Description on two species of genus Platythomisus (Araneae, Thomisidae) from China and Singapore

Abstract Two species of the genus Platythomisus Doleschall, 1859 are studied: P.xiandao Lin & Li, sp. nov. is described based on male and female specimens from Yunnan, China, and P.octomaculatus (C. L. Koch, 1845), the type species of the genus, is redescribed based on female specimens from Singapore. Its male, also from Singapore, is described for the first time.

We have since found matched pairs of two Platythomisus species in collections from Singapore and China. The discovery of one of these species, Platythomisus xiandao Lin & Li sp. nov., from Yunnan represents the first record of this genus in China. Furthermore, specimens of P. octomaculatus (C. L. Koch, 1845) from Singapore have allowed us to provide the first description of the male of the species.

Material and methods
All specimens were preserved in 80% ethanol. Dissected genitalia were cleared in warm 10% potassium hydroxide (KOH) solution before study. Specimens were examined under a LEICA M205C stereomicroscope. Photomicroscopy images were taken with an Olympus C7070 zoom digital camera (7.1 megapixels). Laboratory habitus photographs were taken with a Canon 5D Mark III digital camera equipped with a Canon MP-E 65 mm lens. Photos were stacked with Helicon Focus (version 6.7.1) or Zerene Stacker (version 1.04) and processed in Adobe Photoshop CC2018. Field photographs were taken with a Nikon D800E with a Tamron 90 mm macro lens.
All measurements are in millimeters and were obtained with a LEICA M205C stereomicroscope. Eye sizes are measured as the maximum diameter from either the dorsal or frontal view. Leg measurements are given as follows: total length (femur, patella, tibia, metatarsus, tarsus). The terminology used in the text and figures follows Ono (1988). Distribution maps were generated using ArcMap software (version 10.2).
The types of Platythomisus xiandao Lin & Li, sp. nov. are deposited at the Institute of Zoology, Chinese Academy of Sciences in Beijing (IZCAS). The voucher specimens of P. octomaculatus of this study are kept at the Lee Kong Chian Natural History Museum, National University of Singapore (LKCNHM).
To confirm the species delimitation, a fragment of the cytochrome c oxidase subunit I (COI) was amplified and sequenced. Primer sets for the PCR and cycle sequencing reactions in this study are from Folmer et al. (1994). The GenBank accession numbers are provided in Table 1. MEGA7.0.16 (Kumar et al. 2016) was used for subsequent manual adjustment of the sequences and calculation of pairwise comparisons of uncorrected K2P-distances. COI sequences of Thomisus Walckenaer, 1805 were also obtained from GenBank to calculate intraspecific genetic distance.
Abbreviations: ALE anterior lateral eyes, AME anterior median eyes, PLE posterior lateral eyes, PME posterior median eyes, E embolus, ITA intermediate tibial apophysis, RTA retrolateral tibial apophysis, VTA ventral tibial apophysis, At atrium, CD copulatory duct, S spermathecae. with strikingly contrasting color patterns on the carapace and opisthosoma. Typically, the epigyne has sclerotized margins and a conspicuous epigynal atrium; spermathecae longer than wide, well-sclerotized, and not divided into compartments. The male is much smaller than female (1:3 or more). Palp with VTA, ITA and RTA; tegulum flat, disk-shaped; tegular ridge present; embolus slender.
Epigyne (Figs 3A, B) with atrium shaped like a funnel with a broad neck, the length of atrium to the middle width of the atrium 1:1.5, the length of anterior margin to the length of posterior margin 2:1. CD short, approximately half the length of the spermathecae. Spermathecae stout, with almost parallel sides anteriorly.
Intraspecific variations: While the holotype has eight spots on the dorsum, as illustrated by Koch (1845), mature specimens seen or photographed in Singapore, Brunei, Thailand, and East and West Malaysia possess only seven dorsal spots but with the eighth spot on the ventrum. In some juvenile females, there are only five dorsal spots on the opisthosoma. The number of spots on the carapace varies between two and four pairs in mature females. The general coloration of live male specimens varies from yellow to red.
Distribution. The type locality "Ostindien", meaning "East Indies", refers to Indonesia today. Within Indonesia, the species was recorded in Java as Platythomisus phryniformis by Doleschall (1859) and in Padang, Sumatra by Hasselt (1882). However, we failed to find any specimens of the species during field trips in the country. This species has been recorded in Singapore, Brunei, Thailand, and East and West Malaysia (Koh and Leong 2014). A report of P. octomaculatus from Assam, India (Yadav et al. 2017) is clearly misidentified. We suggest it may be P. xiandao sp. nov. Natural history. Individuals live among low-lying tree foliage in or around degraded forests and mangrove swamps. Eggs are laid between leaves and sealed with thick silk. The egg sacs are guarded by the mother until the spiderlings hatch in about 2 weeks. Etymology. The specific name is derived from the Chinese word "xiandao" (noun), the name of the Strategic Priority Research Program of the Chinese Academy of Sciences (CAS). The program has made it possible for the biodiversity research team in the CAS to remain as an integral cluster to fulfil all its ambitious goals.
The two species can also be diagnosed by their somatic differences. The males of P. xiandao sp. nov. have seven black spots on the opisthosoma (Fig. 4G) and a reddish sternum (Fig. 4H); the males of P. octomaculatus have only three distinct black spots on the opisthosoma (Fig. 4C) and a black sternum (Fig. 4D). The females of P. xiandao sp. nov. have larger black patches on the carapace (Fig. 4A) and a black patch at the center of ventrum extending posteriorly to connect with the black area surrounding the spinnerets through a narrow neck (Fig. 4F), while the black patch at the ventrum of P. octomaculatus females is broadly oblong and well-separated from the spinnerets (Fig. 4B).
Epigyne (Fig. 3C, D) with bell-shaped atrium, the length of atrium to the middle width of the atrium 1:1.4, the length of anterior margin to the length of posterior margin 1:1. CD short, about one-fourth the length of the spermathecae. Spermathecae comparatively slender, shaped like a sea cucumber or hot-dog sausage.
Natural history. Individuals of this species hide under the leaves. Remarks. Based on the 647 bp-aligned sequences, the COI uncorrected K2P-distance between P. octomaculatus and P. xiandao sp. nov. is 0.073. The result far exceeded the maximum value of intraspecific genetic distance for Thomisidae.