Research Article |
Corresponding author: Takafumi Nakano ( nakano@zoo.zool.kyoto-u.ac.jp ) Academic editor: Danilo Harms
© 2021 Yusuke Sugawara, Yoh Ihara, Takafumi Nakano.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Sugawara Y, Ihara Y, Nakano T (2021) A new species of Cybaeus L. Koch, 1868 (Araneae, Cybaeidae) with simple genitalia from central Japan is the sister species of C. melanoparvus Kobayashi, 2006 with elongated genitalia. Zoosystematics and Evolution 97(1): 223-233. https://doi.org/10.3897/zse.97.64473
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Spiders of the genus Cybaeus L. Koch, 1868 exhibit two major centers of diversity: Western North America and Japan. Several Japanese Cybaeus possess an elongated embolus in the male palp and elongated tubular spermathecae in the female genitalia. Here we describe Cybaeus koikei sp. nov. from central Honshu, Japan, which has an unelongated embolus and bulbous spermathecae. Phylogenetic analyses using nuclear and mitochondrial gene markers clearly support the monophyly of C. koikei sp. nov. and Cybaeus melanoparvus Kobayashi, 2006, a species with elongated genitalia. Both species share a similar habitus and a cluster of robust setae on the lateral surface of the male palpal patella. The latter is considered a synapomorphy for C. koikei sp. nov. and C. melanoparvus. A supplementary description of the spermathecae of C. melanoparvus is also provided.
Arachnida, Cybaeus koikei sp. nov., molecular phylogeny, RTA clade, spermatheca
Epigean spiders of the genus Cybaeus L. Koch, 1868 are remarkably diverse in Western North America and the Japanese Archipelago (
The extraordinary species-richness of Japanese Cybaeus may be caused by ecological attributes, such as poor dispersal abilities. Cybaeus spiders are not known to disperse via ballooning (
The morphological diversity of genitalia in Cybaeus is also noteworthy (
The Cybaeus fauna in central Honshu, especially around Lake Biwa, was well documented by
Cybaeus spiders were collected from central Honshu (Fig.
Map showing collection localities of samples in the present study. Circles, locations of the present specimens of Cybaeus koikei sp. nov.; squares, locations of the present specimens of Cybaeus melanoparvus Kobayashi; triangles, known localities of C. melanoparvus in
Terminology of morphological characters and the chaetotaxy of leg macrosetae follows
Three nuclear and three mitochondrial markers for phylogenetic analyses were selected following previous studies (
Phylogenetic relationships of the Cybaeus spiders were inferred based on the dataset comprising 28S, ITS-1, H3, COI, 12S and 16S sequences. In addition to the newly obtained 8 sequences of C. koikei sp. nov. and C. melanoparvus, 85 sequences of 17 species (see dataset in
Samples of the Cybaeus species used for the molecular analyses. The information on the voucher is accompanied by the collection locality and the INSD accession numbers. Sequences marked with an asterisk (*) were obtained for the first time in this study. Samples marked with two asterisks (**) were only used for the neighbor network analysis.
Taxa | Voucher # | Locality | INSD # | |||||
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28S rRNA | ITS-1 | histone H3 | COI | 12S rRNA | 16S rRNA | |||
C. koikei sp. nov. |
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Hanase Pass, Kyoto, Honshu | LC601900* | LC601903* | LC601902* | LC601901* | ||
C. koikei sp. nov.** |
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Hanase Pass, Kyoto, Honshu | LC601897* | |||||
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Hanase Pass, Kyoto, Honshu | LC601898* | ||||||
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Hanase Pass, Kyoto, Honshu | LC601899* | ||||||
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Yokotani Valley, Shiga, Honshu | LC601904* | ||||||
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Yokotani Valley, Shiga, Honshu | LC601905* | ||||||
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Yokotani Valley, Shiga, Honshu | LC601906* | ||||||
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Yokotani Valley, Shiga, Honshu | LC601907* | ||||||
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Mt. Shirataki, Shiga, Honshu | LC601908* | ||||||
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Mt. Shirataki, Shiga, Honshu | LC601909* | ||||||
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Mt. Horai, Shiga, Honshu | LC601910* | ||||||
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Mt. Nosaka, Fukui, Honshu | LC601911* | ||||||
C. melanoparvus Kobayashi, 2006 |
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Sakauchihirose, Gifu, Honshu | LC601893* | LC601896* | LC601895* | LC601894* | ||
C. melanoparvus Kobayashi, 2006 ** |
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Mt. Bungen, Shiga, Honshu | LC601892* | |||||
C. aikana Ihara, Koike & Nakano, 2021 |
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Mt. Yuwandake, Amamioshima Island | LC552248 | LC552250 | LC552249 | LC552246 | LC552247 | |
C. amamiensis Ihara, Koike & Nakano, 2021 |
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Mt. Yuwandake, Amamioshima Island | LC552236 | LC552239 | LC552238 | LC552237 | LC552234 | LC552235 |
C. ashikitaensis (Komatsu, 1968) |
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Itsuki, Kumamoto, Kyushu | LC552192 | LC552195 | LC552194 | LC552193 | LC552191 | |
C. daimonji Matsuda, Ihara & Nakano, 2020 |
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Mt. Daimonjiyama, Kyoto, Honshu | LC529207 | LC529208 | LC529206 | LC529209 | LC529211 | LC529210 |
C. fuujinensis (Komatsu, 1968) |
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Fujindo Cave, Kumamoto, Kyushu | LC552187 | LC552190 | LC552189 | LC552188 | LC552186 | |
C. gotoensis (Yamaguchi & Yaginuma, 1971) |
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Iana Cave, Fukuejima Island, Goto Islands | LC552201 | LC552204 | LC552203 | LC552202 | ||
C. hikidai Ihara, Koike & Nakano, 2021 |
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Mt. Nagodake, Okinawajima Island | LC552264 | LC552267 | LC552266 | LC552265 | LC552262 | LC552263 |
C. ishikawai (Kishida, 1940) |
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Near Ryugado Cave, Kochi, Shikoku | LC552276 | LC552278 | LC552277 | LC552274 | LC552275 | |
C. itsukiensis Irie, 1998 |
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Tsuzurasedo Cave, Kumamoto, Kyushu | LC552182 | LC552185 | LC552184 | LC552183 | ||
C. kodama Ihara, Koike & Nakano, 2021 |
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Hanayama Trail, Yakushima Island | LC552215 | LC552218 | LC552217 | LC552216 | ||
C. kompiraensis (Komatsu, 1968) |
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Kompirado Cave, Kochi, Shikoku | LC552179 | LC552181 | LC552180 | LC552178 | ||
C. kunisakiensis Ihara, 2003 |
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Mt. Futagosan, Oita, Kyushu | LC552197 | LC552200 | LC552199 | LC552198 | LC552196 | |
C. kumadori Ihara, Koike & Nakano, 2021 |
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Mt. Yaguradake, Kuroshima Island, Mishima Islands | LC552225 | LC552228 | LC552227 | LC552226 | LC552223 | LC552224 |
C. okumurai Ihara, Koike & Nakano, 2021 |
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Kunigami, Tanegashima Island | LC552280 | LC552282 | LC552281 | LC552279 | ||
C. striatipes Bösenberg & Strand, 1906 |
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Mt. Rausudake, Shari, Hokkaido | LC552174 | LC552177 | LC552176 | LC552175 | ||
C. tokunoshimensis Ihara, Koike & Nakano, 2021 |
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Mt. Inokawadake, Tokunoshima Island | LC552253 | LC552256 | LC552255 | LC552254 | LC552251 | LC552252 |
C. yakushimensis Ihara, Koike & Nakano, 2021 |
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Shiratani-unsuikyo Valley, Yakushima Island | LC552207 | LC552209 | LC552208 | LC552205 | LC552206 |
Phylogenetic trees were reconstructed using maximum likelihood (ML) and Bayesian inference (BI). The best-fit partition scheme and models for both analyses were identified based on the corrected Akaike information criterion (AICc) using PartitionFinder v. 2.1.1 (
To confirm whether males and females of the present specimens belong to C. koikei sp. nov., and also to recognize their geographic structures, genetic relationships among 12 samples of C. koikei sp. nov. and two individuals of C. melanoparvus were inferred using relatively fast-evolving nuclear ITS-1 sequences. A neighbor network analysis was conducted using Neighbor-Net (
The obtained BI (mean ln L = –10901.95; Fig.
Bayesian inference tree (mean ln L = –10901.95) for 3428 bp of 28S rRNA, ITS-1, H3, COI, 12S rRNA and 16S rRNA markers. Numbers on nodes represent ML bootstrap values and Bayesian posterior probabilities. Species names colored in black and those in red denote that they possess ‘type 1’, and ‘type 2’ genitalia, respectively.
The SplitsTree network (Fig.
Family Cybaeidae Banks, 1892
Amaurobius tetricus C.L. Koch, 1839.
‘Small-sized’ Japanese Cybaeus. Both sexes of C. koikei are most similar to those of C. melanoparvus. Although males of these two species resemble each other in lacking a palpal PA and having a palpal tibia that is almost as long as the palpal patella (Figs
Holotype: Japan • ♂; Kyoto Prefecture, Kyoto City, Sakyo, Hanase Pass; 35°9.98'N, 135°47.58'E; 14 Oct. 2020; T. Nakano leg.; under a stone along a mountain stream;
Additional specimens: Japan • 1 ♂; Kyoto Prefecture, Nantan City, Ashiu; 35°17.97'N, 135°44.19'E; 14 Nov. 2007; N. Koike leg.;
Japan, Kyoto Prefecture, Kyoto City, Sakyo, Hanase Pass (35°9.98'N, 135°47.58'E).
Male (holotype,
Carapace (Fig.
Mouthparts. Chelicerae slightly geniculate, promargin of fang furrow with 3 teeth (median one largest), retromargin with 4 teeth and 3 or 4 denticles, and basally with lateral condyle. Labium wider than long.
Leg macrosetae. Leg I: tibia p4, r0, v2-2-2-2; metatarsus p4, r1, v2-2-2. Leg II: tibia p3, r0, v2-2-2-2; metatarsus p4, r2, v2-2-3.
Abdomen (Fig.
Palp (Fig.
Cybaeus koikei sp. nov., male holotype (
Color (Fig.
Female (paratype,
Carapace (Fig.
Mouthparts. Chelicerae slightly geniculate, teeth and denticles of fang furrow not observable and covered by long setae; basally with lateral condyle. Labium wider than long.
Leg macrosetae and abdomen (Fig.
Genitalia (Figs
Cybaeus koikei sp. nov., schematic drawing of epigyne and spermathecae based on female paratype (
Colour (Fig.
Males. Measurements (mean±1SD, followed by ranges in parentheses; n = 19, including holotype and paratypes): CL 2.05±0.11 (1.87–2.23), CW 1.50±0.10 (1.33–1.65); CW/CL 0.73±0.03 (0.70–0.82); TibIL 1.45±0.07 (1.31–1.59); TibIL/CL 0.71±0.02 (0.68–0.74). Legs longer than those of females.
Females. Measurements (n = 42, including paratypes): CL 2.06±0.17 (1.67–2.31), CW 1.41±0.12 (1.06–1.57); CW/CL 0.68±0.02 (0.64–0.75); TibIL 1.30±0.12 (1.04–1.51); TibIL/CL 0.63±0.03 (0.53–0.68).
The specific name is dedicated to Mr Naoki Koike who assembled the large collection of Japanese Cybaeus spiders that is now kept at Kyoto University, including the specimens of this new species.
This species constructs a ‘V-shaped’ retreat (Fig.
According to the nuclear ITS-1 sequences obtained from the holotype male (
Two species, C. daimonji and C. kiiensis Kobayashi, 2006 whose spermathecae are grouped into ‘type 1’, occur in sympatry with C. koikei sp. nov. through montane habitats on the western side of Lake Biwa. However, they are clearly distinguishable by body size: the body length of C. koikei sp. nov. reaches ca. 4 mm whereas that of C. daimonji and C. kiiensis reaches ca. 6 mm and ca. 2.5 mm, respectively (
Cybaeus melanoparvus
Kobayashi, 2006: 41–42, figs 53–57;
Japan • 1 ♂, 1 ♀; Gifu Prefecture, Ibi-gun, Ibigawa Town, Sakauchihirose; 35°36.77'N, 136°25.16'E; 27 Oct. 2012; N. Koike leg.;
(Figs
Cybaeus melanoparvus Kobayashi, from Mt. Bungen, Shiga Prefecture (
The present specimens were unquestionably identified as C. melanoparvus by features of the male palp and female genitalia; that is, the remarkably developed conductor and complicated tubular spermathecae.
Cybaeus melanoparvus Kobayashi, schematic drawing of epigyne and spermathecae, based on female specimen (
The present study could successfully document the positions of PP and BG in the spermathecae of this species for the first time. Because PPs were located at the dorsal surface of the duct near its anterior tip, this tubular structure, which was referred to as an ‘anterior duct’ by
Cybaeus koikei sp. nov. shares generally similar external features with C. melanoparvus; that is ‘small-sized’ body length and blackish color, as well as a cluster of robust setae on the lateral surface of the male palpal patella (see also
Given the close sister relationship between C. koikei sp. nov. and C. melanoparvus, their morphological similarities, especially the cluster of robust setae on the palpal patella, are probably synapomorphies between the two species. The positions of primary pores and Bennett’s glands in their spermathecae are noticeable as well. Although the tubular spermathecae of C. melanoparvus are complex, features of its primary pores and spermathecal base are essentially concordant with those of C. koikei sp. nov.; the primary pores of both species are located mid-anteriorly and their globular spermathecal bases are directed antero-laterally. These similarities imply that the spatial positions of the spermathecal head and base in C. melanoparvus have not been drastically changed from their most recent common ancestor.
The geographical range of C. koikei sp. nov. and C. melanoparvus is also noteworthy. The new species inhabits montane forests along the western side of Lake Biwa and C. melanoparvus is known only from montane regions at the eastern side of the lake (Fig.
Our previous study (
The authors are grateful to Naoki Koike for providing specimens, and to three anonymous reviewers and Dr Danilo Harms (Universität Hamburg) for their constructive comments and suggestions on this manuscript. We also thank Dr Koshiro Eto (Kitakyushu Museum of Natural History & Human History) for allowing the last author to use his map-graphic, and Dr Harry Taylor (Edanz Group) for editing a draft of this manuscript. This study was supported by JSPS KAKENHI Grant Number JP18K14780.
Table S1
Data type: molecular data
Explanation note: Primers for polymerase charin reactions (PCR) and cycle sequencing reactions, and PCR conditions used in this study.
Table S2
Data type: molecular data
Explanation note: The selected partitioning schemes and molecular evolutionary models for the phylogenetic analyses.