Theridiosoma nigrivirgatum, Suzuki & Hiramatsu & Tatsuta, 2022

Suzuki, Yuya, Hiramatsu, Takehisa & Tatsuta, Haruki, 2022, Two new species and a new genus of ray spiders (Araneae, Theridiosomatidae) from the Ryukyu Islands, southwest Japan, with notes on their natural history, ZooKeys 1109, pp. 67-101 : 67

Theridiosoma nigrivirgatum sp. nov.

[New Japanese name: Jyabara-karakara-gumo] Figs 1 , 2 , 3 , 11 , 12C , 13A-C , 15A

Type material.

Holotype: Japan, Okinawa Is. (Okinawa Prefecture): ♂ (NSMT-Ar 21717), Urasoe City, Nakama, Urasoe-daikoen Park (26°14'50.2"N, 127°43'49.8"E, alt. 112 m), 8 Mar. 2021, Y. Suzuki leg. Paratypes: 2 ♀, same data as the holotype; 1 ♂ 1 ♀ (NSMT-Ar 21718), Urasoe City, Nakama, Urasoe-daikoen Park (26°14'59.2"N, 127°43'54.6"E, alt. 64 m), 16 Apr. 2021, Y. Suzuki leg.; 1 ♂ 1 ♀ (NSMT-Ar 21719), Nakagami District, Nishihara Town, Senbaru (26°15'01.8"N, 127°45'57.8"E, alt. 104 m), 25 Apr. 2021, Y. Suzuki leg.

Other material examined.

Japan, Okinawa Is. (Okinawa Prefecture): 10 ♀, Naha City, Shuri-sueyoshi Town, Sueyoshi-koen Park (26°13'45.0"N, 127°42'49.8"E, alt. 49 m), [7 Mar. 2021 (1 ♀), 8 Mar. 2021 (9 ♀)], Y. Suzuki leg. ; 5 ♀, Nakagami District, Nishihara Town, Tanabaru , Tanabaru Gusuku (26°14'44.3"N, 127°45'16.4"E, alt. 141 m), 8 Apr. 2021, Y. Suzuki leg. ; 2 ♂, Kunigami District, Kunigami Village, Yona (26°44'35.2"N, 128°14'55.1"E, alt. 195 m), 19 Sep. 2021, Y. Suzuki leg. ; 1 ♀, Ôgusuku (26°17'09.5"N, 127°48'13.1"E, alt. 136 m), Nakagami Distirct, Kitanakagusuku Village , R. Serita leg. Kume Is. (Okinawa Prefecture): 1 ♀ 2 juv., Shimajiri District, Kumejima Town, Jyanado (26°20'46.2"N, 126°47'52.0"E, alt. 16 m), 10 Sep. 2021, Y. Suzuki leg. Aka Is. (Okinawa Prefecture): 1 ♀, Shimajiri District, Zamami Village, Aka , streamside at dim forest (26°11'47.11"N, 127°16'57.09"E, alt. 65 m), 16 Mar. 2022, Y. Suzuki leg.

Etymology.

The specific name is a Latin adjective derived from the black striped pattern on the dorsal abdomen of the new species.

Diagnosis.

Males of the new species resemble T. alboannulatum Suzuki, Serita & Hiramatsu, 2020 in having two parallel embolic apophyses exposed from conductor and lacking a conductor projection on the male palp. They can be distinguished by the presence of one embolic apophysis longer than another and the shape of the sclerotized distal margin of conductor beneath embolic apophyses: a ridge separates the two triangular surfaces and sharply cornered at the terminal of the ridge in T. nigrivirgatum sp. nov. (Figs 2C , 3C ), while a ridge is lacking in T. alboannulatum ( Suzuki et al. 2020: fig. 12E, F). Females of the new species resemble those of T. diwang Miller, Griswold & Yin, 2009 in having a small and narrow slit on the posterior margin of the epigynal plate, but can be distinguished by the shape of the vulva: genital plate is bell-shaped and longer than wide; spermathecae are positioned at the anterior part of the vulva in T. nigrivirgatum sp. nov. (Figs 2G , 3G ), while the vulva is wider than long, copulatory ducts extend anteriorly, and the position of spermatheca is lower than the anterior margin of the copulatory ducts in T. diwang ( Miller et al. 2009: fig. 3G). Both sexes can be distinguished from congeners by their abdominal color and patterns: a dark marking on the anterior dorsum, two pairs of dark markings on the dorsolateral side, and dark striped markings on the posterior dorsum (Fig. 1 ).

Description.

Male (holotype, NSMT-Ar 21717). Measurements. Body 1.02 long. Carapace 0.45 long, 0.46 wide, and 0.36 high. Eye size and interdistances, AME 0.054, ALE 0.047, PME 0.050, PLE 0.042, AME-AME 0.022, AME-ALE 0.017, PME-PME 0.012, PLE-PLE 0.030. Leg length: leg I 0.47 + 0.17 + 0.31 + 0.29 + 0.20 = 1.44; leg II 0.38 + 0.15 + 0.26 + 0.24 + 0.18 = 1.21; leg III 0.23 + 0.13 + 0.14 + 0.18 + 0.13 = 0.81; leg IV 0.30 + 0.13 + 0.20 + 0.20 + 0.15 = 0.98. Abdomen 0.58 long, 0.60 wide, 0.80 high.

Carapace oval, wider than long (CaL/CaW 0.98). Chelicerae with three teeth on promargin. Abdomen oval and wider than long (AL/AW 0.97).

Coloration and markings (Fig. 1A-D ). Carapace, chelicerae, and legs dark yellowish brown (turning to yellowish brown in ethanol). Cephalic groove stained with dark spots. Anterolateral margin of carapace dark grey. Mouthparts dark yellowish brown. Sternum pale yellowish brown with black lateral margins. Eyes on the dark bases. Legs yellowish brown with femora pale and lacking annulations. Abdomen pale yellowish brown with a dark greyish marking on anterior dorsum, two pairs of dark greyish spots on dorsolateral sides, and dark-colored longitudinal stripes on posterior dorsum. Spinnerets and ventral side of abdomen dark grey.

Palp (Figs 2A-D , 3A-D ). Palpal patella with a strong retrolateral macroseta. Paracymbium hook-like with a blunt tip. Tegulum bulbous. Embolic division covered with a semitransparent conductor and composed of several apophyses. Conductor lacking conductor projection. Two long and parallel bristle-like embolic apophyses exposed from the conductor. Posterior margin of the embolic division strongly sclerotized with angular corners, the middle one pointed, the retrolateral one blunt, a ridge separates two triangular surfaces: one is covered by embolic division and the other is not (Fig. 3C ). Tegular surface beneath conductor weakly sclerotized with denticles. Median apophysis narrower toward the pointed tip.

Female (paratype: NSMT-Ar 21718). Measurements. Body 1.31 long. Carapace 0.51 long, 0.50 wide, 0.41 high. Eye size and interdistances: AME 0.057, ALE 0.058, PME 0.060, PLE 0.053, AME-AME 0.019, AME-ALE 0.032, PME-PME 0.009, PLE-PLE 0.043. Leg length: leg I 0.61 + 0.20 + 0.29 + 0.26 + 0.19 = 1.55; leg II 0.40 + 0.16 + 0.24 + 0.19 + 0.16 = 1.15; leg III 0.24 + 0.15 + 0.14 + 0.17 + 0.13 = 0.83; leg IV 0.40 + 0.17 + 0.23 + 0.20 + 0.14 = 1.97. Abdomen 0.86 long, 0.87 wide, 0.90 high.

Carapace oval and almost as long as wide (CaL/CaW 1.02). Chelicerae with three teeth on promargin. Abdomen oval and as long as wide (CaL/CaW 0.99).

Coloration and markings (Fig. 1E-H ). Carapace and chelicerae pale yellowish brown. Lateral margin of carapace dark grey. Eyes on the dark bases. Eyes, mouthparts, sternum, and legs as in male. Abdomen yellowish brown with dark greyish markings similar to the male, and dark orange markings on the dorsum and sides.

Genitalia (Figs 2E-G , 3E-G ). Epigyne a wide plate with a short and narrow slit in the middle of the posterior margin. Vulva. Copulatory ducts moderately complicated. Spermathecae rounded triangular and juxtaposed. Fertilization ducts with curved tips.

Variations. The color and patterns of the abdomen vary: male specimens collected from Northern Okinawa lack longitudinal stripes on the posterior dorsum of the abdomen.

Taxonomic justification.

Theridiosoma nigrivirgatum sp. nov. can safely be assigned to the genus according to the male palpal morphology: embolus short and tubular, and embolus apophyses fragmented into several long bristle-like parts.

Remarks.

The males and females are considered to be the same species because of the similarity of body color and patterns and their sympatric occurrences. Although this species sympatrically occurred with T. dissimulatum on southern Okinawa Island (Fig. 11 ), no other undescribed candidates were collected.

Distribution.

Japan (Okinawa, Kume and Aka Islands; Fig. 11 ).

Habitat.

The new species inhabits forest floors of secondary forests, bushes, and grasslands. The species is frequently collected from an open environment covered by Poaceae grasses, where T. dissimulatum is never found (Fig. 12C ). The habitat of this species resembles that of T. alboannulatum (Fig. 12D ).

Web morphology.

This species weaves a concave orb web with radial anastomosis and a tension line connected to substrates (Fig. 13A-C ). A spider drags a tension line with a strong force so that the web is deformed to a conical shape. The web is similar to that of the congeners.

Egg sac.

pale whitish brown and spherical with a long horizontal line and a short stalk (Fig. 15A ).

Figures

Figure 1. Theridiosoma nigrivirgatum sp. nov., male holotype (NSMT-Ar 21717 A-D) and female paratype (NSMT-Ar 21718 E-H) A, E habitus, dorsal view B, F habitus, lateral view C, G habitus, ventral view D, H abdomen, posterior view. Scale bars: 0.5 mm.

Figure 2. Theridiosoma nigrivirgatum sp. nov., male holotype genitalia (NSMT-Ar 21717 A-D) and female paratype genitalia (NSMT-Ar 21718 E-G) A retrolateral view B ventral view C posterior-ventral view D prolateral view E ventral view F ventral view G dorsal view. Abbreviations: C conductor CD copulatory ducts E embolus EA embolic apophysis FD fertilization ducts MA median apophysis PC paracymbium S spermatheca ST subtegulum T tegulum. Scale bars: 0.1 mm.

Figure 3. Theridiosoma nigrivirgatum sp. nov., male holotype genitalia (NSMT-Ar 21717 A-D) and female paratype genitalia (NSMT-Ar 21718 E-G) A retrolateral view B ventral view C posterior-ventral view D prolateral view E ventral view F ventral view G dorsal view. Abbreviations: C conductor CD copulatory ducts E embolus EA embolic apophysis FD fertilization ducts MA median apophysis PC paracymbium S spermatheca ST subtegulum T tegulum. White and black arrows indicate a ridge that separate the two triangular surfaces and a sharply cornered terminal of the ridge, respectively. Scale bars: 0.1 mm.

Figure 11. Distribution of theridiosomatid species in the Ryukyu Islands, Japan.

Figure 12. Habitats of theridiosomatid species in Ryukyu Islands A streamside in dim forest at Iriomote Island B forest floor of secondary forest at Kume Island C grassland at Kume Island D grassland at Yonaguni Island E crevices on limestone rocky wall at Iriomote Island.

Figure 13. Web of Theridiosoma and Zoma spiders at Ryukyu Islands, Japan A-C web of Theridiosoma nigrivirgatum sp. nov. D-E web of Theridiosoma alboannulatum F-H web of Zoma dibaiyin. Abbreviations: RA radial anastomosis SS sticky spirals TL tension line.

Figure 15. Egg sacs of theridiosomatid species A egg sac of Theridiosoma nigrivirgatum sp. nov. (cap opened) B egg sac of Theridiosoma dissimulatum C egg sac of Theridiosoma alboannulatum D-E egg sac of Sennin tanikawai sp. nov.