Nesticella insulana, 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 insulana sp. nov.

Figs 9A-J , 10E-H , 16B (Japanese name: donan-horahimegumo ドナンホラヒメグモ)

Material examined.

♂ Holotype: Japan: Okinawa Pref., Yonaguni-jima Is.: Mantabaru Forest Park (満田原森林公園), 54 m, humid forest litter in a narrow valley, 24.45652°N, 122.97692°E, 3.Mar.2021, K. Eguchi leg. (NSMT-Ar 25257).

Paratypes: 4♀, same locality and date as the holotype, K. Eguchi leg. (NSMT-Ar 25258) ; 5♀, same locality and date, 112 m, 24.45678°N, 122.97675°E, F. Ballarin leg. (FBPC) .

Other material examined.

1♂ subad., same locality and date as the holotype, 115 m, humid forest litter, 24.45660°N, 122.97584°E, F. Ballarin leg. (FBPC) ; 1♀ subad., 54 m, humid forest litter in a small valley near route 216, 24.44740°N, 122.96827°E, 04.Mar.2021, F. Ballarin leg. (FBPC).

Etymology.

The specific name is derived from the Latin adjective insulanus (= islander). It refers to the distribution of the species, limited to the island of Yonaguni-jima.

Diagnosis.

The new species is closely related to Nesticella odonta (Chen, 1984) from Zhajinag Province, China. Male of the new species can be distinguished from male of N. odonta by the wider distal process I of paracymbium (Di-I), the smaller and blunter distal process II (Di-II), and by the more curved ventral process II (vs thinner and sharper Di-I, wider Di-II, and straighter Ve-II in N. odonta ) (Figs 9A, B, D , 10E-G cf. Lin et al. 2016: figs 24A, B, D). Female of N. insulana sp. nov. can be separated from female of N. odonta by the narrower, longer, and more arrow-like scapus (Sc) of the epigyne (vs wider, more trapezoidal, and shorter scapus in N. odonta ) (Figs 9E-G , 10H cf. Lin et al. 2016: fig. 25E-G). The general shape of genitalia in both male and female allows to easily discern N. insulana sp. nov. from all the other Japanese congeners of the N. brevipes group.

Description of male

(holotype). Habitus as in Fig. 9H . Total length 1.81. Prosoma 0.91 long, 0.83 wide. Carapace rounded, yellowish with darker areas around borders and central area. Cervical groove and fovea distinct. Eyes well developed. Eyes measurements: AME = 0.05, ALE = 0.08, PME = 0.08, PLE = 0.08, AME-ALE = 0.04, ALE-PLE = 0.01. Chelicerae, labium, maxillae, and sternum of same color as carapace. Legs yellowish often with dark annulations on femur, and tibia. Legs measurements as follows: I 5.98 (1.65, 0.43, 1.58, 1.59, 0.73), II 4.35 (1.25, 0.31, 1.13, 1.06, 0.60), III 3.33 (0.98, 0.36, 0.70, 0.76, 0.53), IV 4.67 (1.43, 0.33, 1.19, 1.04, 0.68). Opisthosoma greyish with large dark marks on dorsal and lateral sides.

Male palp as in Figs 9A-D , 10E-G . Cymbium relatively short, 4-6 thicker setae on distal-prolateral margin (Fig. 9D ). Paracymbium with 2 distal processes (Di-I, II) and 2 flat, lobated ventral processes (Ve-I-II): distal process I (Di-I) wide and lobated, hook-like when observed laterally, with tip headed ventral-retrolaterally; distal process II (Di-II) short and blunt, headed frontally; ventral process I (Ve-I) shorter, headed anteriorly; ventral process II (Ve-II) long and curved, headed antero-retrolaterally (Figs 9A-D , 10E-I Embolus (E) long and filiform, origin of embolus positioned at ~ 4:00 o’clock on radix (Rx). Radical apophysis (Ra) strongly sclerotized, triangular, and sharp, ending with a pointed tip. Conductor with 3 distinct processes (Cp, Cr, Cm) and a half-transparent distal lobe (Cl). Prolateral process of conductor (Cp) flat, ribbon-like, headed counter-clockwise, wrapped around embolus. Retrolateral process of conductor (Cr) wide and thick, curved inside, bearing a small sclerotized apophysis (Ca). Median process of conductor (Cm) strongly sclerotized, thin, spine-like ribbon-like, with a ribbon-like lobe wrapped around its prolateral side. (Figs 9A-C , 10E, F ).

Description of female

(one of the paratypes). Habitus as in Fig. 9I . Total length 2.05. Prosoma 0.91 long, 0.84 wide. Cephalic area as in Fig. 9J . Carapace piriform. Eyes measurements: AME = 0.05, ALE = 0.07, PME = 0.08, PLE = 0.08, AME-ALE = 0.04, ALE-PLE = 0.01. Coloration and other details as in male. Legs measurements as follows: I 5.45 (1.61, 0.45, 1.41, 1.33, 0.65), II 3.98 (1.19, 0.41, 0.93, 0.89, 0.56), III 3.04 (0.88, 0.34, 0.67, 0.64, 0.51), IV 4.29 (1.39, 0.40, 1.09, 0.92, 0.49).

Epigyne and vulva as in Figs 9E-G , 10H . Scapus (Sc) short and stumpy, arrow-like, ~ 2 × wider than long, with sloped borders and narrower, slightly rounded tip (Figs 9E, F , 10H ). Copulatory opening (Co) at the inner-lateral sides of scapus. Internal ducts slightly visible through the transparent tegument, shaped as curly bracket. Copulatory ducts (Cd) thick, strongly bent in middle trait, curving first laterally and then anteriorly before reaching spermathecae. Insemination ducts thin, coiled around copulatory ducts. Spermathecae (S) small and rounded, separated from each other by ~ 1.5 × their diameter (Fig. 9G ).

Size variation.

Female (based on 5 specimens): total length 1.90-2.57, prosoma length: 0.82-1.05, prosoma width: 0.78-0.93.

Distribution.

Endemic to Yonaguni-jima Is., western Ryukyus. Known only from the type locality (Fig. 16B ).

Habitat and ecology.

Nesticella insulana sp. nov. inhabits the shadowed and humid forests covering the hills of the central-western area of Yonaguni-jima Island. This species builds simple scaffold webs in the empty spaces among the leaf litter accumulated in narrow valleys, under rotten wood and on vegetated cliffs. Despite several attempted surveys, this species was not collected in other parts of the island.

Nesticella quelpartensis group

Figures

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).