Phricotelphusa sukreei Ng & Yeesin & Promdam 2022, new species
Creators: name: Ng, Peter K. L.
name: Yeesin, Pun
name: Promdam, Rueangrit
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Gecarcinucidae
Phricotelphusa
Phricotelphusa sukreei

description: Phricotelphusa sukreei, new species
(Figs. 1–3, 5A–E)
Material examined. Holotype: male (26.7 × 20.2 mm) (ZRC 2021.0815), in a tree-hole of high mountains, 1355 m asl, Srinagarindra District, Phatthalung Province, Peninsular Thailand, coll. P. Yeesin, 13 March 2017. Paratype: 1 female (27.1 × 20.3 mm) (ZRC 2021.0824), same data as holotype; 2 males (26.9 × 21.2 mm, 20.3 × 16.4 mm) (PSUFTM-0001), high mountains, 1355 m asl, Srinagarindra District, Phatthalung Province, Peninsular Thailand, coll. P. Yeesin, 17 December 2016; 2 males (23.1 × 18.4 mm, 21.2 × 17.0 mm) (PSUZC-CRU-0146), same data as above.
Accepted by: Tohru Naruse
1 Lee Kong Chian Natural History Museum, National University of Singapore, 14 Science Drive 4, Singapore 117543, Republic of Singapore;Email:peterng@nus.edu.sg
2 Department of Technology and Industries, Faculty of Science and Technology, Prince of Songkla University, Pattani, Thailand; Email: punyeesin@gmail.com
3 Princess Maha Chakri Sirindhorn Natural History Museum, Prince of Songkla University, Hat Yai, Songkhla, 90110, Thailand; Email: rueangrit.p@psu.ac.th (* corresponding author)
Comparative material. Phricotelphusa limula (Hilgendorf, 1882): 11 males, 5 females (ZRC 2005.0107), Tone Sai Waterfall, Phuket, Thailand, coll. D.C.J. Yeo, 19 February 2001. Phricotelphusa aedes (Kemp, 1923): holotype female (25.8 × 18.6 mm) (ZSI C 602 /1) [photographs examined], Khao Ram, Nakhon Si Thammarat mountains, southern Thailand, coll. Malcolm Smith, no date; 1 male (17.5 × 13.2 mm), 1 female (19.5 × 15.3 mm) (ZRC 2012.0215), Phrommalok waterfall, Phrommakhiri District, Nakhon Si Thammarat Province, southern Thailand, coll. P. Naiyanetr, 8 March 1965; 2 males (22.7 × 17.4, 13.3 × 11.3) (PSUZC-CRU-0102),> 700 m asl, Khao Ram Rome, Ron Phibun District, Nakhon Si Thammarat Province, southern Thailand, coll. R. Promdam. Phricotelphusa hymeiri Ng & Lee, 2012: holotype male (20.5 × 16.5 mm) (ZRC), inside Loposang Cave, Wang Mu Forest Reserve, Perlis, Peninsular Malaysia, coll. K. Hymeir, March 2008.
© National University of Singapore
ISSN 2345-7600 (electronic) | ISSN 0217-2445 (print)
Diagnosis. Carapace subovate, broader than long; dorsal surfaces gently granulose to rugose; branchial regions gently inflated dorsally and laterally; frontal margin not protruding beyond level of external orbital tooth; anterolateral margin distinctly convex; epibranchial tooth spiniform, sharp, separated from external orbital angle by notch; epistome relatively wide longitudinally, lateral part of posterior margin almost straight or gently sinuous; third maxilliped ischium without visible oblique median sulcus; exopod without flagellum, not reaching distal edge of ischium; antennular fossa relatively narrow, rectangular in shape; ambulatory legs very long; male pleon broadly T-shaped, reaching imaginary longitudinal line joining median edge of bases of chelipeds; telson shorter than somite 6 with gently concave lateral margins; G1 relatively long, terminal segment gently curved, relatively longer, cone-shaped, ca. 0.3 times subterminal segment; G2 distal segment ca. 0.3 times length of basal segment.
Description of male. Carapace subovate, broader than long; regions distinct; dorsal surfaces gently granulose to almost smooth; antero- and posterolateral regions lined with short, strong oblique striae; cervical grooves broad, shallow (Fig. 2A–C). Branchial regions gently inflated dorsally and laterally (Figs. 2B, C, 3A). Frontal margin wide, not protruding anteriorly beyond level of external orbital tooth, gently sinuous, median part deflexed downwards, without trace of median pseudo-frontal triangle (Figs. 2B, C, 3A). Anterolateral margin distinctly convex, not clearly demarcated from posterolateral margin; epibranchial tooth spiniform, distinct, sharp, separated from external orbital angle by distinct notch; external orbital angle broadly triangular, outer margin ca. 2–2.5 times length of inner margin, base ends at base of epibranchial tooth; epigastric and postorbital cristae sharp, distinct, rugose, separated by shallow oblique groove; epigastric cristae relatively weaker, anterior of distinctly sharp, convex postorbital cristae, separated by median groove; postorbital crista ends before cervical groove, not forming continuous crest to epibranchial tooth (Fig. 2A–C). Posterior margin of carapace almost straight (Fig. 2A–C). Suborbital, pterygostomial, and subhepatic regions gently rugose to smooth (Fig. 3A, B). Epistome relatively wide longitudinally; posterior margin with wide median triangular lobe, lateral margin almost straight with margin appearing gently sinuous (Fig. 3A). Eyes relatively large, completely filling orbits; cornea large, fully pigmented. Antennular fossa relatively narrow, rectangular in shape (Fig. 3A).
Third maxilliped relatively short, quadrate; ischium with undiscernible oblique median sulcus; exopod does not reach distal edge of ischium, flagellum absent (Fig. 3D).
Left male cheliped larger; outer surfaces of chelipeds gently rugose and granulose, without sharp spines or spinules; inner margin of merus with distinct granules; carpus with sharp inner distal tooth and smaller sub-basal spine; outer surface of palm gently rugose to granulose, especially lower half; ventral margin of pollex with numerous small denticles, outer surface with 2 rows of low tubercles and 2 shallow longitudinal grooves; cutting edges of both fingers with blunt teeth and denticles (Fig. 2A, D).
Ambulatory legs very long, slender; second pair longest; merus unarmed, dorsal margin gently serrated but not spiniform; outer surfaces in first to third pairs rugose; propodus with row of small movable ventral spines; dactylus gently curved, with 2 rows of strong spines on margins (Figs. 2A, 3F).
Anterior thoracic sternum relatively narrow, smooth; no visible suture between sternites 2 and 3; sternite 2 and 3 marked by low concave ridge; sternites 3 and 4 completely fused (Fig. 3B). Suture for sternites 4/5, 5/6, and 6/7 medially interrupted, with deep median longitudinal groove on sternite 6; sternite 5 with 2 parallel longitudinal grooves medially; press-button locking mechanism represented by low rounded tubercle on anterior third of sternite 5 (Fig. 3C).
Male pleon T-shaped, reaching imaginary transverse line joining median edge of bases of chelipeds; telson shorter than somite 6 with concave lateral margins, tip rounded; somite 6 rectangular with concave lateral margin; somites 3–5 trapezoidal; sternite 2 subequal in width to somite 3 (Fig. 3B, E).
G1 almost straight with terminal segment slightly curved outwards; terminal segment relatively long, gently curved, cone-shaped, ca. 0.3 times subterminal segment; distal part covered with numerous very small scale-like spines and setae on outer margin, tip appears bifurcate (Fig. 5A–C). G2 distal segment ca. 0.3 times length of basal segment; distal part of distal segment gently serrate (Fig. 5D, E).
Female. Pleon wide, ovate, covering most of thoracic sternum; telson broadly triangular with strongly convex lateral margin (Fig. 3G). Vulva large, almost round, without operculum, submedian in position on sternite 6 (Fig. 3H).
Colour. Bright red on all dorsal aspects and surface of all ambulatory legs (Fig. 1B–F). Ventral surfaces of carapace and chelipeds are violet to purplish (Fig. 1F).
Etymology. We take pleasure in naming this species after Sukree Hajisime of the Prince of Songkla University. He has been a good friend to the first author for many years, and has been very supportive of his staff in the university, including the two co-authors.
Remarks. Of the twelve known species, the form of the epibranchial tooth of P. limula, P. sirindhorn, and P. aedes is distinctive, being acutely triangular and appearing almost spiniform, a character shared by P. sukreei, new species. All other congeners have the epibranchial tooth shorter, broader, and dentiform. In this group of species with spiniform epibranchial teeth, P. sirindhorn (from Ranong, southern Thailand) is distinctive in that the surface of the carapace is very smooth and the postorbital cristae are very low (cf. Naiyanetr, 1989: fig. 1a, b). Phricotelphusa limula (from Phuket island, southern Thailand) is easily separated by having the epigastric and postorbital cristae fused or almost so, being separated by only a shallow fissure, effectively forming one clear ridge on each side of the carapace (cf. Bott, 1970: pl. 8 fig. 88), the antennular fossa are relatively wider, being subrectangular in shape (cf. Bott, 1970: pl. 8 fig. 90), and the ambulatory legs are covered with scattered short, coarse setae. Phricotelphusa aedes was synonymised under P. limula by Bott (1970: 52), but Naiyanetr (1988b, 1992, 1998), Ng (1988b), Ng & Naiyanetr (1993), and Yeo & Ng (1999) recognised it as a valid taxon although no discussion was provided. The carapace of P. aedes is relatively wider than the other two members of this group of species, the epigastric cristae are positioned anterior of the postorbital cristae, the postorbital crista is long, gradually joining the epibranchial tooth, the antennular fossa is narrower and more slit-like, and the ambulatory legs are relatively longer (Fig. 4; Kemp, 1923: pl. 4 fig. 12). Ng & Lee (2012) treated P. aedes as a valid species, provided a figure of a male specimen and compared it with P. hymeiri; but the G1 structures were not figured.
Phricotelphusa sukreei, new species, is most similar to P. aedes in the carapace armature and proportions, and its proportionately longer ambulatory legs. The two species are, however, easily separated. In P. sukreei, new species, the postorbital crista forms a distinct convex crest, clearly separated from the anteriorly placed epigastric crista by a space, and ends before the cervical groove, not forming a continuous crest to the epibranchial tooth (Fig. 2B, C) (versus postorbital crista longer, closer to the epigastric crista, and gradually joins the epibranchial tooth via gentle convexity in P. aedes, Fig. 4A, D, E); the branchial regions are more inflated, with the lateral carapace margin prominently swollen and convex (Fig. 2B, C) (versus branchial regions lower and less inflated with the lateral carapace margin only gently convex in P. aedes, Fig. 4A, D, E); the base of the external orbital tooth ends at the base of the epibranchial tooth (Fig. 2B, C) (versus there is a relatively wide gap between the base of the external orbital tooth and the epibranchial tooth in P. aedes, Fig. 4A, D, E); the lateral margin of the posterior margin of the epistome is almost straight with the margin appearing gently sinuous (Fig. 3A) (versus margin concave in P. aedes, Fig. 4F); the surface of the ischium of the third maxilliped is smooth, without an oblique median groove (Fig. 3D) (versus distinct oblique median groove visible in P. aedes, Fig. 4C); the exopod of the third maxilliped is short, not reaching the distal edge of the ischium (Fig. 3D) (versus the exopod of the third maxilliped just reaches to the distal edge of the ischium in P. aedes, Fig. 4C); and the G1 terminal segment is proportionately longer and gently curved (Fig. 5A–C) (versus relatively shorter and straighter in P. aedes, Fig. 5F–H).
The type specimens of Phricotelphusa sukreei, new species, were found on the tree trunk and the forest floor, with one collected from a tree-hole located on the top of a ridge (about 1,355 m asl). It appears to be primarily arboreal as most of the specimens were collected from this habitat. Phricotelphusa aedes also appears to have arboreal habits from Nakhon Si Thammarat Province in southern Thailand (Figs. 4, 6). Like P. sukreei, this species has long ambulatory legs and has been collected from tree-holes (Fig. 6C, D). For crabs that live in montane forest ridges which lack a source of running water, phytotelms are an important habitat for what are essentially still semiaquatic animals (see discussion for the arboreal gecarcinucid Kani maranjandu Kumar, Raj & Ng, 2017 from India, and reviews of arboreal crabs in Ng et al., 2015; Kumar et al., 2017; Naruse & Ng, 2020).
In Thailand, the only freshwater crab species known to be arboreal is the sesarmid Geosesarma krathing Ng & Naiyanetr, 1992 (cf. Ng & Naiyanetr, 1992; Raungprataungsuk et al., 2006), but it only climbs small shrubs and is probably mainly terrestrial in habits. From the available data, P. sukreei should be the first confirmed primarily arboreal freshwater crab reported from Thailand.
description: Published as part of Ng, Peter K. L., Yeesin, Pun & Promdam, Rueangrit, 2022, Phricotelphusa sukreei, a new species of arboreal freshwater crab (Crustacea: Brachyura: Gecarcinucidae) from Thailand, pp. 451-460 in Raffles Bulletin of Zoology 70 on pages 451-459, DOI: 10.26107/RBZ-2022-0025, http://zenodo.org/record/7400001