Callobius cavernarius, Xiang & Pan & Yu & Xiao & Sun & Cheng, 2022

Xiang, Ke, Pan, Jinbin, Yu, Jiaojiao, Xiao, Lehui, Sun, Shao-Kai & Cheng, Ran, 2022, Two New Species of the Spider Family Amaurobiidae from the Ryukyu Islands, Japan, Bulletin of the National Museum of Nature and Science. Series A, Zoology (Zoology) 48 (4), pp. 139-146 : 142-144

Callobius cavernarius sp. n.

[Japanese name: Erabuhoraana-gakejigumo] ( Figs. 1A–B , 2A–B , 3A , 4 , 5 )

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Type material. Holotype ˁ, JAPAN: Ginsuido Cave, Okinoerabu Island , Kagoshima Pref., 28 April 2004, T. Tamura leg. (NSMT-Ar 22142) . Paratypes: 2˂, same data as the holotype (NSMT-Ar 22143); 1ˁ, Suirendo cave, Okinoerabu Island, Kagoshima Pref., 30 April 2004, T. Tamura leg. (NSMT-Ar 22144); 1 ˂, Ogimi, Ogimi-son, Kunigami-gun, Okinawajima Island , Okinawa Pref., 19 December 2021, Y. Suzuki leg. (NSMT- Ar 22145)

Other materials examined. 1 ˁ, 6 ˂, Shoryudo Cave, Okinoerabu Island , Kagoshima Pref., 9 December 2021, Y. Suzuki leg. 2 ˁ, 2 ˂, Shoryudo Cave, Okinoerabu Island , Kagoshima Pref., 6 March 1982, M. Shimojana leg : 5 ˁ, 3˂, Suirendo Cave, Okinoerabu Island , Kagoshima Pref., 6 March 1982, M. Shimojana leg. 2ˁ, 3˂, Ogimi, Ogimi-son, Kunigami-gun , Okinawajima Island , Okinawa Pref., 19 December 2021, Y. Suzuki leg.

Etymology. The specific name is derived from the Latin adjective cavernarius lconcerning caves,z referring to the discovery of the type specimens in caves.

Diagnosis. Male specimens of Callobius cavernarius sp. n. can be distinguished from other congeners by the narrow cymbium, the long tibia and the trapezoidal MP with an extremely small projection in the palp. Female can be distinguished by the triangular lateral lobes located distant from each other in the epigyne and the semicircular spermathecae of the internal genitalia. As an example, the differences from C. breviprocessus that lives in the most neighboring areas are shown ( Figs. 1 , 2 ). For differences from the other two species, C. yakushimensis and C. amamiensis in the Ryukyu Islands, refer to Okumura et al., 2020. The body size of the species is also much larger than the other species living on Okinawajima Island ( Fig. 3 ).

Description. Male (holotype). Total length 9.8, carapace 5.5 long, 3.8 wide; abdomen 4.3 long, 2.7 wide; sternum 2.3 long, 1.9 wide. Eye sizes and interdistances AME 0.19, ALE 0.26, PME 0.21, PLE 0.24; AME-AME 0.09, AME- ALE 0.11, PME-PME 0.21, PME-PLE 0.30, AME-PME 0.31, ALE-PLE 0.10. MOA; anterior width 0.47, posterior width 0.63, length 0.71. Leg measurements: I: 27.7 (7.1, 9.2, 7.5, 3.9); II: 19.2 (5.3, 6.6, 4.8, 2.5); III: 16.5 (4.8, 5.4, 4.3, 2.0); IV: 21.8 (6.1, 7.0, 6.0, 2.7).

Palp ( Figs. 1A–B , 5A–C ): three projections present in the lateral to dorsal portion of long tibia; RTA thick and has a small process in the tip, DP slightly curved and pointed in the tip, MP trapezoid with an extremely small projection, cymbial excavation clear; CO thin and semitransparent, median apophysis large and claw-shaped, embolus short and conglutinates with the tegulum.

Chelicerae: promargin with 5 teeth, retromargin with 5 teeth.

Colouration: carapace yellowish brown with indistinct radial flecks, dorsum of abdomen blackish brown but grayish brown only in the anteromedian part, and venter blackish brown with white lines in both lateral sides, sternum yellowish brown, chelicerae blackish brown, maxillae and labium brown, legs yellowish brown without ring flecks.

Female (one of paratypes). Total length 10.4, carapace 3.9 long, 2.4 wide; abdomen 6.5 long, 4.7 wide; sternum 1.7 long, 1.6 wide. Eye sizes; AME 0.13, ALE 0.20, PME 0.16, PLE 0.18. Distances between eyes; AME-AME 0.11, AME- ALE 0.10, PME-PME 0.15, PME-PLE 0.28, AME-PME 0.21, ALE-PLE 0.08. MOA; anterior width 0.37, posterior width 0.47, length 0.50. Leg measurements: I: 14.3 (4.0, 4.9, 3.4, 2.0); II: 11.5 (3.3, 3.9, 2.7, 1.6); III: 10.2 (3.0, 3.4, 2.5, 1.3); IV: 13.0 (3.8, 4.6, 3.4, 1.2).

Epigyne and internal genitalia ( Figs. 2A–B , 5D–E ): lateral lobes almost semicircular, swollen and distant from each other, median lobe almost circular from the posterior view, ectal lobe and posterior lobe absent. SP semicircular and distant from each other, fertilization ducts small and indistinct.

Chelicerae: promargin with 6 teeth on the left, and 5 on the right, retromargin with 6 teeth on the left, and 5 teeth on the right.

Colouration: almost same as that of the male holotype.

Distribution: Okinoerabu Island, Okinawajima Island ( Fig. 6 )

Remarks. Although the number of the marginal teeth in the female type specimen using for the description is different between the right che- licera and the left one, we considered this is a case of variation because the variation of the number of the marginal teeth can easily occurs ( Okumura et al. 2020). The main habitat of this new species is in caves in Okinoerabu Island, but some specimens have also been collected from the ground in the mountainous areas on Okinawajima Island.

Figures

Fig. 1. Comparison of male palps of Callobius cavernarius sp. n. (A–B); C. shimojanai sp. n. (C–D); and C. breviprocessus (E–F). Male palp (left), dorsal view (A, C, E); same, ventral view (B, D, F). Scale bars=0.5mm.

Fig. 2. Comparison of female genital organs of Callobius cavernarius sp. n. (A–B); C. shimojanai sp. n. (C–D); and C. breviprocessus (E–F). Epigyne, ventral view (A, C, E); female internal genitalia (B, D, F). Scale bars=0.5mm.

Fig. 3. Comparison of body appearance of female specimens. Callobius cavernarius sp. n. (A); C. shimojanai sp. n. (B); and C. breviprocessus (C). Scale bars=10mm.

Fig. 4. Callobius cavernarius sp. n.; one specimen of female paratypes. Scale bar=5mm.

Fig. 5. Copulatory organs of Callobius cavernarius sp. n. holotype (A, B, C), paratypes (D, E). Male palp (left), ventral view (A); same, retrolateral view (B); same, dorsal view (C); epigyne, ventral view (D); female internal genitalia (E). Scale bars=0.5 mm.

Fig. 6. Distribution records of Callobius cavernarius sp. n. and C. shimojanai sp. n. including three closely related species living on the Ryukyu Islands.