Parasesarma corallicum, Ng & Davie & Li, 2016

Ng, Peter K. L., Davie, Peter J. F. & Li, Jheng-Jhang, 2016, On the identities of Parasesarma carolinense (Rathbun, 1907) and Parasesarma sigillatum (Tweedie, 1950), with description of a new species from Taiwan (Crustacea: Brachyura: Sesarmidae), Raffles Bulletin of Zoology 64, pp. 257-268 : 264-266

Parasesarma corallicum sp. nov.

( Figs. 1E–H ; 4 ; 5H–K ; 6N–T ; 7B )

Material examined. Holotype: male (9.5 × 7.0 mm) ( NMMBCD 4697 ), Hsiangchiaowan, Kenting, Pingtung, southern Taiwan, coll. J.-J. Li, 10 August 2015 . Paratypes: 1 male (10.0 × 7.3 mm) ( ZRC), same data as holotype ; 1 male (10.3 × 7.6 mm), 1 female (8.0 × 5.8 mm) ( NMMBCD 4698 ), Hsiangchiaowan , Kenting, Pingtung, southern Taiwan, coll. J.-J. Li, 21 August 2015 ; 2 males (8.1 × 5.7 mm, 6.3 × 4.7 mm), 1 female (6.9 × 4.7 mm) ( ZRC), Wanlitung , Kenting, Pingtung, southern Taiwan, coll. J.-J. Li, 5 July 2014 ; 1 male (9.1 × 6.1 mm) ( NMMBCD 4699 ), Wanlitung , Kenting, Pingtung, southern Taiwan, coll. J.-J. Li, 20 July 2014 ; 1 male (8.8 × 6.4 mm), 1 female (8.8 × 6.3 mm) ( QM), Wanlitung , Kenting, Pingtung, southern Taiwan, coll. J.-J. Li, 21 July 2014 ; 2 males (9.0 × 6.6 mm, 8.6 × 6.0 mm) ( QM), Wanlitung , Kenting, Pingtung, southern Taiwan, 6 August 2014 ; 1 ovigerous female (8.3 × 5.8 mm) ( NMMBCD 4700 ), Wanlitung , Kenting, Pingtung, southern Taiwan, coll. L.-K. Tseng, 28 July 2014 ; 3 male (11.3 × 7.6 mm – 8.1 × 5.6 mm), 1 female (10.7 × 7.8 mm) ( NMMBCD 4701 ), Hsiangchiaowan , Kenting, Pingtung, southern Taiwan, coll. J.-J. Li, 2 Nov 2014.1 ovigerous female (7.7 × 5.3 mm) (NMNS-7548-001), Wanlitung, Kenting, Pingtung, southern Taiwan, coll. L.-K. Tseng, 25 October 2014 ; 1 male (8.0 × 5.7 mm) (NMNS-7548-002), Wanlitung , Kenting, Pingtung, southern Taiwan, coll. J.-J. Li, 3 May 2014 .

Diagnosis. Carapace 1.34–1.47 times broader than long; lobes of frontal margin separated by broad, relatively deeper concavity ( Fig. 4A–C ); upper surface of cheliped palm with 2 transverse pectinate crests, primary (distal-most) crest with row of 16 or 17 tall pectinate teeth, tip of each tooth gently curved, secondary crest with 11 or 12 relatively lower pectinate teeth ( Figs. 4H ; 7B ); inner surface of palm with low obliquely transverse submedian granulated ridge ( Fig. 4I ); dorsal surface of dactylus with 15 or 16 triangular tubercles, each dactylar tubercle with distinct transverse ridge ( Fig. 4E, F, H ); inner distal margin of lamelliform process of merus lined with acutely triangular teeth ( Fig. 4E, F ); ambulatory legs short, stout; merus of third leg 2.3 times as long as wide; upper margin of merus with subdistal spine; propodus of third leg 2.7 times as long as wide; dactylus of third and fourth legs 0.8 and 0.9 times length of propodus, respectively ( Figs. 4A ; 5H–K ); male telson semicircular, ca. 1.2 times length of pleonal somite 6 ( Fig. 6O ); G1 relatively slender, straight; apical process bent at 90º from the vertical, chitinous distal part long, aperture terminal ( Fig. 6P–S ).

Colour in life. Dorsal surfaces of carapace light brown with patches of white ( Fig. 1E, H ), with brown areas sometimes uniformly coloured ( Fig. 1G ). Ambulatory legs whitishgrey with patches of brown ( Fig. 1E–H ). Chelae yellow to yellowish-brown ( Fig. 1E–H ).

Etymology. The name is derived from its habit of living near coral reefs.

Habitat. The specimens of Parasesarma corallicum n. sp. were active among sandy substrates around the highly eroded dead coral areas in the supralittoral zone. Most of this area is dry to moist. The crabs hide deep in numerous crevices in the dead coral during the day, and were observed only in the evening and at night. Parasesarma corallicum n. sp. occurs sympatrically with Stelgistra stormi (De Man, 1895) , Nanosesarma andersonii (De Man, 1895) (both Sesarmidae ) and Grapsus albolineatus (Latreille, in Milbert, 1812) ( Grapsidae ).

Remarks. The specimens of this species were consistent in all the diagnostic characters examined. One ovigerous female (7.7 × 5.3 mm) (NMNS-7548-001), however, lacked a subdistal spine on the merus of first and fourth left ambulatory legs These spines were probably eroded as the crabs moved around the coral crevices.

See discussion for comparisons with P. carolinense s. str. and P. sigillatum .

Figures

Fig. 1. Colour in life. A–D, Parasesarma sigillatum, Cocos-Keeling Islands; E–H, Parasesarma corallicum n. sp., Taiwan. A, male, not preserved; B, female (8.7 × 6.4 mm) (QM-W28343); C, D, male (9.4 × 6.9 mm) (QM-W28342); E, F, male, Hsiangchiaowan, Taiwan (10.3 × 7.6 mm) (NMMBCD 4698); G, Holotype, same data (9.5 × 7.0 mm) (NMMBCD 4697); H, Wanlitung, Taiwan (8.0 × 5.7 mm) (NMNS-7548-002).

Fig. 4. Parasesarma corallicum n. sp., holotype male (9.5 × 7.0 mm) (NMMBCD 4697), Taiwan. A, overall habitus; B, dorsal view of carapace; C, frontal view of cephalothorax; D, anterior thoracic sternum and sternopleonal cavity; E, dorsal view of left cheliped; F, dorsal view of right cheliped; G, outer view of right chela; H, dactylar tubercles of right chela; I, inner view of left chela.

Fig. 5. Left ambulatory legs. A–C, Parasesarma carolinense (Rathbun, 1914), holotype male (9.2 × 7.0 mm) (USNM 32861), Caroline Islands; D–G, Parasesarma sigillatum (Tweedie, 1950), male (9.5 × 6.8 mm) (ZRC 1965.8.2.269), Cocos-Keeling Island; H–K, Parasesarma corallicum n. sp., holotype male (9.5 × 7.0 mm) (NMMBCD 4697), Taiwan. A, D, H, first ambulatory leg; B, E, I, second ambulatory leg; C, F, J, third ambulatory leg; G, K, fourth ambulatory leg. Legs of all species to scale.

Fig. 6. A–F, Parasesarma carolinense (Rathbun, 1914), holotype male (9.2 × 7.0 mm) (USNM 32861), Caroline Islands; G–M, Parasesarma sigillatum (Tweedie, 1950), male (9.5 × 6.8 mm) (ZRC 1965.8.2.269), Cocos-Keeling Island; N–T, Parasesarma corallicum n. sp., holotype male (9.5 × 7.0 mm) (NMMBCD 4697), Taiwan. A, G, N, left third maxilliped; B, H, male pleon; O, male pleon (somites 1 and 3 broken); C, P, ventral view of left G1; D, Q, dorsal view of left G1; E, ventral view of right G1; F, distal chitinous part of right G1 (ventral view); I, ventral view of right G1; J, dorsal view of right G1; K, distal chitinous part of right G1 (ventral view); L, distal chitinous part of right G1 (dorsal view); M, right G2; R, distal chitinous part of left G1 (ventral view); S, distal chitinous part of left G1 (dorsal view); T, left G2. Setae for all structures denuded. Scale bars = 0.5 mm [A–E, G–J, M–Q, T]; 0.1 mm [F, K, L, R, S].

Fig. 7. Details of pectinate crests on chela. A, Parasesarma sigillatum (Tweedie, 1950), lectotype male (10.7 × 7.6 mm) (NHM 1950.4.17.4), Cocos-Keeling Island; B, Parasesarma corallicum n. sp., holotype male (9.5 × 7.0 mm) (NMMBCD 4697), Taiwan. Arrow points to direction of dactylar finger. Scales = 0.5 mm.