Cybaeus koikei, Sugawara & Ihara & Nakano, 2021

Sugawara, Yusuke, Ihara, Yoh & Nakano, Takafumi, 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), pp. 223-233 : 223

Cybaeus koikei sp. nov. Figures 4 , 5 , 6 , 7

Diagnosis.

‘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 6C , 8D ), they can be clearly distinguished by their simple and small palpal bulb (Fig. 6B ) whereas C. melanoparvus have a well-developed palpal bulb (Fig. 8B ). Females of C. koikei are clearly distinguishable by their relatively simple spermathecae (Fig. 6E ); C. melanoparvus has highly complex spermathecae (Fig. 8F ).

Material examined.

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; KUZ Z3744 . Paratypes: Japan • 1 ♀; same locality as for holotype; 35°09.85'N, 135°47.51'E; 14 Oct. 2020; T. Nakano leg.; under a stone along a forest trail; KUZ Z3743 • 1 ♂; same locality as for holotype; 35°9.65'N, 135°47.19'E; 24 Sep. 2012; N. Koike leg.; KUZ Z2364 • 1 ♂; same data as for preceding; NSMT-Ar 20964 • 8 ♀♀; same data as for preceding; KUZ Z2365 • 1 ♀; same data as for preceding; KUZ Z3741 ; 1 ♀; same data as for preceding; NSMT-Ar 20965 .

Additional specimens: Japan • 1 ♂; Kyoto Prefecture, Nantan City, Ashiu ; 35°17.97'N, 135°44.19'E; 14 Nov. 2007; N. Koike leg.; KUZ Z2335 • 1 ♀; Kyoto Prefecture, Kyoto City, Kita, Kumogahata-detanicho ; 35°7.92'N, 135°42.7'E; 7 Nov. 2012; N. Koike leg.; KUZ Z2419 • 4 ♀♀; same data as for preceding; KUZ Z3742 • 1 ♂; Shiga Prefecture, Takashima City, Yokotani Valley ; 35°18.34'N, 135°53.96'E; 21 Oct. 2020; Y. Sugawara leg.; under a stone along a mountain stream; KUZ Z3748 • 1 ♀; same data as for preceding; KUZ Z3745 • 1 ♀; same data as for preceding; KUZ Z3747 • 1 juv.; same data as for preceding; KUZ Z3746 • 1 ♀; same locality as for holotype; 35°9.46'N, 135°47.24'E; 16 Oct. 2019; K. Matsuda leg.; under a stone along a mountain stream; KUZ Z2824 • 2 ♀♀; same locality as for holotype; 18 Jun. 2008; N. Koike leg.; KUZ Z3751 • 1 ♀; same locality as for holotype; 30 Nov. 2008; N. Koike leg.; KUZ Z3752 • 1 ♂; Kyoto Prefecture, Kyoto City, Sakyo, Ohara-kochihiracho , Amida -ji Temple ; 35°8.27'N, 135°49.64'E; 2 Nov. 2008; N. Koike leg.; sifted from fallen leaves; KUZ Z3753 • 1 ♂; Shiga Prefecture, Otsu City, Mt. Shirataki ; 35°14.61'N, 135°52.57'E; 24 Oct. 2012; N. Koike leg.; KUZ Z3754 • 3 ♂♂; same data as for preceding; KUZ Z3755 • 6 ♀♀; same data as for preceding; KUZ Z3756 • 1 ♀; same data as for preceding; KUZ Z3757 • 4 ♂♂; Shiga Prefecture, Otsu City, southeast of Mt. Horai ; 35°11.81'N, 135°53.49'E; 24 Oct. 2012; N. Koike leg.; KUZ Z3759 • 1 ♀; same data as for preceding; KUZ Z3758 • 6 ♀♀; same data as for preceding; KUZ Z3760 • 5 ♂♂; Fukui Prefecture, Tsuruga City, Mt. Nosaka ; 35°36.16'N, 136°1.66'E; 25 Oct. 2012; N. Koike leg.; along a forest trail; KUZ Z3762 • 1 ♀; same data as for preceding; KUZ Z3761 • 9 ♀♀; same data as for preceding; KUZ Z3763 .

Type locality.

Japan, Kyoto Prefecture, Kyoto City, Sakyo, Hanase Pass (35°9.98'N, 135°47.58'E).

Description.

Male (holotype, KUZ Z3744; Figs 4A , 5A, B ). Measurements (mm). CL 2.04, CW 1.53; head 0.91 wide; abdomen 1.71 long, 1.32 wide; ocular area 0.27 long, 0.59 wide; sternum 0.95 long, 0.93 wide. Leg formula, IV > I > II > III; length of legs (femur + patella + tibia + metatarsus + tarsus): leg I 6.03 (1.70 + 0.68 + 1.44 + 1.41 + 0.80); leg II 5.58 (1.55 + 0.64 + 1.28 + 1.33 + 0.78); leg III 4.96 (1.41 + 0.58 + 0.93 + 1.26 + 0.77); leg IV 6.31 (1.67 + 0.60 + 1.41 + 1.75 + 0.87).

Carapace (Fig. 5A ). Head narrow, ca. 0.59 × as wide as thoracic region; thoracic region almost as high as head. AER straight in frontal view; PER almost straight in dorsal view; AME smallest, < 1/2 diameter of other eyes; ocular area ca. 2.1 × wider than long. Clypeus shorter than median ocular area.

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. 5B ). Oval; mid-posterior part widest. Colulus with two groups of 1 or 2 setae.

Palp (Fig. 6A-C ). Patella without PA, lateral surface covered with cluster of robust setae. Tibia almost as long as patella; RTA plate-like, occupying 2/3 of length of tibia. Cymbium ca. 2 × longer than wide, slightly expanded prolaterally. Genital bulb circular in ventral view. Conductor: distal part unelongated; proximal arm short, hooked. Embolus simple, originating and terminating, respectively, at ca. 11 o’clock and ca. 5 o’clock in ventral view.

Color (Fig. 5A, B ). Carapace: head brown, with reticulate dark brown markings; thoracic region yellowish brown, with radiating dark brown bands. Chelicerae, maxillary lobe and labium yellowish brown. Sternum beige. Legs beige to yellowish brown, darker distally, with pale to dark brown annulations. Abdomen: dorsally dark olive-brown with pale brown chevron-like markings; ventrally pale brown.

Female (paratype, KUZ Z3743; Fig. 5C, D ). Measurements (mm). CL 2.17, CW 1.51; head 1.00 wide; abdomen 2.03 long, 1.35 wide; ocular area 0.31 long, 0.66 wide; sternum 1.00 long, 0.98 wide. Leg formula, IV > I > II > III; length of legs (femur + patella + tibia + metatarsus + tarsus): leg I 5.39 (1.57 + 0.62 + 1.34 + 1.20 + 0.66); leg II 5.05 (1.54 + 0.60 + 1.13 + 1.14 + 0.64); leg III 4.51 (1.35 + 0.55 + 0.89 + 1.10 + 0.61); leg IV 5.71 (1.64 + 0.60 + 1.30 + 1.45 + 0.72).

Carapace (Fig. 5C ). Head ca. 0.66 × as wide as thoracic region; thoracic region slightly higher than head. AER almost straight in frontal view; PER slightly recurved in dorsal view; AME smallest, < 1/2 diameter of other eyes; ocular area ca. 2.1 × wider than long. Clypeus shorter than median ocular area.

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. 5D ). Same as for male holotype.

Genitalia (Figs 6D, E , 7 ). Posterior margin of epigynal plate weakly ‘M’ -shaped. Atrium located posteromedially on epigyne and with 2 distinct copulatory openings. CPs separated on both sides of atrium; CD long running anteromedially. Each of SH and SS slightly bulbous; SH small, with a few primary pores anteromedially; SS running posteromedially; SB large, globular, directed anterolaterally; Bennett’s gland located anteriorly at connection between SS and SB.

Colour (Fig. 5C, D ). Carapace: head brown, with reticulate dark brown markings; thoracic region yellowish brown, with radiating dark brown bands. Chelicerae, maxillary lobe and labium dark yellowish-brown. Sternum light yellowish-brown. Legs pale brown to yellowish brown, darker distally, with medium to dark brown annulations. Abdomen: dorsally dark olive-brown with pale brown chevron-like markings; ventrally light yellowish-brown to brown.

Variation.

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).

Etymology.

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.

Remarks.

This species constructs a ‘V-shaped’ retreat (Fig. 4B ), which is the most common type of retreat among Japanese Cybaeus ( Ihara 2006, 2009b; Ihara et al. 2021). Because all specimens collected in 2019 and 2020 were found under stones, it is possible that this species prefers to construct its retreat on the underside of stones rather than in decaying substrates.

According to the nuclear ITS-1 sequences obtained from the holotype male ( KUZ Z3744) and the paratype female ( KUZ Z3743), the males and females examined in this study clearly belong to the same species newly described here. Their ITS-1 sequences through the overlapping aligned positions (451 bp) are completely identical to each other.

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 ( Kobayashi 2006; Matsuda et al. 2020). Additionally, males of C. koikei sp. nov. are conclusively distinguishable from those of C. daimonji and C. kiiensis by the lack of PA on its palp. Males of both C. daimonji and C. kiiensis possess a PA on their pedipalp ( Kobayashi 2006; Matsuda et al. 2020).

Figures

Figure 4. Cybaeus koikei sp. nov. and its retreat. A. Dorsal view of holotype male (KUZ Z 3744); B. Retreat of paratype female (KUZ Z 3743); photo taken at the type locality; OP, opening of retreat. Scale bars: 1 mm (A.); 5 mm (B.).

Figure 5. Cybaeus koikei sp. nov., male holotype (KUZ Z 3744: A, B) and female paratype (KUZ Z 3743: C, D). A, C. Prosoma, dorsal view; B, D. Abdomen, dorsal view. Scale bars: 500 µm.

Figure 6. Cybaeus koikei sp. nov., male holotype (KUZ Z 3744: A-C) and female paratype (KUZ Z 3743: D, E). A. Cymbium of left palp, dorsal view; B. Bulb of left palp, ventral view; EM, embolus; PCO, proximal arm of conductor; C. Left palp, retrolateral view; RTA, retrolateral tibial apophysis; D. Epigyne, ventral view; PME, posterior margin of epigynal plate; E. Spermathecae, dorsal view; BG, Bennett's gland; CD, copulatory duct; FD, fertilization duct; PP, primary pore; SB, spermathecal base; SH, spermathecal head; SS, spermathecal stalk. Scale bars: 250 µm (A, B.); 500 µm (C.); 100 µm (D, E.).

Figure 7. Cybaeus koikei sp. nov., schematic drawing of epigyne and spermathecae based on female paratype (KUZ Z 3743). A. Ventral view; CD, copulatory duct; CP, copulatory pore; FD, fertilization duct; PME, posterior margin of epigynal plate; SB, spermathecal base; SH, spermathecal head; SS, spermathecal stalk; B. Dorsal view; BG, Bennett's gland; CD, copulatory duct; FD, fertilization duct; PP, primary pore; SB, spermathecal base; SH, spermathecal head; SS, spermathecal stalk. Duct from CP to before SH colored in red; SH to before SB colored in blue; SB colored in green. Scale bar: 50 µm.

Figure 8. Cybaeus melanoparvus Kobayashi, from Mt. Bungen, Shiga Prefecture (KUZ Z 3765), male (A-D) and females (E, F). A. Cymbium of left palp, dorsal view; B. Bulb of left palp, ventral view; PCO, proximal arm of conductor; C. Bulb of left palp, prolateral view; EM, embolus; D. Left palp, retrolateral view; PCO, proximal arm of conductor; RTA, retrolateral tibial apophysis; E. Epigyne, ventral view; PME, posterior margin of epigynal plate; F. Spermathecae, dorsal view; BG, Bennett's gland; FD, fertilization duct; PP, primary pore; SB, spermathecal base; SH, spermathecal head; SS, spermathecal stalk. Scale bars: 500 µm (A-D.); 100 µm (E, F.).