Two new species of Hymenaphorura Bagnall, 1948 (Collembola, Onychiuridae) from Romania and an updated key to the genus

Abstract Two new species of the genus Hymenaphorura from Romania, H. urbanasp. nov. and H. kalinderasp. nov., are described and illustrated. Hymenaphorura urbana has a postantennal organ (PAO) with 13–15 simple vesicles, abdominal terga I–III with subequal setae p2 and p3, abdominal tergum V granular area with 3+3 distinct, long macrosetae, and H. kalinderasp. nov. has PAO with 9–12 simple vesicles, one border seta, abdominal terga I–III with setae p2 slightly longer than setae p3, abdominal tergum V granular area with 4+4 distinct macrosetae. Remarks on H. subsimilis Bagnall, 1948 are given. An updated key for the world distributed species of Hymenaphorura is presented.


Introduction
The genus Hymenaphorura Bagnall, 1948 is mainly characterized by two diagnostic apomorphies within the Hymenaphorurini: the presence of four guard setae on the antennal III sense organ and the lack of labial papillae E. Other characters of importance include: the absence of pseudocellus (pso) on the posterior part of the head, the body with only dorsomedial pseudocelli and the postantennal organ with simple vesicles, sometimes bilobed, located parallely or obliquely to the long axis of the organ, absence of the chaeta d0 on head, number of chaetae in the distal whorl of tibiotarsi (9 or 11), and structure of furcal rudiment (Pomorski 1998(Pomorski , 2001. Of the 46 species of Hymenaphorura known globally (Bellinger et al. 1996(Bellinger et al. -2020Paśnik and Weiner 2018), five species have been recorded in Romania: Hymenaphorura subsimilis (Bagnall, 1948), H. polonica Pomorski, 1990, H. nova Pomorski, 1990, H. valdegranulata (Stach, 1954) (see Stan and Weisner 1978), and H. ioni Buşmachiu, Popa & Weiner, 2014.
During a study of some collembolan material collected in the last six years from Romania, two new species of Hymenaphorura were revealed and are described in this paper.

Sampling and preparation
Samples of leaf litter and soil were collected between 2013 and 2017 and extracted with Berlese funnels. The specimens were cleared in lactic acid and KOH and subsequently mounted on slides using Marc Andre II or Swan's medium.
Labial papillae types are distinguished after Fjellberg (1999). Setae on the anal valves are named following Yoshii (1996). The nomenclature of the tibiotarsal chaetotaxy follows Deharveng (1983). Setae on furcal area are notated after Weiner (1996) and Paśnik and Weiner (2017). The pseudocelli, parapseudocelli, and pseudopores formulae give the number of pseudocelli, parapseudocelli, or pseudopores per halftergum (dorsally) or half sternum (ventrally). The tibiotarsus chaetotaxy formula is expressed as the total number of setae (number of setae in row C, number of setae in row B, number of setae in row A+T), for example: 18 (1, 8, 9).
antennal Diagnosis. Body with distinct areas of coarser granules. Dorsal pso formula as 10/011/11112, ventral pso absent. PAO with 9-12 simple vesicles, parallel or oblique in relation to the long axis of this organ and one border seta. Abd. terga I-III with setae p 2 and p 3 subequal. Abd. tergum V granular area with 4+4 distinct macrosetae. Distal tibiotarsal whorl with 11 setae.
Antennae and head. Antennae almost as long as head. Antennal segment I with 8 setae, antennal segment II with 15 setae. AIIIO consisting of four guard setae, five papillae, two smooth sensory rods, two granulated sense clubs: granulated and bent (Fig.  1A), ventro-lateral microsensillum present. Second external papilla in AIIIO forked in holotype, simple in two other specimens. Antennal segment IV with one distinct sensillum, small subapical organite in deep, narrow pit and latero-external microsensillum in the last posterior row of setae (Fig. 1A).
Dorsal chaetotaxy. Dorsal chaetotaxy as in Figs 1C, 2A-H always with some asymmetry. Seta d0 on the head absent. Body with macro-and meso/microsetae, sensory setae s well distinguished on head, abdominal terga I, IV and V, their formula per half tergum: 2/000/10012.
Thoracic terga II and III with strong lateral microsensilla (ms). Thoracic tergum I with 7(6)+7(6) setae. Thoracic terga II and III with 5+5 macrosetae and 4+4 microsetae along midline. Abdominal terga I-III with 5+5 macrosetae and 3+3 microsetae along midline. Setae p 2 and p 3 on abdominal terga I-III subequal. Granulated area of abdominal terga I-III with 4+4 setae, in row p of abdominal tergum V with 4+4 macrosetae as p 2 , p 5 , m 4 , a 4 . One macroseta in the set of setae on subcoxae 1 and abdominal pleura I-IV and 2 macrosetae on abdominal pleurum V. Abdominal tergum V with medial seta p 0 (absent in juvenile), VI with medial setae a 0 and p 0 . Anal spines as long as inner edge of claw III and 2.5 times as long as their basal diameter. Basal papillae low.
Ecology. This species is found in litter samples in mixed fir and beech forest. Etymology. The name of the new species is inspired by the name of the ski slope: Kalinderu, Buşteni town, Prahova county, Romania.   Pomorski, 2001 (Russia), and H. subsimilis Bagnall, 1948 (Romania) form a group of more similar species with 11 setae in the tibiotarsal distal whorl, with the pso formula 10/011/11112, and with one setae on the border of the PAO. The new species differs from these species by the number of s-setae on Abd. V (2+2 vs 1+1), by the presence of four setae on each of the granulated areas of Abd. I-III and by its smaller size (Table 1). A comparison with H. subsimilis, a species described from the same county (Prahova), is rather difficult because only one type specimen is not in good condition (see Remarks for H. subsimilis). These species differ in their size: H. subsimilis is larger than H. kalindera sp. nov. (1.01 mm vs 0.81 mm), and H. subsimilis has Th. I with 4+4 setae (juvenile specimens?) in one row vs 7+7 or 6+7 setae in two rows in the new species. Abd. V has 1+1 s-setae in H. subsimilis vs with 2+2 s-setae in the new species. The shape of vesicles in PAO are transversally lobed in H. subsimilis vs bean-like in shape in the new species. The upper anal valve setae in c-row are equal in the new species and, in H. subsimilis, seta c0 is longer than setae c2. Table 2 Hymenaphorura nova - Diagnosis. Body with distinct areas of coarser granules. Dorsal pso formula as 10/011/11112, ventral pso absent. PAO with 13-15 simple vesicles, parallel or oblique in relation to the long axis of this organ (Fig. 3B) and one border seta. Abd. terga I-III with subequal setae p2 and p3. Abd. tergum V granular area with 3+3 distinct, long macrosetae. Distal tibiotarsal whorl with 11 setae.
Antennae and head. Antennae almost as long as head. Antennal segment I with 8 setae, antennal segment II with 16 setae. AIIIO consisting of four guard setae, five papillae, two smooth sensory rods, two granulated sense clubs: ribbed and bent, ventrolateral microsensillum present. Second external papilla in AIIIO not forked. Antennal segment IV without distinct sensilla, small subapical organite in deep, narrow pit and latero-external microsensillum last posterior row of setae (Fig. 3A).
Ecology. This species lives in the urban habitats of Bucharest. Etymology. The species name refers to the urban area where it was sampled (Latin, urbanus).
Dorsal chaetotaxy. Dorsal chaetotaxy as in Fig. 4B always with some asymmetry. Seta d 0 on the head absent. Body with macro-and meso-microsetae and sensory setae s (slightly distinguished) on head, abdominal terga I, IV and V, their formula per half tergum: 2/000/10012.
LEGS. Distal whorl of tibiotarsi with 11 setae. Empodial appendage with small, narrow basal lamella, length of empodium is about 2/3 of inner edge of claw.   Bagnall, 1948. A postantennal sensory organ and anterior cephalic pseudocellus B thoracic tergum II C abdominal tergum V.

Remarks.
In the Collembola collection in the Natural History Museum, London, only a single type microscope slide exists of Hymenaphorura subsimilis, which was described by Bagnall (1948). This slide is in a poor condition, with some characters not well visible or completely invisible. Salmon (1959) redescribed the type specimen, but without details of the chaetotaxy. We had an opportunity to study this type specimen, and we found that the description of H. subsimilis was probably based on a juvenile or anomalous specimen, because there is only seta a1 in the medial part of terga (Figs 6A, 5D) without m 1 or p 1 and also with only 4+4 setae on Th. I.

Updated key to the known species of Hymenaphorura
The key presented below is based on the key by Paśnik and Weiner (2018). Recently described species have been added and some mistakes were corrected. Hymenaphorura nova has setae p 2 and p 3 on Abd. terga I-III subequal (not p 2 shorter than p3 as according to Paśnik and Weiner 2018) and H. anatolii Pomorski, 2001 has setae p2 longer than p3 (not p2 is four times longer than p3 as described by Paśnik and Weiner 2018 Claw with denticle, empodial appendage length equals to inner edge of claw, granulated area developed --type c1 according to Arbea & Jordana (1994) .. ........... H. dentifera (Stach, 1934); Europe (Carpathians and the Sudetes Mountains) -Claw without denticle, empodial appendage length equals ⅔ of inner edge of claw, granulated areas on the body reduced -type a according to Arbea & Jordana (1994 (Stach, 1934); Europe: Slovenia

Conclusion
As we mentioned in the Introduction, 46 species and the two species newly described here belong to the genus Hymenaphorura. European species are the most numerous (28); there are 12 North American species and eight from the Far East. It is possible * H. polonica -in the description Pomorski (1990) mentioned 1+1 poorly developed macroseta on Abd. V, while specimens from the type locality and other places have 3+3 macrosetae.