Protura from Hainan Island, China: new species, checklist and distribution

Abstract More than 1500 proturan specimens from Hainan Island are systematically studied. An annotated list of all species of Protura from Hainan Island is provided and their geographical distribution is discussed. The genus Paracondeellum is reported from Hainan Island for the first time, and Paracondeellum paradisumsp. nov. is described. The type species Paracondeellum dukouense (Tang & Yin, 1988) is redescribed based on syntype, and the lectotype and paralectotype are designated. The characters of the genus Paracondeellum are redefined, and the two known species are compared in detail. The Protura fauna of Hainan Island is mainly composed of species from the Oriental region, with 91% of the species belonging to the families Berberentulidae and Eosentomidae.


Introduction
Protura is a group of tiny soil-dwelling arthropods with more than 800 described species (Bu et al. 2012(Bu et al. , 2017Galli et al. 2018). The diagnosis, distribution, and key to 76 known genera and seven families of Protura worldwide were recently given by Galli et al. (2018). So far, there are 214 species belonging to 43 genera recorded in China (Bu et al. 2012(Bu et al. , 2017Qian et al. 2018).
Hainan Island is the second largest island of China and is located off the southernmost point of the mainland (18°10'-20°10'N, 108°37'-111°03'E; Fig. 1). The tropical forest landscape on Hainan Island is one of the hotspots for biodiversity in China, with a high floral diversity and over 6000 species of insects recorded (Huang 2002). In recent years, many rare insects, such as belonging to Zoraptera, have been found on Hainan Island (Yin et al. 2015).
There are several previous publications on the Protura from Hainan Island. The first study reported 14 species of Eosentomidae from Hainan (Yin 1986). Then, eight species of the genus Kenyentulus (Berberentulidae) were described (Yin 1987). Later, 24 species of Protura were recorded in Hainan Province with Fujientomon dicestum Yin, 1977 and Pseudanisentomon yongxingense Yin, 1988 included (Yin 1999(Yin , 2002. In 2004, the Protura from Jianfengling Mountain were investigated again. In 2005, Amphientulus sinensis Xiong, Xie & Yin, 2005 was described and seven new records and three undetermined species were newly added (Xiong 2005;Xiong et al. 2005). One of these undetermined species was subsequently described as Anisentomon hainanense Xiong, Bu & Yin, 2008(Xiong et al. 2008. In 2011 and 2017, we investigated the soil fauna of Hainan Island on several occasions and collected many proturan specimens. In the present paper, Protentomidae is recorded for the first time and one new species of genus Paracondeellum Yin, Xie & Zhang, 1994 is identified and described. We checked the syntypes of the type species of Paracondeellum dukouense (Tang & Yin, 1988), designated a lectotype and paralectotype, and redescribed it in detail. In addition, based on more than 1500 proturans collected in Hainan Island from 1984 to 2017, a checklist is presented and the distribution of Protura on Hainan Island is summarized.

Materials and methods
Most of specimens were collected between 1984 and 2004, and more recent specimens were collected during the expeditions in 2011 and 2017. All localities sampled so far are listed in Table 1 and shown in Figure 1. All specimens were extracted by means of the Tullgren funnels from soil and humus samples and preserved in 75% ethanol. They were mounted on slides using Hoyer's solution and dried in an oven at 50 °C.
Observations were made with a phase contrast microscope (Leica DM 2500). Photos were taken by a digital camera (Leica DMC 4500). Line drawings were made using a drawing tube. All specimens are deposited in the collections of Shanghai Abbreviations used in the text follow the paper by Bu and Yin (2007). Head setae and pores are named according to Rusek et al. (2012) and Shrubovych (2014). The arrangement of the taxa follows the system proposed by Yin (1999).

Taxonomy Family Protentomidae Ewing, 1936
Genus Paracondeellum Yin, Xie & Zhang, 1994 Diagnosis. Habitus short and robust. Pseudoculi circular without lever. Calyx of maxillary glands globular and smooth. Foretarsal sensilla of the exterior side reduced; interior sensilla b' absent. Abdominal appendages I-II two-segmented each with four setae, III uni-segmented with two setae. Tergites II-VII without or with few anterior setae. Sternites II-III each with three posterior setae. Sternites IV-VII each with nine posterior setae; sternite VIII with four setae in one row. Female squama genitalis short, with pointed acrostyli (Yin 1999;Galli et al. 2018).
Distribution. China (Hainan) Remarks. The genus Paracondeellum Yin, Xie & Zhang, 1994 is endemic to China and was previously known by a single species, P. dukouense, from Sichuan and Yunnan provinces. Paracondeellum paradisum sp. nov. differs from P. dukouense in the shape of foretarsal sensilla, pseudoculus, and female squama genitalis, and in the body chaetotaxy. A comparison of the morphology of these two species is given in Table 4.  Tables 3, 4 Diagnosis. Paracondeellum dukouense (Tang & Yin, 1988) is characterized by the one pair of A-setae on tergite I, absence of A-setae and P1a seta on tergites II-VI, absence of A-setae and nine pairs of P-setae (P2a present) on tergite VII, tergites IX and X with 14 and 12 setae respectively, absence of seta d4 on head, and female squama genitalis with pointed acrostylus.
Tergites I-VII with pores psm and al, VIII with pores psm only, IX-XI without pores, XII with single median pore. Pores on sternites I-VI not observed due to the opacity of the old specimens (Fig. 5H, J); three posteromedial pores observed on sternite VII (Fig. 5I), VIII with posteromedial pore (Fig. 5L), IX-XI without pores, XII with one pair of sal pore.
Distribution. China (Sichuan, Yunnan). Remarks. Paracondeellum dukouense was originally described based on two syntypes (Tang and Yin 1988). In the original description (Tang and Yin 1988) and in the monograph of Yin (1999), most important characters such as foretarsal sensilla, pseudoculus, maxillary gland, as well as body chaetotaxy were briefly described and illustrated. After careful study of type specimens under a modern phase contrast microscope with higher resolution, we find that sensillum c' is present on the foretarsus and that some of the setae on the body were previously ignored due to the lower resolution of the microscope used. We correct here these mistakes in the original description and supplement the description of head chaetotaxy, the porotaxy, and the shapes of setae on the body. Table 4 compares P. dukouense with the new species.

List of species from Hainan Island Family Protentomidae Ewing, 1936
Paracondeellum paradisum sp. nov.
Description. The description is given above.
Sampling localities in Hainan Island are still sparse, and additional collection of proturans should be made in the future, so as to reveal the true diversity and provide a better understanding of the biogeography of Protura on the Hainan Island.