A new species of Trachelas L. Koch, 1872 (Araneae, Trachelidae) from Tajikistan

Abstract A new species of trachelid spiders, Trachelas crewsaesp. nov. is described from south-western Tajikistan based on both sexes. The new species is closely related to T. vulcani Simon, 1896 from South-East Asia but differs in the conformation of the copulatory organs and color pattern.


Introduction
Trachelidae Simon, 1897 is a small spider group recently elevated to the family-level, consisting of 246 species in 19 genera (Ramírez 2014;WSC 2020). Trachelas L. Koch, 1872 is the most speciose genus of the family, accounting for 89 valid species distributed worldwide except for polar regions, Australia and New Zealand, with most of the species being known from the Americas (Platnick and Shadab 1974a, b;WSC 2020). The genus is well studied in the Palaearctic and Indomalayan regions thanks to several revisions dealing with the Mediterranean, Russian and south Chinese species (Bosselaers et al. 2009;Zhang et al. 2009;Marusik and Kovblyuk 2010;Jin et al. 2017).
To date, only a single Trachelas species -T. minor O. Pickard-Cambridge, 1872, one of the most widespread species of the family -is known from Central Asia: viz., from Turkmenistan and Uzbekistan (Mikhailov 2013). While examining spiders recently collected by the senior author from Tajikistan, we found Trachelas specimens that belong to an undescribed species similar to the Indomalayan T. vulcani Simon, 1896. The goal of this paper is to provide a detailed description and diagnosis of this new species.

Material and methods
Specimens were photographed using a Canon EOS 7D camera attached to an Olympus SZX16 stereomicroscope and a SEM JEOL JSM-5200 scanning electron microscope at the Zoological Museum, University of Turku, Finland. Photographs were taken in a dish filled with alcohol, with cotton at the bottom. The epigyne was macerated in a KOH/water solution until the soft tissues were dissolved. Digital images were prepared using Helicon Focus software (https://www.photo-soft.ru/helicon-focus/). All measurements are in millimeters. Length of leg segments were measured on their dorsal sides. Leg measurements are shown as: femur, patella, tibia, metatarsus, tarsus (total length). The terminology follows Jin et al. (2017), with some modifications. The types will be deposited in the Zoological Museum of the Moscow State University, Russia (ZMMU; curator: K.G. Mikhailov). Diagnosis. The male of the new species resembles those of T. vulcani in having a similar long, coiled embolus and long, apically oriented patellar apophysis (Pa) but can be distinguished from it by having a distinct abdominal scutum occupying 2/3 of the abdomen length (vs. absent) (cf. Figs 1A, B and 4A), the patellar apophysis (Pa) with almost parallel edges (vs. triangular), the Ͻ-shaped sperm duct (Sd) (vs. Jshaped) and the haematodocha (Hd) being almost as wide as the tegulum in ventral view (vs. significantly narrower) (cf. Figs 2B-D, F, 3B and 4D). Males of both species are also distinguishable in the relative length/width ratio of the palpal femur (as long as cymbium in the new species vs. shorter than cymbium) (cf. Fig. 4B, C), and the much longer embolus with its base situated postero-retrolaterally vs. antero-prolaterally. The female of T. crewsae sp. nov. also resembles that of T. vulcani in having copulatory ducts packed in several coils and primary receptacles (Pr), consisting of two subunits, but can be separated from the latter by the copulatory openings (Co) situated laterally (vs. anteriorly) (cf. Fig. 3D, G), the copulatory ducts (Cd) packed in four tight coils (vs. three loose coils) and the secondary receptacles (Sr) directed posteriad (vs. anteriolaterad) (cf. Fig. 3E, F, H). Both sexes of T. crewsae sp. nov. differ reliably from those of T. vulcani in having an abdominal colour pattern formed by transverse dark grey stripes (cf. Figs 1A-F, 4A). Palp as in Figs 2A-F, 3A-C, 4B; femur as long as cymbium, three times longer than wide, with wide ventral groove (Fg) occupying an anterior third of segment; patellar apophysis finger-like as long as patella's width, with a pointed tip; tegulum expanded anteriorly; Ͻ-shaped sperm duct poorly visible; embolus (Em) long, whip-like, coiled almost across entire tegulum; tegular apophysis (Ta) small, claw-shaped.

Taxonomy
Female. Total length 2.7. Carapace: 1.2 long, 1.06 wide. Coloration as in the male, with lighter dorsal abdominal pattern (Fig. 1D-F Epigyne as in Fig. 3D-F; epigynal plate semitransparent, through which the copulatory ducts and primary receptacles are clearly visible; fovea divided by septum 'db' shaped; copulatory openings small, located at anteriorly on fovea; copulatory ducts, forming four coils, packed in helix directed posteriolaterad; connecting ducts (Cn) looped; secondary receptacles small; primary receptacles consisting of two subunits, connected by a narrow constriction; fertilization ducts (Fd) weakly sclerotized.
Etymology. The new species is named after our colleague Sarah C. Crews (San Francisco, USA), who continuously helps us with editing the English and providing fruitful comments on our manuscripts.
Distribution. Known only from the type locality ( Fig. 5A-C).

Discussion
Trachelas vulcani, the sibling species of T. crewsae sp. nov., was described from Java, Indonesia (Simon 1896 (Fig. 5A). Based on the figures from the aforementioned papers, specimens of T. vulcani from different localities differ in details of the male palp and epigyne. Ono and Ogata (2018) argued that these differences lie within the range of species variation, considering the wide species range. However, it is also possible that all separated populations of T. vulcani could belong to different, closely related species. It is necessary to re-examine the holotype of T. vulcani in order to resolve the matter. The present diagnosis of T. crewsae sp. nov. from T. vulcani is based on the Chinese specimens considered by Jin et al. (2017: figs 5, 6, 7, 8, 9A, B).