Thampramon tonvuthi, Ng, Peter K. L. & Vidthayanon, Chavalit, 2013

Ng, Peter K. L. & Vidthayanon, Chavalit, 2013, Thampramon tonvuthi, a new genus and new species of cavernicolous crab (Crustacea: Decapoda: Brachyura: Potamidae) from Thailand, Zootaxa 3652 (2), pp. 265-276 : 267-275

publication ID	https://doi.org/ 10.11646/zootaxa.3652.2.4
publication LSID	lsid:zoobank.org:pub:02E6C74A-4381-42F5-87F5-75ECEBFE2EC9
DOI	https://doi.org/10.5281/zenodo.6163721
persistent identifier	https://treatment.plazi.org/id/6F4C87D7-FFA2-3771-A5FC-FE63B08027A5
treatment provided by	Plazi
scientific name	Thampramon tonvuthi
status	sp. nov.

Treatment

Thampramon tonvuthi View in CoL sp. nov.

( Figs. 1–7 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 )

Material examined. Holotype: male (39.7 × 31.1 mm) (NIFI CR 00062), Tham Phra Wangdaeng, Baan Chompu southwest of Thung Salaeng Luang National Park, 400 m from cave entrance, Thailand, coll. C. Vidthayanon & Pranee Nang-gnam, 29 November 2008. Paratypes: 1 male (26.8 × 21.6 mm) (NIFI), same data as holotype; 1 male (33.9 × 27.8 mm) (ZRC 2012.1126), same area as holotype, 16.8379°N 100.877°E, cave entrance, coll. C. Vidthayanon, 8 October 1997; 1 female (45.9 × 35.4 mm) (NIFI CR 00063), same locality as holotype, in twilight zone, near side entrance of cave, above flowing stream, coll. D. Smart, 27 August 2002; 1 female (42.7 × 36.3 mm) (ZRC 2012.1127), same locality as holotype, in twilight zone of cave, ca. 100 m from entrance, on wet rock wall, 4 m above stream above bat guano, coll. D. Smart, 28 August 2002.

Diagnosis. As for genus.

Description of male. Carapace wider than long, subquadrate ( Figs. 1 View FIGURE 1 A, 2A–C). Dorsal surface almost smooth; regions poorly demarcated; not prominently swollen; H-shaped median groove distinct, deep; cervical grove very shallow, separating postorbital cristae from short crista that reaches anterolateral margin ( Fig. 2 View FIGURE 2 A–C). Epigastric cristae well developed, swollen, surface rugose, not sharp; divided medially by deep Y-shaped groove; postorbital crista separated from epigastric cristae by shallow groove, relatively sharp, almost smooth ( Fig. 2 View FIGURE 2 A–C). Frontal region almost flat ( Fig. 3 View FIGURE 3 A–C). Frontal margin prominently sinuous, 2 lobes separated by broad, shallow sinus; outer margin convex, confluent with supraorbital margin ( Figs. 2 View FIGURE 2 A–C, 3A–C). Supraorbital margin prominently sinuous, with median part convex, without trace of fissure ( Fig. 2 View FIGURE 2 A–C). External orbital angle triangular, outer margin gently serrated, longer than inner margin, tip not projecting beyond level of frontal margin; separated from anterolateral margin by deep V-shaped cleft ( Fig. 2 View FIGURE 2 A–C). Epibranchial tooth sharp but relatively short, rest of anterolateral margin short, gently serrated, gently curving to join posterolateral margin ( Fig. 2 View FIGURE 2 A–C). Posterolateral margin distinctly convex, converging strongly to gently convex posterior carapace margin ( Fig. 2 View FIGURE 2 A–C). Suborbital margin gently concave, entire, lined with fine granules ( Figs. 3 View FIGURE 3 A–C). Orbit relatively large, almost completely filled by large eyes ( Figs. 2 View FIGURE 2 A–C, 3A–C). Eyestalk elongated; cornea ovate, well developed, completely pigmented, with small, distal tuft of short setae ( Figs. 1 View FIGURE 1 A, B, 2A–C, 3A–C). Sub-orbital and pterygostomian regions smooth; sub-branchial region rugose ( Figs. 1 View FIGURE 1 B, 3A–C). Epistome subrectangular, relatively narrow longitudinally; posterior margin with prominent median triangle, lateral margins gently sinuous ( Fig. 3 View FIGURE 3 A–C). Third maxilliped quadrate; ischium subrectangular with submedian oblique sulcus; merus quadrate with median part depressed; exopod slender, reaching to just beyond distal edge of ischium, with well-developed flagellum which just reaches beyond width of merus ( Fig. 7 View FIGURE 7 A, B).

Chelipeds elongated ( Figs. 1 View FIGURE 1 A, B, 2A–C, 5D). Basis-ischium short, inner margin with 5 granules. Merus with inner margin serrulated, inner distal angle with short spine; outer surface rugose ( Figs. 1 View FIGURE 1 A, B, 2A–C, 5D). Carpus with outer surface rugose; inner distal angle with prominent sharp tooth, outer distal margin with small sharp granules ( Figs. 1 View FIGURE 1 A, 2A–C, 5D). Chela elongated; relatively slender fingers, slightly longer than palm; outer surface of palm gently rugose, not granulated; subventral margin of palm with very low longitudinal keel ( Fig. 5 View FIGURE 5 A–C). Pollex with distinct low subventral longitudinal keel with adjacent shallow groove; dactylus almost smooth; tips of fingers corneous; cutting edges each with 2 or 3 broadly triangular teeth and numerous denticles ( Fig. 5 View FIGURE 5 A–C).

Ambulatory legs conspicuously long; second leg longest, fourth leg shortest ( Figs. 1 View FIGURE 1 A, B, 2A–C, 6A). Dorsal margin of merus slightly cristate, varying from uneven to serrulated, subdistal angle visible but not produced to form spine ( Figs. 2 View FIGURE 2 A–C, 6A). Carpus elongated with dorsal margin gently serrulated ( Fig. 6 View FIGURE 6 A). Propodus distinctly laterally flattened with dorsal and ventral margins serrulated ( Fig. 6 View FIGURE 6 A). Dactylus long, gently falcated with proximal part almost straight ( Fig. 6 View FIGURE 6 A); second and third dactylus longest, first and fourth shortest ( Fig. 2 View FIGURE 2 A–C).

Thoracic sternum relatively smooth; somites 2, 3 completely fused without trace of sutures, forming wide triangular plate; sternites 3, 4 fused but with lateral sutures just visible as shallow depressions; sterno-abdominal cavity reaching to imaginary line joining median parts of cheliped coxae ( Fig. 4 View FIGURE 4 A, D). Press-button abdominal locking mechanism peg-like, directed anteriorly, on posterior half of somite 5.

Male abdomen triangular, all somites, telson free ( Figs. 1 View FIGURE 1 B, 4A–F). Telson as long as broad, with concave lateral margins ( Fig. 4 View FIGURE 4 A, D); somites 4–6 progressively longitudinally broader, more trapezoidal in shape ( Fig. 4 View FIGURE 4 B, E). Somites 1, 2 wide, reaching across thoracic sternum, completely covering thoracic somite 8; somite 2 with lateral margins rounded; somite 1 very narrow ( Fig. 4 View FIGURE 4 C, F).

G1 relatively more slender, almost straight; subterminal segment tapering to neck-like structure; distal segment short, basal part swollen, curved with open tip, with pronounced dorsal flap, deeply concave anteriorly ( Fig. 7 View FIGURE 7 C, D). G2 long, basal part subquadrate, flagellum shorter than basal segment ( Fig. 7 View FIGURE 7 E)

Females. The gastric and branchial regions of the two female paratypes ( Fig. 3 View FIGURE 3 C) are slightly more swollen and convex compared to those of males ( Fig. 3 View FIGURE 3 A, B). The female abdomen is rounded and completely covers the thoracic sternum. The vulva is large, occupying almost the entire width of somite 6 along its inner portion, the opening covered by a weakly chitinised membrane without operculum ( Fig. 6 View FIGURE 6 B).

Variation. The postorbital crista varies from very sharp in the holotype male and females to low and less developed in one paratype male (ZRC 2012.1126). The postorbital cristae are slightly sinuous in the two smaller paratype males (26.8 × 21.6 mm, NIFI; 33.9 × 27.8 mm, ZRC 2012.1126), but are straight in the holotype male and in the females. These differences can probably be explained by size. The lateral margins of the median triangular lobe of the posterior margin of the epistome in the largest holotype male are also more crenulated ( Fig. 3 View FIGURE 3 A) than those of the smaller males and females ( Fig. 3 View FIGURE 3 B, C). In the holotype male, the larger chela is stout and inflated ( Fig. 5 View FIGURE 5 A); in the smaller paratype male (ZRC 2012.1126), this chela is less inflated and the dentition is weaker ( Fig. 5 View FIGURE 5 C). The male abdomen varies slightly in shape. It is relatively more triangular in shape in the two smaller male paratypes (26.8 × 21.6 mm, NIFI; 33.9 × 27.8 mm, ZRC 2012.1126), having the lateral margins of somites 4–6 gently convex to almost straight ( Fig. 4 View FIGURE 4 B), and the lateral margins of the telson concave ( Fig. 4 View FIGURE 4 A). In the largest male specimen (39.7 × 31.1 mm, NIFI CR 00062) (the holotype), the abdomen is broader, mainly because the lateral margins of somites 4–6 are more prominently convex ( Fig. 4 View FIGURE 4 E), with the lateral margins of the telson almost straight ( Fig. 4 View FIGURE 4 D).

Colour in life. Dorsal carapace orange-brown; chelipeds yellowish-white; ambulatory legs purple-brown on dorsal surface; ventral surfaces dirty-white to yellow-white ( Fig. 1 View FIGURE 1 ).

Etymology. The name is in honor to Mr. Pituk Tonevuth, a community leader in Thailand who has devoted his life to protect the limestone areas in the type locality from impacts by rock quarry concessions, and he has now succeeded in having the entire areas protected as part of the Thung Salaeng Luang National Park.

Ecology. The type locality, Tham Phra karst and Klong Chompu, is in the Nan River subcatchment and part of the Chao Phraya Basin. The basin includes several limestone caves and their associated subterranean streams. Most of the area is dry evergreen forest, with patches of limestone vegetation. The area has a large number of endemic taxa, being the only known habitat of cavefishes like Neolissocheilus subterraneus Vidthayanon & Kottelat, 1993 (Cyprinidae) , Schistura deansmarti Vidthayanon & Kottelat, 1993 , S. spiesi Vidthayanon & Kottelat, 1993 (Nemacheilidae) ; a lizard Crytodactylus aurobalteatus Sumontha, Panitwong & Deein, 2010 (Gekkonidae) ; and an undescribed species of Macrobrachium (Palaemonidae) . Much of the area remains unexplored and the endemic biodiversity is probably much higher. The area meets the criteria established by the Ramsar Convention (International Convention on Wetlands of International Importance) as a key conservation site, and will be proposed as such in the near future.

Thampramon tonvuthi gen. et sp. nov. inhabits cave floors with humid and muddy sand substrates, from just beyond the cave entrance (rarely) to over 600 m deep. It has also been found climbing on the cave walls. While Thampramon tonvuthi gen. et sp. nov. has only been obtained from inside caves so far, it does not appear to be a troglobite (see Holthuis 1986; Guinot 1988). Although it has the long ambulatory legs and chelipeds often observed in many cavernicolous species, it still possesses well-developed eyes with a fully pigmented cornea and has relatively bright colours on its carapace and legs. Thampramon tonvuthi gen. et sp. nov. probably also forages in the surrounding forests at night, as do a number of similar terrestrial and semiterrestrial freshwater crabs ( Gecarcinucidae , Potamidae ) and land crabs ( Gecarcinidae ) associated with cave habitats (Ng 1991; Ng & Sket 1996; Ng & Lee 2012). Two species of gecarcinid land crabs, Discoplax longipes A. Milne-Edwards, 1973 (from New Caledonia and Guam) and D. gracilipes Ng & Guinot, 2001 (from the Philippines) were found to be common in the associated karst forests after dark and not obligate cave dwellers as was originally thought (see Ng & Guinot 2008). These karst crabs are thus primarily nocturnal animals that forage during the day inside the dark environment of caves.