A new trapdoor spider of Cyclocosmia Ausserer, 1871 from southern China (Araneae, Halonoproctidae)

Abstract Background The genus Cyclocosmia Ausserer, 1871 previously included ten species from North America and Asia, six of which have been recorded from China. New information A new species, Cyclocosmiaruyi Yu & Zhang sp. n., is described and diagnosed, based on both sexes from Guangxi Province, China. Morphological characters for the early stages of juveniles of the new species are also provided.


Introduction
Trapdoor spiders of the genus Cyclocosmia Ausserer, 1871, are currently known from Southeast Asia (south China, Thailand, Vietnam and Laos) and the coast of the Gulf of Mexico (southern United States and Mexico) (World Spider Catalog 2023).These spiders are famous in their unique opisthosomal discs bearing orderly ribs and grooves, as well as exquisite muscle impressions.They show interesting defence behaviour of their unusual burrow, which is composed of a wide vestibule and a narrow basal tube (Schwendinger 2005: 225).When disturbed, spiders will commonly retreat to the lower portion of their burrow and use the opisthosomal disc as a false bottom.They are relatively rare in collections and previous studies have shown that this rarity is due to both their demanding requirements of habitat and the well-camouflaged trapdoor that is difficult to find (Gertsch and Platnick 1975).However, in some areas, they are locally abundant with relatively high density (Schwendinger 2005: 240).
Previous studies indicated Cyclocosmia are very long-lived spiders like some other mygalomorphs, with more than 12 years of life span and taking at least five years to become mature (Gertsch andPlatnick 1975: 2, Schwendinger 2005: 250).Some species do not reproduce annually; they potentially take a full year to brood eggs and can reproduce more than 300 spiderlings one time (Schwendinger 2005: 240, 250).Wildcaught spiderlings with fully developed opisthosomal discs were considered at least in the third instar (Schwendinger 2005: 237).However, no complete record for the early stages of juvenile Cyclocosmia has been documented and the life history of Cyclocosmia is still poorly known in some respects.
In this study, we describe a new species of Cyclocosmia, based on both sexes from Guangxi Province, China, herein named Cyclocosmia ruyi Yu & Zhang, sp. n.During the survey of this new species in 2022, we obtained its egg sacs and brought them into the laboratory for observations and rearing (Figs.1-3; see under Biology).The early stages of juveniles of the new species are preliminarily reported and the opisthosomal disc of the new species is confirmed to develop in the second instar.

Materials and methods
All specimens, preserved in 75-95% ethanol, were examined under a ZEISS Stemi 305 stereomicroscope.The photographs of genitalia were taken by an Olympus BX53 microscope equipped with a Kuy Nice CCD Camera.Photographs of specimens were stacked by the Helicon Focus 7 software and retouched in the Adobe Photoshop CC 2019 software.Specimens were measured in millimetres by the dedicated tool of Leica LAS V. 4.3 software.The measurements of palps are shown as: total length (femur, patella, tibia, tarsus) (male palpal tarsus measured cymbium only); measurements of legs are shown as: total length (femur, patella, tibia, metatarsus, tarsus).Leg formulae are arranged from longest to shortest.Spinations are given as left/right or a single number, if no variation was observed between both sides.Female vulvae were cleared with Pancreatin (BBI Life Sciences).Distributions of Asian Cyclocosmia spp.were mapped using ArcMap 10.5 (Esri Inc.).All specimens studied are deposited in the Museum of Hebei University, Baoding, China (MHBU) or Collection of Kun Yu, Hanzhong, China (CKYH).
Cytochrome c oxidase subunit 1 (COI) sequences of new species and five other Cyclocosmia species (C. lannaensis, C. latusicosta, C. ricketti, C. sublatusicosta and C. subricketti) were amplified using universal primers LCO1490 (forward) and HCO2198 (reverse) (Folmer et al. 1994).PCR products were sent to Azenta Life Sciences, Inc. (Tianjin, China) for sequencing.Sequences were uploaded to the National Center for Biotechnology Information (NCBI) and GenBank accession numbers and voucher information are shown in Table 1 (data released from 5 April 2023).COI sequences of C. truncata and C. loricata were downloaded from NCBI (GenBank accession numbers as shown in Table 1).Sequences were imported into MEGA-X (Kumar et al. 2018) for multiple alignment and calculation of genetic distances.Three species of Cyclocosmia ( C. siamensis Schwendinger, 2005, C. liui Xu, Xu & Li, 2017and C. torreya Gertsch & Platnick, 1975) were not included in our molecular analysis due to lacking specimens or accessible data in the public database.

Variation between adults (both sexes).
Count of radial ribs on female disc: 42-46 (n = 4); count of radial ribs on male disc: 44-48 (n = 2).Outlines of tip edges of embolus are slightly different in two males: relatively protracted in one, whereas relatively blunt in another one; apophysis of embolic tip show different sizes amongst two individuals (Fig. 6D-E).No obvious variation of embolic details observed between two palps in same individual.

Diagnosis
The new species can be distinguished from the American congeners, Cyclocosmia loricata A new trapdoor spider of Cyclocosmia Ausserer, 1871 from southern China ...

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, by the more dense pores on spermathecae and the tips of spermathecae not processing lateral lobes (Fig. 7A-B, Fig. 9C-F), whereas the pores are relatively sparse and the lobes are well developed in the latter three species (see Gertsch and Platnick (1975): figs. 25-27).

Etymology
The specific epithet is from the Chinese "如意" (rú yì), it is an auspicious blessing, meaning "everything goes well"; noun in apposition.

Biology
All specimens were collected from moist slopes beside path cuts or hillside with abundant leaf litter (Fig. 1B).Burrows are usually with moss nearby.The entrance of burrow is closed by a thin trapdoor comprised of dead leaves, twigs and moss, sometimes with an extended rim (Fig. 1C-D).The burrow internally presents a wide upper and median portion (vestibule) and a constricted basal tube (Fig. 1E).Burrows of adult females are ca.7-11 cm deep, shallower in juveniles.Two mature males were obtained in early October, one matured in captivity from a subadult collected earlier (MHBU-ARA-00023660); another one was collected from the wild (MHBU-ARA-00023658).The collection of dust and soil on the body, shrunken abdomen and abrasion of some claws, indicate the latter one had perhaps been mature for some time.Two females were observed each carrying one egg sac on 3-4 August 2022.Daytime temperatures on those days ranged from a maximum of 30°C to a minimum of 20°C at night (perhaps relatively stable inside the burrow).When burrows were excavated, those females first tried to threaten by biting, before retreating to the constricted basal tube and blocking it with their abdominal disc, but leaving their egg sac behind themselves (Fig. 1F-G).
Two egg sacs were soon opened by the first author in the laboratory (10 August 2022).One of them had 147 live first instar spiderlings and same of eggshells (Fig. 3 A-B), the other had 158 fresh dead first instars, some eggshells and four eggs ready to hatch (this latter sac may have been ruined by accidental extrusion during carriage); no unfertilised eggs found.Living spiderlings were placed in a sunless incubator with 27°C and 95% humidity to nurture.After ca.3-4 weeks (1-6 September 2022), they started to moult into second instars (Fig. 3C-E).The practical period of first instar stage is unknown, because the hatching time is uncertain, but presumably not too much longer.First instar spiderlings present a few of small spines on the front surface of the chelicerae, which do not seem homologous to those of the rastellum because of their deviation in position, arrangement and shape.These spines were developed before the hatching (Fig. 8C) and partly missing in some emerged first instars, which indicates they may be potentially used to puncture the eggshell.The opisthosomal disc was shaped up after moulting to second instar, three pairs of muscle impression were positionally corresponding to rows of impression II-IV in first instar; rows of impression I and V of first instar disappeared after moulting into second instar.These spiderlings seem very sensitive to light (even in early stage of first instar when their eyes were not well developed), they were very agitated under artificial lighting, but soon regained their sedentary composure after lighting was removed.

Distribution
Known only from the type locality of Guangxi, China (Fig. 13).

Figure 1 .
Figure 1.Habitats (A-B) and burrows (C-E) of Cyclocosmia ruyi Yu & Zhang sp.n.A Landscape of type locality; B Microhabitat; C-D Burrow of holotype female, trapdoor closed (C) and opened (D); E Profile of burrow of paratype female (MHBU-ARA-00023657), with arrows indicating constricted basal tube; F-G Holotype female using opisthosomal disc as the false bottom of burrow, with egg sac (F) and egg sac removed (G).Figures are copyright 2023 Kun Yu.

Figure 3 .
Figure 3. Living spiderlings of Cyclocosmia ruyi Yu & Zhang sp.n.A First instar spiderlings in egg sac; B first instar spiderlings, with eggshells; C Late stage of a first instar spiderling, pre-moult; D Second instar spiderlings, back view; E Comparison.

Figure 8 .
Figure 8. Cyclocosmia ruyi Yu & Zhang sp.n., egg and early stages of spiderlings.A-C Pre-hatching egg; D-F First instar spiderling; G-J Second instar spiderling; C Chelicerae of embryo, with arrow indicating row of spines; I Chelicerae; J Opisthosomal disc.A, C, I Front; B, F Lateral; D, G Dorsal; E, H Ventral; J Back.

Figure 13 .
Figure 13.Distribution records of Cyclocosmia species in Asia.

Table 2 .
Interspecific genetic distance matrix (based on p-distance model) on COI sequences of eight species of Cyclocosmia.