presence or absence and position is treated as a phylogenetic signal. The value of individual chaetae is uncertain, given the limited number of phylogenetic analyses based on morphological characters. For instance, Cassagnau (1974) claims that the phylogenetic weight is not uniform across all dorsal chaetae and that axial and subaxial chaetae in the anterior segments, i.e. the head and thoracic segments 2 and 3, are most informative. In addition to confirming the latter statement, our analysis shows that most of the synapomorphies concern the head (characters 17, 24, 26, 28) and thoracic (characters 40, 41, 42, 43) chaetae.

However, chaetotaxy is identified by some authors (e.g. Deharveng 1989b; Palacios-Vargas et al. 2010) as a major source of homoplasy. This is often linked to the widespread process of reduction of individual chaetae, which often occurs in parallel in different evolutionary lineages (e.g., Fjellberg 1984). The cladistic analysis presented here supports this view, indicating a significant amount of homoplasy, particularly with regard to chaetotaxy-related characters.

Although all Collembola have chaetae, only a few, such as the Neanurinae, are characterised by the presence of cuticular protrusions known as tubercles. These tubercles rank second in importance as a source of characters in our analysis. However, the majority of the characters analysed are homoplasies. The only character representing a synapomorphy specific to the E. tatricola, E. dudichi and E. incolorata group is the ‘L4’ chaeta within the ‘So+L’ tubercle.

The insufficient support for the various clades can be attributed to the limited number of morphological characters available for phylogenetic analysis. This problem is prevalent in both the taxonomy of Neanurinae and Collembola as a whole. This issue is unsurprising because springtails are relatively small organisms with a restricted number of morphological characters. The increase in recently described species results in an insufficient number of characters that can be used in taxonomy to identify species and in phylogenetic analyses to infer relationships. In the systematics of springtails, it is now prevalent to use a combination of multiple characters to identify taxa. While this approach remains effective in systematics, it poses significant challenges in phylogenetic analyses. Such an approach results in a deficiency of defining synapomorphies for taxa. Consequently, the support for cladistic analyses is weakened. As a result, the systematics of Collembola (including Neanuridae) is based on the Linnaean system rather than the phylogenetic relationships. The analysis that is presented in this paper is also subject to the same issues. The analysis divides the species of Endonura into distinct groups, however, it is challenging to determine the extent to which this is a result of relationships or similarities among species.

Further research is needed to clarify the relationships among Endonura species, especially through the use of a combination of morphological characters and molecular methods.

5. Declarations

Funding statement: The authors have no funding to report.

Conflict of Interest: The authors have no conflicts of interests to declare.Authors’ contributions: A.S. was responsible for the identification of the species, the preparation of the taxonomic section of the paper, interpretation of data and the revision of the manuscript. N.K. collected and determined material for the study and contributed to the present research’s conception and design. G.P. conducted the phylogenetic analyses with constructive discussions and made suggestions and revisions to the manuscript. All authors read and approved the final manuscript.

6. Acknowledgements

We wish to express our sincere thanks to Collectors: Boris Efeikin, Dmitry Shitikov, Alexander Sharikov, Mikhail Potapov (Moscow), Alexander Kremenitsa (Essentuki). Ivan Kuchiev (Alagir).

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  • Simiczyjew B, Skarżyński D, Smolis A, Pomorski RJ, Mazurkiewicz-Kania M (2018) Structure and function of the male ventral organ in Onychiuroides granulosus (Collembola: Onychiuridae). European Journal of Entomology 115: 134–139. https://doi.org/10.14411/eje.2018.012
  • Simón Benito JC, Palacios-Vargas JG (2008) Two new species of Paranura (Collembola: Neanuridae) from Southeastern Mexico. Annals of the Entomological Society of America 101(4): 683–688.
  • Smolis A (2007) Kalanura–a new genus of Neanurini (Collembola, Neanuridae, Neanurinae) from Siberia, with description of four new species. Zootaxa 1511: 1–16.
  • Smolis A (2008) Redescription of four Polish Endonura Cassagnau, 1979 (Collembola, Neanuridae, Neanurinae), with a nomenclature of the ventral chaetae of antennae. Zootaxa 1858: 9–36.
  • Smolis A (2009) Redescription and lectotype designation of Thaumanura carolii (Stach, 1920) (Collembola, Neanuridae), with remarks on its biology. Deutsche Entomologische Zeitschrift 56(1): 73–83.
  • Smolis A (2011) Xylanura oregonensis, a new genus and species of saproxylic springtail (Collembola: Neanuridae: Neanurinae) from North America, with a key to genera of the tribe Neanurini. Pan-Pacific Entomologist 87(1): 15–26.
  • Smolis A (2016) On the identity of some poorly known species of the genus Endonura Cassagnau, 1979 (Collembola, Neanuridae, Neanurinae). Zootaxa 4173(3): 237–250. http://doi.org/10.11646/zootaxa.4173.3.3
  • Smolis A, Bernard EC (2017) Intricatonura fjellbergi, a new peculiar genus and species of Neanurini (Collembola: Neanuridae: Neanurinae) from Great Smoky Mountains National Park. Florida Entomologist 100(4): 725–730. https://doi.org/10.1653/024.100.0419
  • Smolis A, Deharveng L (2006) Vitronura mascula, a new species of Neanurinae (Collembola: Neanuridae) from northern Vietnam, with a key to the species of the genus. Revue Suisse de Zoologie 113(2): 263–268.
  • Smolis A, Deharveng L (2017) Neanura judithae n. sp. from Polish Carpathians, with an updated and illustrated key to all species of the genus Neanura MacGillivray, 1893 (Collembola: Neanuridae). Zoosystema 39(1): 37–47. https://doi.org/10.5252/z2017n1a5
  • Smolis A, Deharveng L, Kaprus’ IJ (2011) Studies on the non-European Endonura Cassagnau, 1979 (Collembola, Neanuridae, Neanurinae). Zootaxa 3004: 45–56.
  • Smolis A, Greenslade P (2020) New Lobellini (Collembola: Neanuridae) from Queensland contribute to understanding distribution and ecology of Australian fauna. Austral Entomology 59: 253–264. https://doi.org/10.1111/aen.12460
  • Smolis A, Kaprus’ I (2003) A new species of the genus Endonura Cassagnau, 1979 from Israel (Collembola: Neanuridae). Genus 14: 325–329.
  • Smolis A, Kaprus’ I (2009) Redescription of Endonura cretensis (Ellis, 1976) (Collembola: Neanuridae: Neanurinae) with a new record from Israel. Annales Zoologici 59: 1–6. https://doi.org/10.3161/000345409X432538
  • Smolis A, Kuznetsova N (2016) Remarkable diversity of the genus Endonura Cassagnau, 1979 (Collembola: Neanuridae: Neanurinae) in the Caucasus. Zootaxa 4200(1): 47–82. https://doi.org/10.11646/zootaxa.4200.1.2
  • Smolis A, Kuznetsova N (2018) The genera Albanura Deharveng, 1982 and Persanura Mayvan et al., 2015 are no longer monotypic: description of new species from the Caucasus (Collembola, Neanuridae, Neanurinae, Neanurini). ZooKeys 737: 1–12. https://doi.org/10.3897/zookeys.737.21191
  • Smolis A, Paśnik G (2020) Phylogenetic analysis of the tribe Neanurini questions tribal classification of the subfamily Neanurinae (Collembola: Neanuridae). Organisms Diversity & Evolution 20: 497–509 https://doi.org/10.1007/s13127-020-00446-z
  • Smolis A, Shayanmehr M, Kuznetsova N, Lafooraki EY (2017) Three new remarkable species of the genus Endonura Cassagnau from the Middle East and Central Asia (Collembola, Neanuridae, Neanurinae, Neanurini). ZooKeys 673: 135–151. https://doi.org/10.3897/zookeys.673.12084
  • Smolis A, Skarżyński D, Kahrarian M, Kaprus IJ (2016) Redescription of Protanura papillata Cassagnau and Delamare Deboutteville, 1955 (Collembola, Neanuridae, Neanurinae), with new records from Middle East, and with supplemented diagnosis and key to the genus. Zootaxa 4092(2): 293–300. https://doi.org/10.11646/zootaxa.4092.2.11
  • Smolis A, Skarżyński D, Pomorski RJ, Kaprus’ I (2007) Redescription of Endonura taurica (Stach, 1951) and E. quadriseta Cassagnau & Péja, 1979, and description of two new species of the genus Endonura Cassagnau, 1979 (Collembola: Neanuridae: Neanurinae) from the Crimea (Ukraine). Zootaxa 1442: 19–35.
  • Smolis A, Skarżyński D (2020) Contribution to the knowledge of Neanurinae of northwestern Iran with description of seven new species (Collembola, Neanuridae). ZooKeys 992: 105–138. https://doi.org/10.3897/zookeys.992.56921
  • Stach J (1929) Verzeichnis der Apterygogenea Ungarns. Annales Musei Nationalis Hungarici, Budapest 26: 282–283.
  • Templeton R (1836) Thysanura hiberbnicae, or descriptions of such species of springtailed insects (Podura and Lepisma, Lin.) as have been observed in Ireland. Transactions of the Entomological Society of London 1(2): 89–98. https://doi.org/10.1111/j.1365-2311.1838.tb00147.x
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