Indochinamon malipoense Zhang & Sun

Dang, Khai, Hoang, Anh Tram & Do, Cuong, 2024, A new species of the genus Indochinamon Yeo & Ng, 2007 (Crustacea: Brachyura: Potamoidea: Potamidae) and a new country record from Northern Vietnam, Zootaxa 5437 (4), pp. 560-570 : 567-569

Indochinamon malipoense Zhang & Sun , in Zhang, Pan, Hao & Sun, 2020

( Figs. 7–8 )

Indochinamon malipoense Zhang & Sun , in Zhang, Pan, Hao & Sun, 2020: 12–15 , 17, fig. 7–12. [type locality: Malipo County, Wenshan Prefecture, Yunnan Province, China].— Pan, Ng & Sun 2022: 327, fig. 7.— Shi et al. 2023: 582, fig. 7.

Material examined: 2 males (80 × 65 mm, 76 × 58 mm) (Experta collection 2023.004; 2023.005), Lac Thuy district , Hoa Binh province, Vietnam, purchased from local people, 23 June 2023 .

Diagnosis: Carapace broader than long, dorsal surface glabrous, gently convex; regions indistinctly defined ( Fig. 7A ); anterolateral margin lined with obvious granules, appear serrated ( Fig. 7A ). cervical groove shallow, indistinct; H-shaped groove between gastric and cardiac regions prominent ( Fig. 7A ). Frontal margin gently convex, appears entirely in dorsal view ( Fig. 7B ). Third maxilliped exopod with short flagellum that reaches half of the merus width ( Fig. 8A ). Outer surface of chela line with prominent granules, fingers of major chela short, stout, slightly curved inwards, subequal to palm, outer surface lined with nodules, cutting edges of both fingers with variously sized sharp teeth and denticles ( Fig. 7D ). Minor chela similar to major chela in form but relatively more slender ( Fig. 7E ). Male pleon triangular, lateral margin of somite 6 convex ( Figs. 7C , 8C ). Telson triangular, tip rounded ( Figs. 7C , 8C ). G1 stout, tip of terminal segment not reaching pleonal locking mechanism in situ ( Fig. 8B ). G2 elongate, strongly curved, much longer than G1 ( Fig. 8B, F ).

Live colouration: The dorsal carapace is honey yellow, the H-shaped groove in the middle, frontal surface, ambulatory legs and chelipeds are dark purple. Some other individuals have light red ambulatory legs and chelipeds, sky blue carapace or fully ivory white. There are no distinct difference between these individuals of different colours, these color variations usually found together in the same area and habitat.

Habitat: This species often lives near streams or clefts on limestone mountains. They often move on the forest floor day and night but are more active and often seen at night. Sometimes they are also found in the water of forest streams and rock crevices containing water.

Remarks: Indochinamon malipoense was first described in Malipo County, Yunnan, China ( Zhang et al. 2020), approximately 340 km north from the new recording site. Previously, it was only known from Yunnan, this species is recorded in Vietnam for the first time, bringing the total number of species of Indochinamon in Vietnam to 14.

Compared to the specimens collected in Yunnan in the original description, the specimens we collected in Vietnam had most of the morphological characteristics matching the description and figures by Zhang et al. (2020) despite it being remarkably larger in size. In the original description, G1 of the holotype has a terminal segment that is less distally curved than the specimen from Vietnam, which is clearly visible in dorsal view ( Fig. 8E ; cf. Zhang et al. 2020: fig. 8C), this may possibly be caused by the slight differences in the position of the G1 placed for imaging, besides, they can also be variations within a species. A deeper study of these differences should probably be done in a future, currently, we find that the specimens from Hoa Binh province best match the description and figures of I. malipoense and we recognize it as a new record for Vietnam.

Indochinamon malipoense can be distinguished from I. datii n. sp. by the following: 1) a subtrapezoidal carapace with gently convex frontal margin ( Fig. 7B ; cf. Zhang et al. 2020: fig. 7B) (versus transversely ovate carapace and nearly straight frontal margin in I. datii n. sp.; Fig 1B ); 2) the merus of the third maxilliped of I. malipoense is trapezoidal in shape and the exopod with the short flagellum reaches half of the merus width ( Fig. 8A ; cf. Zhang et al. 2020: fig. 8A) while that in I. datii n. sp., is subquadrate with elongate and slender flagellum that reaches two-thirds of the merus width ( Figs. 2A , 6A ); 3) the G1 characteristics of I. datii n. sp. and I. malipoense are similar but the angle between the subterminal and the terminal segment of I. datii n. sp. ( Figs. 2A , 6A ) is larger than I. malipoense ( Fig. 8A ), the G1 tip of I. datii n. sp. is also more pointed ( Fig. 2D, E ) than I. malipoense ( Fig. 8D, E ). The length ratio of the G2 subterminal segment to terminal segment of I. malipoense is 1.2 ( Fig. 8F ) (versus 1.4 in the new species; Fig. 2H ). Furthermore, I. datii n. sp. is a fully aquatic species and rarely leaves the water while I. malipoense is a semi-terrestrial species.

Figures

FIGURE 1. Indochinamon datii n. sp. holotype, male (61 × 49 mm) (VNMN 2022.001); A, dorsal habitus; B, frontal view of cephalothorax; C, anterior thoracic sternum and pleon, ventral view; D, outer view of major chela; E, outer view of minor chela (dactylus tip broken).

FIGURE 2. Indochinamon datii n. sp. holotype, male (61 × 49 mm) (VNMN 2022.001);A, left third maxilliped, external view; B, sterno-pleonal cavity with G1 and G2 in situ, ventral view; C, male pleon, external view; D, left G1, ventral view; E, left G1, dorsal view; F, distal part of left G1, ventral view; G, distal part of left G1, dorsal view; H, left G2, dorsal view.

FIGURE 6. Indochinamon datii n. sp., holotype, male (61 × 49 mm) (VNMN 2022.001). A, left third maxilliped, external view; B, left G1, ventral view; C, left G1, dorsal view; D, left G2, dorsal view; E, distal part of left G1, ventral view; F, distal part of left G1, dorsal view.

FIGURE 7. Indochinamon malipoense Zhang & Sun in Zhang, Pan, Hao & Sun, 2020 (80 × 65 mm) (Experta collection 2023.004). A, dorsal habitus; B, frontal view of cephalothorax; C, anterior thoracic sternum and pleon, ventral view; D, outer view of major chela; E, outer view of minor chela.

FIGURE 8. Indochinamon malipoense Zhang & Sun in Zhang, Pan, Hao & Sun, 2020 (80 × 65 mm) (Experta collection 2023.004).A, left third maxilliped, external view; B, sterno-pleonal cavity with G1 and G2 in situ, postero-ventral view; C, male pleon, external view; D, left G1, ventral view; E, left G1, dorsal view; F, left G2, dorsal view.