Sennin tanikawai, 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

Sennin tanikawai sp. nov.

[New Japanese name: Iriomote-hora-ana-karakara-gumo] Figs 6 , 7 , 8 , 9 , 10 , 11 , 12E , 14A-G , 15D-E

Type material.

Holotype: Japan, Iriomote Is. (Okinawa Prefecture): ♂ (NSMT-Ar 21722), Yaeyama District, Taketomi Town, Haiminaka, Ôtomi-Daini-Do Cave, 31 Mar. 1985, A. Tanikawa leg. Paratypes: 2 ♀ (NSMT-Ar 21723), 27 Mar. 1995, A. Tanikawa leg.; 9 ♂ (NSMT-Ar 21724-21725), 31 Mar. 1985, A. Tanikawa leg.; 1 ♀ (NSMT-Ar 21726), 1 Aug. 1970, Y. Shirota leg.; 2 ♀ (NSMT-Ar 21727), 27 Oct. 1977, N. Tsurusaki leg.; above paratypes are collected at same locality as the holotype; 1 ♂ (NSMT-Ar 21728), a small opening of Ôtomi-Daini-Do Cave (24°17'09.4"N, 123°53'24.9"E, alt. 10 m), 24 Jun. 2021, Y. Suzuki leg.

Additional material examined.

Japan, Iriomote Is. (Okinawa Prefecture): 1 ♀, Yaeyama District, Taketomi Town, Haemi , Ôtomi-daiichi-do Caves (24°17'31.0"N, 123°52'45.7"E, alt. 30 m), 3 May 2021, Y. Suzuki leg. ; 1 ♀, Yaeyama District, Taketomi Town, Takana , Yutsun-Do Caves , a small cave on coastal cliff (24°23'08.90"N, 123°53'27.89"E, alt. 10 m), 21 Mar. 2019, Y. Suzuki leg. ; 1 ♀, Takana, Yutsun-Do Caves , a large cave opening on coastal cliff (24°23'05.88"N, 123°53'25.00"E, alt. 7 m), 28 Mar. 2008, T. Hiramatsu leg. ; 6 ♂ 7 ♀, Takana, Yutsun-Do Caves , a large cave opening on coastal cliff (24°23'05.88"N, 123°53'25.00"E, alt. 7 m), 1 May 2021, Y. Suzuki leg. ; 2 ♀, Takana, Yutsun-Do Caves , cavities of rocks on coastal cliff (24°23'04.96"N, 123°53'23.82"E, alt. 10m), 22 Jun. 2021, Y. Suzuki leg. ; 3 ♀, Takana, Yutsun-Do Caves , a cave beside Shirahama-haemi-sen road (24°23'06.5"N, 123°53'31.2"E, alt. 27 m), 24 Jun. 2021, Y. Suzuki leg. ; 1 ♂ 1♀, Haemi , limestone rocky walls in a secondary forest (24°16'08.48"N, 123°52'01.52"E, alt. 16 m), 24 Jun. 2021, Y. Suzuki leg.

Etymology.

The specific name is patronym dedicated to Dr. Akio Tanikawa, a Japanese arachnologist who has contributed remarkably to the elucidation of the spider fauna in Iriomote Island and offered us many specimens including type specimens.

Diagnosis.

Males of this species can be distinguished from the allied Sennin coddingtoni comb. nov. by the following characteristics: cymbial apophysis is wider in relation to palpal tibia length while it is almost the same length as S. coddingtoni comb. nov. (CAW/PTL = 2.41 in S. tanikawai sp. nov., also see Fig. 9A , B ; 1 .00 in S. coddingtoni comb. nov.; also see Zhu et al. 2001: fig. 7); median apophysis of S. tanikawai sp. nov. is longer and narrower dorsally (MAL/MAW 1.63; Fig. 9E ) compared to that of the latter (MAL/MAW 0.85, based on Chen 2010: fig. 24); the less-sclerotized distal part of median apophysis is lanceolate with pointed tip on ventral terminal in S. tanikawai sp. nov. (arrows in Figs 7E , 9E ), while that of S. coddingtoni comb. nov. is falcate ( Chen 2010: fig. 24). Females of S. tanikawai sp. nov. can be distinguished from S. coddingtoni comb. nov. by the following characteristics: longer epigynal scape (ESL/VW 0.46 in S. tanikawai sp. nov., Fig. 10 ; 0.16 in S. coddingtoni comb. nov., based on Chen 2010: fig. 19); tip of spermatheca is strongly curved anteriorly in S. tanikawai sp. nov., whereas it is almost straight in S. coddingtoni comb. nov.; the course of copulatory ducts: ducts from both sides juxtaposed at the middle of vulva ventral to spermathecae and continue posteriorly straight toward epigynal scape, then make a right-angle turn and apart laterally (arrows in Figs 8C , 10C ), while in S. coddingtoni comb. nov. the ducts apart to each other ventrally to the spermatheca and curved laterally ( Zhu et al. 2001: fig. 5).

Description.

Male (NSMT-Ar 21722). Measurements. Body 2.30 long. Carapace 1.07 long, 1.10 wide, 0.72 high. Eye size and interdistances: AME 0.09, ALE 0.09, PME 0.10, PLE 0.08, AME-AME 0.02, AME-ALE 0.03, PME-PME 0.03, PLE-PLE 0.08, Leg length: leg I 1.62 + 0.53 + 1.30 + 1.08 + 0.50 = 5.03; leg II 1.30 + 0.49 + 1.03 + 0.91 + 0.49 = 4.22; leg III 0.70 + 0.39 + 0.56 + 0.63 + 0.38 = 2.66; leg IV 0.93 + 0.40 + 0.73 + 0.69 + 0.38 = 3.14. Abdomen 1.32 long, 1.44 wide, 1.61 high.

Carapace oval, wider than long (CaL/CaW 0.97). Chelicerae with six teeth on promargin with the largest one positioned close to the fang base, no teeth on retromargin (Fig. 6D ). Anterior eye row recurved, posterior eye row straight. Cymbial apophysis of palp 0.297 long, 0.111 wide. Macrosetae: leg I: femur r1-p1, patella d1, tibia d2-r1-p1; leg II: femur r1, patella d1, tibia d2-r1; leg III: patella d1, tibia d1; leg IV: patella d1, tibia d1. Abdomen oval, wider than long (AL/AW 0.92). Abdomen covered with long and thin setae.

Coloration and markings (Fig. 6 ). Carapace, mouthparts, sternum, and legs dark yellowish brown (turning to yellowish brown in ethanol). Eyes on dark bases. Legs lacking annulation. Abdomen pale yellowish grey, dorsum of abdomen with two pairs of sigilla.

Palp (Figs 7 , 9 ). Palpal patella with a strong dorsal macroseta. Paracymbium hook-like with a sharp tip. Cymbial lamella robust. Dorsal cymbial apophysis oblong, plate-like with blunt tip, extending anterior-retrolaterally. Tegulum large, bulbous, and occupying a large part of the palpal organ. Embolic division is a complex of long bristle-like apophyses, entirely covered with translucent conductor, and none of the embolic apophyses are exposed. Embolus short, blunt, and covered with a membrane. Three embolic apophyses conspicuous, EA 1 thickest, protruding middle of embolic division, S-shaped and sharper distally; EA 2 longest among them, bristle-like, basal part swelled, forming a loop at the ventro-prolateral side, distal part along with EA 1; EA 3 thinnest, protruding from prolateral side of embolic division. Median apophysis with a deep groove dividing it into two parts, distal translucent, weakly sclerotized and sharper ventrally, basal triangular, strongly sclerotized with narrower dorsally and spatula-like at ventral tip, MAL 1.07, MAW 0.66.

Female (paratype, NSMT-Ar 21723). Measurements. Body 2.37 long. Carapace 1.05 long, 1.06 wide, 0.65 high. Eye size and interdistances: AME 0.10, ALE 0.10, PME 0.12, PLE 0.09, AME-AME 0.02, AME-ALE 0.04, PME-PME 0.03, PLE-PLE 0.08. Leg length: leg I: 1.43 + 0.49 + 1.01 + 0.87 + 0.48 = 4.28; leg II: 1.22 + 0.45 + 0.85 + 0.70 + 0.40 = 3.62; leg III: 0.77 + 0.40 + 0.52 + 0.56 + 0.37 = 2.62; leg IV: 0.90 + 0.36 + 0.71 + 0.59 + 0.38 = 2.94. Abdomen 1.58 long, 1.45 wide, 1.49 high.

Carapace oval, as long as wide (CaL/CaW 0.99). Chelicerae with five teeth on promargin with the largest one positioned close to fang base, no teeth on posterior margin (Fig. 6H ). Anterior eye row recurved, posterior eye row straight. Macrosetae: leg I: femur p1, patella d1, tibia d2-r1-p1; leg II: patella d1, tibia d2-r1; leg III: patella d1, tibia d1; leg IV: patella d1, tibia d1. Abdomen as in male (AL/AW 1.09).

Coloration and markings (Fig. 6 ). As in male.

Genitalia (Figs 8 , 10 ). Epigyne a wide plate with an epigynal scape protruding from the posterior margin, epigynal scape spoon-like, and convex ventrally. Anterior margin of epigynal plate with a pair of dark-colored, sclerotized extensions protruding anteriorly from anterolateral side. Vulva. Spermatheca elliptical, longer laterally juxtaposed at the tip. Copulatory bursae developed. Course of copulatory ducts complicated: originating from copulatory bursae at ventral side, touching each other along the mesial line of the vulva, running posterior-dorsally under spermathecae, bend at a right angle toward laterally, curving anterior-dorsally at lateral side of vulva, forming a coil at lateral side of spermathecae, and then connecting to spermathecae. Fertilization ducts running under copulatory ducts and tip dorsally.

Variations.

There is a variation in the color of the abdomen: some individuals with dark grey abdomen, while others with pale yellowish grey abdomen. Course of embolic apophyses also varies among individuals: EA 2 tightly coiled with distal part along with EA 1 and EA 3 running below EA 1 in some individuals including the type specimens, while EA 2 loosely coiled with distal part apart from EA 1 and EA 2 running above EA 1.

Remarks.

Males and females are considered the same species because no other candidates were sympatric.

Distribution.

Japan (Iriomote Island; Fig. 11 ).

Habitat.

The new species inhabits entrance or insides of limestone caves and crevices of limestone rocky walls (Fig. 12E ). Spiders are found in high density at the entrance and twilight zones of humid caves, while sparsely deep inside the dark zone. Its general morphology (pigmented body, eight developed eyes, etc.) and habitat suggest that the species is troglophilic rather than obligate troglobite.

Web morphology.

The newly reported species built a conventional orb web with an open hub and two hub loops (Fig. 14A-C ). The web was almost vertical, and the tension line extended upward obliquely from the upper side of the hub to the surface of the rock (Fig. 14D ). The angle of the trapline was approximately 60° to the horizontal plane. The spider sat upward and held a trapline by both forelegs and grasped radii by legs III, and put legs IV on the hub (Fig. 14E ). The web turned conical shape (Fig. 14D ), but it seemed to be less distorted than that of Theridiosoma spp. The mean web diameter was 11.6 × 10.1 (cm vertical × horizontal) (n = 9), number of radii: 17 ± 2.3 (SD), and number of sticky spirals: 14.5 ± 2.5 (SD) (n = 8). As a result of observation of 209 webs in June 2021, it was found that some individuals do not make tension lines. The percentage of webs with a tension line was as follows: female adult, 77% and juvenile, 33% in Yutsun-do Cave; female adult, 67% and juvenile, 45% in Ôtomi-Daiichi-Do Cave. Juveniles were more likely to build ordinary webs lacking tension lines than adults at both sites. When a web is disturbed by wind, the spider immediately escapes from the web running along the tension line (n = 22, see Suppl. material 1). After the escape, some spiders try to hide themselves into limestone rock crevices.

Web-building behavior.

(n = 5). (1) Frames and radii were laid. (2) The spider returned to the hub and made a temporary spiral as a circle. (3) The spider pulled out a sticky line by using only the outer leg IV several times while touching the temporary spiral by the inner leg IV (in T. epeiroides Bösenberg & Strand, 1906, it draws out a sticky line using both legs IV alternately [ Shinkai and Shinkai 1985]). (4) After drawing a sticky line, the spider walked to the frame along a radius holding it by the outer leg IV, shifted it inward, and then attached it to the radius (Fig. 14F ; see Suppl. material 2). (5) The spider turned to the hub by drawing a new sticky line by the outer leg IV and moved the next radius along the temporary spiral (Fig. 14F ). (6) The spider repeated sequences (3) to (5) and laid sticky spirals from outside to inside. (7) After finishing laying the sticky spirals, the temporary spiral was removed. (8) The spider moved near the hub and bit off the radius. (9) After biting off the radius, it changed the direction and attached its spinnerets to the radius and drew out a radius. The elongated radius was attached to the hub (Suppl. material 3). Thus, all radii were elongated (Fig. 14G ). (10) The spider returned to the hub, laid two hub loops, and bit out its center. It ingested the ball of threads using both forelegs and digested it. (11) The spider held a tension line, and the web formed a cone. It took approximately one hour to complete the web.

Egg sac.

Spherical and dark brown. The size was approximately 3 × 2 (mm, height × width), which was suspended with a long vertical line on the roof of a cave (Fig. 15D, E ). This vertical line (pendant line) ranged from 2.5 to 5.3 cm, and the mean was 4.1 cm (n = 4). There was a single attachment point of the egg sac. The junction of the upper end of the egg sac and the lower end of the pendant line resembled a hatch, similar to a cap like structure in Theridiosoma . The lower end of the pendant line was thickened. The egg sac is cleaved at the joint. The egg sac of K. upperyangtzica resembles that of S. tanikawai sp. nov. but can be distinguished by the shape of ‘cap’ (thickened end of the pendant line): almost as long as wide in the former while clearly longer than wide in the latter ( Chen 2010: fig. 29 vs. Fig. 15E ).

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 6. Sennin tanikawai sp. nov., male holotype (NSMT-Ar 21722 A-D) and female paratype (NSMT-Ar 21723 E-H) A, E habitus, dorsal view B, F habitus, lateral view C, G eye region, dorsal view D, H chelicera, anterior view. Scale bars: 0.5 mm (A, B, E, F); 0.1 mm (C, G, D, H).

Figure 7. Sennin tanikawai sp. nov., male holotype genitalia (NSMT-Ar 21722) A-D male palp F-J embolic division A retrolateral view B prolateral view C dorsal view D ventral view E median apophysis, ventral view F posterior-ventral view G ventral view H anterior-dorsal view I posterior-dorsal view J prolateral view. Abbreviations: C conductor CA cymbial apophysis CL cymbial lamella E embolus EA embolic apophysis ED embolic division EM embolus MA median apophysis PC paracymbium ST subtegulum T tegulum. Arrow in E indicates the tip of less-sclerotized region of median apophysis. Scale bars: 0.1 mm.

Figure 8. Sennin tanikawai sp. nov., female paratype genitalia (NSMT-Ar 21723) A epigyne, ventral view B epigyne, lateral view C vulva, dorsal view D vulva, anterior view. Abbreviations: CB copulatory bursae CD copulatory ducts ES epigynal scape FD fertilization ducts S spermatheca. Arrows in A, D indicate a pair of sclerotized extensions on the anterior margin of epigynal plate. Arrow in C indicates a pair of copulatory ducts juxtaposed. Scale bars: 0. 1 mm.

Figure 9. Sennin tanikawai sp. nov., male holotype genitalia (NSMT-Ar 21722) A-D male palp F-J embolic division A retrolateral view B prolateral view C dorsal view D ventral view E median apophysis, ventral view F posterior-ventral view G ventral view H anterior-dorsal view I posterior-dorsal view J prolateral view. Abbreviations: C conductor CA cymbial apophysis CL cymbial lamella E embolus EA embolic apophysis ED embolic division EM embolus MA median apophysis PC paracymbium ST subtegulum T tegulum. Arrow in E indicates the tip of less-sclerotized region of median apophysis. Scale bars: 0.1 mm.

Figure 10. Sennin tanikawai sp. nov., female paratype (NSMT-Ar 21723) A epigyne, ventral view B epigyne, lateral view C vulva, dorsal view D vulva, anterior view E course of copulatory duct. Abbreviations: CB copulatory bursae CD copulatory ducts ES epigynal scape ESL epigynal scape length FD fertilization ducts S spermatheca VW vulva width. Arrows in A, D indicate a pair of sclerotized extensions on the anterior margin of epigynal plate. Arrow in C indicates the pair of copulatory ducts juxtaposed. 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 14. Web structure and building behavior in Sennin tanikawai sp. nov. (A-G) and Theridiosoma epeiroides (H) A orb web, frontal view B orb web, illustrated C open hub, frontal view D orb web, lateral view E spider holding tension line with forelegs F process of weaving sticky spirals by S. tanikawai sp. nov. G radial elongation behavior in S. tanikawai sp. nov. H web building processes of Theridiosoma epeiroides. Blue lines indicate elongated portion of radii. Abbreviations: HL hub loops OH open hub RD radii SS sticky spiral TL tension line TS temporary spiral.

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.