Biodiversity surveys reveal eight new species of freshwater crabs (Decapoda: Brachyura: Potamidae) from Yunnan Province, China

Yunnan Province is known to host the highest species diversity of the true freshwater crabs in China; 50 species have been recorded from the province by 2017. In 2004, our team conducted a biodiversity survey of the freshwater crabs in Yunnan Province to determine how well the diversity of crabs in the area has been characterized. We collected a total of 25 species, of which nine species proved to be new to science, and eight of which are described here. These include four species of the genus Indochinamon Yeo & Ng, 2007, two species of the genus Potamiscus Alcock, 1909, and one species each of the genera Pararanguna Dai & Chen, 1985, and Parvuspotamon Dai & Bo, 1994. The new species of Pararanguna and Parvuspotamon represent the second species of respective genera, which are here redefined. Detailed comparisons with morphologically allied species are provided. Photographs of the type specimens of their comparative species which are poorly illustrated in the literature are also provided to allow better understanding of their morphology. This study brings the number of the freshwater crabs of Yunnan Province to 58. Since about 13.8% of the number of species (eight out of 58 species) is increased by surveys conducted within a relatively short period, it is most probable that the species diversity of this group is still understudied in Yunnan Province.


INTRODUCTION
China is the world's most species-rich country for the freshwater crabs, with more than 200 species recorded from the country (Dai, 1999;Cumberlidge et al., , 2011). Cumberlidge et al. (2011: 46) had made the observation that "(d)ozens of new species remain undescribed," and several recent discoveries have Department of Parasitology, Medical College of Nanchang University, Nanchang (NCU MCP); the Zoological Reference Collection (ZRC), Lee Kong Chian Natural History Museum (previously Raffles Museum of Biodiversity Research), National
Remarks. Indochinamon contains 38 species, including four new species described in the present study, from southeast China (Yunnan and Guangxi), Vietnam, Laos, Thailand, Myanmar, northeastern India to Himalaya. The type species of the genus is Potamon villosum Yeo & Ng, 1998, from northern Laos. Yeo & Ng (2007: 283) raised eight diagnostic characters for the genus: "(i) carapace low, with relatively flat dorsal surface; (ii) epigastric cristae separated from postorbital cristae by distinct groove; (iii) postorbital cristae not confluent with epibranchial tooth; (iv) third maxilliped exopod with well-developed flagellum; (v) ambulatory legs relatively stout; (vi) male pleon narrowly triangular; (vii) male sterno-pleonal cavity reaching imaginary line joining middle of bases of cheliped coxae; and (viii) G1 terminal segment relatively short and stout, with the groove for the G2 marginal in position, and lacking a dorsal flap." In the key to the genera of Chinese Potamidae, Dai (1999: 85, in Chinese) characterized Indochinamon (as Potamon) by the following characters: (1) the distance between mesial ends of thoracic sutures 4/5 is shorter than the one-third distance between sternal press-buttons of locking mechanism; (2) the G1 terminal segment tapers, without any protrusion; (3) the exopod of the third maxilliped has developed flagellum; and (4) G1 terminal segment is stout, conical. It is, however, difficult to apply the first character to Indochinamon species. For example, the proportion of the distance between mesial ends of thoracic suture 4/5 to the distance between sternal press-buttons of locking mechanism is smaller than one-third in I. ahkense sp. n. and I. tujiense, but that is larger than one-third in I. parpidum and I. lui. Inochinamon boshanense is also shown to have a larger value than one-third in this character (Dai, 1999: fig. 96 (3)). This is probably because the mesial ends of the sutures are not always clear and mesially continued gradually as depression, so it is difficult to standardize the measurement.  (ZRC 2013.0551), two males (larger 35.6 Â 27.4 mm), two females (larger 32.5 Â 24.9 mm) (RUMF-ZC-2366), same data as holotype.
Etymology. The species is named after the locality in which it was first found.
The new species is also similar to I. tannanti (Rathbun, 1904) and I. orleansi (Rathbun, 1904) in the shapes of the G1. Indochinamon ahkense sp. n. can be distinguished from I. tannanti by its flatter carapace (vs. slightly convex), having the epistome posterior margin divergent posteriorly (vs. almost straight), and the proportionally wider telson  reaching postorbital cristae; epigastric cristae strong, raised, rounded, distinctly anterior to postorbital cristae; postorbital cristae sharp, breaking out into granules just before reaching epibranchial tooth, slanting posterolaterally toward anterolateral margin, not confluent with epibranchial teeth; branchial region and regions behind epigastric and postorbital cristae rugose; frontal margin gently sinuous; antennular fossae rectangular (Fig. 7B) in anterior view; external orbital angle broadly triangular, ) narrowly triangular; telson broadly triangular, lateral margins distinctly concave; somite 6 trapezoidal, proximal width about 2.1 times its median length, lateral margins convex; lateral margins of somites 3 straight. G1 ( Fig. 9) terminal segment short, subconical, with bulge of constant width that gradually tapers distally along inner margin, obliquely bent outward (ca. 45 ), curved distally with narrowly tapered tip, groove for G2 marginal; subterminal segment gently sinuous, slender, with cleft on upper part of outer margin. Vulva (Fig. 10) inverted narrow triangular, opening directed mesioventrally, located posterior to mesial end of suture 5/6, lateral end widely produced as short eave, opening covered with membrane. Etymology. The species name is an arbitrarycombination of par, Latin for "resemble," with the species name I. hispidum (Wood-Mason, 1871), alluding to the similarity in the shape of their G1 terminal segments.
Remarks. Indochinamon parpidum sp. n. closely resembles I. hispidum (Wood-Mason, 1871), in general carapace morphology and the short, subconical G1 terminal segment, which is obliquely bent outward and curved distally, with a low, broad bulge on extensor margin. However, I. parpidum sp. n. can be distinguished from I. hispidum by the following characters: the bulge of the G1 terminal segment is gradually tapered distally along the extensor margin (vs. bulge narrow, with constant width along extensor margin); the G1 terminal segment is strongly and obliquely bent outward (ca. 45 ), with a narrowly tapered tip (vs. G1 terminal segment obliquely bent outward to a lesser degree (ca. 30 ), with a broadly tapered tip); the G1 subterminal segment has a cleft on the distal part of the outer margin (vs. G1 subterminal segment without cleft on upper part of outer margin), and the shape of the vulva is inverted narrow triangular (vs. vulva oval) (Figs. 9A-9C and 10 vs. Dai, 1999: fig. 94 (4, 5, 8)). Dai & Chen (1985) described two subspecies of I. hispidum, i.e., I. h. jianchuanense (Dai & Chen, 1985) and I. h. boshanense (Dai & Chen, 1985). The former was distinguished from I. h. hispidum by its deeper grooves of the dorsal surface of the carapace, obtuse external orbital angle, a greater degree of the bent of the G1 terminal segment, and convex ventrolateral margin of the vulva, whereas the latter was differentiated from the type subspecies by a greater degree of the bent of the G1 distal segment. Dai & Chen (1985) indicated that the degree on the bent of the G1 terminal segment of I. h. boshanense is over 60 , but judging from the photograph of the G1 of the holotype (Fig. 6H) and the original description, its degrees against the mesial margin of the subterminal segment is ca. 80 . Although the two subspecies were erected to full species by Ng, Guinot & Davie (2008) without explanation, we consider the differences raised by Dai & Chen (1985) are significant to recognized them as full species.
Indochinamon parpidum sp. n. is morphologically similar to I. jianchuanense and I. boshanense. The new species can be distinguished from I. jianchuanense by the following characters: the extraorbital angle is sharp (vs. extraorbital angle obtuse), and the G1 terminal segment bends outward to a lesser degree (ca. 45 ) with a narrowly tapered tip (vs. terminal segment with stronger bend, ca. 60 ), and the G1 subterminal segment is more slender (vs. more stouter) ( (7)).
Etymology. The species is named after the locality in which it was first found.
Remarks. Indochinamon tujiense sp. n. closely resembles I. boshanense (Dai & Chen, 1985), in its general carapace morphology and in the short, subconical G1 terminal segment being strongly bent obliquely outward, with a slight hump along the outer margin at the proximal end and a sinuous outer margin. However, I. tujiense sp. n. can be The new species is also morphologically similar to I. jianchuanense (Dai & Chen, 1985), but the former can be differentiated from the latter by the greater degree of the bent of the G1 terminal segment (ca. 70 ) (vs. bent to a lesser degree, ca. 60 ); and the relatively larger bulge on the extensor margin of G1 terminal segment (vs. bulge narrower); and the oval vulval opening (vs. the transversely narrow vulval opening) (Figs. 13 and 14 vs. Fig. 4I; Dai & Chen, 1985: fig. 1 (4, 5, 9); Dai, 1999: fig. 95 (4, 5, 8)).
The new species can be distinguished from I. menglaense (Dai & Cai, 1998) by the anterolateral margin of the carapace being lined with rounded granules (vs. anterolateral margin lined with spine-like granules); the slightly concave lateral margins of male telson (vs. distinctly concave); the constantly wide bulge on the extensor margin of G1 The new species differs from I. boshanense in the following characters: the mesial margin of the G1 subterminal segment is more produced subdistally in dorsal view (vs. mesial margin straight, oblique, not produced subdistally); the G1 terminal segment bends to a lesser degree (ca. 70 ) (vs. terminal segment with stronger bend, ca. 80 ); the bulge on the extensor margin of the G1 terminal segment is larger (vs. smaller); and the shape of the vulva is oval (vs. vulva transversely narrow) (Figs. 13 and 14 vs. Fig. 6H; Dai & Chen, 1985: fig. 2 (4, 5, 9); Dai, 1999: fig. 96 (4, 5, 8)).
Etymology. The species is named after its collector, Lu Yong Feng.
The new species is morphologically also similar to I. jianchuanense (Dai & Chen, 1985), but the former can be distinguished from the latter by the following characters: the G1 terminal segment is shorter and stouter (vs. G1 terminal segment longer and slender); the bulge on the extensor margin of the G1 terminal segment is more produced distally (vs. bulge more gradually narrowed distally); and the shape of the vulva is oval  Diagnosis. Body size relatively small (largest individual with CW 22.0 mm). Carapace relatively high, with gently convex dorsal surface, epigastric and postorbital cristae very low, not continuous, postorbital cristae not confluent with epibranchial tooth. Third maxilliped exopod without flagellum. Ambulatory legs relatively slender. Male sterno-pleonal cavity reaching imaginary line joining middle of bases of cheliped coxae. Male pleon broadly triangular. G1 relatively slender, straight to gently sinuous; terminal segment stout, straight, length about 0.6-0.8 time that of subtemirnal segment, tip truncate, ventral layer produced outward to form large semicircular dorsal flap, groove for G2 marginal.
Remarks. Dai & Chen (1985) used the name Ranguna (Pararanguna) semilunatum consistently in the paper. The inclination is to assume the gender of the subgenus is neuter as the species named is neuter. The Latin "lunatum" means "crescent-shaped" and the gender is neuter (masculine "lunatus," feminine "lunata"). The genus Ranguna Bott, 1966, on the other hand, is clearly feminine even though Bott (1966) did not specify the gender when he recognized it as a subgenus of Potamiscus Alcock, 1909. We, however, cannot extrapolate from Dai & Chen's (1985) paper that they wanted the gender of Pararanguna to be neuter; regardless of the fact that it should be also feminine since it was based on Ranguna. The reason is that they only established Pararanguna as a subgenus of Ranguna; and the Code (International Commission on Zoological Nomenclature (ICZN), 1999) mandates that the gender of the species must match that of the genus-in this case, Ranguna, which already is feminine. Dai & Chen's (1985) used of the neuter "semilunatum" must thus be regarded as a lapsus. The name "semilunatum" also cannot be regarded as a noun, it was neither stated nor etymologically correct. As such, it must be regarded as an adjective. In the present classification were Pararanguna is treated as a full genus (Ng, Guinot & Davie, 2008), it is thus necessary to treat this name as derived from the feminine Ranguna, i.e., Pararanguna is also feminine. As such, the gender of the constituent species is also feminine, i.e., Pararanguna semilunata. When Pararanguna was established, Dai & Chen (1985), compared it with Ranguna and listed two diagnostic characters, i.e., (1) more prominent post-frontal lobe and post-orbital cristae, and (2) the first pleopod being tapered and directed outward, but they did not specify which genus has these character states. Specimens of Pararanguna semilunata examined in this study, including paratypes, have very low post-frontal crista and post-orbital crista (Fig. 19A), and subconical G1 terminal segment, with a bulge of increasing distal width along the extensor margin (Fig. 19E). This indicates that the two diagnostic characters listed by Dai & Chen (1985) were of Ranguna sensu Bott (1968Bott ( , 1970. The genus Ranguna had taxonomic problems. Ranguna was established by Bott (1966) with Potamon (Potamon) rangoonensis Rathbun, 1904, as type species, although he did not examine the type specimen (see Türkay & Naiyanetr, 1989;Ng, 1990;Holthuis, 1990). Bott (1970) included 16 species and two subspecies in Ranguna. Türkay & Naiyanetr (1987) redescribed the holotype of Potamon rangoonensis, the type species of Ranguna, and found that it is not what they thought of "Ranguna" sensu Bott (1968Bott ( , 1970) that mesial ends of thoracic suture 4/5 is about equal to the one-third distance between sternal press-buttons of locking mechanism, (2) the terminal segment of G1 is longer than half the length of G1 subterminal segment; (3) the exopod of the third maxilliped lacks flagellum. The above first character in Pararanguna semilunatum is 35.6% (calculated from Dai, 1999: fig. 200 (3)), but this is difficult to determin whether it is "about equal to the one-third." This character is also discussed for Indochinamon (see remarks of Indochinamon). The differences between above four genera are very distinct; the terminal segment of Pararanguna has a roundly truncate tip and well-developed semicircular dorsal flap (vs. terminal segment cylindrically stick-shaped without dorsal flap in Aparapotamon, terminal segment gently incurved with distal dorsal lobe larger than ventral lobe in Tenuipotamon, terminal segment tapered and distally curves inward in Parvuspotamon).
Etymology. The species name is derived from hemicyclium, Latin for semicircle, alluding to the dorsal flap of the G1 terminal segment.
Remarks. Pararanguna hemicyclia sp. n. closely resembles the only congener, Pararanguna semilunata (Dai & Chen, 1985), in its general carapace morphology and in the stout, straight G1 terminal segment which is rounded with a slight subdistal constriction, possessing a truncate tip and a well-developed, high, broad dorsal flap. However, P. hemicyclia can be distinguished from Pararanguna semilunata by the following suite of diagnostic characters: the anterolateral margin of the carapace is less convex laterally (vs. anterolateral margin strongly convex laterally); the dorsal surface is gently convex with distinctly demarcated regions (vs. dorsal surface convex and inflated with weakly demarcated regions); the antennular fossae appear subtriangular in anterior view (vs. antennular fossae rectangular in anterior view); the external orbital angle is acutely triangular with an obvious cleft demarcating it from the epibranchial tooth (vs. external orbital angle obtusely triangular with a slight cleft demarcating it from epibranchial tooth); the median tooth of the epistome posterior margin has an acute tip (vs. median tooth with an obtuse tip); the carpi of the chelipeds have well-developed, acute spines on the inner margin (vs. chelipeds carpi with low, obtuse spines on inner margin); the male pleon is broadly triangular with telson having gently convex lateral margins (vs. male pleon relatively narrowly triangular with telson having almost straight lateral margins); the dorsal flap of the G1 terminal segment has the median part being higher and the proximal end of the dorsal flap does not reach the proximal end of the distal segment (vs. dorsal flap with a lower apex in median part and proximal end of dorsal flap reaching proximal end of distal segment). (Figs. 20, 21 and 22A-22C vs. Dai & Chen, 1985: fig. 16 (4, 5, 7), pl. 1 fig. 5; Dai, 1999: fig. 200, pl. 25 fig. 1).
Distribution. Dashan Village, Xueshan Town, Fengqing County, Yunnan Province, China. The collection site is located in the Lincang and Lancang Rivers Natural Reserve.
Remarks. Dai & Bo (1994) compared Parvuspotamon with Yarepotamon Dai & Türkay, 1997, which has been known from Guangdon and Guanxi Provinces. They distinguished the two genera by the following characters: the carapace is more glabrous (vs. finely rugose in Yarepotamon), the postorbital criste are blunt (vs. sharp in Yarepotamon), the epibranchial tooth is blunt (vs. prominent in Yarepotamon), the exopod of the third maxilliped lacks a flagellum (vs. absent or with vestigial flagellum in Yarepotamon), and a groove for G2 on G1 placed laterally (vs. medially in Yarepotamon). Furthermore, they recognized more morphological differences between Parvuspotamon yuxiense and Yarepotamon gracilipa in the length to width ratio of the telson (1.1 vs. 1.4), and the G1 subterminal segment being 1.8 times as long as terminal segment (vs. 2.1 in Y. gracilipa), and the G2 subterminal segment is about 1.4 times as long as terminal segment (vs. two times in Y. gracilipa).
Parvuspotamon is morphologically more similar to Pararanguna, Aparapotamon, and Tenuipotamon, which are exclusively or partially distributed in Yunnan Provice, in their low to very low postorbital and postfrontal cristae and the absence of the flagellum from the third maxilliped exopod. These genera can, however, be easily distinguished from each other by the condition of the G1 terminal segment (see Remarks of Pararanguna).
According to the key to genera of Chinese Potamidae (Dai, 1999: 85, in Chinese), the abovementioned four Yunnan genera are supposed to have relatively long G1 distal segment (more than half the length of that of subteminal segment). This key should be amended to accommodate Parvuspotamon dixuense sp. n., G1 terminal segment of which is slightly shorter than half the length of the G1 subterminal segment (ca. 0.4). This change is also necessary for Tenuipotamon, as Tenuipotamon huaningense has relatively short G1 terminal segment (Dai & Bo, 1994: fig. 2 (4); Dai, 1999: fig. 206 (4)).
Etymology. The species is named after the locality in which it was found.
Remarks. Parvuspotamon dixuense sp. n. closely resembles the only congener, P. yuxiense Dai & Bo, 1994, in its general carapace morphology and in the long, slender, subconical G1 terminal segment with curved outer margin, truncate tip and slender subterminal segment. However, P. dixuense can be distinguished from P. yuxiense by the following characters: the G1 terminal segment is gently bent outward, with a straight inner margin (vs. G1 terminal segment curved inward, with a concave inner margin); the groove for G2 runs along the ventral side of the G1 terminal segment (vs. groove for G2 being marginal along the G1 terminal segment); a shelf is present at the lateral margin between the G1 terminal and subterminal segments (vs. shelf absent); and the G2 terminal segment is less than half the length of the basal segment (G2 terminal segment more than half the length of the basal segment) (Fig. 26 vs. Fig. 19F; Dai & Bo, 1994: fig. 3 (4-6); Dai, 1999: fig. 216 (4-6)).
The two species described in this paper share these characters. In the key to genera of Chinese Potamidae (Dai, 1999: 85, in Chinese), one of the characters that characterizes Potamiscus is: the distance between mesial ends of thoracic suture 4/5 is shorter than the one-third distance between sternal press-buttons of locking mechanism. However, the mesial end of the suture 4/5 is placed near the base of lateral slope of the sterno-pleonal cavity, which is nearly vertical, and the mesial end is not always clear and mesially continued gradually as depression, it is difficult to standardize the measurements. Diagnosis. Carapace (Fig. 28A) distinctly broader than long CW 1.20 times CL, dorsal surface (Fig. 28B) relatively flat, cervical grooves indistinct, weakly developed, reaching Etymology. The species name is derived from an arbitrary combination of the Latin "fumario" (=chimney) and -atus (a suffix to form adjective indicating the possession of a thing or a quality), alluding to the possession of chimney-like G1s.
Etymology. The specific name is derived from the Latin "crassus" (=thick, fat), alluding its very stocky G1.
Remarks. Like the previous species, Potamiscus crassus sp. n. was also found together with Aparapotamon grahami (Rathbun, 1931). However, it can be easily distinguished from the latter species by the narrowly triangular male telson, the absence of the flagellum on the exopod of the third maxilliped, and its distinct G1 structure. Potamiscus crassus sp. n. most closely resembles Potamiscus yongshengensis Dai & Chen, 1985, in general carapace morphology and in the subconical G1 terminal segment appearing longitudinally twisted as well as possessing a truncate tip. However, Potamiscus crassus sp. n. can be easily distinguished from Potamiscus yongshengensis by the following characters: the epibranchial tooth is poorly developed and not triangular (vs. epibranchial tooth more developed and triangular); male telson is narrow, with the lateral margins being proximally narrowed abruptly (vs. male telson broadly triangular, with lateral margins of telson being only slightly concave); and the G1 terminal segment has a broadly rounded tip (vs. G1 terminal segment with a narrowly rounded tip) (Figs. 31A, 32A and 33A-33D vs. Figs. 19D and 19H;Dai & Chen, 1985: fig. 5 (4, 5, 7), pl. 1 fig. 6; Dai, 1999: fig. 102 (2, 4, 5), pl. 12 fig. 5). Distribution. The type specimens were purchased by Mrs. Yang Chang Man at a market in the outskirts of Kunmin City.

CONCLUSIONS
The present study described eight new species of potamid freshwater crab of the genera Indochinamon Yeo & Ng, 2007, Pararanguna Dai & Chen, 1985, Parvuspotamon Dai & Bo, 1994, and Potamiscus Alcock, 1909. The present study added four species to the genus Indochinamon, and the genus currently contains 38 species Naruse, Quynh & Yeo, 2011;Do, Nguyen & Le, 2016;present study). Nineteen out of the 38 species are distributed in China, of which 18 species are known from Yunnan. Potamiscus is also distributed in Indochina and southern China ). The present study added two species, and the genus now contains 16 species, seven of which have been recorded from Yunnan. Pararanguna and Parvuspotamon were monotypic genera, but the present study described one species each for the two genera. Both genera are endemic to Yunnan Province. Yunnan was already known to host the highest number of freshwater crab species in the provinces of China, and the present study further added eight species and brings the number to 58. It is noteworthy that seven out of eight new species described in the present study were collected by local colleagues and students at our request within a relatively short period in February, 2004. Also, considering the fact that more and more species have been discovered from Yunnan as well as other provinces of China