A review of Solenysa spiders from Japan (Araneae, Linyphiidae), with a comment on the type species S. mellotteei Simon, 1894

Abstract The present paper gives a review of Solenysa species from Japan and provides a solution for the species bearing the generotype name Solenysa mellotteei Simon, 1894. A total of six species are recorded, including two new species Solenysa macrodonta sp. n. and Solenysa trunciformis sp. n. The species collected from Kawasaki (NSMT-Ar 11154) and Hachioji should be the generotype Solenysa mellotteei, with Solenysa akihisai Tu, 2011, syn. n. as its junior synonym. To distinguish these congeneric species from each other, their genital characters are provided in detail based on images collected by scanning electron microscopy and light microscopy.


Introduction
The spider genus Solenysa was erected by Simon (1894) to accommodate the linyphiid species, S. mellotteei Simon, 1894, which was collected from Japan by a French diplomat, A. Mellottée. Other Solenysa species were described successively from other places in Japan, the Chinese mainland, Taiwan, and the Korean Peninsula (see review by Tu and Li 2006). In recent studies, several new species were sorted from the Solenysa collections deposited in the Department of Zoology, National Museum of Nature and Science (ex National Science Museum, Tokyo), Japan (Tu et al. 2007, Tu and Hormiga 2011, Ono 2011). Prior to this study, there were five Solenysa species reported from Japan: S. mellotteei Simon, 1894 (type locality: Yokohama, Kanagawa Prefecture), S. akihisai Tu, 2011 (type locality: Hachioji, Tokyo), S. ogatai Ono, 2011 (type locality: Okazaki-shi, Aichi Prefecture), S. partibilis Tu, Ono & Li, 2007 (type locality: Mt. Ibuki-yama, Shiga Prefecture) and S. reflexilis Tu, Ono & Li, 2007 (type locality: Itsuki-mura, Kumamoto Prefecture). According to results of a phylogenetic analysis based on morphological data, the twelve known Solenysa species were divided into four groups, and the four species from Japan share a complex of genital characters, forming the S. mellotteei group (Tu and Hormiga 2011).
As more species were recognized, a problem regarding the type species of Solenysa emerged. Generally, the Solenysa species occurring in Japan are endemic, have a restricted distribution with little overlap (Fig. 7). Small in body size, similar in somatic features and genital morphology, it is difficult to distinguish them from each other without examining their genitalia in detail (Tu and Hormiga 2011). Consequently, all Solenysa spiders collected from the islands of Japan have long been identified as S. mellotteei (Oi 1960, Yaginuma 1986, Irie and Saito 1987, Chikuni 1989, Lee et al. 2004, Tu and Li 2006. Redescriptions for the species currently bearing the generotype name, S. mellotteei, in reviews of Solenysa were not based on the type material Li 2006, Tu andHormiga 2011) and the species are different from those collected from the places more adjacent to the inferred type locality (Ono 2011). It is necessary to make a review to distinguish the species of the S. mellotteei group and to establish the identity of the generotype S. mellotteei. From the materials collected throughout the islands of Japan, we identified six species in total, including two new species and one new synonymy. In the present study, all these Solenysa spiders were studied by using scanning electric microscopy (SEM) and light microscopy to show genital characters in detail. Descriptions for the new species and redescriptions for the known species are presented.

Materials and methods
Specimens were examined and measured by using a Leica MZ16A stereo microscope. Further details, such as epigynes, were studied with a Leica DM5500B compound microscope. Digital images were taken with a Leica DFC 500 camera and as a composite of multiple focus images assembled using the software package Leica Application Suite. Epigynes were cleared in methyl salicylate (Holm 1979) for examination under the microscope and temporarily mounted as described by Grandjean (1949) and Coddington (1983). SEM images were taken by using a Hitachi S-3400N scanning electron microscope at China Agriculture University. For SEM examination, the specimens were prepared as described by Álvarez-Padilla and Hormiga (2008). The non-chitinous abdominal tissue was digested with Sigma Pancreatin LP 1750 enzyme complex to expose the internal structures for examination. Due to the unavailability of specimen, no SEM image provided for the male palp of S. reflexlis.

Anatomical abbreviations used in the text and figures
Description. See Tu and Li (2006) and Tu and Hormiga (2011). Distribution. Japan, Chinese mainland, Taiwan, Korea.
Comments. The subfamily placement of Solenysa remains controversial as its complex type of male palp with well developed lamella characteristica and terminal apophysis is like those in Micronetinae Hull, 1920, but the simple type of epigyne is like those in Erigoninae Emerton, 1882. Based on the movable epigyne, Saaristo (2007) included it in his new subfamily Ipainae Saaristo, 2007. However, the results of a phylogenetic analysis of Linyphiidae queried the monophyly of "ipaines", and suggested that "micronetines" and erigonines form a monophyletic group (Arnedo et al. 2009). Furthermore, the results of a phylogenetic analysis of erigonines based on morphological data showed that all Solenysa species form a monophyly robustly supported by a long list of synapomorphies, and other synapomorphies suggested its close relationship with erigonines although its sister group remained unresolved (Tu and Hormiga 2011). Accordingly, the well-developed lamella characteristica and terminal apophysis in Solenysa should be regarded as homologous to those of "micronetines" and secondarily lost in erigonines; their simple type epigyne also derived from the complex type of "micronetines". The morphology of solenoid in Solenysa is different from the extensive basal parts in Acanoides beijingensis Sun, Marusik &Tu, 2014 andA. hengshanensis (Chen &Yin, 2000) (Sun et al. 2014: figs 4G, 5G), and in Wubanoides uralensis (Pakhorukov, 1981), Epibellowia enormita (Tanasevitch, 1988) and E. septentrionalis (Oi, 1960) (Tanasevitch 1996: figs 7-9). Whether the movable epigyne has a single origin or independently evolved multiple times in linyphiids needs to be tested in future studies.
A phylogenetic analysis based on morphological data (Tu and Hormiga 2011) suggested that the twelve known Solenysa species are divided into four clades. Among them, the four species occurring in Japan formed a monophyletic clade, unambiguously supported by the following synapomorphies: the presences of hook shaped cymbial probasal process, half rounded Solenysa tegular triangle and copulatory grooves enter the spermathecae from the outer sides.
Diagnosis. Males of S. mellotteei group are distinguished from all other three groups by the spiral plate-shaped embolus (Fig. 3E), the hook-shaped cymbial probasal process and by the half rounded Solenysa tegular triangle ( Fig. 2A). Females are characterized by the dorsoventrally folded solenoid (Figs 4C, 5C), the spherical spermathecae and the pocket shaped copulatory grooves entering the spermathecae from the outer sides ( Fig. 1D).
Description. All Solenysa species have quite uniform somatic morphology. Somatic characters as in the genus description (see also Li 2006, Tu andHormiga 2011).
Male palp ( Fig. 2A-B). Tibia twice as long as patella, with proximal process furnished by two long bristles. Cymbium with hook-like proximal process and small retrolateral process, forming articulation with proximal arm of U-shaped paracymbium. Tegulum with half rounded Solenysa tegular triangle and stout distal suprategular apophysis. Embolic division (Fig. 6): embolus spiral plate shaped with two apophyses, one at outer margin, and one distally (Fig. 3E). Radix embedded within membranous area connecting terminal apophysis and lamella characteristica (Figs 1C, 2B). Terminal apophysis divided into three parts, with median one as enlarged sclerite. Lamella characteristica with three well-developed branches, anterior branch (LC 1 ) stout and extending forward, following embolus trajectory; median one (LC 2 ) long and slender, dragging backwards and pointing forward, bifid in some species (Fig. 3A); posterior one (LC 3 ) sharp and strongly sclerotized, bifid in some species (Fig. 3B).
Distribution. Japan (Honshu, Shikoku, Kyushu, Fig. 7). Diagnosis. Solenysa mellotteei is similar to S. partibilis and S. ogatai in male palps having the posterior branch of lamella characteristica (LC 3 ) divided into two parts (Fig. 6A, C, D), and in females having an apple-shaped epigyne. Males can be distinguished by: the anterior part of LC 3 is flag-shaped in S. mellotteei (Fig. 2B), long spike-shaped in S. ogatai (Fig. 3C) and S. partibilis (Fig. 3D); the posterior part of LC 3 S-curved in S. ogatai (Fig. 3C), L-curved in S. partibilis (Fig. 3D). Females can be distinguished by the inverse triangular epigynal collar and the dorsal plate as wide as long in S. mellotteei (Fig. 4A, Tu and Hormiga 2011: fig. 8I), the dorsal plate wider than long in S. partibilis and S. ogatai (Fig. 5B, D), and the epigynal collar more than four times wider than long in S. ogatai (Fig. 5B), less than twice wider than long in S. partibilis (Tu and Hormiga 2011: fig. 11I).

Solenysa mellotteei Simon, 1894
Description. S. mellotteei has somatic morphology typical of Solenysa (Fig. 1A, B, E) and a genital pattern of the S. mellotteei group ( Fig. 2A-B). For somatic and genital characters, see the description provided by Tu and Hormiga (2011) for S. akihisai, the junior synonym of S. mellotteei.
Comments. The problem with the identification of the generotype Solenysa mellotteei arose because Solenysa species occurring in Japan, previously all identified as S. mellotteei, are now distinguished as six species. Since most of them have restricted distributions without any overlap (Fig. 7), it has long remained ambiguous which species is the original S. mellotteei described by Simon (1894). The type material of S. mellotteei was not located (Tu and Li 2006), and the original description by Simon (1894) did not provide detailed information about the type locality. According to Ono (2011), the French diplomat A. Mellottée, who had spent only two years in Japan, stayed in the foreign settlement at Yokohama and collected spiders in the surrounding area. All his collections were contributed to the National Museum of Natural History, Paris (Ono 1987, Takahashi 2000 and studied by Simon (1886aSimon ( , 1886bSimon ( , 1889Simon ( , 1893Simon ( , 1894Simon ( , 1895. For that reason, Ono (2011) inferred the type locality of S. mellotteei should be Yokohama, Kanagawa Prefecture. In the first review of the genus by Tu and Figure 2. Solenysa mellotteei. A male palp, retrolateral B ditto, ventral C anterior part of male abdomen, ventral, shows epiandrous fusules absent and smooth book lung cover D female palp, shows tarsus claw absent E male chelicera, ectal, shows stridulatory striae F female chelicerae. ATA anterior terminal apophysis; DSA distal suprategular apophysis; E embolus; LC lamella characteristica; LC 1 anterior LC branch; LC 2 median LC branch; LC 3 posterior LC branch; MTA median terminal apophysis; P paracymbium; PBP probasal cymbial process; PTA posterior terminal apophysis; PTP proximal tibial process; RLP cymbial retrolateral process; STT Solenysa tegular triangle; T tegulum. [Scale bars: mm] Li (2006), the redescription of S. mellotteei was based on a pair of specimens sent by a Japanese scholar and did not include any collecting data. In the phylogenetic revision of Solenysa (Tu and Hormiga 2011), the supplementary material of the same species did not come from the type locality, but from Esuzaki, Susami-cho, Wakayama Prefecture. However, specimens collected from Hachioji, Tokyo, which is much closer to the type locality (Fig. 7), were proposed as a new species S. akihisai. In the present study we examined material collected from three localities adjacent to Yokohama: Hachioji, Kawasaki (NSMT-Ar 11154) and Miura (Fig. 7), as well as specimens from Mito, and found that they are the same species, which should bear the generotype name S. mellotteei, and S. akihisai is a junior synonym of it. The materials collected from Wakayama Prefecture, and those from Shikoku Island are proposed here as a new species S. trunciformis sp. n. Diagnosis. The male palp of Solenysa macrodonta sp. n. is similar to those of S. trunciformis sp. n. and S. refrexilis in the presence of a central tooth at the membranous area embedded the radix (Figs 1C, 3A, 6B), the forked apex of the median branch of lamella characteristica and the long spike-shaped posterior branch (Fig. 3A-B). They can be distinguished from each other by the median part of terminal apophysis, which has a serrate margin in S. macrodonta sp. n. (Fig. 3A), but with two anterior protrusions in S. trunciformis sp. n. (Fig. 3B) and S. refrexilis (Tu et al. 2007: fig. 1D), which is truncate in the former species and pointed in the latter species. The short epigyne of S. macrodonta sp. n. is similar to those of S. partibilis and S. reflexilis, having the dorsal plate wider than long (Fig. 5D). They can be distinguished from each other by the maximum width in ventral view; at the anterior part in S. partibilis (Fig. 5C), in the middle in S. macrodonta sp. n. (Fig. 4C), and posterior in S. reflexilis (Fig. 4E), which also has a straight posterior margin.
Male palp (Fig. 3B). General male palpal characters are as in the description for the S. mellotteei group. Embolic division (Fig. 6B): radix embedded in the central membranous area connecting with terminal apophysis and lamella characteristica, from where a central tooth protrudes. Median part of terminal apophysis as large sclerite with serrated margin. Anterior branch of lamella characteristica reduced, stout and extending forward following embolus; the median branch ribbon-like, long and slender, dragging backwards, then folding forward, with forked apex, one sharp, one with threaded margin; the posterior long spike-shaped and strongly sclerotized.
Epigyne (Fig. 4C-D). Twice as wide as long in ventral view, with maximum width in the middle. Posterior margin centrally incised. Dorsal plate wider than long.
Etymology. The species name is based on the Latin 'macrodontus' in reference to the large central tooth protruding from the membranous area connecting with terminal apophysis and lamella characteristica (Fig. 3A).
Distribution. Japan (Honshu, Fig. 7).  Diagnosis. The genital characters of S. ogatai are very similar to those of S. partibilis (Figs 3C-F, 6C-D). The male palp is diagnosed by the posterior branch of the lamella characteristica with two long free ends, the longer one in S. ogatai is sigmoid curved in ventral view (Fig. 3C), almost a circle in anterior view (Fig. 3E), while in S. partibilis L-curved in ventral view (Fig. 3D), half circle in anterior view (Fig. 3F). The epigyne can be distinguished by the epigynal collar, which is more than four times wider than long in S. ogatai (Fig. 5B), but less than twice as wide than long in S. partibilis (Tu and Hormiga 2011: fig. 11I).
Description. Somatic characters as in the genus description and for genital characters see Ono (2011).

Solenysa reflexilis
Distribution. Japan (Kyushu, Fig. 7).  ) are similar to those of S. macrodonta sp. n. and S. refrexilis; to distinguish them see the diagnosis for S. macrodonta sp. n. The female is distinguished by the apple-shaped epigyne with a rectangular epigynal collar (Fig. 5F).
Description. Somatic characters as in the genus description and genital characters as in the descriptions for S. mellotteei by Tu and Li (2006) and Tu and Hormiga (2011).
Etymology. The species name comes from the Latin 'trunciformis' in reference to truncate apex of anterior protrusion in front of median terminal apophysis (Fig. 1C).