Protura (Arthropoda, Hexapoda) of the Middle East, with the description of a new species

Abstract In 2021 as part of a research on apterygotes in Iran 18 specimens of Protura were collected; 14 of them were identified as Acerella muscorum (Ionesco, 1930), one was an Acerentomon belonging to the affine group, three were female specimens of a new species of Acerentulus described in this paper. Like other species belonging to confinis group, Acerentulus iranicus sp. nov. has a complete row of posterior setae (18) on tergite VII, a long foretarsal sensillum a almost reaching seta γ3, and sensilla b and c almost of the same length, both passing the base of seta γ3. The closest species to A. iranicus sp. nov. is A. setosus Szeptycki, 1993 from Western Caucasus (Russia). This species differs from the new species for its smaller pseudoculi, the ratio between mesothoracic setae P1 and P2, the presence of a doubled pore on tergite XII, and the longer foretarsal sensillum a. The partial description of an undetermined specimen of Acerentomon belonging to the affine group is outlined too. A key to the Protura species known from the Middle East is provided. http://www.zoobank.org/urn:lsid:zoobank.org:pub:A0243956-A081-4D5D-8FEA-361CA7123852


Introduction
To date more than 800 species of Protura, belonging to three orders, seven families and 77 genera are known worldwide (Szeptycki 2007;Galli et al. 2018;Galli & Rellini 2020). One of the less studied areas as regards this group of euedaphic microarthropods is the Middle East (see https://www.britannica.com/place/Middle-East), with the vast majority of data referring to Israel.
In the course of 2021 soil samples were collected in Iran as part of a research on apterygotes, some proturans were extracted and subsequently examined. The purpose of this paper is to integrate what is already known about this taxon from the Middle East with the new records, also describing a new species belonging to the genus Acerentulus, confinis group (Shrubovych et al. 2019) and outlining a partial description of an Acerentomon male specimen belonging to the affine group. A key for identification of the species of Protura of this region is also provided.

Material and methods
Soil samples of 1 kg each were collected in two localities of the Mazandaran province ( Figure 1) and extracted by means of Berlese-Tullgren funnels for five days. Specimens were preserved in 70% ethanol.
For the identification, proturans were incubated at 40-50°C for 24 hours in lactic acid to make them clear, then mounted on slides in Marc André II medium. Specimens were then observed and identified to species and life-stage levels with the aid of an interference contrast microscope (Leica DM LB2), a Leica DFC 295 camera and Leica Application Suite Vers. 3.8.
This system was also used to examine and take diagnostic measurements of each Acerentulus iranicus sp. nov. and Acerentomon sp. 1 specimen (see Nosek 1973). For the description of morphological characters, the terminology used by Szeptycki (1991), Rusek et al. (2012), and Shrubovych (2014) was adopted. In particular for the ratios between measurements, the following acronyms were used: LR = labral ratio = length of the head (without rostrum)/length of the rostrum starting from the base of labial setae PR = pseudoculus ratio = length of the head (without rostrum)/length of pseudoculus CF = head length/hind part of maxillary gland length TR = tarsus ratio = length of foretarsus/length of claw EU = empodium/unguis ratio = length of empodium/length of foretarsal claw BS = base/sommet ratio = distance of foretarsal sensillum t1 from the base of tarsus/distance of t1 from the apex of tarsus.

Results
Totally in the two sampling sessions 18 specimens of Protura were collected, belonging to three species. These new data are added to those relating to nine species already known from the Middle East area in literature (even though not strictly belonging to the Middle East area, we included also a record from a locality in Azerbaijan about ten kilometers far from the border with Iran). Some in depth data on each species are reported below.

List of Protura of the Middle East
ORDER ACERENTOMATA FAMILY PROTENTOMIDAE

Taxonomic account
Acerentulus iranicus sp. nov. Foretarsus length 88 μm (n = 2), claw 26 μm, without inner tooth or outer flap, TR = 3.4; empodium length 4 μm, EU = 0.15; S-shaped seta nearly as long as claw, 27 μm. Sensillum t1 claviform: BS = 0.34-0.35 (n = 2); t2 slender; t3 shaped like a willow leaf. Sensillum a passing the base of d; b and c almost of the same length; d slightly closer to c than to e, passing e; e long, reaching the base of g; f halfway between e and g, passing the base of claw. Sensillum a' swordshaped and distal to t1, short, not reaching the base of b'; b' reaching the base of c'; c' thin, its apex barely reaching the base of claw. Ventral seta β1 thin, 6 μm long, as long as the interior seta δ4; δ4 situated proximally to c' (Figures 4(f,g)).
Ethymology. The name iranicus refers to the country where type specimens have been collected.

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S. Vahedi Moghadam et al. Shrubovych et al. 2019) according to the long foretarsal sensillum a almost reaching seta γ3, and to sensilla b and c of similar length (b is just slightly longer than c). A key to the species belonging to such group is available in Shrubovych et al. (2019). Moreover, the new species is characterized by the absence of seta P1a on tergites I-VI and by the presence of three pairs of A-setae and a complete row of P-setae on tergite VII. Among those species sharing these characters, A. xerophilus Szeptycki, 1979 differs for the chaetotaxy of tergites I-VI, for the presence of pores on meso-and metasternum and for a much longer tarsus (98-102 μm; TR = 3.9-4.4).
Acerentulus palissai Nosek, 1967 shows a different dorsal chaetotaxy of segments II-VI and its sensillum c is significantly longer than b. Acerentulus confinis maderensis Tuxen, 1982 shares with the new species the same chaetotaxy, but it has shorter sensilla b and c barely reaching seta γ3, sensillum c' is nearly at the same level of seta δ4, its body size is smaller (length = 850 μm) and its tarsus is longer (98 μm). The closest species to A. iranicus sp. nov. results to be A. setosus Szeptycki, 1993. This last species differs from the one described here for its smaller pseudoculi (6-7 μm, PR = 15-19), the ratio between mesothoracic setae P1 and P2 (almost of the same length), the presence of a doubled pore on tergite XII, and the longer foretarsal sensillum a (passing seta γ3). The type locality of A. setosus (Krasnodar Krai, Russia, 50 km far from the Black Sea) seems to support the close affinity with A. iranicus sp. nov. also from a geographical point of view.  *We suggest to modify the name given to this pore by Galli and Capurro (2013) in anteromedial (am) more in line with the nomenclature proposed by Shrubovych (2014 . Ratios: LR = 3, PR = 11.6, CF = 5.6, TR = 2.8, BS = 0.56, length ratio of setae 1:2 on pronotum as 2.5:1, ratio P1:P1a:P2 on mesonotum as 1.1:1:1. The head length could be not exact since the head capsule seems to be a bit deformed due to the preparation, therefore in the diagnosis we did not consider LR, CF and PR ratios which were considered not fully reliable. Head without additional setae d6; frontal pore placed in line with the anterior margin of pseudoculi; rostrum very long, a bit longer than labial setae; pseudoculi subcircular, slightly longer than broad; maxillary gland typical of genus Acerentomon, with a short proximal part; labial palps with a large leafshaped basal sensillum (Figures 6(a,e) and 7(a,b)). Foretarsal sensillum a large, reaching halfway the bases of c and d; sensillum b long, sword-shaped, reaching the base of t3 (Figure 6(b)); d rather short, slightly passing t3. Tarsal pore present near the base of sensillum c. Pleural pectine VI with five to six distinct teeth; comb VIII with 14 irregular teeth; hind margin of pleurite VIII with five teeth; hind margin of abdomen XII with six to seven teeth ( Figure 6(c,d,f)). Striate band well developed followed by a row of minute granules which is straight and continuous on tergite, curved on pleurites and discontinuous on sternite (Figure 6(c,d)). Chaetotaxy and porotaxy are shown in Tables III and IV, respectively. Male squama genitalis is illustrated in Figure 7(c). Female squama genitalis unkown.

Remarks.
The Acerentomon specimen examined belongs to the "affine group" sensu Nosek (1973) being characterized by the presence of 4/2 setae on sternite VIII, and tergite VII without seta x. Unfortunately we were unable to fully describe a new Acerentomon species based on the only male specimen collected. Anyway it can be distinguished from all the other species belonging to the "affine group" by some characters which are summarized below (see Tuxen 1964;Nosek 1973).
Acerentomon affine Bagnall, 1912 has a rostrum of medium length, shorter than labial setae. Foretarsal ? Not clearly visible. *The specimen examined has an anomalous chaetotaxy (see text). sensillum b is long, but only reaching halfway between seta γ3 and sensillum t3. Chaetotaxy differs from that of the new specie for the presence of 4 setae on tergite XI and 5/5 on sternite II. The posterior margin of pleurite VIII has 5-7 very small teeth. Ratio BS is 0.75 and TR 2.5.
Acerentomon bagnalli Womersley, 1927 has a much shorter sensillum b only reaching the base of seta γ3. Chaetotaxy is the same of A. affine. Ratio BS is 0.7.
Acerentomon oblongum Womersley, 1927 is very similar to A. affine for many features (TR, foretarsal sensilla size and arrangement, and chaetotaxy). BS is 0.8.
Based on these data, it is rather difficult to choose among those mentioned a more similar species, but it is unquestionable that the specimen described belongs to a new taxon.

Discussion
After this work, the Protura fauna of the Middle East results made up of eleven species, nine of which belonging to order Acerentomata (one Protentomidae and eight Acerentomidae), and two of the order Eosentomata, family Eosentomidae. This richness value must be considered widely underestimated, due to the very low sampling effort in the whole area (null in some countries). In comparison, referring to neighboring countries respectively to the north and south of the Mediterranean, 14 species are  known from Greece (Szeptycki 2007;Galli et al. 2017) and 7 from Algeria (Szeptycki 2007).
The dominant species in the studied locality in Iran is Acerella muscorum for which it has been recorded a sex ratio (1 male vs 13 females) that confirms the population unbalance toward females already known for this species in Italy and for other species all over the world as well (Galli et al. 2019a(Galli et al. , 2019b(Galli et al. , 2021. The remaining four specimens belong to a new Acerentulus species and to an undetermined Acerentomon species.  (Condé, 1948)