Parasesarma parvulum, Li & Rahayu & Ng, 2018

Li, Jheng-Jhang, Rahayu, Dwi Listyo & Ng, Peter K. L., 2018, Identity of the tree-spider crab, Parasesarma leptosoma (Hilgendorf, 1869) (Decapoda: Brachyura: Sesarmidae), with descriptions of seven new species from the Western Pacific, Zootaxa 4482 (3), pp. 451-490 : 474

Parasesarma parvulum n. sp.

( Figs. 15 , 16 , 19G , 20F , 21G )

Material examined. HOLOTYPE: Male (9.6× 8.4 mm) ( NMCR 50702 ), Naujan, Mindoro Island, Philippines, 5 March 2016, W.- B. Chan . PARATYPES: 5 males (10.0× 8.7 mm, 9.9× 8.4 mm, 8.0×6.0 mm, 7.8× 6.8 mm, 7.8× 6.8 mm), 4 females (9.9× 8.2 mm, 9.4× 8.2 mm, 8.8× 7.4 mm, 8.6× 7.3 mm) ( NMCR 50703 ), same data as holotype .—3 males (10.7× 9.7 mm, 10.1× 8.7 mm, 10.1× 8.6 mm), 4 females (11.3× 9.6 mm, 9.7× 8.5 mm, 9.3× 8.1 mm, 9.0× 7.8 mm) (NMNS-7779-026), same data as holotype .—2 males (7.8× 6.8 mm, 8.5× 7.4 mm), 1 female (11.4× 9.8 mm) ( ZRC 2018.0800 ), same data as holotype .

Diagnosis. Carapace ( Figs. 15A, F , 16A ) squarish in general outline, 1.1 times broader than long; regions well defined, separated by shallow grooves; postfrontal region distinct, separated into 4 lobes by deep grooves; front deflexed downwards ( Figs. 15C, D ) margin slightly concave in dorsal view; lateral margin straight, converging posteriorly; cornea extending or just reaching tip of external orbital tooth ( Figs. 15A, F , 16A ). Ischium of third maxilliped with shallow median sulcus, merus with distinct submedian ridge; exopod slender, tip reaching half-length of outer margin of merus, flagellum long. Male cheliped palm with 2 transverse pectinate crests (18 and 10 corneous teeth, distal and proximal crests, respectively) on upper surface; upper surface of dactylus with 10 symmetrical, obliquely elongate dactylar tubercles, proximal tubercles steep, sharp, the others tubercles large, distalmost tubercle indistinct ( Figs. 16C, D , 19G ). Ambulatory legs relatively slender for this species-complex, P3 and P4 about 1.5 times carapace width; P3 and P4 coxae with dense setae; P3 merus 2.5 times as long as broad; P3 propodus 4.8 times as long as broad; P3 dactylus 0.4 times length of propodus ( Fig. 20F ). G1 relatively stout ( Figs. 16E–H , 21G ); apical process corneous, short, bent at angle of 45°, long, stout, ending in rounded tip. G2 longer than quarter length of G1 ( Fig. 21G ).

Colour in life. Colour in general is similar to P. macaco n. sp. (W.-B. Chan, pers. comm.).

Remarks. Parasesarma parvulum n. sp. morphologically resembles juveniles of P. kui n. sp. but can still be distinguished by the granulation on outer surface of palm is relatively minute and the coxae of P3 and P4 with dense setae (see Table 1).

Etymology. The name parvulum derives from the Latin word, meaning young or small, alluding to the relative small size of the present species.

Distribution. So far known from Kalinisan, in Naujan, Oriental Mindoro province, Mindoro Island, Philippines.

Ecology. In Philippines, most of the specimens of P. parvulum found were observed climbing on the mangrove trees Bruguiera gymnorhiza (L.) Lam. and Avicennia marina (Forsk.) Vierh. along the river banks of the estuary, and occurs sympatrically with Parasesarma macaco n. sp. and Metopograpsus latifrons (Grapsidae) (W.-B. Chan, pers. comm.).

Figures

FIGURE 15. Parasesarma parvulum n. sp.. A–E, holotype male (9.6×8.4 mm) (NMCR 50702), Mindoro Island, Philippines; F, G, paratype female (11.3×9.6 mm) (NMNS-7779-026), same locality. A, F, dorsal views; B, E, G, ventral views; C, D, frontal views; E, close-up of base of coxae.

FIGURE 16. Parasesarma parvulum n. sp., holotype male (9.6×8.4 mm) (NMCR 50702), Mindoro Island, Philippines. A, dorsal view of carapace; B–D, tip of left cheliped; E–H, left G1. B, lateral view of pectinated cristae on palm; C, dorsal view of palm and dactylar finger; D, lateral view of dactylar finger; E, G, dorsal (sternal) views; F, H, ventral (pleonal) views; E, F, distal part of G1. Scale bars: 1.0 mm.

FIGURE 19. Outer views of chelae, holotype males. A, Parasesarma leptosoma (17.0×15.2 mm) (ZRC 2000.1718), Kenya; B, P. gecko n. sp. (16.2×14.6 mm) (RUMF-ZC-4710), Okinawa Island, Japan; C, P. macaco n. sp. (13.8×12.3 mm) (NMNS-7779- 005), Pingtung, Taiwan; D, P. kui n. sp. (14.7×13.7 mm) (NMNS-7779-015), Pingtung, Taiwan; E, P. gracilipes n. sp. (13.6×11.9 mm) (MZB Cru 4803), Papua, Indonesia; F, P. purpureum n. sp. (15.9×13.7 mm) (ZRC 2012.0755a), Tioman Island, Peninsular Malaysia; G, P. parvulum n. sp. (9.6×8.4 mm) (NMCR 50702), Mindoro Island, Philippines; H, P. tarantula n. sp. (13.4×11.5 mm) (MZB Cru 4801), Sulawesi, Indonesia.

FIGURE 20. First to fourth ambulatory legs (P2–P5) (from top to bottom), holotype males. A, Parasesarma gecko n. sp. (16.2×14.6 mm) (RUMF-ZC-4710), Okinawa Island, Japan; B, P. macaco n. sp. male (13.8×12.3 mm) (NMNS-7779-005), Pingtung, Taiwan; C, P. kui n. sp. (14.7×13.7 mm) (NMNS-7779-015), Pingtung, Taiwan; D, P. gracilipes n. sp. (13.6×11.9 mm) (MZB Cru 4803), Papua, Indonesia; E, P. purpureum n. sp. (15.9×13.7 mm) (ZRC 2012.0755a), Tioman Island, Peninsular Malaysia; F, P. parvulum n. sp. (9.6×8.4 mm) (NMCR 50702), Mindoro Island, Philippines; G, P. tarantula n. sp. (13.4×11.5 mm) (MZB Cru 4801), Sulawesi, Indonesia.

FIGURE 21. Gonopods of Parasesarma leptosoma species-complex. A, P. leptosoma (17.0×15.2 mm) (ZRC 2000.1718), Kenya; B, P. gecko n. sp., holotype (16.2×14.6 mm) (RUMF-ZC-4710), Okinawa, Japan; C, P. macaco n. sp., holotype (13.8×12.3 mm) (NMNS-7779-005), Pingtung, Taiwan; D, P. kui n. sp., holotype (14.7×13.7 mm) (NMNS-7779-015), Pingtung, Taiwan; E, P. gracilipes n. sp., holotype (13.6×11.9 mm) (MZB Cru 4803), Papua, Indonesia; F, P. purpureum n. sp., holotype (15.9×13.7 mm) (ZRC 2012.0755a), Tioman Island, Peninsular Malaysia; G, P. parvulum n. sp., holotype (9.6×8.4 mm) (NMCR 50702), Mindoro Island, Philippines; H, P. tarantula n. sp., holotype (13.4×11.5 mm) (MZB Cru 4801), Sulawesi, Indonesia.