Phricotelphusa sukreei, Ng & Yeesin & Promdam, 2022

Ng, Peter K. L., Yeesin, Pun & Promdam, Rueangrit, 2022, Phricotelphusa sukreei, a new species of arboreal freshwater crab (Crustacea: Brachyura: Gecarcinucidae) from Thailand, Raffles Bulletin of Zoology 70, pp. 451-460 : 451-459

publication ID	https://doi.org/ 10.26107/RBZ-2022-0025
publication LSID	lsid:zoobank.org:pub:C5BE2993-E53D-4BAB-8260-D9C5A6809C60
DOI	https://doi.org/10.5281/zenodo.7502032
persistent identifier	https://treatment.plazi.org/id/40DD57B8-CAC1-4F31-A108-78C6E04B3D4C
taxon LSID	lsid:zoobank.org:act:40DD57B8-CAC1-4F31-A108-78C6E04B3D4C
treatment provided by	Felipe
scientific name	Phricotelphusa sukreei
status	sp. nov.

Treatment

Phricotelphusa sukreei View in CoL , new species

( Figs. 1–3 View Fig View Fig View Fig , 5A–E View Fig )

Material examined. Holotype: male (26.7 × 20.2 mm) ( ZRC 2021.0815 View Materials ), 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 View Materials ), 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 View Materials ), 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 View Materials ), 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 .

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 View Fig ). Branchial regions gently inflated dorsally and laterally ( Figs. 2B, C View Fig , 3A View Fig ). 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 View Fig , 3A View Fig ). 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 View Fig ). Posterior margin of carapace almost straight ( Fig. 2A–C View Fig ). Suborbital, pterygostomial, and subhepatic regions gently rugose to smooth ( Fig. 3A, B View Fig ). Epistome relatively wide longitudinally; posterior margin with wide median triangular lobe, lateral margin almost straight with margin appearing gently sinuous ( Fig. 3A View Fig ). Eyes relatively large, completely filling orbits; cornea large, fully pigmented. Antennular fossa relatively narrow, rectangular in shape ( Fig. 3A View Fig ).

Third maxilliped relatively short, quadrate; ischium with undiscernible oblique median sulcus; exopod does not reach distal edge of ischium, flagellum absent ( Fig. 3D View Fig ).

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 View Fig ).

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 View Fig , 3F View Fig ).

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 View Fig ). 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 View Fig ).

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 View Fig ).

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 View Fig ). G2 distal segment ca. 0.3 times length of basal segment; distal part of distal segment gently serrate ( Fig. 5D, E View Fig ).

Female. Pleon wide, ovate, covering most of thoracic sternum; telson broadly triangular with strongly convex lateral margin ( Fig. 3G View Fig ). Vulva large, almost round, without operculum, submedian in position on sternite 6 ( Fig. 3H View Fig ).

Colour. Bright red on all dorsal aspects and surface of all ambulatory legs ( Fig. 1B–F View Fig ). Ventral surfaces of carapace and chelipeds are violet to purplish ( Fig. 1F View Fig ).

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 View Fig ; 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 View Fig ) (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 View Fig ); the branchial regions are more inflated, with the lateral carapace margin prominently swollen and convex ( Fig. 2B, C View Fig ) (versus branchial regions lower and less inflated with the lateral carapace margin only gently convex in P. aedes , Fig. 4A, D, E View Fig ); the base of the external orbital tooth ends at the base of the epibranchial tooth ( Fig. 2B, C View Fig ) (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 View Fig ); the lateral margin of the posterior margin of the epistome is almost straight with the margin appearing gently sinuous ( Fig. 3A View Fig ) (versus margin concave in P. aedes , Fig. 4F View Fig ); the surface of the ischium of the third maxilliped is smooth, without an oblique median groove ( Fig. 3D View Fig ) (versus distinct oblique median groove visible in P. aedes , Fig. 4C View Fig ); the exopod of the third maxilliped is short, not reaching the distal edge of the ischium ( Fig. 3D View Fig ) (versus the exopod of the third maxilliped just reaches to the distal edge of the ischium in P. aedes , Fig. 4C View Fig ); and the G1 terminal segment is proportionately longer and gently curved ( Fig. 5A–C View Fig ) (versus relatively shorter and straighter in P. aedes , Fig. 5F–H View Fig ).

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 View Fig , 6 View Fig ). Like P. sukreei , this species has long ambulatory legs and has been collected from tree-holes ( Fig. 6C, D View Fig ). 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.