Arquatopotamon, Chu, Kelin, Zhou, Lijun & Sun, Hongying, 2017

Chu, Kelin, Zhou, Lijun & Sun, Hongying, 2017, A new genus and new species of freshwater crab (Decapoda: Brachyura: Potamidae Ortmann, 1896) from Yunnan Province, China, Zootaxa 4286 (2), pp. 241-253 : 244-245

Arquatopotamon gen. n.

Diagnosis. Carapace Subquadrate, flat, dorSal Surface Smooth ( Fig. 1 A); third maXilliped iSchium about 1.4 timeS aS long aS broad, eXopod without flagellum ( Fig. 1 B, 2B); male abdomen broadly triangular, telSon broadly triangular, with about 1.6 timeS aS broad aS long ( Fig. 1 C, 3B); median grooVe of male thoracic Sternum deep, interruption between SutureS of SterniteS 4/5, 5/6, 6/7 broad ( Fig. 3 A); G1 long, diStal part of Subterminal Segment and terminal Segment arch Shaped (meSioVentral View; Fig. 2 E), tip of terminal Segment reaching Suture between thoracic SterniteS 4/ 5 in situ ( Fig. 3 A); Subterminal Segment about 1.9 timeS aS long aS terminal Segment; terminal Segment tongue-Shaped, diStinctly curVed VentralwardS (Ventral View) ( Fig. 2 D, E, F and G). Female gonoporeS on thoracic SterniteS 5/6, reaching Suture between thoracic SterniteS 4/ 5 in situ, deep, without operculum, poSterior margin with a V-Shaped notch and the anterior portion with a protuberance ( Fig. 3 C, D).

Type species. Arquatopotamon jizushanense sp. n., by monotypy.

Etymology. The genuS name iS deriVed from the Latin arquatus for “arched”, which deScribeS the arched male firSt gonopod of the type SpecieS for the genuS. Potamon iS the type genuS of the family Potamidae . Gender neuter.

Remarks. Although thiS new genuS, Arquatopotamon , iS Similar to Tenuipotamon , Pararanguna , Trichopotamon , Potamiscus , and Aparapotamon by haVing a third maXilliped eXopod without a flagellum, it can be eaSily diStinguiShed from the fiVe related genera by a G1 with an arch-Shaped diStal part of the Subterminal Segment and terminal Segment, the female gonoporeS located on thoracic SterniteS 5/6, and a combination of characterS including the carapace and male telSon ( Table 2; Fig. 4 ; See Dai 1999: pl. 382, fig. 206; Dai 1999: pl. 371, fig. 200; Dai 1999: pl. 366, fig. 198; Dai 1999: pl. 192, fig. 102; Dai 1999: pl. 349, fig. 187). Although the female Sternal gonoporeS (VulVae) in eubrachyuranS are uSually located on Sternite 6 (DaVie et al., 2015; Guinot et al., 2013), they are partially eXpoSed anteriorly to the SterniteS 5/ 6 in the potamiScine genuS Pararanguna ( Dai and Chen, 1986; Dai, 1999) and eVen to the Suture between thoracic SterniteS 4/ 5 in the new genuS. OtherwiSe, the detailS in the female genital duct of the new genuS could not be clearly detected under the microScope. Further Study iS needed for underStanding the three-dimenSional (3D) Structure of the female genital duct, which correSpondS to the Specialized tip of the G1, by uSing LED-Structured illumination microScopy (LED-SIM) ( Ruan et al., 2016; Bai et al., 2017).

1. Tip of G 1 in relation to tubercle of abdominal locking structure, in situ. 2. Female gonopore in thoracic sternite in situ. 3. cf. Dai 1999: pl. 382; fig. 206. 4. cf. Dai 1999: pl. 371; fig. 200. 5. cf. Dai 1999: pl. 366; fig. 198. 6. cf. Dai 1999: pl. 192; fig. 102. 7. cf. Dai 1999: pl. 349; fig. 187.

Comparative materials. Tenuipotamon huaningense Dai & Bo, 1994: 1 male (21.4 × 17.1 mm), NNU 160531 ; 1 female (14.5 × 11.5 mm), NNU 160532; Huaning , Yunnan, May 2016. Pararanguna semilunatum (Dai & Chen, 1985) : 1 male (16.9 × 13.3 mm), NNU 151005; 1 female (20.3 × 16.1 mm), NNU 151012; BaoShan, Yunnan, Otc 2015. Trichopotamon daliense Dai & Chen, 1985 : 1 male (paratype, 23.2 × 19.3 mm), IZCAS CB01528; 1 female (19.3 × 15.8 mm), NNU 160542; Dali , Yunnan, May 2016. Potamiscus yongshengensis Dai & Chen, 1985 : 1 male (28.0 × 22.4 mm), NNU 150951; 1 female (25.7 × 20.6 mm), NNU 150953; YongSheng , Yunnan, Sep 2015. Aparapotamon grahami (Rathbun, 1931) : 1 male (28.2 × 22.2 mm), NNU 150962; 1 female (31.7 × 25.4 mm), NNU 150963; ChuXiong , Yunnan, Sep 2015 .

Figures

FIGURE 1. Arquatopotamon jizushanense gen. n., sp. n. male holotype, 19.4 × 16.4 mm, NNU 160506. A, dorsal vieW; B, frontal vieW of cephalothoraX; C, ventral vieW of cephalothoraX, chelae, and abdomen.

FIGURE 2. Arquatopotamon jizushanense gen. n., sp. n. male holotype, 19.4 × 16.4 mm, NNU 160506. A, outer surfaces of right major chela; B, left third maXilliped; C, left G 2; D-G, left G 1 Without G 2: D, ventral vieW; E, mesioventral vieW; F, dorsal vieW; G, dorsolateral vieW. Scales = 1.0 mm.

FIGURE 3. Arquatopotamon jizushanense gen. n., sp. n. A-B, male holotype, 19.4 × 16.4 mm, NNU 160506. A, sternoabdominal cavity With right G 1 in situ; B male abdomen. C-E, female paratype, 22.3 × 18.5 mm, NNU 160510. C, female thoracic sternum and gonopores; D, right female gonopore; E, female abdomen. Scales = 1.0 mm.

FIGURE 4. The ventral vieW of G 1 of Arquatopotamon jizushanense gen. n., sp. n and allied genera. A, Arquatopotamon jizushanense gen. n., sp. n (holotype male, 19.4 × 16.4 mm, NNU 160506). B, Tenuipotamon huaningense Dai & Bo, 1994 (male, 21.4 × 17.1 mm, NNU 160531). C, Pararanguna semilunatum (Dai & Chen, 1985) (male, 16.9 × 13.3 mm, NNU 151005). D, Trichopotamon daliense Dai & Chen, 1985 (paratype male, 23.2 × 19.3 mm, IZCAS CB 01528). E, Potamiscus yongshengensis Dai & Chen, 1985 (male, 28.0 × 22.4 mm, NNU 150951). F, Aparapotamon grahami (Rathbun, 1931) (male, 28.2 × 22.2 mm, NNU 150962). Scales = 1.0 mm.