 |
| Tiwaripotamon pluviosum
Do, Shih & Huang, 2016
|
Abstract
A new freshwater crab species of the family Potamidae is described from the boundaries of northern Vietnam and southern China. Tiwaripotamon pluviosum sp. nov. can be distinguished from other species by a suite of morphological characters, including a relatively flat carapace, relatively less slender legs, and distinct dorsal flaps on the male first gonopods. Molecular data using the mitochondrial cytochrome oxidase subunit I (COI) also supports this species as being new.
Key words: Tiwaripotamon pluviosum, taxonomy, mitochondrial DNA, cytochrome oxidase subunit I, COI
 |
| Fig. 5. Tiwaripotamon pluviosum sp. nov., male (CW 39.8 mm, SYSU 001205). A, dorsal view; B, frontal view; G, H, a habitat in Duc Quang Commune, Ha Lang District, Cao Bang Province, Vietnam. |
TAXONOMY
Family Potamidae Ortmann, 1896
Subfamily Potamiscinae Ortmann, 1896 (sensu Yeo & Ng, 2003)
Genus Tiwaripotamon Bott, 1970
Type species: Geothelphusa annamensis Balss, 1914, by original designation.
Tiwaripotamon pluviosum sp. nov
Diagnosis. Carapace about 1.3 times broader than long;
transverse, low; dorsal surface relatively flat; glabrous;
regions poorly defined, cervical groves shallow; H-shaped
depression shallow but distinct. Epigastric cristae distinct;
postorbital cristae rounded, confluent with epibranchial tooth.
External orbital angle triangular, outer margin gently convex;
epibranchial tooth small, broadly triangular, separated from
external orbital angle by distinct, broadly triangular cleft.
Ambulatory legs less slender; fourth pair with length of
merus about 4.7 times width. G1 terminal segment distinctly
upcurved, with distinct dorsal flap in proximal part.
Etymology. The name “pluviosum” means rainy, which
refers to the specimens being collected and active during
the rainy season.
Ecological notes. This species inhabits limestone mountains
(Fig. 5G, H), and are most active during the rainy season
(personal observation). Similar to T. vixuyenense (cf. Shih &
Do, 2014), specimens of this species were also found crawling
on the leaves and twigs, with one specimen observed being
one metre above the ground at night.
Remarks. This species fits well within the character
descriptions of Tiwaripotamon defined by Ng & Yeo
(2001) due to the squarish third maxilliped ischium, short
third maxilliped exopod with a short flagellum, slender
legs, broadly triangular male abdomen, and an upcurved
G1 terminal segment (Figs. 1–4). This new species can
be separated from other congeners (see below) by the
relatively flat and transverse dorsal surface of the carapace,
proportionately stouter ambulatory legs and distinct dorsal
flap on the G1.
The G1 of this species resembles T. edostilus in the presence
of a dorsal flap, but it is smaller in size in the latter (versus
larger in this species) (Fig. 2; cf. Ng & Yeo, 2001: fig. 5).
The new species can also be separated from T. edostilus
by the flatter and more transverse carapace (ratios of CW:
CL is 1.3 of this species; 1.2 of T. edostilus; cf. Shih &
Do, 2014) and stouter ambulatory legs (see below). The
carapace of the new species is similar with T. annamense
in the morphology of the anterolateral margin. However,
the two can be easily separated by the presence of a dorsal
flap on the G1 in the former (Fig. 2) and the absence of
such in the latter (Ng & Yeo, 2001: fig. 2D–I). The merus
of the fourth ambulatory leg is about 4.8 times longer than
broad for this species, which is shorter than most congeners:
6.5 for T. vixuyenense, 5.1 times for T. vietnamicum, 5.6
times for large T. edostilus specimens and 5.3 times for T.
xiurenense (unpublished data; Shih & Do, 2014), but longer
than T. pingguoense (4.3 times, unpublished data) and T.
annamense (approximately 4.5 times, estimation derived
from dactylus ratio, Ng & Yeo, 2001).
Van Tu Do, Hsi-Te Shih and Chao Huang. 2016. A New Species of Freshwater Crab of the Genus Tiwaripotamon Bott, 1970 (Crustacea, Brachyura, Potamidae) from northern Vietnam and southern China. RAFFLES BULLETIN OF ZOOLOGY. 64: 187–193.
