First record of theridiosomatid genus Sennin Suzuki, Hiramatsu & Tatsuta, 2022 from Anhui Province, China, with the description of a new species (Araneae, Theridiosomatidiae)

Abstract Background Only two Sennin species are known from the world, Sennincoddingtoni (Zhu, Zhang & Chen, 2001) from China and Sennintanikawai Suzuki, Hiramatsu & Tatsuta, 2022 from Ryukyu Islands. No other Sennin species have been recorded from other locations. New information A new species, Senninshuanglong sp. n. is described from Anhui Province, China. Morphological illustrations, SEMs, living photos, habitat and distribution map are given.


Introduction
The spider family Theridiosomatidiae Simon, 1881 includes 137 species from 20 genera worldwide (World Spider Catalog 2023).At present, 30 species belonging to 12 genera are known from China (World Spider Catalog 2023).Most of these species (21 species) are distributed in southwest China, but there are few records (2 species) in eastern China (World Spider Catalog 2023).They are a widely distributed family of very small body size (usually ≤ 3 mm) and usually found in damp, dark habitats, such as the litter layer of forest or in caves (Zhao and Li 2012).Although many species have been reported in the past 15 years (World Spider Catalog 2023), there are still many poorly-known theridiosomatid and other species (Liu et al. 2022) from southern China with unusual morphological characteristics.
The genus Sennin was established by Suzuki et al. (2022), based on the type species, Sennin tanikawai Suzuki, Hiramatsu & Tatsuta, 2022 recorded from Ryukyu Islands.One Karstia species, recorded from Guizhou Province, China, was transferred to this genus by Suzuki et al. (2022).Now, the genus only consists of these two species mainly recorded from Asia.
In a recent exploration of the limestone caves in Anhui Province, China, one undescribed species of this poorly-known genus was found.The aim of the present paper is to provide a detailed description of this new species whichalso represents the first record of this family from Anhui Province.

Materials and methods
Specimens were examined using a SZ6100 stereomicroscope.Both male and female copulatory organs were dissected and examined in 80% ethanol using an Olympus CX43 compound microscope with a KUY NICE CCD camera.Epigynes were cleared with pancreatin solution (Álvarez-Padilla and Hormiga 2007).Specimens, including dissected male palps and epigynes, were preserved in 75% ethanol after examination.Types are deposited in the Animal Specimen Museum, College of Life Science, Jinggangshan University (ASM-JGSU).
The measurements were taken using a stereomicroscope (AxioVision SE64 Rel.4.8.3) and are given in millimetres.The body lengths of all specimens exclude the chelicerae and spinnerets.Terminology of the male and female genitalia follows Suzuki et al. (2022).
Measurements  Colouration (Fig. 1C and D).Lighter than male.Abdomen lacking ring-like white band, with two pairs of white patches in anterior half part.
Epigyne (Fig. 3, Fig. 4L and M).Epigynal plate wider than long, posteriorly with a protruding, long and banana-shaped epigynal scape, convex ventrally.Copulatory opening very small.Copulatory bursae developed, membranous, touching.Copulatory ducts originating from copulatory bursae, extending along the mesial line of the vulva, running posterior-dorsally under spermathecae, bent at an acute angle towards anteromedially, curving backwards at lateral side of spermathecae, spiralling a circle.Spermathecae located medially, moderate tapering in touching part.Fertilisation ducts short, running under copulatory ducts, medially directed.Females resemble those of S. coddingtoni ( Chen 2010: 7, figs. 19 and 20) and S. tanikawai ( Suzuki et al. 2022: 87, fig. 8) in having the copulatory duct with a coil laterally located, but can be distinguished from it by the very long epigynal scape as same as epigynal length (vs.relative long epigynal scape shorter than epigynal length in S. coddingtoni and S. tanikawai) and the transversal spermathecae with a tapering tip in touching area (vs. the transversal spermathecae without tapering tip; the sloping spermathecae in S. tanikawai) (Fig. 3, Fig. 4L and M).

Etymology
The specific name is a noun in apposition and refers to the type locality.

Ecology
The new species only inhabits deep within limestone caves (Fig. 5A).These spiders build vertical circular webs with the junction of the top and sides of the cave (Fig. 5B  and C).Egg sacs (Fig. 5F) spherical, are suspended with a long vertical line on the roof of the cave near female webs.