Howaia subterranea, 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

Howaia subterranea sp. nov.

Figs 3A-E , 13E , 16B (Japanese name: kaiken-horahimegumo カイケンホラヒメグモ)

Material examined.

♀ Holotype: Japan: Kagoshima Pref.: Okinoerabu-jima Is.: 1♀, Kaikendo cave (海見洞), 3.May.2004 H. Tamura leg. (NSMT-Ar 25253).

Etymology.

The new species is named after the Latin adjective subterraneus (= underground, subterranean). It refers to the troglobitic lifestyle of this species.

Diagnosis.

This species is similar to H. mogera and the other troglobiont species H. alba sp. nov. and N. occulta sp. nov. Howaia subterranea sp. nov. can be distinguished from these species by the different shape of the epigyne, having curved internal ducts (vs straight ducts in the other three species), and a longer scapus (Sc) with an enlarged tip (vs a shorter and more rectangular Sc with a flat distal margin in H. mogera , a shorter and stockier Sc in H. alba sp. nov., and a shorter, tongue-like Sc in N. occulta sp. nov., all of them lacking a clearly enlarged tip) (Figs 3D, E , 13E cf. Figs 1E-G , 2E-G , 4D, H ). In addition, the new species can be easily distinguished from H. mogera and the other Japanese species by the lack of eyes and pigmentation (vs present in the other troglophilic congeners).

Description.

Female (holotype). Habitus as in Fig. 3A, C . Total length 2.65. Prosoma 1.20 long, 0.93 wide. Carapace piriform, uniformly pale yellowish. Eyes strongly degenerated, reduced to white maculae (Fig. 3B ). Cervical groove and fovea indistinct. Chelicerae uniformly brownish. Labium, maxillae, and sternum pale yellowish as carapace. Legs uniformly pale yellowish. Legs measurements (leg III missing): I 6.73 (1.95, 0.46, 1.82, 1.65, 0.85), II 5.24 (1.56, 0.45, 1.29, 1.22, 0.72), III (-), IV 5.75 (1.76, 0.46, 1.54, 1.32, 0.67). Opisthosoma uniformly greyish, covered by long, sparse hairs.

Epigyne and vulva as in Figs 3D, E , 13E . Scapus (Sc) elongated antero-posteriorly, ~ 2 × longer than wide, ending with an enlarged, lobated tip (Figs 3D , 13E ). Copulatory opening (Co) at the inner-lateral sides of scapus. Internal ducts slightly visible through the transparent tegument, shaped as a narrow curly bracket. Copulatory ducts (Cd) bent in middle trait, first trait slightly curved outward then curving anteriorly before reaching spermathecae (Figs 3D, E , 13E ). Insemination ducts (Id) thin, coiled around the copulatory ducts. Spermathecae (S) small and rounded, separated from each other by ~ 2.5 × their diameter (Fig. 3D, E ).

Male. Unknown.

Distribution.

Endemic to Okinoerabu-jima Island. Known only from the type locality (Fig. 16B ).

Habitat and ecology.

Howaia subterranea sp. nov. has probably been collected in the dark zone of the type locality cave. The lack of pigmentation and the strongly reduced eyes further suggest this species as a true troglobiont. Nevertheless, the lack of specimens and additional information do not allow us to define in detail the ecology and micro-habitat preference of this species as well as its precise phylogenetic position. Nevertheless, the morphology of epigyne clearly identify H. subterranea sp. nov. as belonging to the genus Howaia .

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 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 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).