Cybaeus communis Yaginuma, 1972

Sugawara, Yusuke, Ihara, Yoh & Nakano, Takafumi, 2022, Taxonomic Reassessment of Cybaeus communis and Cybaeus maculosus (Araneae: Cybaeidae) from Central Honshu, Japan, Species Diversity 27 (1), pp. 53-60 : 54-59

Cybaeus communis Yaginuma, 1972 [Japanese name: Zara-namihagumo] ( Figs 3–7 )

Cybaeus communis Yaginuma, 1972: 311–312 , fig. 37; Yaginuma 1986: 143, 146, fig. 78-10; Ihara 2009: 154, 155, figs 2-2-30-14, 18, 19.

Cybaeus maculosus Yaginuma, 1972: 312–314 , fig. 38; Yaginuma 1986: 144, 146, fig. 78-12; Ihara 2009: 154. syn. nov.

Emended diagnosis. “Medium-sized” Japanese Cybaeus ( Fig. 3 ). Both C. communis sexes most closely resemble three other medium-sized brown Japanese Cybaeus species: C. kirigaminensis , C. shinkaii , and C. daimonji (see figs 2-2- 30- 14–23 in Ihara 2009; figs 1–5 in Matsuda et al. 2020). Males of C. communis can be clearly distinguished from those of the three species by the lack of a palpal PA (for C. communis , see Fig. 4A, B ; for C. kirigaminensis , see figs 2-2-30-15, 16 in Ihara 2009; for C. shinkaii , see fig. 2-2-30- 17 in Ihara 2009; for C. daimonji , see fig. 3 in Matsuda et al. 2020). Females of C. communis can be distinguished from those of the three species by the spermathecal structures: both the SH and SS in C. communis are more bulbous and developed than in the other species (for C. communis , see Figs 5B , 6 ; for C. kirigaminensis , see fig. 2-2-30- 21 in Ihara 2009; for C. shinkaii , see fig. 2-2-30- 23 in Ihara 2009; for C. daimonji , see fig. 5 in Matsuda et al. 2020).

Material examined. Holotype: male, NSMT-Ar 66, from Yashiki-ana Cave , Fujinomiya City, Shizuoka, Japan (cave entrance: 35.2693°N, 138.6210°E), collected by S. Uéno and K. Kato on 13 December 1969.

Additional materials: 1 female, NSMT-Ar 77, holotype of C. maculosus , from Mado-ana Cave , Fujinomiya City, Shizuoka, Japan (cave entrance: 35.2645°N, 138.6282°E), collect- ed by S. Uéno and K. Kato on 13 December 1969, genitalia missing ( Ken-ichi Okumura , personal communication); 3 males, KUZ Z3966, from the type locality of C . communis, collected by Naoki Koike on 12 November 2011; male, KUZ Z3967, same collection data as KUZ Z3966; male, KUZ Z3968, same collection data as KUZ Z3966; female, KUZ Z3969, same collection data as KUZ Z3966; female, KUZ Z3970, same collection data as KUZ Z3966; male, KUZ Z3971, from the type locality of C . maculosus, collect- ed by Naoki Koike on 12 November 2011; 3 females, KUZ Z3972, same collection data as KUZ Z3971; female, KUZ Z3973, same collection data as KUZ Z3971; 4 males, KUZ Z3974, from Shiraito Waterfall , Fujinomiya City , Shizuoka, Japan (35.3141°N, 138.5896°E), collected by Naoki Koike on 12 November 2011; 3 females, KUZ Z3975, same collection data as KUZ Z3974, male, KUZ Z3976, same collection data as KUZ Z3974; 2 males, KUZ Z3961, from Nihondaira Plateau , Shizuoka City , Shizuoka, Japan (34.9855°N, 138.4633°E), collected by Naoki Koike on 11 November 2011; male, KUZ Z3962, same collection data as KUZ Z3961; male, KUZ Z3963, from Nihondaira Plateau , Shizuoka City , Shizuoka, Japan (34.9900°N, 138.4467°E), collected by Naoki Koike on 11 November 2011; female, KUZ Z3964, same collection data as KUZ Z3963; female, KUZ Z3965, from Nihondaira Plateau, Shizuoka City, Shizuoka, Japan (34.9805°N, 138.4524°E), collected by Naoki Koike on 11 November 2011 .

Type locality. Yashiki-ana Cave , Fujinomiya City, Shizuoka Prefecture, Japan (cave entrance: 35.2693°N, 138.6210°E) .

Description. Male (KUZ Z3967: Figs 3A, B , 4 ). Measurements (mm): CL 2.73, CW 1.86; head 1.10 wide; abdomen 2.40 long, 1.73 wide; ocular area 0.33 long, 0.68 wide; sternum 1.34 long, 1.16 wide; CW/CL 0.68, TibIL/CL 0.73. Leg formula, IV>I>II>III; length of legs (femur+patella+ tibia+metatarsus+tarsus): leg I 8.03 (2.08+0.78+2.00+ 1.86+1.31); leg II 7.48 (2.03+0.77+1.77+1.72+1.18); leg III 6.53 (1.81+0.75+1.41+1.65+0.91); leg IV 8.44 (2.16+ 0.77+1.94+2.32+1.25).

Carapace ( Fig. 3A ). Head narrow, ca. 0.59× as wide as thoracic region; thoracic region almost as high as 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, promargin of fang furrow with 3 teeth (median one largest), retromargin with 3 teeth and 6 denticles, and basally with lateral condyle. Labium wider than long.

Leg macrosetae. Leg I: tibia p4, r0, v2-2-2-2; metatarsus p3, r1, v2-2-3. Leg II: tibia p3, r3, v2-2-1-2; metatarsus p3, r2, v2-2-3.

Abdomen ( Fig. 3B ). Oval; mid-posterior part widest. Colulus two groups of 3 setae.

Palp ( Fig. 4 ). PA lacking. Tibia longer than patella; RTA plate-like, quadrangular, occupying 1/4 of length of tibia. Cymbium relatively wide, ca. 2.2× longer than wide, slightly expanded prolaterally. Genital bulb slightly longer than wide, oval in ventral view. Conductor: distal part short; PCO short, sharply curved at right angle. EM simple, originating and terminating, respectively, at ca. 11 o’clock and ca. 4 o’clock in ventral view.

Color ( Fig. 3A, B ). Carapace: head brown, with reticulate brownish black markings; thoracic region yellowish brown, with radiating brownish black bands. Chelicerae, maxillary lobe and labium reddish brown. Sternum yellowish brown, darker towards margins. Legs yellowish brown, with brown vague annulations. Abdomen: dorsally brown with beige chevron-like markings, small dots, and curved lines; ventrally pale beige.

Female (KUZ Z3969: Figs 3C, D , 5 , 6 ). Measurements (mm): CL 2.75, CW 1.89; head 1.27 wide; abdomen 4.16 long, 2.97 wide; ocular area 0.38 long, 0.79 wide; sternum 1.26 long, 1.11 wide. Leg formula, IV>I>II>III; length of legs (femur+patella+tibia+metatarsus+tarsus): leg I 6.83 (1.85+0.79+1.72+1.52+0.95); leg II 6.69 (1.96+0.83+ 1.57+1.43+0.91); leg III 5.99 (1.68+0.78+1.25+1.45+ 0.83); leg IV 7.69 (1.99+0.81+1.76+2.09+1.03).

Carapace ( Fig. 3C ). Head ca. 0.67× as wide as thoracic region; thoracic region height slightly shorter than head. AER straight in frontal view; PER 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 geniculate, promargin of fang furrow with 3 teeth (median one largest), retromargin with 5 teeth and 6 denticles, and basally with lateral condyle. Labium wider than long.

Leg macrosetae. Leg I: tibia p4, r0, v2-2-2-2; metatarsus p2, r1, v2-2-3. Leg II: tibia p4, r1, v2-2-1-2; metatarsus p3, r1, v2-2-3.

Abdomen ( Fig. 3D ). Oval; mid-posterior part widest. Colulus two groups of 4 or 5 setae.

Genitalia ( Figs 5 , 6 ). PME almost straight. Atrium located posteromedially on epigyne. CPs separated on both sides of atrium; CD thick and short, running anteromedially. SH and SS bulbous; PP located on ventral side of SH; BG locat- ed posteroventrally on SS; SB spherical, located posterolaterally. FD running from connection part between SS and SB, descending posteriorly, and then turned anterodorsally.

Color ( Fig. 3C, D ). Carapace: head brown, with reticulate brownish black markings; thoracic region yellowish brown, with radiating light brownish black bands. Chelicerae, maxillary lobe and labium reddish brown. Sternum yellowish brown, darker towards margins. Legs yellowish brown, with brown vague annulations. Abdomen: dorsally pale brown with beige chevron-like markings and random patterns; ventrally pale beige.

Variation. Males. Measurements (mean±1SD, followed by ranges in parentheses; n=10): CL 2.61±0.15 (2.31–2.78); CW 1.83±0.11 (1.58–1.95); CW/CL 0.70±0.02 (0.68–0.72); TibIL 1.94±0.16 (1.68–2.16); TibIL/CL 0.74±0.04 (0.70– 0.74). Legs slightly longer than those of females. Females. Measurements (mean±1SD, followed by ranges in parentheses; n=8): CL 2.60±0.26 (2.07–2.80); CW 1.75±0.17 (1.44–1.89); CW/CL 0.68±0.01 (0.66–0.69); TibIL 1.61± 0.13 (1.33–1.72); TibIL/CL 0.62±0.02 (0.60–0.64).

Remarks. The female genitalia of the holotype of C. maculosus was not found, but the specimens examined in this study were clearly identified as C. communis / C. maculosus on the basis of previous descriptions ( Yaginuma 1972) and because no other similar species were found at the collection localities.

The nuclear ITS-1 sequences were obtained from four specimens: male and female specimens from the respective type localities of C. communis and C. maculosus . The sequences through the overlapping aligned positions were almost identical (354/355 bp). Additionally, the specimens collected at the type locality of C. maculosus bear the genital characteristics ( Fig. 7 ) that are concordant with those of C. communis ( Figs 4 , 5 ) in both males and females. The results thus clearly confirmed their conspecificity.

In Yaginuma (1972), C. communis and C. maculosus were distinguished using the length to width ratio of the carapace (=CL/CW in this study: 1.4 in C. communis and 1.5 in C. maculosus ). The variation among specimens in this study was as follows: males, CL/CW 1.43±0.03 (1.38–1.47) and females, CL/CW 1.48±0.03 (1.44–1.52). Because the two species were described only on the basis of one sex, as mentioned above, this difference merely reflects sexual dimorphism.

The precedence between the two names by Yaginuma (1972), viz., C. communis and C. maculosus , should be fixed in accordance with Article 24.2 of the International Code of Zoological Nomenclature (hereinafter, Code; International Commission on Zoological Nomenclature 1999), because the two species names, C. communis and C. maculosus , were given in the same work. As the First Reviser, we have given precedence to the name C. communis over C. maculosus for the following reasons: 1) the genital part of the holotype of C. communis exists, whereas that of C. maculosus is currently missing; 2) C. communis is stated in Ihara (2009) with figures, whereas C. maculosus without any figures; and 3) the original description of C. communis ( Yaginuma 1972: 311–312, fig. 37) appears earlier than that of C. maculosus ( Yaginuma 1972: 312–314, fig. 38), and therefore, C. communis has the “position precedence” over C. maculosus in accordance with Recommendation 24 A of the 3rd Edition of the Code ( International Commission on Zoological Nomenclature 1985). Accordingly, C. communis is the valid name for the species whenever C. communis and C. maculosus are considered as belonging to the same species-group taxon.

Cybaeus communis and C. maculosus were originally described based on specimens collected from caves and were deemed troglobitic. The examined specimens were also collected outside caves, and molecular analyses supported their close genetic distance despite their geographic distance. Judging from the phylogenetic relationships and the dark body color ( Fig. 3 ), C. communis is considered an epigeic species that also inhabits caves.

Figures

Fig. 3. Cybaeus communis, from the type locality, male (KUZ Z3967; A, B) and female (KUZ Z3969; C, D). A, C, Prosoma, dorsal view; B, D, abdomen, dorsal view. Scale bars: A–D, 1mm.

Fig. 4. Cybaeus communis, from the type locality, male (KUZ Z3967). A, Left palp, retrolateral view; B, patella of left palp, retrolateral view; C, patella of left palp, dorsal view; D, cymbium of left palp, dorsal view; E, genital bulb of left palp, ventral view. Abbreviations: EM, embolus; PCO, proximal arm of conductor; RTA, retrolateral tibial apophysis. Scale bars: A, 500µm; B–E, 250µm.

Fig. 5. Cybaeus communis, from the type locality, female (KUZ Z3969). A, Epigyne, ventral view; B, spermathecae, dorsal view.Abbreviations: FD, fertilization duct; PME, posterior margin of epigynal plate; SB, spermathecal base; SH, spermathecal head; SS, spermathecal stalk. Scale bars: A, B, 100µm.

Fig. 6. Cybaeus communis, schematic drawing of the epigyne and spermathecae of a female specimen (KUZ Z3969). A, Ventral view; B, dorsal view. Abbreviations: BG, Bennett’s gland; CD, copulatory duct; CP, copulatory pore; FD, fertilization duct; PME, posterior margin of epigynal plate; SB, spermathecal base; SH, spermathecal head; SS, spermathecal stalk.Scale bars: A, B, 100µm.

Fig. 7. Cybaeus communis, from the type locality of C. maculosus, male (KUZ Z3971; A, B) and female (KUZ Z3973; C, D). A, Left palp, retrolateral view; B, genital bulb of left palp, ventral view; C, epigyne, ventral view; D, spermathecae, dorsal view. Abbreviations: EM, embolus; FD, fertilization duct; PCO, proximal arm of conductor; PME, posterior margin of epigynal plate; RTA, retrolateral tibial apophysis; SB, spermathecal base; SH, spermathecal head; SS, spermathecal stalk. Scale bars: A, 500µm; B, 250µm; C, D, 100µm.