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| Nihonella chika Ballarin & Yamasaki, 2021 |
Abstract
A new monospecific genus belonging to the family Linyphiidae Blackwell, 1859, Nihonella gen. nov., is described using an integrative taxonomic approach based on the species N. chika gen. et sp. nov. The new genus is endemic to Western Honshu, Japan, and it shows distinctive genitalic and somatic characters of other genera of the subfamily Erigoninae Emerton, 1882. Nihonella gen. nov. is found only in the twilight and transition zones of caves in Okayama and Nara Prefectures. The phylogenetic position of Nihonella gen. nov. within the subfamily Erigoninae, and its relationship as a sister clade of the species of the group of Savignia Blackwell, 1833 (sensu Millidge 1977), is discussed on the basis of both, morphological and molecular evidence.
Keywords: Caves, endemism, new species, phylogeny, subterranean environment
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| Habitus and habitat of Nihonella chika gen. et. sp. nov. A. ♂, holotype (NSMT-Ar 20909), habitus, dorsal view. B. Ditto, ventral view. C. Ditto, lateral view. D. ♀, paratype (NSMT-Ar 20910), habitus, dorsal view. E. Ditto, ventral view. F. Ditto, lateral view. G. Ditto, cephalic region, frontal view. H. Entrance of Anatoyama Cave, type locality of the species. Scale bar = 1 mm. |
Class Arachnida Cuvier, 1812
Order Araneae Clerck, 1757
Family Linyphiidae Blackwall,1859
Subfamily Erigoninae Emerton, 1882
Nihonella gen. nov.
Diagnosis: The new genus is distinguished from any other genera belonging to the distal Erigoninae clade by the following unique combination of somatic and genitalic characters: Femur I with 1 prolateral spine; Tibia I with 1 dorsal spine; tibial spine formula: 1.1.1.1; male palp with a well-developed distal suprategular apophysis and a hypertrophic ʻsecondaryʼ DSA (Figs 2A–B, 3A–C, 4A–E) (usually presented in Erigoninae as a simple tooth and protruding form a different side of the DSA); a well-developed and uniquely-shaped prolateral tibial apophysis, the same length as the cymbium and partially covering it (Figs 2A–C, 3A–B, D, 4E–F). The unusual chaetotaxy and unique shape of the epigyne, with anteriorly converging lateral walls and two distinct, flat, ovoid inflations of the copulatory ducts, also distinguishes the female of this genus from females of any other genera in distal Erigoninae.
Etymology: The generic name is a combination of the word ʻNihonʼ and the Latin suffix ʻ-ellaʼ. The former refers to the country of Japan where the genus is endemic; the latter is the feminine suffix of ʻ-ellusʼ commonly used in Latin to form the feminine diminutive of a noun. Name in apposition, feminine in gender
Distribution: Endemic to Western Honshu, Japan. Currently known from three caves only (Figs 1H, 6).
Nihonella chika gen. et sp. nov.
Etymology: The specific name is derived from the Japanese word ʻchikaʼ (地下) meaning ʻunderground, subterraneanʼ and thus refers to the habitat of the species, but it is also the pronunciation of a feminine given name in the Japanese language. Name in apposition.
Francesco Ballarin and Takeshi Yamasaki. 2021. Nihonella gen. nov., A New troglophilic Genus of Dwarf Spiders from Japan with a discussion on its phylogenetic position within the subfamily Erigoninae (Araneae, Linyphiidae). European Journal of Taxonomy 733; 1–18. DOI: doi.org/10.5852/ejt.2021.733.1215
