Chinapotamon cf. depressum ( Dai, Song, Li & Liang, 1980 )

Anh, Le Hung, Dong, Dang Van & Tu, Do Van, 2024, First record of the genus Chinapotamon Dai & Naiyanetr, 1994 (Crustacea: Decapoda: Brachyura: Potamidae) from northern Vietnam with description of one new species, Zootaxa 5424 (5), pp. 501-519 : 504-507

Chinapotamon cf. depressum ( Dai, Song, Li & Liang, 1980)

( Figs. 2–3 , 10A )

Tiwaripotamon depressum Dai, Song, Li & Liang, 1980: 371–372 , pl. 1: 3, fig. 3.

Chinapotamon depressum — Dai & Naiyanetr 1994: 54–56, fig. 5.— Dai 1999: 93–94, fig. 43, pl. 4 fig 5.— Ng et al., 2008: 161.— Ji et al., 2016: 81.— Ng, 2017: 6–7.— Chu et al., 2018: 2.— Zou et al. 2018: 2, 10–13.

Material examined. 3 males (34.9 × 26.8 mm, 34.4 × 26.3 mm, 32.5 × 25.2 mm), 1 female (27.2 × 21.3 mm), IEBR-FC-CDx01, Vietnam, Cao Bang Province, Ha Lang District, Duc Quang Commune, Coong Hoai Village , a small stream in Lung Roi 2, N 22°43’25.2” E 106°40’29.3”, coll. Do V. T., Le H.A. & Dang V.D., 14 May 2019; 1 male (31.5 × 24.8 mm), 1 female (33.9 × 26.6 mm), IEBR-FC-CDx02, Vietnam, Cao Bang, Ha Lang, Duc Quang, Coong Hoai village , a small stream in Lung Roi 2, N 22°43’41.5” E 106°40’09.5”, coll. Do V. T., Le H.A. & Dang V.D., 15 May 2019; 1 male (31.1 × 24.9 mm), 1 female (27.8 × 21.8 mm), IEBR-FC-CDx03, Vietnam, Cao Bang, Ha Lang, Duc Quang, Coong Hoai village , a small stream in Khau Noc , N 22°43’46.6” E 106°40’09.3”, coll. Do VT., Le HA., Dang VD., 15 May 2019; 1 male (27.9 × 21.5 mm), 1 female (33.8 × 26.2 mm), IEBR-FC-CDx04, Vietnam, Cao Bang, Ha Lang, Duc Quang, Coong Hoai village , a small stream, N 22°42’45.8” E 106°39’53.8”, coll. Do V. T., Le H.A. & Dang V.D., 15 May 2019.

Remarks. The specimens collected from Ha Lang District, Cao Bang Province, Viet Nam, which is near the border with Guangxi, China, agree with descriptions and figures of C. depressum such as the medium-sized carapace; the carapace dorsal surface being gently convex; distinct epigastric and postfrontal cristae; the deep cleft between the external orbital and epibranchial teeth; the distinct anterolateral crista; the rugose anterolateral region; the concavity between frontal margin lobes is broad and shallow ( Figs. 2A, B ); the ischium of third maxilliped is quadrate, about 1.4–1.5 times longer than broad ( Fig. 2C ); a small gap between the fingers of the male major chela when closed ( Fig. 3A ); the male thoracic sternites 3 and 4 are completely fused, being demarcated only by an oblique concavity ( Fig. 3B ); and the G1 terminal segment is relatively slender and is bent at about 30° outwards ( Figs. 3C ). There are a few minor differences when we compared our specimens with the descriptions of C. depressum in Dai & Naiyanetr (1994), Dai (1999), Ng (2017) and Zou et al. (2018): the last ambulatory merus is proportionately stouter, 2.5 times as long as than wide ( Fig. 2A ) (vs. 3.3 times as long as wide; cf. Ng, 2017: table 1; Zou et al., 2018: table 2); when the fingers of male major chela closes, there is a larger ovate gap between the fingers ( Fig. 3A ) (vs. linear small gap cf. Dai 1999: pl. 4, Fig. 5 ; cf. Zou et al., 2018: table 2). The live colouration of the specimens from China is unknown while our specimens showed orange–brown dorsal carapace, light purple outer and inner of chelae and white ventral surface ( Fig. 10A ). The type locality of C. depressum, Baise district, Guangxi province, is geographically close to the locality of our specimens, Cao Bang province. Due to the morphological similarities and the proximity to the type locality, we identified that our specimens may belong to C. depressum . An integrative approach, including DNA analysis, is necessary to gain insight into the intraspecific or interspecific variations of these populations.

Figures

FIGURE 2. Chinapotomon cf. depressum, male (CW 34.9 mm), IEBR-FC-CDx01. A, carapace, dorsal view; B, frontal view of cephalothorax; C, right third maxilliped.

FIGURE 3. Chinapotomon cf. depressum, male (CW 34.9 mm), IEBR-FC-CDx01. A, chelae outer view; B, ventral view; C, sternopleural, cavity showing G1s and G2s.

FIGURE 5. Chinapotamon cf. pusillum, male (CW 15.9 mm), IEBR-FC-CPx01. A, ventral view of cephalothorax; B, sternopleonal cavity showing G1s and G2s.

FIGURE 10. The colour photographs of Chinapotamon species from Vietnam. A, Chinapotomon cf. depressum, male (CW 34.9 mm), IEBR-FC-CDx01; B, Chinapotamon cf. pusillum, male (CW 15.9 mm), IEBR-FC-CPx01; C, Chinapotamon insulare sp. nov., holotype, male (CW 28.9 mm), IEBR-FC-CIx01.