Nesticella okinawaensis (Yaginuma 1979)

Ballarin, Francesco & Eguchi, Katsuyuki, 2023, Integrative taxonomic revision of the genera Nesticella and Howaia in Japan with the description of five new species (Araneae, Nesticidae, Nesticellini), ZooKeys 1174, pp. 219-272 : 219

Nesticella okinawaensis (Yaginuma 1979)

Figs 12A-J , 13A-D , 15E , 16B (Japanese name: okinawa-horahimegumo オキナワホラヒメグモ)

Nesticus okinawaensis Yaginuma 1979: 275, pl. 6, figs 6-8 (♂♀): Yaginuma 1986: 55, fig. 31.7 (♂♀).

Howaia okinawaensis Lehtinen and Saaristo 1980: 59 (♂♀, transferred from Nesticus ).

Nesticella okinawaensis Kamura and Irie 2009: 353, figs 111, 112 (♂♀).

Type locality.

Japan, Okinawa honto Is., Kakinohana,Tamagusuku-son, Yaaji-gama Cave.

Material examined.

Japan: Kagoshima Pref.: Amami-Ōshima Is .: 1♂, 1♀, Amami-shi, Naze , forest litter, 15.Mar.2020 , R. Serita leg. (FBPC); Okinoerabu-jima Is . : 1♀, Murauchi Shindō cave (村内新洞), 4.May.2004, H. Tamura leg. (MNHAH); 1♀, China-cho, Ginsuido cave (銀水洞), 27.Apr.2004 , H. Tamura leg. (MNHAH); Okinawa Pref.: Okinawa-honto Is .: 2♀, Kunigami-gun, Motobu-cho, Izumi, 216 m, forest litter along the road, 26.63968°N, 127.93916°E, 17.Nov.2020; 1♀, Kunigami-son, Yona, Yambaru Park, 185 m, humid forest litter, 26.74755°N, 128.22347°E, 25.Feb.2021; 1♂, 10♀, same locality, 132 m, 26.75168°N, 128.22227°E, 28.Feb.2021 ; 2♀, same locality, 206 m, 26.74536°N, 128.22545°E, 28.Feb.2021 ; 2♀, same locality, 55 m, 2 6.75803°N, 128.22167°E, 01.Mar.2021 , all F. Ballarin leg. (FBPC); 1♂, 1♀, Ogimi-son, Okuni-rindo Pass , 7.Mar.2020 , Y. Suzuki leg. (YSPC); Kume-jima Is . : 2♀, Shimajiri-gun, Maja, 95 m, litter in a broadleaf forest, 26.34819°N, 126.80254° E, 18.May.2022, F. Ballarin leg. (FBPC); 1♀, Uegusuku, 263 m, litter in a broadleaf forest, 26.37577°N, 126.76990°E, 18.May.2022, F. Ballarin leg. (FBPC).

Diagnosis.

Male of Nesticella okinawaensis can be distinguished from male of other Japanese congeners by the short and stocky beak-like median process of conductor (Cm) with a long ventral process (vs a longer, smaller, or thinner Cm, with a smaller or lacking ventral process in other species), by the presence of a long, lobated distal apophysis on the retrolateral process of conductor (Ca) (vs small Ca in N. silvicola sp. nov. or lacking in other species), and by the shape of paracymbium having an elongated distal process I (Di-I) and a lobated and complex distal process II (Di-II) (vs a shorter Di-I, and a missing, simpler, smaller or thinner Di-II in other species) (Figs 12A-D , 13A-C cf. Figs 1A-D , 2A-D , 4A-C, E-G , 5A-D , 6A-D , 7A-C, E-G , 8A-D , 9A-D , 10A-C, E-G ). Female of N. okinawaensis is easily distinguished from female of other Japanese species by the shape of the internal copulatory ducts (Cd), thin and convoluted (vs thicker and less convoluted Cd in other species) (Figs 12E-G , 13D cf. Figs 1E-G , 2E-G , 3D, E , 4D, H , 5E-G , 6E-G , 7D, H , 8E-G , 9E-G , 10D, H , 11C-E , 13E, F ).

Redescription of male

(from Yambaru Park, Okinawa-honto). Habitus as in Fig. 12H . Total length 1.89. Prosoma 1.02 long, 0.90 wide. Carapace rounded, yellowish with dark cephalic area, median stripe, and margins. Cervical groove and fovea distinct. Eyes well developed. Eyes measurements: AME = 0.04, ALE = 0.09, PME = 0.09, PLE = 0.09, AME-ALE = 0.03, ALE-PLE = 0.00. Chelicerae, labium, maxillae, and sternum of the same yellowish color as carapace. Legs yellowish with dark annulation on femur, patella, tibia, metatarsus, and tarsus. Legs measurement: I 5.46 (1.51, 0.40, 1.41, 1.41, 0.53), II 4.68 (1.41, 0.38, 1.17, 1.16, 0.56), III 3.43 (1.07, 0.33, 0.77, 0.83, 0.43), IV 5.15 (1.57, 0.41, 1.39, 1.21, 0.57). Opisthosoma dark grey with whitish dorsal mark on dorsal-anterior side.

Male palp as in Figs 12A-D , 13A-C . Cymbium elongated, five or six robust setae on the distal and distal-prolateral margin (Fig. 12D ). Paracymbium with 2 distal processes (Di-I-II) and 1 ventral process (Va). Distal process I (Di-I) long, laterally flattened, slightly bent internally, ending with a small lobated tip; distal process II (Di-II) wide, proximal part laterally flattened, headed frontally, distal part lobated, headed internally bearing 2 small spurs. Ventral process of paracymbium (Va) wide, flat, triangularly shaped. (Figs 12A, B, D , 13A, C ). Embolus (E) long and filiform, origin of embolus positioned at ~ 4:30 o’clock on radix (Rx). Radical apophysis (Ra) strongly sclerotized, rectangularly shaped, flat, and stocky with granulated surface. Conductor with 3 distinct processes (Cp, Cr, Cm) and a half-transparent distal lobe (Cl). Prolateral process (Cp) long and flat, ribbon-like, headed counterclockwise, wrapped around embolus. Retrolateral process (Cr) wide and thick, curved internally, distally bearing a long, lobated apophysis (Ca) and a flat, triangular outgrowth in the central part. Median process of conductor (Cm) beak-like, short and stocky, strongly sclerotized, with a long, strongly sclerotized ventral process (Figs 12A-C , 13A, B ).

Redescription of female

(from Yambaru Park, Okinawa-honto). Habitus as in Figs 12I , 15E . Total length 1.84. Prosoma 0.87 long, 0.72 wide. Carapace piriform. Cephalic area as in Fig. 12J . Eyes well-developed. Eyes measurements: AME = 0.03, ALE = 0.08, PME = 0.08, PLE = 0.08, AME-ALE = 0.03, ALE-PLE = 0.00. Legs measurements: I 6.13 (1.51, 0.41, 1.36, 1.28, 0.57), II 3.66 (1.09, 0.36, 0.85, 0.83, 0.53), III 2.58 (0.70, 0.31, 0.56, 0.55, 0.46), IV 4.26 (1.33, 0.40, 1.04, 0.98, 0.51). Coloration and other details as in male.

Epigyne and vulva as in Figs 12E-G , 13D . Scapus (Sc) short, rectangular, elongated laterally, ~ 2 × wider than long, bearing a flat posterior margin (Figs 12E, F , 13D ). Copulatory opening (Co) at the inner-lateral sides of scapus. Internal ducts slightly visible through the transparent tegument, shaped as 2 inverted round brackets. Copulatory ducts (Cd), thin, coiled, reaching the spermathecae after 2 coils. Insemination ducts (Id) thin. Spermathecae (S) small and rounded, separated from each other by ~ 2.5 × their diameter (Fig. 12G ).

Size variation.

Male (based on 3 males) Total length: 1.85-1.89, prosoma length: 1.01-1.02, width: 0.88-0.90. Female (based on 8 females) Total length: 1.68-2.07, prosoma length: 0.88-0.92, width: 0.79-0.81.

Distribution.

Nesticella okinawaensis is distributed in the islands forming the Central Ryukyu arc (Fig. 16B ). The new records for Amami-Ōshima and Okinoerabu-jima islands herein reported extend the known distribution of this species ~ 200 km to the North-East. Currently, N. okinawaensis is recorded from the islands of Amami-Ōshima, Okinoerabu-jima, Okinawa-honto, and Kume-jima ( Yaginuma 1979; Tanikawa and Sasaki 1999; and this work) but its presence in other minor islands of the Central Ryukyu is also probable.

Habitat and ecology.

Nesticella okinawaensis dwells in humid and shadowed habitats such as caves, narrow valleys, and vegetated cliffs. This species builds simple scaffold webs in empty spaces in the leaf litter or under logs and superficial rocks, as well as in recesses of the walls and floor of caves, usually in the twilight zone.

Remarks on intraspecific variation.

The general coloration and the dorsal pattern of the opisthosoma appear rather variable in N. okinawaensis , changing among populations living in different areas or different islands or even single individuals. Populations living in the northern area of Okinawa-honto Is. often show a darker pattern, with less clear marks often reduced to a single whitish spot on the dorsal-anterior side (Figs 12I , 15E ); populations from Kume-jima Is. often have a whitish continuous stripe along the median line of the opisthosoma, while populations from Amami-Ōshima Is. usually have a general lighter pattern with numerous larger light marks partially fused to each other (Fig. 12H ). The shape of scapus also shows minor variability among specimens from different islands with the samples from Kume-jima Is. and Okinoerabu-jima Is. generally having a slightly narrower scapus. A high degree of genetic variation is also observed between population distributed in different islands (e.g., Amami Is.-Kumejima Is. = 7.3-7.8%; Amami Is.-Okinawa Is. = 7.5%; Kumejima Is.-Okinawa Is. = 5.6-6.7%).

Remarks on systematic.

Nesticella okinawaensis was provisionally included in the N. brevipes group by Lin et al. (2016) on the basis of published drawings only. Our molecular analysis, and a detailed morphological comparison of this species with the type material of N. brevipes , suggest that N. okinawaensis is in fact far related to the N. brevipes group and it belongs to a distinct clade. In addition, this species seems to have a basal position within the genus Nesticella (Fig. 14 ). Nevertheless, the phylogeny reconstructed in this work is based on a single gene fragment and includes only a part of the known Nesticella species. Preliminary analysis including more species (e.g., species of the N. phami group) seem to confirm the monophyly of N. okinawaensis although the support of the main nodes decreases substantially. Wider and more detailed molecular and morphological studies including a larger number of species and gene fragments are necessary to confirm the phylogenetic position of N. okinawaensis within Nesticella .

Figures

Figure 1. Howaia mogera A male palp (holotype), ventral view B same, retrolateral view C same, ventro-prolateral view D same, dorsal view E female epigyne ventral view (specimen from Tokyo area) F same after dissection, shape variation G vulva, dorsal view H habitus of male (specimen from Tokyo area) I habitus of female J cephalic area of female, frontal view. Abbreviations: Cd - copulatory duct; Co - copulatory opening; Id - insemination duct; S - spermatheca; Sc - scapus. Scale bars: 0.2 mm (A-G, J); 1.0 mm (H, I).

Figure 2. Howaia alba sp. nov. A male palp (holotype), ventral view B same, retrolateral view C same, ventro-prolateral view D same, dorsal view E female epigyne (one of the paratypes), ventral view F same, shape variation G vulva, dorsal view H habitus of male (holotype) I habitus of female (one of the paratypes) J cephalic area of female, frontal view. Abbreviations: Cd - copulatory duct; Co - copulatory opening; Id - insemination duct; S - spermatheca; Sc - scapus. Scale bars: 0.2 mm (A-G, J); 1.0 mm (H, I).

Figure 3. Howaia subterranea sp. nov. A habitus of female (holotype) B cephalic area of female, frontal view C habitus of female, lateral view D female epigyne, ventral view E vulva, dorsal view. Abbreviations: Cd - copulatory duct; Co - copulatory opening; Id - insemination duct; S - spermatheca; Sc - scapus. Scale bars: 1.0 mm (A, C); 0.2 mm (B, D, E).

Figure 4. Genitalia of Howaia mogera and H. alba sp. nov. A male palp of H. mogera, ventral view B same, retrolateral view C detail or paracymbium, dorsal view E female epigyne, ventral view E male palp of H. alba sp. nov., ventral view F same, retrolateral view C detail or paracymbium, dorsal view H female epigyne, ventral view. Abbreviations: Cl - lobe of conductor; Cm - median process of conductor; Co - copulatory opening; Cp - prolateral process of conductor; Cr - retrolateral process of conductor; Di - distal process of paracymbium; E - embolus; P - paracymbium; Ra - radical apophysis; Rx - radix; S - spermatheca; Sc - scapus; Sd - sperm duct; St - subtegulum; Te - tegulum; Ve - ventral process of paracymbium. Scale bars: 0.2 mm.

Figure 5. Nesticella brevipes A male palp (paratype), ventral view B same, retrolateral view C same, ventro-prolateral view D same, dorsal view E female epigyne (holotype), ventral view F same, female from Kyushu G vulva, dorsal view H habitus of male (old specimen from Kyushu); I habitus of female (specimen from Shikoku); J cephalic area of female, frontal view. Abbreviations: Cd - copulatory duct; Co - copulatory opening; Id - insemination duct; S - spermatheca; Sc - scapus. Scale bars: 0.2 mm (A-G, J); 1.0 mm (H, I).

Figure 6. Nesticella terrestris A male palp (one of the topotypes), ventral view B same, retrolateral view C same, ventro-prolateral view D same, dorsal view E female epigyne (topotype), ventral view F same after dissection, shape variation G vulva, dorsal view H habitus of male (topotype) I habitus of female J cephalic area of female, frontal view. Abbreviations: Cd - copulatory duct; Co - copulatory opening; Id - insemination duct; S - spermatheca; Sc - scapus. Scale bars: 0.2 mm (A-G, J); 1.0 mm (H, I).

Figure 7. Genitalia of Nesticella brevipes and N. terrestris A male palp of N. brevipes, ventral view B same, retrolateral view C detail or paracymbium, dorsal view E female epigyne, ventral view E male palp of N. terrestris, ventral view F same, retrolateral view C detail or paracymbium, dorsal view H female epigyne, ventral view. Abbreviations: Cl - lobe of conductor; Cm - median process of conductor; Co - copulatory opening; Cp - prolateral process of conductor; Cr - retrolateral process of conductor; Di I-II - distal process (es) I and II of paracymbium; Do - dorsal process of paracymbium; E - embolus; P - paracymbium; Ra - radical apophysis; Rx - radix; S - spermatheca; Sc - scapus; Sd - sperm duct; St - subtegulum; Te - tegulum; Ve I-II - ventral processes I and II of paracymbium. Scale bars: 0.2 mm.

Figure 8. Nesticella silvicola sp. nov. A male palp (holotype), ventral view B same, retrolateral view C same, ventro-prolateral view D same, dorsal view E female epigyne (one of the paratypes), ventral view F same, from shape variation G vulva, dorsal view H habitus of male I habitus of female J cephalic area of female, frontal view. Abbreviations: Cd - copulatory duct; Co - copulatory opening; Id - insemination duct; S - spermatheca; Sc - scapus. Scale bars: 0.2 mm (A-G, J); 1.0 mm (H, I).

Figure 9. Nesticella insulana sp. nov. A male palp (holotype), ventral view B same, retrolateral view C same, ventro-prolateral view D same, dorsal view E female epigyne (one of the paratypes), ventral view F same, from shape variation G vulva, dorsal view H habitus of male I habitus of female J cephalic area of female, frontal view. Abbreviations: Cd - copulatory duct; Co - copulatory opening; Id - insemination duct; S - spermatheca; Sc - scapus. Scale bars: 0.2 mm (A-G, J); 1.0 mm (H, I).

Figure 10. Genitalia of Nesticella silvicola sp. nov. and N. insulana sp. nov. A male palp of N. silvicola sp. nov., ventral view B same, retrolateral view C detail or paracymbium, dorsal view E female epigyne, ventral view E male palp of N. insulana sp. nov., ventral view F same, retrolateral view C detail or paracymbium, dorsal view H female epigyne, ventral view. Abbreviations: Cl - lobe of conductor; Cm - median process of conductor; Co - copulatory opening; Cp - prolateral process of conductor; Cr - retrolateral process of conductor; Di I-II - distal process (es) I and II of paracymbium; Do - dorsal process of paracymbium; E - embolus; P - paracymbium; Ra - radical apophysis; Rx - radix; S - spermatheca; Sc - scapus; Sd - sperm duct; St - subtegulum; Te - tegulum; Ve I-II - ventral processes I and II of paracymbium. Scale bars: 0.2 mm.

Figure 11. Nesticella occulta sp. nov. A habitus of female (holotype) B cephalic area of female, frontal view C female epigyne, ventral view D same, shape variation E vulva, dorsal view. Abbreviations: Cd - copulatory duct; Co - copulatory opening; Id - insemination duct; S - spermatheca; Sc - scapus. Scale bars: 1.0 mm (A, C); 0.2 mm (B, D, E).

Figure 12. Nesticella okinawaensis A male palp, ventral view (specimen from Yambaru) B same, retrolateral view C same, ventro-prolateral view D same, dorsal view E female epigyne, ventral view (specimen from Yambaru) F same after dissection, shape variation (specimen from Amami-Ōshima Is.) G vulva, dorsal view (specimen from Yambaru) H habitus of male (specimen from Amami-Ōshima Is.) I habitus of female (specimen from Yambaru) J cephalic area of female, frontal view. Abbreviations: Cd - copulatory duct; Co - copulatory opening; S - spermatheca; Sc - scapus. Scale bars: 0.2 mm (A-G, J); 0.5 mm (H, I).

Figure 13. Genitalia of Nesticella okinawaensis, Howaia subterranea sp. nov., and N. occulta sp. nov. A male palp of N. okinawaensis, ventral view B same, retrolateral view C detail or paracymbium, dorsal view D female epigyne, ventral view; E H. subterranea sp. nov., female epigyne, ventral view F N. occulta sp. nov. female epigyne, ventral view. Abbreviations: Ca - apophysis of the retrolateral process of conductor; Cl - lobe of conductor; Cm - median process of conductor; Co - copulatory opening; Cp - prolateral process of conductor; Cr - retrolateral process of conductor; Di I-II - distal processes I and II of paracymbium; E - embolus; P - paracymbium; Ra - radical apophysis; Rx - radix; S - spermatheca; Sc - scapus; Sd - sperm duct; St - subtegulum; Te - tegulum; Ve - ventral process of paracymbium. Scale bars: 0.2 mm.

Figure 14. Combined phylogenetic tree based on COI gene fragment reconstructed using maximum likelihood (ML) on RAxML and Bayesian inference (BI) on MrBayes. Support at each node denotes the ML bootstrap value (BV) and BI posterior probability (PP). Nodes highly supported by at least one method (BV ≥ 70 or PP ≥ 0.95) are highlighted by a black dot. Branch lengths were scaled concerning the number of substitutions per site. Each species corresponding to monophyletic clades are represented with different branch colors, species from Japan are highlighted with a colored background: red = H. mogera, azure = H. alba sp. nov., yellow = N. occulta sp. nov., violet = N. insulana sp. nov., light green = N. silvicola sp. nov., blue = N. brevipes, orange = N. terrestris, dark green = N. okinawaensis. The tree is rooted using the species Wraios longiembolus. The right lines denote the results of the species delimitation analysis based on morphological (MO) and molecular (ASAP, mPTP, and bPTP) data.

Figure 15. Nesticella and Howaia species in life and their natural habitats A female of H. mogera B female of N. terrestris C female of H. alba sp. nov. D female of N. occulta sp. nov. E female of N. okinawaensis F example of the epigean habitat of Nesticella species in the Ryukyus G habitat of H. alba sp nov. (dark zone of Tsuzupisuki-abu cave) H habitat of N. occulta sp. nov. (dark zone of Kabirano-ana cave) (all photos by F. Ballarin).

Figure 16. Distribution of Nesticella and Howaia species in mainland Japan and Ryukyu Archipelago A distribution of N. brevipes and N. terrestris in mainland Japan and neighboring countries B distribution of Nesticella and Howaia species endemic to the Ryukyu Archipelago C distribution of H. mogera in mainland Japan and neighboring countries D distribution of H. mogera in the Ryukyu Archipelago and neighboring countries. Colored squares refer to the type localities of the species, colored dots indicate the locations of specimens whose morphology has been checked during this study, dashed areas refer to the generally known distribution of the species, question marks refer to unclear distributions (see " remarks on misidentifications " of N. brevipes and N. terrestris).