Nesticella silvicola, Ballarin & Eguchi, 2023

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 silvicola sp. nov.

Figs 8A-G , 10A-D , 16B (Japanese name: Yamako-horahimegumo ヤマコホラヒメグモ)

Material examined.

♂ Holotype: Japan: Kagoshima Pref., Yakushima Is.: Koseda, Nagamine , 29.Mar.2023, S. Konishi leg. (NSMT-Ar 25254).

Paratypes: Japan: Kagoshima Pref., Yakushima Is.: 1♀, Koseda , 190 m, broadleaf forest litter on a gentle slope, 30.38286°N, 130.62455°E, 24.Sep.2021, F. Ballarin leg. (RMUF) ; 2♀, Isso , 130 m, broadleaf forest litter bordering a sugi plantation near a river, 30.43615°N, 130.48129°E, 27.Sep.2021, F. Ballarin leg. (NSMT-Ar 25255) ; 1♀, Miyanoura, 15. July. 1990, A. Tanikawa leg. (FBPC) ; 1♀, Miyanoura , 341 m, humid broadleaf forest litter in a humid valley near a creek, 30.39696°N, 130.55584°E, 27.Sep.2021, F. Ballarin leg. (FBPC) ; 1♀, Anbo , 224 m, broadleaf forest litter, 30.28375°N, 130.61619°E, 27.Sep.2021, F. Ballarin leg. (FBPC) ; 1♀ Jhonji-dake , 18.Feb.2023, S. Konishi leg. (NSMT-Ar 25256)

Etymology.

The specific name is derived from the Latin adjective silvicolus (= inhabiting woods, sylvan). It refers to the habitat of the species, living in the forests of Yakushima Is.

Diagnosis.

This species is closely related to N. brevipes and N. terrestris . Male of N. silvicola sp. nov. can be distinguished from male of N. terrestris by the stockier distal process of paracymbium (Di), the sharper radical apophysis (Ra), and by the wider ventral process II of paracymbium (Ve-II), (vs sharper Di, rounder Ra, and thinner Ve-II in N. terrestris ). (Figs 8A-D , 10A-C cf. Figs 6A-D , 7E-G ). In addition, the origin of the embolus (E) from the radix is located in a different position in the two species (4:30 o’clock in N. silvicola vs 6:00 o’clock in N. terrestris ) (Figs 8A , 10A cf. Figs 6A , 7 ). Male of the new species can be easily separated from male of N. brevipes by the single distal process of paracymbium (Di), a wider radical apophysis (Ra), and a thicker median process of conductor (Cm) (vs two Di, a slimmer Ra, and a thinner Cm in N. brevipes ). (Figs 8A-D , 10A-C cf. Figs 5A-D , 7A-C ).

Female of N. silvicola sp. nov. can be distinguished from female of the other Japanese congeners of the N. brevipes group, by the general shape of genitalia, having a short scapus (Sc) with a flat distal margin, more squared lateral margins and strongly bent internal ducts (vs a longer and lobated Sc with straight ducts in N. brevipes , a more lobated scapus with rounder distal margins and straight internal ducts in N. terrestris , or a narrower and more trapezoidal scapus in N. insulana sp. nov. (Figs 9E-G , 10F cf. Figs 5E-G , 6E-G , 7D, H , 8E-G , 10D ). The smaller size further allows a quick separation of N. silvicola sp. nov. from N. terrestris (females 1.84-1.94 vs 2.31-3.30).

Description of male

(holotype). Habitus as in Fig. 8H . Total length: 1.91. Prosoma 0.97 long, 0.86 wide. Carapace rounded, yellowish with slightly darker margins and central area. Cervical groove and fovea distinct. Eyes well developed. Eyes measurements: AME = 0.04, ALE = 0.08, PME = 0.08, PLE = 0.08, AME-ALE = 0.03, ALE-PLE = 0.00. Chelicerae, labium, maxillae, and sternum of same color as carapace. Legs yellowish with slightly darker annulation on distal femur, tibia, and metatarsus. Legs measurements: I 5.63 (1.60, 0.43, 1.48, 1.48, 0.64), II 4.28 (1.25, 0.38, 1.05, 1.06, 0.54), III 3.91 (1.00, 0.31, 0.82, 0.81, 0.47), IV 4.58 (1.44, 0.41, 1.16, 1.13, 0.44). Opisthosoma greyish with couples of slightly darker marks on anterior and dorsal side gradually merging to each other toward the posterior side.

Palp as in Figs 8A-D , 10A-C . Cymbium relatively short, covered with sparse setae, some thicker setae on distal-prolateral margin (Fig. 8D ). Paracymbium with a single distal process (Di), two ventral processes (Ve-I-II), and a dorsal apophysis (Do): distal process (Di) stumpy, headed ventrally and retrolaterally, hook-like when observed laterally; ventral process I (Ve-I) sharp and slim, headed internally; ventral process II (Ve-II) lobated, headed internally; dorsal apophysis (Do) lobated, wide and flat (Figs 8A-D , 10A-C ).Embolus (E) long and filiform, origin of embolus positioned at ~ 4:30 o’clock on radix (Rx). Radical apophysis (Ra) strongly sclerotized, wide and stumpy, triangular, ending with a rounded tip. Conductor with 3 distinct processes (Cp, Cr, Cm) and a half-transparent distal lobe (Cl). Prolateral process of conductor (Cp) flat, ribbon-like and headed counterclockwise, wrapped around embolus. Retrolateral process of conductor (Cr) wide and thick, curved inside. Median process of conductor (Cm) thick and strongly sclerotized, spine-like, ending blunt, with a ribbon-like lobe wrapped around its prolateral side. (Figs 8A-C , 10A, B ).

Description of female

(one of the paratypes). Habitus as in Fig. 8I . Total length: 1.87. Prosoma 0.88 long, 0.78 wide. Cephalic area as in Fig. 8J . Eyes measurements: AME = 0.04, ALE = 0.08, PME = 0.08, PLE = 0.08, AME-ALE = 0.03, ALE-PLE = 0.00. Coloration and other details as in male. Legs measurements: I 4.65 (1.33, 0.40, 1.21, 1.10, 0.61), II 3.68 (1.10, 0.37, 0.86, 0.82, 0.53), III 2.09 (0.89, 0.30, 0.62, 0.63, 0.46), IV 3.96 (1.22, 0.33, 1.02, 0.88, 0.53).

Epigyne and vulva as in Figs 8E-G , 10D . Scapus (Sc) very short and wide, rectangular, ~ 2.5 × wider than long, ending with a flat posterior margin slightly concave in the center (Figs 8E, F , 10D ). Copulatory opening (Co) at the inner-lateral sides of scapus. Internal ducts slightly visible through the transparent tegument, shaped as 2 angled brackets pointing towards each other. Copulatory ducts (Cd), short and thick, bent in the central trait, proximal part of ducts heading slightly internally, distal part heading laterally before reaching spermathecae. Insemination ducts (Id) thin, coiled around copulatory ducts. Spermathecae (S) small and rounded, separated from each other by ~ 1.5 × their diameter (Fig. 8G ).

Size variation.

(based on 5 females). Total length: 1.84-1.94, prosoma length: 0.86-0.99, prosoma width: 0.78-0.84.

Distribution.

Known only from Yakushima Is. in western Japan (Fig. 16B ).

Habitat and ecology.

Nesticella silvicola sp. nov. inhabits the shadowed and humid broadleaf and mixed forests covering the mountain slopes in Yakushima Is. This species builds simple scaffold webs in the empty spaces and recesses between the leaf litter and under rotten logs.

Figures

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 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).