﻿Description of two Stenohya species from China (Pseudoscorpiones, Neobisiidae), with comments on the exaggerated sexual dimorphic pedipalp in this genus

﻿Abstract Two Stenohya species belonging to the family Neobisiidae are diagnosed, described, and illustrated from China: Stenohyaspinatasp. nov. from Chongqing Municipality, and Stenohyahuangi Hu & Zhang, 2012 from Fujian Province. The male of S.huangi is reported for the first time. Diagnostic characters of this species are restricted based on the holotype and the new specimens. In addition, a key and a distribution map of the Stenohya species from China are provided, and the potential function of the exaggerated sexual dimorphic pedipalp in the genus Stenohya is discussed.


Introduction
The Asian pseudoscorpion genus Stenohya was erected and placed in Hyidae Chamberlin, 1930by Beier (1967, with the type species S. vietnamensis Beier, 1967, whose holotype is a tritonymph. After reviewing some Asian species originally ascribed to the genus Microcreagris Balzan, 1892, Ćurčić (1983) erected the genus Levigatocreagris, with Levigatocreagris gruberi Ćurčić, 1983 as the type species. However, Harvey (1991) regarded Stenohya as a senior synonym of Levigatocreagris, and transferred Stenohya to the family Neobisiidae Chamberlin, 1930 based on the presence of the venom apparatus only in the fixed chelal finger and a non-lanceolate trichobothrium t.
In this paper two Stenohya species with sexual dimorphic pedipalps are described and illustrated from China: Stenohya spinata sp. nov. and S. huangi. Males of S. spinata sp. nov. have several strong thorns and spinous apophyses on the pedipalpal femur, patella and chela, whereas females lack these structures. The males of S. huangi, described here for the first time, have thinner pedipalps than females.

Materials and methods
All specimens were examined, illustrated and measured using a Leica 205A stereomicroscope with a drawing tube. A detailed examination was carried out with an Olympus BX53 general optical microscope. Temporary slide mounts were prepared in glycerol. Figures were edited and formatted using Adobe Photoshop 2022. The specimens are preserved in 95% alcohol and deposited in the Museum of Hebei University (MHBU), Baoding, China. Terminology and mensuration largely follow Chamberlin (1931), except for the nomenclature of the pedipalps and legs, and the terminology of trichobothria (Harvey 1992); the term "rallum" (for flagellum) is adopted from Judson (2007).
Legs (Figs 6K, L, 7F, G). Leg I: femur 4.32-5.24, patella 3.44-3.62, tibia 5.00-5.46, basitarsus 4.31-4.70, telotarsus 4.10-5.10 times longer than deep; femur 1.19-1.52 times longer than patella, telotarsus 0.93-1.18 times longer than basitarsus. Leg IV: femur + patella 4.86-5.10, tibia 6.95-7.16, basitarsus 4.13-4.64, telotarsus 6.85-7.50 times longer than deep; telotarsus 1.34-1.38 times longer than basitarsus; tibia with 3 submedial tactile setae (TS = 0. Remarks. Like some other Stenohya species, Stenohya spinata sp. nov. has exaggerated sexually dimorphic pedipalps, with those of the males armed with several strong thorns and spinous apophyses, which are absent in females. The presence of distinct apophyses on male pedipalps has been previously described in six Stenohya species: S. hamata (Leclerc & Mahnert, 1988), S. curvata, S. meiacantha, S. bicornuta, S. dongtianensis, and S. jiahensis. Stenohya spinata can be distinguished from them by the position and shape of the projections on pedipalps, e.g. the chelal hand of males of S. hamata have a thorn-like projection on the ventral surface near the base of the fingers pointing distally downwards (Leclerc and Mahnert 1988); in S. curvata, males have a spine-like projection on the prolateral side of the chelal hand near the base of the fingers, they also have one or two small bulges between the projection and the finger ; in S. meiacantha, males have a spine-like projection on the prolateral side of the chelal hand near the base of the fingers (Yang and Zhang 2013); in S. bicornuta, the male chelal hand has a projection on the prolateral surface near the base of the fingers, and this projection with two horn-like bulges at the top (Guo et al. 2019); in S. dongtianensis, the male pedipalpal femur with one distal tubercle on the prolateral surface, chelal hand with 14 large tooth-shaped tubercles in the middle (retrolateral view) (Li and Shi 2023); in S. jiahensis, the male pedipalpal femur with one distal tubercle (many small bulges) and one basal tubercle on prolateral surface, chelal hand with 42 tooth-shaped tubercles (retrolateral view)   (Li and Shi 2023); while in S. spinata, males have strong peg-like thorns on the median prolateral surface of the pedipalpal femur and patella, and have 16 or 17 spinous apophyses on the median dorsal side of chelal hand.
Pedipalps (Figs 9I-K, 10C, D). Pedipalps long and slender (Fig. 10D). Apex of pedipalpal coxa rounded, with 4 long setae; femur straight, with tubercles on the median prolateral position, the other sections smooth; patella claviform, smooth; chelal fingers long and slender (Figs 9J, K, 10C, D). Trochanter 2.21-2.35, femur 7.64-7.96, patella 6.32-6.45, chela (with pedicel) 5.23-5.48, chela (without pedicel) 4.98-5.19 times longer than broad, movable finger 1.32-1.43 times longer than hand (with pedicel). Fixed chelal finger with 8, movable finger with 4 trichobothria: eb, esb, ib, and isb located basally of fixed chelal finger, est, et, and it situated distally of fixed chelal finger, ist situated midway between isb and it, nearer to it than to isb, b and sb closer to each other situated on the basal half, and st and t closer to each other situated on the distal half of the movable finger (Figs 9I, 10C); venom apparatus present only in fixed chelal finger, venom duct short (Fig. 9I); fixed finger with 71-77 pointed teeth, staggered arrangement of small and large teeth; movable finger with 30-33 teeth situated at median to distal position, rounded at median position, while pointed at distal position.
Legs. Leg I: femur 5.93-6.21, patella 3.80-4.38, tibia 5.17-5.73, basitarsus 4.67-5.00, telotarsus 5.11-5.56 times longer than deep; femur 1.42-1.52 times longer than patella, telotarsus 1.09-1.11 times longer than basitarsus. Leg IV: femur + patella 5. 18-6.46, tibia 8.40-8.86, basitarsus 5.18-5.50, telotarsus 6.50-7.10 times longer than deep; telotarsus 1.18-1.21 times longer than basitarsus; basitarsus with 2 tactile setae (TS = 0.13-0.16, 0.86-0.89), telotarsus with 3 tactile setae (TS = 0.14-0.19, 0.33-0.38, 0.56-0.58); subterminal tarsal seta bifurcate. Remarks. Stenohya huangi was described from a single female specimen by Hu and Zhang (2012). Although one of the original diagnostic characters is the presence of about 30 teeth on the movable chelal finger (Hu and Zhang 2012), we found a total of 47 teeth after inspection of the holotype. The most basal   14 teeth are rounded, while the other teeth have pointed tops (Fig. 11B). Herein, we describe more specimens of S. huangi from the type locality (Gushan Mountain in Fuzhou City, Fujian Province, China), including seven adult males, which allows the first description and illustrations of the male. Like some other species of Stenohya, S. huangi have sexually dimorphic pedipalps in which  Table 1. Numbers of teeth on movable chelal finger and proportions of pedipalpal femur and patella in male Stenohya species without apophyses on pedipalps.   males have thinner pedipalps than females. Based on the holotype and the new specimens, we refine the diagnosis of S. huangi. Males of S. huangi have fewer teeth on the movable chelal finger and very slender pedipalps without apophyses. They can be easily separated from the males of other Stenohya species with unarmed pedipalps, by the number of teeth on the movable chelal finger, and the proportions of pedipalpal femur and patella (Table 1).

Discussion
Until now, seven of 23 Stenohya species have been recorded as having peculiar apophyses on the male pedipalps. Stenohya spinata is the most exaggerated one, with various apophyses on the pedipalpal femur, patella, and chelal hand, while apophyses are absent on the pedipalpal patella in the other six species. We propose three hypotheses to explore the function of these apophyses on male pedipalps. Hypothesis 1: The apophyses are helpful for holding the female's pedipalps during mating. In some cheliferoid pseudoscorpions, sperm transfer is achieved by mating dances with bodily contact (Weygoldt 1966a(Weygoldt , 1969. Mating commences when the male grasps the female's pedipalp and ends when the spermatophore is transferred (Palen-Pietri et al. 2019). If these Stenohya pseudoscorpions have mating behavior that involves direct male-female contact, the apophyses on the male pedipalps may be used to increase the contact area, thus being helpful when holding the female's pedipalps during mating. However, neobisiid pseudoscorpions have not been reported to have direct mating behavior, and there is no contact between male and female during sperm transfer (Weygoldt 1966a(Weygoldt , 1969Zeh and Zeh 1997). Furthermore, in these five Stenohya species, females lack special morphological structures to correspond to the modified male pedipalps, like a mortise and tenon structure that allows interaction between the two.
Hypothesis 2: The exaggerated male pedipalp is used to attract females for copulation. The pedipalp is the most important sensory organ in pseudoscorpions (Stemme and Pfeffer 2021), and it likely plays an important role in intraspecific communication. The exaggerated pedipalp of these Stenohya pseudoscorpions may be used for courtship display or bodily contact during mating. It should be noted that this hypothesis is also based on the presence of mating behavior in these species. In addition, mechanoreception may well be more useful than photoreception for pseudoscorpions (Weygoldt 1969;Tizo-Pedroso and Del-Claro 2008). Males are more likely to attract females for copulation using their pedipalps to make bodily contact with females if this hypothesis is true.
Hypothesis 3: The armed pedipalp is used as a weapon to fight with conspecific males. Animal weapons are very diverse structures, exhibiting different sizes and shapes within and between species (Emlen 2008; Rico-Guevara and Hurme 2019). Dimorphism ultimately results from differential selection acting on traits that have sex-dependent benefits and costs, leading the same trait toward different optima in each sex (Boisseau et al. 2020). The pedipalpal chela is a pseudoscorpions most effective defensive weapon, and males often use their pedipalpal chelae and fingers to fight with each other (Weygoldt 1966b). The apophyses on the pedipalps of these Stenohya pseudoscorpions may be helpful in fighting between intraspecific males during territorial defense or vying for mating opportunity. It is worth noting that males with larger chela have an advantage in the transfer of spermatophores, which can be attributed to their increased likelihood of interrupting mating and replacing smaller males under high-density conditions (Zeh 1987).
The Neobisiidae family is identified as having a reproductive strategy based on non-pairing sperm-transfer behavior, which may result in the lack of dancing behavior within this group (Weygoldt 1966a(Weygoldt , 1969Zeh and Zeh 1997). This would provide further support for hypothesis three. Nevertheless, there remains a significant gap in knowledge for the majority of pseudoscorpion species. In the absence of actual observations, each of these hypotheses discussed above seems to provide supporting and opposing evidence at the same time. Therefore, we believe that a key effort for future work should be focused on investigating the life histories of these Stenohya species that display sexual dimorphism. Ideally, the developmental evolution of sexual dimorphism should be inferred to in combination with their phylogenetic relationships. Future research efforts should also exploit recent advances in the fields of morphometrics, statistics, bioinformatics, and biomechanics. A more comprehensive and deep understanding of structure-function relationships in sexual dimorphism will provide better insight into the underlying evolutionary drivers of pseudoscorpion sexual dimorphism.