A checklist of spiders from Yongxing Island, South China Sea, with taxonomic notes on four species of goblin spiders

Abstract Background Yongxing Island (about 1.85 km2) isthe largest island of the Xisha Islands. It is located in the Western South China Sea and belongs to the tropical ocean monsoon climate zone. Yongxing Island is quite rich in biological resources, for example, plants and birds which have been well documented. However, there are limited reports on spider resources in Yongxing Island. New information A preliminary checklist of spiders of the Yongxing Island is provided, based on a short-term study undertaken in January 2008. A total of 23 species, belonging to 21 genera and 11 families, were recorded from the area, which forms baseline information of spiders of the Yongxing Island. Amongst these, Oonopidae, Pholcidae, Araneidae and Salticidae were found to have more species in the area. Brignolia parumpunctata (Simon, 1893), Opopaea apicalis (Simon, 1893), Opopaea deserticola Simon, 1891 and Xyphinus baehrae Kranz-Baltensperger, 2014 were firstly reported from China, for which we provide taxonomic description in this paper.


Introduction
Yongxing Island (Fig. 1), also known as Woody Island of the Paracel Islands and originating from coral reef, is the largest island of the Xisha Islands (Ye 1996). This area belongs to tropical marine monsoon climate, characterised by dampness and heat (Zhao et al. 1994). The annual mean lowest and highest temperatures are 22.9°C and 28.9°C and the annual rainfall is about 1505 mm (Zhao et al. 2017). Soil of Yongxing Island consists of phosphatic lime type and was formed in the late Holocene (Yu et al. 1995). The above environmental conditions endow the Island with suitable natural habitat and high biodiversity potential. In the sea, tropical marine organisms abound, while on land, tropical plants are luxuriant, with many bird species and other terrestrial organisms (Zhao et al. 1994). Nevertheless, the reports of spiders in the locality are extremely limited up to now.
Oonopids are tiny haplogyne spiders with usually six eyes often gathered together (Tong 2013). According to World Spider Catalog (2021), the family consists of 1874 species in 114 genera distributed mainly in the Tropics and Subtropical Regions. Up to now, a total of 14 genera with 85 species of oonopids are known in China (World Spider Catalog 2021). In the present paper, four species belonging to three genera are reported and illustrated from China for the first time, thereby increasing the total of oonopids to 89 species.

Materials and methods
Specimens were collected through intensive hand searching and afterwards stored in 75% alcohol and examined using a Leica M205C stereomicroscope. Further details were studied under a Leica DM2500 compound microscope. All illustrations were made using a drawing tube and inked on ink jet plotter paper. Vulvae of females were cleared in lactic acid.
The following abbreviations are used in the text: ALE-anterior lateral eyes; PLE-posterior lateral eyes; IZCAS-Institute of Zoology, Chinese Academy of Sciences in Beijing. Cephalothorax. Carapace and sternum yellow; legs and abdomen pale yellow; chelicerae brownish-yellow. Sides of carapace with finely longitudinal striae; dorsal area smooth with some mesially pointing hairs at lateral edges. Eyes six in two rows, rather large, nearly equally-sized; posterior eyes in a straight row, touching each other ( Fig. 2A). Base of fang without ornament (Fig. 2C). Labium wider than long, endites with membranous tips (Fig. 2B).
Abdomen. Dorsal scutum oval-shaped, covering nearly whole abdomen. Lobes on anterolateral corners of petiolar tube distinct, ridges developed, but without forming a scutal cove.
Male palp. Palp (Fig. 3A Epigynum. Genital area with a small knoblike projection, most of which showing inverted V-shaped ridges (Fig. 2D), a few are inverted Y-shaped. Two internal apodemes rise from the anterior border of post epigastric furrow; a strongly-twisted duct runs from the anterior border of the postepigastric furrow ending in the middle of the knob-like projection (Fig. 2E).

Distribution
America, Australia, China (new record), Gambia, India, Indonesia, Pakistan, Pacific Is., Philippines, Seychelles, Sierra Leone, Sri Lanka, Yemen.  Cephalothorax. Sides of carapace yellowish-brown; dorsally yellow; chelicerae, sternum yellow; legs and abdomen light yellow. Carapace with a dark brown patch behind eyes, dorsally with a few rows of short hairs. Sides of carapace with finely longitudinal striae. Eyes six in two rows, rather large, nearly equally-sized, ALE slightly separated, touching posterior lateral eyes; posterior eyes in procurved row, touching each other ( Fig. 4A and C). Base of fang with two plumose hairs on lateral sides (Fig.  4F). Labium wider than long, endites with membranous tip (Fig. 4B). Legs. Leg I: femur with a row of dorsal setae, 3 retrolateral setae; patella without setae; tibia with a ventral seta; tarsus with distinct strong setae. Leg II, III and IV similar to leg I.
Male palp. Patella of palp ( Fig. 5A and B) significantly larger than cymbiobulbus; cymbiobulbus with a clavate protrusion at base and three branches at the end. Epigynum. Postgynal depression of epigastric area shallow, with inverted V-shaped sclerotisation situated posterior to epigastric furrow; parmula black, small ( Fig. 4D and E).

Distribution
China (new record), Ecuador, Indonesia, Mexico, Pacific Is., Panama, Philippines, Seychelles, Thailand, USA.  Cephalothorax. Sides of carapace yellowish-brown; dorsally deep yellow; scutum yellow; chelicerae, sternum, legs and ventral scutum yellow. Sides of carapace with finely longitudinal striae; dorsal area smooth with some mesially pointing hairs at lateral edges. Eyes rather large, PLE relatively smaller; compactly arranged, ALE slightly separated, touching posterior lateral eyes; posterior eyes in slightly recurved row, touching each other Fig. 6A and C). Base of fang without ornaments. Labium wider than long, endites with pointed tip (Fig. 6B). Legs. Leg I: femur smooth, with some hairs; patella with a ventral seta; tibia with distinct hairs, a row of ventral setae and 2-3 trichobothria; tarsus with distinct strong setae. Leg II, III and IV similar to leg I, except femur II with a ventral setae.
Abdomen. Dorsal scutum oval-shaped, covering nearly entirely abdominal length. Lobes on anterolateral corners of petiolar tube distinct, ridges developed, forming a scutal cove.
Male palp (Fig. 7A and B). Patella of palp significantly larger than cymbiobulbus; cymbiobulbus with two protrusions at middle and a curving extension to the end. Epigynum. Postgynal depression of epigastric area shallow; parmula black ( Fig. 6D and E).

Distribution
Brazil, Caribbean, China (new record), Germany, Japan, Middle East, Pacific Is., Philippines, Spain, USA to Panama, Venezuela.  Cephalothorax. Carapace yellow-grey; chelicerae yellow to brownish-yellow; sternum yellow; legs and abdomen light yellow. Sides of carapace with reticulate veins, dorsal area without hairs. Margin of carapace without distinct setae or denticle. Eyes six in two rows, rather large, nearly equally-sized, compactly arranged, ALE slightly separated, posterior eyes in slightly retrocurved row, touching each other (Fig. 8A and, C). Base of fang with two plumose hairs on lateral sides ( Fig. 8D and E). Labium wider than long, endites with membranous tip (Fig. 8B). Legs. Leg I: femur with 2 rows of setae; patella without setae; tibia with 2 ventral setae, 2 dorsal setae and a dorsal trichobothrium; tarsus without setae. Leg II, III and IV similar to leg I.
Abdomen. Dorsal scutum oval-shaped, covering nearly entirely abdominal length. Lobes on anterolateral corners of petiolar tube distinct, ridges developed, but without forming a scutal cove; opercula large, oval-shaped.
Male palp. Cymbium separated from bulb, with two robust spurs. Bulb with numerous membranous outgrowths on terminal part (Fig. 9A, B). Epigynum. Postgynal depression of epigastric area shallow. An arc process visible originating from near the middle of epigastric sulcus ( Fig. 8F and G).

Distribution
China (new record), India to Australia.   Diagnosis: see Lin and Li (2009)