Taxonomic review of the Asian Trogloneta species (Araneae, Mysmenidae)

Abstract Five Trogloneta species from Southwest China and Japan are reviewed that two new combinations and a new synonymy are proposed in the current paper: T.nojimai (Ono, 2010), comb. n. is transferred from Mysmena, T.yunnanense (Song & Zhu, 1994), comb. n. (= T.denticocleari Lin & Li, 2008, syn. n.) is transferred from Pholcomma of the Theridiidae, T.speciosum Lin & Li, 2008, T.uncata Lin & Li, 2013, and T.yuensis Lin & Li, 2013. The female of T.yuensis is described for the first time. An identification key and diagnoses are provided for these species, as well as new photographs or illustrations of the genital organs and habitus of T.yuensis and T.yunnanense.


Introduction
The genus Trogloneta Simon, 1922 (= Troglonata, lapsus calami) was erected by Simon (1922) on the basis of an interesting cave spider from France which originally thought to be a member of the Mysmeneae group, and placed in the family Theridiidae Sundevall, 1833. It was later transferred to Symphytognathidae Hickman, 1931 by Gertsch (1960), and placed in Mysmenidae Petrunkevitch, 1928 by Forster and Platnick (1977). Brescovit and Lopardo (2008) reviewed a taxonomic history and proposed a syncretic diagnostic for Trogloneta. Recent phylogenetic study indicates that Trogloneta is sister to the clade comprising Maymena Gertsch, 1960 plus Mysmenopsinae (Lopardo andHormiga 2015), and a consistent diagnosis is also presented for this genus.
Currently, Trogloneta consists of eleven described species (World Spider Catalog 2018), and these members are mainly distributed in Europe, China, Brazil, USA, Madeira, and Canary Island, and prefer to living in cryptic microhabitats such as deciduous layer (e.g., T. cantareira, T. cariacica, and T. mourai in Brescovit and Lopardo 2008), or forest canopy (e.g., T. speciosum in Lin and Li 2008) or even in dark caves (e.g., T. granulum in Simon 1922, "T. denticocleari" and T. uncata in Lin and Li 2008, 2013b.
In this paper we provide a brief revision of Trogloneta species from Asia. The female of T. yuensis Lin & Li, 2013 is described for the first time. An identification key is also provided for these Asian Trogloneta species.

Materials and methods
Specimens were collected by hand and preserved in 95% ethanol. They were examined using a Leica M205 C stereomicroscope. Further details were studied under an Olympus BX43 compound microscope. The epigynes were removed and treated with lactic acid before being photographed. Photographs were taken with a Canon EOS 60D wide zoom digital camera (8.5 megapixels) mounted on an Olympus BX 43 compound microscope. The images were montaged using Helicon Focus 3.10 (Khmelik et al. 2006)  Diagnosis. Trogloneta nojimai can be distinguished from other congeners but except of T. yuensis by the globular abdomen in both sexes ( Figure 1A, B), the palp with a long embolus and a distinctly extended cymbial conductor ( Figure 1E), and a long and narrow scape in the epigyne ( Figure 1G, H). It seems more similar to T. yuensis in share with the structure of palp and the configuration of epigyne, but differs from the latter by the abdomen without a dorsal-posteriorly pointed tubercle in both sexes ( Figure 1A, B vs. Figure 6A, B, E, F), a straight embolic end and lack of cymbial process ( Figure 1E, F vs. Figure 7A-D), and by the oval spermathecae ( Figure 1G vs. Figure 8C, D).
Taxonomic justification. Although the type material of this species has not been examined for this study, the shape of palpal bulb, the configuration of epigyne, the patterns of eyes arrangement, and the distinctly elevated, conical carapace in male leave little doubt that it should be a member of the genus Trogloneta, but not    Diagnosis. This species differs from all species of Trogloneta by the absence of anterior median eyes and the posteriorly pointed abdomen in both sexes (Figure 2A, B, F, G).
Remarks. This is the only species of Trogloneta spider ever found living in the tropical rainforest canopy, and is also a relatively rare six-eyed mysmenid species. We have tried to collect it again in the type locality, hoping to obtain some samples for molecular study but unfortunately, more material was not found.

Trogloneta uncata
Distribution. China (Yunnan). Somatic characters ( Figure 6A, C, E). Coloration: carapace black centrally and marginally, thoracic region dim yellow. Clypeus black. Sternum pale yellow, with a pair of shoulder dark speckles. Abdomen pale yellow, modified by irregular dark spots. Prosoma: carapace sub-round dorsally, conical laterally. Cephalic pars sharply raised, slope forward and backward. Ocular area at apex. AME black, others white. AME  smallest, ALE largest. ALE>PLE>PME>AME. ARE and PRE distinctly procurved. Chelicerae pale yellow, shorter than endites, fang furrow with two promarginal and a single retromarginal teeth. Labium pale, triangular, no fused to sternum. Sternum cordiform, truncated posteriorly. Legs: each segments pale yellow, except tarsi, other segments modified by grey rings distally. A subdistal sclerotized femoral spot on leg I ventrally, but none on leg II. A clasping macroseta on metatarsus I submesial prolaterally. A dorsal seta on each patella distally and tibia proximally. Three trichobothria on tibiae I, II, and IV respectively, but four on tibia III. All metatarsi and tarsi lack trichobothrium. Opisthosoma: elliptic dorsally, triangular laterally, with a tubercle dorso-posteriorly. Spinnerets at lowest position, the anterior ones black, and the posterior ones pale. Colulus small, tongue-shaped. Anal tubercle pale. Palp ( Figure  7A-D): larger than half carapace, strongly sclerotized. Femur 2.5× as long as patella. Patella short. Tibia wider than long, conical, bears a dorsal trichobothrium and a few long setae ventro-marginally. Cymbium large, paracymbium flattened, bears dense long setae. A long cymbial process (aquiline distally, constricted proximally) arisen from inner side subdistal margin of cymbium. Cymbial fold distinct, with long setae. Cymbial conductor extended distally, membranous, attaching with a cluster of setae. Tegulum smooth. Spermatic duct long, visible through subtegulum. A long, fingerlike apophysis derives from the junction between tegulum and subtegulum. Embolus long, arched, gradually tapering to form a hooked end. Embolic end with accessory membrane, hidden behind cymbial conductor.  Figure 6B, D, F) as in male, but larger size and lighter colour than male, ocular area more anterior than in male. Epigyne : Epigynal area elevated ventrally. A long and narrow scape curving basally, copulatory opening at scape distally ( Figure 8B). Epigynal plate transversely rugose ( Figure 8A, C). Inner vulval structure peculiar ( Figure 8D). Copulatory ducts long and bell-shaped proximally ( Figure 8D), most duct areas translucent and coiled around the spermathecae (Figure 8C, D). Atrium broad, subquadrate. Spermathecae clavate, curved. Fertilisation ducts stem from the spermathecae baso-dorsally ( Figure 8D). Inside accessory gland connected with the base of spermathecae ventrally ( Figure 8C).

Trogloneta yuensis Lin & Li, 2013
Remarks. The species is original described on the basis of only a male specimen from Jinyun Mt. of Chongqing City that was donated by Prof Zhisheng Zhang (Southwest University in Chongqing, China) (Lin and Li 2013a). Since then, we have conducted two supplementary collections in the type locality, and not obtained female samples. During 2018, when Mr Guchun Zhou (Hunan Normal University in Changsha, China) was investigating the spider diversity of Yuelu Mt in Changsha City, a large number of samples of this species were obtained by sieving the surface deciduous layers. He presented us with some material for this study.
Taxonomic justification. The type material of Pholcomma yunnanense has been examined as well as its related literatures in this study, the habitus features, the body size, the shape of protruded epigyne with an inflexed space, the broad epigynal plate, the configura-   (Song & Zhu, 1994) comb. n., male left palp (A-D). A prolateral B retrolateral C dorsal D ventral. Abbreviations: Cy cymbium; CyC cymbial conductor; CyF cymbial fold; CyFs setae on cymbial fold; CyP cymbial process; E embolus; Et embolic tip; TA tegular apophysis; Pa patella; PC paracymbium; SD spermatic duct; T tegulum; Ti tibia. Scale bars: 0.20 mm. Figure 11. Trogloneta yunnanense (Song & Zhu, 1994) comb. n., female epigyne (A, B) and vulva (C, D, lactic acid-treated). A, C ventral B lateral D dorsal. Abbreviations: Acc accessory gland; At atrium; CD copulatory ducts; FD fertilization ducts; S spermathecae; Sp scape. Scale bars: 0.20 mm. tion of vulva with a pair of far apart, globular spermathecae depicted in the type and original illustrations (Song and Zhu 1994: figs 4A-C) leave little doubt that the identification is correct. The original illustrations of epigyne and vulva of Pholcomma yunnanense by Song and Zhu (1994) are rather simple and show some differences in comparison with those of Trogloneta denticocleari (Lin & Li, 2008: fig. 17A, D-E), but we have examined the type of Pholcomma yunnanense and the plentiful specimens of Trogloneta denticocleari. Therefore, we consider these subtle differences as being intraspecific variation. To further confirm our judgments using DNA barcoding, a survey at the type locality was specially conducted in August 2018. Unfortunately, the habitat of type locality had become so dry that no samples were obtained. Nevertheless, there are valid reasons to think they are synonyms and T. yunnanense (Song & Zhu, 1994), comb. n. is proposed and transferred from the genus Pholcomma of Theridiidae, as well as T. denticocleari proposed as a new synonym.

Discussion
After this study, the genus Trogloneta contains twelve nominal mysmenid species. Among its members, three species live in caves (T. yunnanense, T. granulum, and T. uncata), and the other nine are found in surface leaf litter (T. canariensis, T. cantareira, T. cariacica, T. madeirensis, T. mourai, T. nojimai, T. paradoxa, and T. yuensis) or in forest canopy (T. speciosum). Although the genus Trogloneta is widely distributed in Europe, Asia, North to South America, and in parts of the Atlantic islands, its many members are clearly endemic species according to the original literature. However, there are two exceptions, and they are T. granulum and T. yunnanense. The former as the type species of this genus was first found in caves of France, and later reported to be widespread on the surface Beech forest floor and in caves of many European countries, such as Austria, Czech Republic, France, Germany, Italy, Poland, and Slovakia. The latter as a new combination proposed in the current paper is also widely distributed in the isolated limestone caves in Southwest China. So far it has not yet been found on the surface. We know that the caves are relatively closed and isolated habitats: why they have such a distribution pattern, how do they get into caves to eventually colonise them, how does the isolation mechanism of the population work, and other questions are worth further study.