A new species of Arrhopalites Boerner (Collembola, Symphypleona, Arrhopalitidae) from China, with a key to the Asian species of the caecus group Author Godeiro, Nerivania Nunes https://orcid.org/0000-0002-1669-6124 Shanghai Natural History Museum, Shanghai Science & Technology Museum, Shanghai 200041, China & Department of Entomology, College of Plant Protection, Nanjing Agricultural University, 210095, Nanjing, China nerivania@gmail.com Author Zhang, Feng https://orcid.org/0000-0002-1371-266X Department of Entomology, College of Plant Protection, Nanjing Agricultural University, 210095, Nanjing, China Author Bellini, Bruno Cavalcante https://orcid.org/0000-0001-7881-9436 Department of Botany and Zoology, Biosciences Center, Federal University of Rio Grande do Norte, Natal, Rio Grande do Norte, Brazil text ZooKeys 2022 2022-05-20 1102 163 176 http://dx.doi.org/10.3897/zookeys.1102.81247 journal article http://dx.doi.org/10.3897/zookeys.1102.81247 1313-2970-1102-163 858E536906844DE7AE5C5482472191BA 016AD5CFD72859D382A2EB728342F84E Arrhopalites brevicornis sp. nov. Figs 1 , 2 , 3 , 4 Type material. Holotype on slide "SNHM00001" : female, Jilin Province, China, 44°33'N , 123°31'E , 2013, in soil samples from the Ecological Research Station for Grassland Farm, July 2013, Bing Zhang leg. Paratypes on slides: 9 females on slides, same data as holotype. Besides the type material, 78 specimens are kept in 98% ethanol at the SNHM, plus several paratype slides are kept at the laboratory of Entomology, NJAU, China. Diagnosis. Female. Antennae short, about 1.4 times the head length. Ant IV not subdivided and short, about twice or less the length of Ant III. Eyes 1+1. Clypeal area a-f lines with 7(+1)/7/5/4-5/5/6 chaetae respectively, plus 3 central chaetae with unclear homologies, frontal area A-C lines with 1/1/2(+1) short stout spines. Small abdomen, dorsal anal valve with 2 cuticular spines per side and 4 sword-shaped smooth chaetae (ms1, mps1-3), ventral anal valves with 2 cuticular spines each and 3 sword-shaped smooth chaetae (mi3, mpi1-2), subanal appendage long, similar in length to mi3, mpi1-2, with a spatulated and apically serrated apex. Manubrium with 5 chaetae on each side, dens ventral formula from the apex to the basis as 3,2,1,1,1, dorsally with 16 chaetae. Mucro with both edges serrated, apically swollen. Ungues I slender, III broad, all with an underdeveloped tunica, unguiculus III with 2 inner teeth. Description. Female . Body (head + trunk) length of type series (females, N = 4) ranging between 0.71 and 0.81 mm, average 0.74 mm, holotype with 0.75 mm. Habitus as in Fig. 1 . Specimens pale yellowish with brownish spots of pigment on frontal and dorsal head and dorso-lateral large abdomen. Body chaetae smooth and acuminate, with the exception of the subanal appendage. Figure 1. Arrhopalites brevicornis sp. nov.: habitus of specimen fixed in ethanol. Head (Figs 1 , 2 ). Antennae shorter than the body, with 0.32 mm in the holotype (Fig. 1 ), ratio antennae: head length of the holotype 1.3:1, type series average 1.4:1. Holotype antennal segments ratio of Ant I:II:III:IV as 1:1.6:2.3:4.3, and of type series ( N = 4) as 1:1.3-2.7:2.1-3.3:3.8-6.7. Ant IV short and stout, about twice or less the size of Ant III (in holotype, ratio Ant III:IV = 1:1.87), without subsegments, with about 87 regular chaetae of different sizes distributed in apparently 13 whorls (Fig. 2A ). Ant III slightly swollen with 17 chaetae, Ape, Ae, Ap, Ai, Aa, Api, and Aai present, Api slightly reduced, Aai as the accessory microsensillum, sense rods not swollen inside separate invaginations (Fig. 2B ). Ant II with 13 regular chaetae, Ant I with 7, the two more apical reduced (Fig. 2C ). Eyes 1+1, head length (eyes to mouth) of holotype 0.25 mm. Clypeal area a-f lines with 7(+1)/7/5/4-5/5/6 chaetae respectively, plus 3 central chaetae of unclear homologies; interantennal area α and β lines with 2/1(+1) short chaetae respectively, plus 2+2 small oval organs (pseudopores) and 1+1 large circles lacking tegument granules near the lateral chaetae on α line; frontal area A-C lines with 1/1/2(+1) short stout spines, D line with 2 elongate thinner erect chaetae (Fig. 2D ). Ventral groove with 2 surrounding chaetae from lines a and b, labial basomedian field with 4, basolateral field with 5 chaetae (Fig. 2E ). Labial papilla E lateral finger-shaped, not reaching the papilla apex, other labial structures unclear. Maxillary outer lobe apical chaeta longer than the basal one, sublobal plate with three sublobal hairs (Fig. 2F ). Distal margin of the clypeus with 3 prelabral chaetae, labral chaetotaxy with 2(+1) p, 2(+1) m and 2 a chaetae, all subequal (Fig. 2G ). Figure 2. Arrhopalites brevicornis sp. nov. head A left Ant IV (dorsal side) B left Ant III (ventral side) C left Ant I-II (dorsal side) D anterior head - left side shows the complete chaetotaxy, * marks unpaired chaetae, white arrow points to chaeta present or absent, large dashed circle on central clypeal region marks asymmetrical chaetae E ventral head chaetotaxy - right side shows the complete chaetotaxy, including labial basomedian and basolateral fields F left maxillary outer lobe and sublobal plate G prelabral chaetae and labrum. Trunk (Fig. 3A, B ). Trunk length of holotype 0.5 mm. Large abdomen: thorax continuous with abdomen, without any constrictions. Th II with 1 a and 3 m chaetae; Th III with 1 a and 3 m chaetae; Abd I with 5 a, 4 m and 1 p chaetae, respectively. Three chaetae (1-3) on the upper side of bothriotrichum A, plus accessory a1 nearby its alveolus; b1 accessory chaeta between B and C bothriotricha, c2 just under C, c1 absent; bothriotricha A-C misaligned, with B bothriotrichum closer to C than A; dorso-posterior longitudinal series dI-1, dII-1, dIII-1 with 5-7, 9-10 and 6-8 chaetae, respectively; two rows with 3 chaetae each between C and D bothriotricha; D with 4 surrounding chaetae posteriorly; parafurcal area (furcula basis) with 8 regular chaetae; ventral complex with 1 chaeta (Fig. 3A ). Small abdomen of the female: dorsal anal valve with as2-4, ms1-5?, mps1-3, and ps1-2 chaetae, ms1 and mps1-3 sword-shaped and smooth, 2 cuticular spines surrounding mps2; ventral anal valves each with ai1-6, ami1-2, mi1-5, mpi1-2, and pi1-3 chaetae, mi3 and mpi1-2 sword-shaped and smooth, mi5 as the subanal appendage long (similar in length to mi3, mpi1-2) with a spatulated and apically serrated apex (sometimes one of the lateral edges is also distally serrated), curved toward the genital opening, 2 cuticular spines surrounding mpi2 (Fig. 3B ). Genital plate of the female unclear. Figure 3. Arrhopalites brevicornis sp. nov. trunk, proximal legs and furca A large abdomen and coxae chaetotaxy (right side) B female's small abdomen (left side) C right manubrial chaetotaxy (dorsal side) D right dens ventral chaetotaxy E right dens dorsal chaetotaxy F mucro. Abdominal appendages (Fig. 3C-F ) Collophore with 1 distal chaeta on each side, with a pair of a little wrinkled, almost smooth, sacs. Tenaculum with 3 teeth on each ramus plus the basal tubercle, with a single unpaired apical chaeta. Furcal size length in holotype: manubrium = 75 µm ; dens = 113 µm ; and mucro = 75 µm (ratio 1:1.5:1). Manubrium with 5 dorsal chaetae on each side, the most proximal thinner than the others (Fig. 3C ); dens ventral (or anterior) formula from the apex to the basis as 3,2,1,1,1, all chaetae enlarged except for the most proximal one, (Fig. 3D ); dens dorsally (or posteriorly) with 16 chaetae, 7 of them on the lateral edges of the more distal region more robust, almost spine-like (Fig. 3E ). Mucro apically swollen with both edges serrated from the basis until almost the apex (Fig. 3F ). Legs. (Figs 3A , 4 ) Epicoxae, subcoxae and coxae I-III with 1,0,1/1,1,4/1,1,4 chaetae, respectively, coxae II-III with 1 long and 1 tiny chaeta each (Fig. 3A ). Trochanters I-III with 4 chaetae each, II-III with 1 chaeta each modified as an anterior trochanteral organ (Fig. 4A-C ). Femurs I-III with 13/13/14 chaetae respectively, of which 1/1/3 as reduced chaetae (Fig. 4A-C ). Tibiotarsi without oval organs, tibiotarsus I region F with 3 chaetae (FPae, FPe, and FPpe), whorls I-V with 9,8,8,8,9 chaetae respectively, whorl I without clearly modified chaetae except for a larger dorsal one, whorl V with 2 ventro-distal chaetae (Fig. 4D ). Tibiotarsus II region F with 3 chaetae (FPae, FPe, and FPpe), whorls I-V with 9,8,8,8,7 chaetae respectively, whorl I without clearly modified chaetae except for a slightly larger dorsal one, whorl V with 1 ventro-distal chaeta (Fig. 4E ). Tibiotarsus III region F with 4 chaetae (FPae, FPe, FPpe, and FSa), whorls I-V with 9,8,8,8,7 chaetae respectively, whorl I without clearly modified chaetae except for a slightly larger dorsal one, whorl V with 1 ventro-distal chaeta (Fig. 4F ). Foot complexes I-III with 2 pretarsal chaetae each, 1 anterior and 1 posterior; ungues (claws) without cavity or pseudonychia, but with an underdeveloped tunica covering about 2/3 up to 3/4 of the dorsal ungues, lateral lamellae apparently lacking teeth, each unguis with one internal tooth; unguis I slender, III broad (Fig. 4D-F ). Unguiculi (empodia) never surpassing the ungues, unguiculus I almost reaching the apex of unguis I, unguiculi II-III clearly shorter; unguiculi I-II with one proximal internal tooth each, unguiculus III with 2 more distal teeth (Fig. 4D-F ). Figure 4. Arrhopalites brevicornis sp. nov. legs A-C trochanters and femurs I-III (anterior side), respectively D-F tibiotarsi and empodial complexes I-III (anterior side), respectively. Male. Not found, species possibly parthenogenetic. Etymology. The new species was named after its short antenna (from Latin brevi - = short; cornis = "horns" , antennae). Distribution and habitat. The new species was collected and only recorded in Jilin Province, Changling County, at the Ecological Research Station for Grassland Farm (ERSGF). This region is characterized by a semi-arid continental monsoon climate, with cold, dry winters and warm, rainy summers. Annual mean temperature in the region ranges from 4.68 to 6.48 °C, and annual precipitation is 280 to 400 mm with about 70% falling in the June-August period (Changling County Climate Station, Jilin Province). Changling County is located at a transitional zone of cropping and grazing, with high economical potential. However, drastic environmental disturbances are happening in this region, like sand and dust storms, emergence of saline-alkali soils, and land over-utilization. Remarks. Arrhopalites brevicornis sp. nov. belongs to the A. caecus (Tullberg, 1871) group of species sensu Vargovitsh (2013) , according to its ventral (or anterior) dental chaetotaxy (3, 2, 1, 1, 1). Currently, there are ten other Asian species of the genus which belong to this group: A. antrobius Yosii, 1954, A. abchasicus Vargovitsh, 2013, A. caecus , A. coreanus Park & Kang, 2007, A. gul Yosii, 1966, A. macronyx Vargovitsh, 2012, A. minor Park & Kang, 2007, A. minutus Yosii, 1970, A. potapovi Vargovitsh, 2015 and A. pukouensis , ( Bellinger et al. 1996-2022 ; Vargovitsh 2012 , 2013 , 2015 ). Arrhopalites brevicornis sp. nov. can be distinguished from all of them especially by the unguiculus III with 2 internal teeth (0-1 in all other species). Also, the combination of antennae less than 2 times the size of the head, Ant IV without annulations, 1+1 eyes, dorsal head with 9 spines, 2+2 regular spines per side on the anal valves, circumanal chaetae without basal serrations, subanal appendage long and apically serrated, similar in length to mi3, mpi1-2, manubrium with 5+5 and dorsal dens with 16 chaetae is unique among the Asian species of the Arrhopalites caecus group (see Table 1 ). Table 1. Comparison between the Asian species of Arrhopalites from the Arrhopalites caecus group.

Species	A. antrobius	A. abchasicus	A. caecus	A. coreanus	A. gul	A. macronyx	A. minor	A. minutus	A. potapovi	A. pukouensis	A. brevicornis sp. nov.
Distribution	Japan	Abkhazia	Cosmopolitan	S. Korea	S. Korea	Abkhazia	S. Korea	Japan	Russia	China	China
Cave species	Yes	Yes	No	No	Yes	Yes	No	No	No	No	No
Body size (mm)	1.3	0.9	up to 1.0	0.7	1.2	1.2	0.5	0.5	up to 0.88	up to 1.3	0.71-0.81
Color pattern	unpigmented	unpigmented or with dorsal spots	unpigmented or with dorsal spots	with dorsal spots	unpigmented or with dorsal spots	with dorsal spots	with lateral spots	unpigmented	unpigmented, only eyes pigmented or with dorsal spots	unpigmented	with dorso-lateral spots
Ant IV annulations	4	5-7	(-)	(-)	7	7-8	(-)	(-)	(-/+)5-6	(-)	(-)
Ant at least 2 x longer than head	Yes	Yes	No	Yes	Yes	Yes	No	No	No	No	No
Head dorsal spines	?	9	6-13	10 (possibly more)	(+)	(-)	9	13	13	(-)	9
Eyes	0+0	1+1	1+1	1+1	1+1	0+0?	1+1	1+1	1+1	0+0	1+1
Ungues I;II;III tunica	(+);(+);(+)	(-);(-);(-)	(-/+);(+);(+)	(+);(+);(+)	(-);(-);(-)	(-);(-);(-)	(+);(+);(+)	(-);(-);(+)	(-/+);(-/+);(-/+)	(-);(-);(-)	(+);(+);(+)
Ungues I-III inner tooth	(+)	(-/+)	(+)	(+)	(-/+)	(-)	(+)	(+)	(+)	(+)	(+)
Unguiculus III inner teeth	0	1	1	1	0-1	1	1	0	0-1	1	2
FAV cuticular spines (per side)	2+2	2+2 to 0+0	2+2	0+0	0+0	0+0	0+0	2+2	2+2(1+1 enlarged)	0+0	2+2
Subanal appendage shape	long, apically pointed	long, apically serrated	long, apically serrated	long, apically pointed	short, apically blunt	long, apically pointed	long, apically pointed	short, apically serrated	short, apically serrated	short, apically serrated	long, apically serrated
ms1 chaeta shape	not forked	not forked	not forked	forked	not forked	not forked	not forked	not forked	not forked	not forked	not forked
Circumanal basally serrate chaetae	(-)	(+)	(+)	(-)	(+)	(+)	(-)	(-)	(+)	(-)	(-)
Tenaculum chaetae	1	1	1-2	1	1	1-2	1	?	1	1	1
Manubrium dorsal chaetae	?	5+5	?	5+5	4+4	5+5	9+9	4+4	5+5	5+5	5+5
Dorsal dens chaetae	more than 10	16	15?	16	16	16	14-16	14	15	15	16

Legends: Ant = antennal segment(s); S. = South; (-) = absent; (+) = present; (-/+) = absent or present;FAV = Female's anal valves. Data based on the original descriptions, with the exception of A. caecus (based on Bretfeld 1999 ; Fjellberg 2007 ; and Vargovitsh 2013 ). Concerning the species recorded from localities closer to Jilin Province, China, the South Korean A. coreanus , A. gul and A. minor share a similar color pattern, number of eyes, the presence of dorsal spines on head and number of dorsal dens chaetae with the new species. However the later differs from them by: the absence of Ant IV annulations (7 of A. gul ); antennae less than 2 times the size of the head (at least two times in A. coreanus and A. gul ); all ungues tunicate (without tunica on A. gul ); female's subanal appendage apically serrated (pointed in A. coreanus and A. minor , and blunt in A. gul ); dorsal anal valve chaeta ms1 not forked (forked in A. coreanus ); circumanal chaetae without basal serrations (with in A. gul ) and manubrium with 5+5 chaetae (4+4 in A. gul , 9+9 in A. minor ). The only other species of the Arrhopalites caecus group registered from China is A. pukouensis , from Nanjing, Jiangsu District, approximately 1800 km distant from the type location of the new species. Both species are vastly different as A. pukouensis is unpigmented (vs. pigmented), has no eyes and dorsal head spines (vs. 1+1 eyes and 9 spines, respectively), its ungues are devoid of tunica ( vs. present); its female's anal valves have no cuticular spines and their subanal appendage is short (vs. 2+2 spines per side and the subanal appendage is long, respectively) and its dorsal dens shows 15 chaetae (vs. 16 in the new species). A detailed comparison of the morphology and the known distribution of all the cited species is presented in Table 1 . We also provide a key of all Asian species of Arrhopalites caecus group below.