Three new species and one new record of Torrenticolidae (Acari, Hydrachnidia) from Wuyishan with an updated key for Chinese fauna

Abstract. New data of Torrenticolidae Piersig, 1902 are presented in this paper from Wuyishan National Nature Reserve, P. R. China. Three new species, Torrenticola suptilisrostrum Gu & Guo sp. nov., Torrenticola spinextension Gu & Guo sp. nov. and Torrenticola wuyiensis Gu & Guo sp. nov. are described and illustrated in detail, and one new record for Chinese fauna is given, Torrenticola dentifera Wiles, 1991, which was originally described from Malaysia. In addition, an updated key is provided to all species of Torrenticolidae in China.

one new record for Chinese fauna is given, Torrenticola dentifera Wiles, 1991, which was originally described from Malaysia.

Material and methods
Water mites were collected, preserved, cleaned and mounted following Jin (1997). Abbreviations used for morphological terms follow Jin (1997), Goldschmidt (2007). Abbreviations used for the chaetotaxy and nomenclature of glandularia used follows Jin (1997). Abbreviations of dorsal plate arrangements used follows Wiles (1997). Abbreviations used for institutional abbreviations follow Zhang(2018).
All measurements are given in µm, length of palp and leg segments are given as dorsal length, following Goldschmidt (2007). Measurements for paratype are given in brackets. All the specimens examined are deposited in GUGC.

Diagnosis
Idiosoma elliptical; dorsal plate arrangement: 2+2p+1; dorsal plate with a colour pattern, hour-glassshaped with pale "shoulder-patches"; infracapitular bay V-shaped; E 4 on the same line with the 4 th pair of acetabula; infracapitular rostrum extremely slender and slightly curved towards the dorsum.

Etymology
The specific name is from the Latin words "suptilis" (slender) and "rostrum" (beak), referring to the slender rostrum; used as a noun in apposition.

Female (n = 1)
Body. Body features same as for the male.

Remarks
The new species, Torrenticola suptilisrostrum sp. nov., is similar to T. fagei E. Angelier, 1949 (Martin 2009). The new species shares the character of an infracapitular rostrum extremely slender and slightly curved towards the dorsum with T. fagei. However, T. suptilisrostrum sp. nov. differs from the latter by E 4 on the same line with the 4 th pair of acetabula (5 th in T. fagei); dorsal plate 2+2p+1 (dorsal plate 4+1 in T. fagei); P-2 robust and compact (P-2 relatively thin and long in T. fagei).

Diagnosis
Idiosoma elliptical; dorsal plate arrangement: 4+1; infracapitular bay narrow U-shaped; V 1 anterior to V 2 , V 2 almost at the same level of Ap; P-2 with a laterally compressed, apically serrated and spine-like ventrodistal extension.

Etymology
Named after the shape of ventral extension on P-2. The specific name is from Latin words "spina" (thorn), there we used "spin-" and "extension" (extension or prolongation); used as a noun in apposition.

Male (n = 1)
Body. Idiosoma elliptical, L/W ratio 1.5 (Fig. 5B). Dorsal plate arrangement: 4+1 (Fig. 5A). Infracapitular bay U-shaped, Cx-II-III mL relatively long; E4 on same line with 4 th pair of acetabula; V 1 anterior to V 2 , V 2 slightly rostral to Ap (Fig. 5B). Ejaculatory complex with well-developed anterior keel and proximal arms (Fig. 5C). Gnathosoma dorsal apodeme short and pointed, ventral apodeme long and wide (Fig. 5D). Palp: P-1 long, with one dorsal seta; P-2 short and wide, with three dorsal setae, laterally compressed, apically serrated and spine-like ventrodistal extension, one very short seta laterally at the base of extension; P-3 with two dorsal setae, and one ventral seta on ventral prolongation; P-4 with one tiny dorsal seta and two ventral extensions, bearing one long and three short setae (Fig. 6A). Legs I-IV as shown in Fig. 6B-E: the claw of Leg-I damaged.

Remarks
By having a laterally compressed, apically serrated and spine-like ventrodistal extension on P-2, and one very short seta laterally at the base of extension, this new species is similar to T. borneoensis Pešić & Smit, 2014(Pešić & Smit 2014. But there are obvious differences: dorsal plate arrangement is 4+1 in T. spinextension (2+1 in T. borneoensis); ventral extension of P-3 is smooth in T. spinextension (serrate in T. borneoensis); two ventral extensions on P-4 are close to each other in T. spinextension (markedly apart from each other in T. borneoensis).

Remarks
This new species is similar to Torrenticola ussuriensis (Sokolow, 1940) in the shape of the palp and dorsal plates,. T. ussuriensis was originally described by Sokolow (1934) from the Primory Territory in the Russian Far East, and later reported from River Inôzava in Japan (Enami 1940), and from Korea (Pešić et al. 2013). Differences between T. wuyiensis and T. ussuriensis are given in Table 1.

Female (n = 1)
Body. Body features same as male except: L 4 on the same line with 3 rd pair of acetabula. Legs I-IV as shown in Fig. 16A-D: claw of Leg-III damaged.

Remark
Torrenticola semicolor Viets, 1977 and Torrenticola alargada Goldschmidt, 2007, reported to be new records to Chinese fauna, were rechecked to be mis-determinated. So they are not included in the key.

Discussion
As a result of human production and living behaviors, the environment has been severely deteriorated, especially water pollution has caused damage to various water ecosystems and greatly reduced species diversity. Torrenticolid water mites live in different running waters, and are possible monitoring organisms of water quality (Goldschmidt 2009(Goldschmidt , 2016. Therefore, it is critical to investigate the diversity of Torrenticolidae.
At present, there are more than 600 torrenticolid species described all over the world, but only 28 species in China. And even in China, more than 50% of these species are found in Southwest China . So in the near future, species identification of torrenticolid water mites is still one of the biggest problems to be resolve in China. Further survey of water mites should be carried out to the other regions in China.