Trapdoor spiders of the genus Cyclocosmia Ausserer, 1871 from China and Vietnam (Araneae, Ctenizidae)

Abstract A species of the genus Cyclocosmia Ausserer, 1871 collected from Guizhou Province, China is diagnosed and described as new to science: Cyclocosmia liui Xu, Xu & Li, sp. n. (♀). New records of Cyclocosmia latusicosta Zhu, Zhang & Zhang, 2006 (♀) from China (Yunnan Province) and Vietnam (Vinh Phuc Province, Ninh Binh Province), and Cyclocosmia ricketti (Pocock, 1901) collected from Jiangxi Province, China are also reported in this study.


Introduction
The mygalomorph family Ctenizidae is ancient, long-lived, regionally endemic and dispersal-limited, and thus is of long-standing and persistent conservation significance in many regions of the world (Zhu et al. 2006;Opatova et al. 2013Opatova et al. , 2016. Ctenizids are widely distributed in east and southeast Asia, north and south America, the Mediterranean region, southern Africa and Australia (World Spider Catalog 2016). These medium-sized, ground-dwelling spiders usually construct silk-lined burrows underground, which open to the surface with a trapdoor. Trapdoors covered with a layer of leaf litter and/or a sheet of moss match the background well, thus making them very difficult to spot in the field (Gertsch and Wallace 1936;Gertsch and Platnick 1975;Hunt 1976;Bond and Coyle 1995).
Despite being a small genus, Cyclocosmia contains some of the most fascinating spiders in the world (Buchli 1969;Gertsch and Platnick 1975). Their abdomens are abruptly truncated and finish in a hard, heavily sclerotized disc that is enhanced by a series of raised ribs separated by narrow grooves (Gertsch and Platnick 1975). This acts as a distinctive morphological defence to cope with intruders, such as predators, into the borrow. When the spider retreats head-first into its burrow, the abdominal disc fits tightly against the round walls of the burrow and forms an impenetrable false trapdoor (Gertsch and Wallance 1936;Gertsch and Platnick 1975). Cyclocosmia spiders usually build their burrows in steeply sloping banks of sandy clay (Fig. 1A). The trapdoor is usually made of silk mixed with soil and covered with a layer of leaf litter and/or moss. Like many other ctenizids, Cyclocosmia spiders are very difficult to find in the field because the remarkably effective camouflage of their trapdoors. Therefore, they are often regarded as one of the rarest spiders (Gertsch and Wallance 1936;Gertsch and Platnick 1975;Zhu et al. 2006).
Cyclocosmia is currently represented by seven nominal species: two in the USA (C. torreya Platnick, 1975 andC. truncata (Hertz, 1841)), one in Mexico and Guatemala (C. loricata (C. K. Koch, 1842)) and four in East and Southeast Asia (C. latusicosta Zhu, Zhang &Zhang, 2006 andC. ricketti (Pocock, 1901) in China, C. lannaensis Schwendinger, 2005 in China andThailand, C. siamensis Schwendinger, 2005 in Thailand and Laos) (World Spider Catalog 2016). In this study, three Cyclocosmia species collected from China and Vietnam are diagnosed and described, one of which is believed to be new to science. One of the species is a new record from China (Yunnan) and Vietnam, based on the morphology of female specimens. Ideally, both male and female specimens would be included in the description of new species; however, it is extremely difficult to obtain adult males of trapdoor spiders. Indeed, we were unable to obtain male Cyclocosmia specimens in this study. By searching and digging burrows, we obtained a few immature and/or adult female specimens. Males are short-lived and leave the burrow immediately after they reach maturity to search for females (Haupt and Shimojana 2001;Haupt 2003). Therefore, collecting males is only possible at certain times of the year, and therefore is not feasible during each field trip.

Materials and methods
Specimens were studied using an Olympus SZX16 stereomicroscope. Anatomical details were examined and photographed with on Olympus BX51 compound microscope and a Canon 7D camera. Genitalia were cleared in boiling KOH for a few minutes to dissolve soft tissues. All the specimens were deposited at the Centre for Behavioural Ecology and Evolution (CBEE), College of Life Sciences, Hubei University, Wuhan, China. All lengths are given in millimetres. Leg and palp measurements are given in the following order: total length (femur + patella + tibia + metatarsus + tarsus).

Diagnosis. The genus
Cyclocosmia differs from all the other genera of Ctenizidae by the abruptly truncated abdomen forming a heavily sclerotized disc that is enhanced by a series of raised ribs and grooves (Gertsch and Platnick 1975) (Fig. 1B-D, I-L). Genera Galeosoma and Idiosoma of the family Idiopidae have the similar abdominal form as Cyclocosmia, but the genus Galeosoma can be distinguished from Cyclocosmia by the distinctly truncated abdomen without ribs or grooves, and the genus Idiosoma can be distinguished from Cyclocosmia by the moderately truncated abdomen, even though with ribs or grooves. Moreover, the arrangement of eyes is also different, Cyclocosmia with two eye rows, yet the two genera of Idiopidae with three eye rows (Gertsch and Platnick 1975;Zhu et al. 2006). Diagnosis. Cyclocosmia ricketti differs from other species of Cyclocosmia by the character of 23-33 radiating ribs on each side of abdominal disc (Fig. 1I-L), and parallel-sided spermathecae (Fig. 1G, H). It can be distinguished from C. latusicosta by the lack of the elevated central zone inside the upper pair of muscle impressions ( Fig.  1I-L). More details see Zhu et al. 2006.
Description. Female (XUC-2013-013). Total length, including chelicerae, 14.00; carapace 6.50 long, 5.40 wide; abdomen 6.50 long, 9.30 wide. Carapace red-brown and smooth, with a few marginal hairs in the front of ocular area, four long bent bristles in longitudinal row running through ocular area, the posterior two bristles have been damaged (Fig. 1D). Ocular area with a black ring around each eye of the anterior eye row and a black band in front of fovea. Cervical groove and radial furrows distinct. Fovea deep and procurved, U-shaped, its greatest width occupying one fourth of carapace width at that point. Eyes set on low tubercle, ocular 0.70 long, 1.70 wide anteriorly, 1.70 wide posteriorly. Clypeus height 0.60. Anterior eye row straight and posterior eye row recurved, both rows almost equal in length. Ratio of eyes, ALE: AME: PLE: PME (0.40: 0.25: 0.30: 0.20). ALE-AME 0.25, AME-AME 0.20, PLE-PME 0.10, PME-PME 0.70. MOA 0.70 long, 0.70 wide in front, 1.10 wide at back. Chelicerae red-brown, inner margin with eight teeth and six denticles, outer margin with seven teeth and four denticles. Rastellum raised on prominent angled projection and consisting of many short black teeth. Labium yellow-brown, 1.10 long, 1.20 wide, with three black cuspules anteriorly. Maxilla yellow-brown, 2.30 long, 1.50 wide, with a few black cuspules at base.
Distribution. China (Fujian, Hunan, Jiangxi, Zhejiang, Sichuan). Remarks. Cyclocosmia ricketti was diagnosed and described based on the holotype female collected from Fujian, and since then, according to the character of the abdominal disc with 23-33 ribs on each side, researchers have identified specimens collected from Hunan, Zhejiang, Sichuan as C. ricketti. Here, a specimen collected from Jiangxi is also identified as C. ricketti on the basis of this character; C. ricketti was not recorded in Jiangxi before. Males remain unknown. Description. Female. Total length, including chelicerae, 17.10-30.20; chelicerae 2.60-4.90 long; carapace 7.50-14.50 long, 6.71-12.50 wide; abdomen 9.30-11.60 long, 12.20-18.50 wide. Carapace red-brown and smooth, with a few marginal hairs and a long bristle in front of ocular area, six long bent bristles in longitudinal row and two bristles in latitudinal running through ocular area ( Fig. 2A). Ocular area black, with a black band in front of fovea and beside ocular area respectively. Cervical groove and radial furrows distinct. Fovea deep and procurved, U-shaped, its greatest width occupying one fifth of carapace width at that point. Eyes set on low tubercle, ocular 0.90 long, 2.00 wide anteriorly, 2.00 wide posteriorly, occupying one fourth of carapace width at that point. Clypeus height 2.40. Both anterior and posterior eye rows straight and almost equal in length. Ratio of eyes, ALE: AME: PLE: PME (0.38: 0.25: 0.20: 0.20). ALE-AME 0.28, AME-AME 0.28, PLE-PME 0.02, PME-PME 0.80. MOA 0.80 long, 0.78 wide in front, 1.20 wide at back. Chelicerae red-brown, inner margin with six teeth and one denticle, outer margin with seven teeth and four denticles. Rastellum raised on prominent angled projection and consisting of many short black teeth. Labium yellow-brown, 1.40 long, 1.40 wide, with three black cuspules anteriorly. Maxilla yellow-brown, 15.90 long, 1.20 wide, with a few black cuspules at base.
Abdomen funnel-shaped and dark yellow-brown ( Fig. 2A). Caudal disc slightly convex, 11.00 in transversal diameter and 10.20 in longitudinal diameter, with two rids running dorso-ventrally (with small interrupt at the groove outer the upper pair muscle impressions) and 24/25 (17-1-2013), 23/25 (XUC-2016-017), 24/23 (LH-2016-002), 28/26 (LH-2016-003), 23/24 (LH-2016-004), 22/23 (LH-2016-005) radiating ribs on each side (Fig. 2D-I). Abdominal disc with six well-marked muscle impressions. All rims within the muscle impression zone with distinct granular structures in different sizes (Fig. 2D-I). Four spinnerets, with inner pair small and one-segmented, and outer pair longer and three-segmented. Paired spermathecae sack-like, parallel-sided, each one with a length 1.7-2.0 times its width (Fig. 2J-N  Etymology. The specific name is taken from the family name of the collector Fengxiang Liu, who joined all collecting trips and has worked on spiders for a few decades. Diagnosis. Female of C. liui sp. n. can be distinguished from C. ricketti by abdominal disc with 33/34 ribs on each side, the rims of the upper pair muscle impressions with distinct granular structures in almost same size, the groove around the six well-marked muscle impressions dark red colour, and the middle pair muscle impressions with an elevated central zone connected to the inner rim of muscle impression (Fig. 3C). It is similar to C. latusicosta in the shape of spermathecae, but can be distinguished from the latter by abdominal disc with 33/34 ribs on each side (Fig. 3C).
Description. Total length, including chelicerae, 22.50; chelicerae 3.40 long; carapace 9.70 long, 8.00 wide; abdomen 11.50 long, 14.20 wide. Carapace dark brown and smooth, with a few marginal hairs and a long bristle in the front of ocular area, three long bent bristles in longitudinal row running through ocular area (Fig. 3A). Carapace widest at coxae II. Ocular area black. Cervical groove and radial furrows distinct.
Fovea deep and procurved, U-shaped, its greatest width occupying one fourth of carapace width at that point. Eyes set on low tubercle, ocular 1.00 long, 2.24 wide anteriorly, 2.20 wide posteriorly, occupying one fourth of carapace width at that point (Fig.  3A). Clypeus height 2.10. Both anterior and posterior eye rows straight and almost equal in length. Ratio of eyes, ALE: AME: PLE: PME (0.53: 0.34: 0.43: 0.33). ALE-AME 0.35, AME-AME 0.25, PLE-PME 0.05, PME-PME 1.00. MOA 1.00 long, 0.93 wide in front, 1.66 wide at back. Chelicerae red-brown, inner margin with eight teeth and six denticles between, outer margin with seven teeth and three denticles between. Rastellum raised on prominent angled projection and consisting of many short black teeth. Labium brown, 1.90 long, 1.70 wide, with three black cuspules anteriorly. Maxilla dark-brown, 18.5 long, 1.5 wide, with a few black cuspules at base. Sternum 5.50 long, 5.00 wide, with large, irregularly shaped sigilla in the centre (Fig. 3E).
Abdomen funnel-shaped and dark brown. Caudal disc slightly convex (Fig 3A, B), 13.20 in transversal diameter and 12.30 in longitudinal diameter, with two rids running dorso-ventrally (with small interrupt at the groove outer the upper pair muscle impressions) and 34/35 radiating ribs on each side (Fig 3C). Abdominal disc with six well-marked muscle impressions, the middle pair muscle impression with an elevated central zone connected to the inner rim of muscle impression. Four spinnerets, with inner pair small and one-segmented, and outer pair much longer and three-segmented (Fig. 3D). Paired spermathecae sack-like, parallel-sided, the length of each one is more or less two times its width (Fig. 3F), length = 1.09 mm, width = 0.56 mm.