Parasesarma jamelense ( Rathbun, 1914 )

Rahayu, Dwi Listyo & Li, Jheng-Jhang, 2013, A New Species Of The Genus Parasesarma (Crustacea: Brachyura: Sesarmidae) From Taiwan And The Philippines, And Redescription Of P. Jamelense (Rathbun, 1914), Raffles Bulletin of Zoology 61 (2), pp. 633-639 : 633-636

Parasesarma jamelense ( Rathbun, 1914)

( Figs. 1–3)

Sesarma (Parasesarma) moluccensis jamelensis Rathbun, 1914: 81

Sesarma (Parasesarma) jamelensis – Tesch, 1917: 178; Serène, 1968: 108 (list)

Parasesarma jamelense – Ng et al., 2008: 222 (list)

Material examined. — Holotype, male (11.5 × 10.0 mm) ( USNM 45917 ), River station , “Point Jamelo”, Batangas, Luzon, Philippines, 20 feet, seine, 13 Jul.1908 . Paratypes, male (11.1 × 9.7 mm), 2 females (12.5 × 10.5 mm; 10.5 × 9.4 mm) ( USNM 120524 ), same locality as holotype .

Diagnosis. — Carapace 1.2 times broader than long; regions well defined; postfrontal region separated into 4 lobes by

narrow, deep grooves; frontal margin bilobed from dorsal view, each lobe broadly convex; exorbital tooth directed obliquely outwards; eyes not extending beyond edge of exorbital tooth. Upper surface of cheliped palm with two transverse pectinated crests (one crest with 18 corneous teeth, the other with 11); outer surface of palm striated proximally, slightly granular distally, inner surface of palm with several tubercles; dorsal surface of dactylus with 10–11 symmetrical tubercles; first, second tubercles small, third to ninth tubercles prominent, last two tubercles indistinct; tubercles obliquely transverse. Ambulatory legs robust, flattened, broad; P4 merus approximately 2.3 times as long as broad; P4 propodus about 2.9 times as long as broad; P4 dactylus about 0.8 length of propodus, slightly recurved. Male telson semicircular, evenly rounded, slightly longer than sixth somite. G1 slender, straight; apical pectinated process long, tip truncate, bent at an angle of 45º.

Redescription. — Carapace 1.2 times broader than long ( Fig. 1); regions well defined, separated by well-marked grooves; lateral carapace surface lined with strong oblique striae; dorsal surface with sparse, scattered tufts of short setae, lateral margins with short setae. Postfrontal region distinct, separated into 4 similar lobes by narrow, deep grooves; median lobes approximately equal in width as lateral lobes. Front deflexed downwards ( Fig. 2B ), frontal margin bilobed from dorsal view, each lobe broadly convex, separated by broad median concavity. Supraorbital margin entire, gently convex. Exorbital tooth triangular, directed obliquely outwards, representing point of greatest width; lateral carapace margin entire; gently sinuous, subparallel along most of length before curving to join straight posterior margin; antero-, posterolateral margins not demarcated, without trace of indentation. Eyestalks not extending beyond exorbital tooth.

Basal segments of antenna, antennule adjacent, not separated by septum; basal antennular segment swollen. Antennal flagellum relatively long, entering orbit. Third maxilliped with shallow median sulcus on surface of ischium, surface of merus with distinct submedian ridge; exopod slender, tip overreaching half length of merus outer margin, flagellum long; inner margin of merus, ischium with long setae, proximal outer margin of ischium, base of exopod with long, densely packed setae.

Chelipeds subequal, large, robust ( Figs. 1, 2C ). Upper surface of palm with 2 transverse pectinated crests ( Fig. 2D ). Primary (distalmost) crest composed of 16–18 teeth; proximal crest well developed, shorter than primary, with 10–11 teeth; crests followed by row of blunt tubercles; row of small tubercles below proximal crest. Outer surface of palm striated proximally, slightly granular distally; inner surface of palm with several tubercles. Fixed finger smooth on outer, inner surfaces. Cutting edges of fixed finger, dactylus with variably sized, rounded teeth. Dorsal surface of dactylus with 10–11 symmetrical, obliquely transverse tubercles ( Fig. 2D ), first two proximal tubercles small, obscured by adjacent low tubercles, third to ninth tubercles large; distal two tubercles usually indistinct; several low tubercles on proximal third of dactylus, and scattered tubercles along proximal third of inner edge. Fingertips spoon-like, chitinous; proximal gap distinct when fingers closed. Carpus inner angle not produced, outer margin, dorsal surface striated. Merus outer margin tuberculate, with small subdistal spine; inner margin tuberculate ending in large subdistal spine; outer surface with striation, inner surface with longitudinal row of setae, scattered setae near upper margin.

Ambulatory legs robust, flattened, broad; P3, P4 longest, about 1.4 times carapace width. P4 merus approximately 2.3 times as long as broad; propodus 2.9 times as long as broad; dactylus about 0.8 length of propodus. Anterior margin of meri with acute subdistal spine, unarmed terminally; upper surface with transverse striations anteriorly; carpi with 2 longitudinal carinae on outer surface; propodi with inferior longitudinal carina along entire length, and few stiff setae; dactyli slightly recurved, terminating in acute chitinous tip. Except on meri, ambulatory legs with few stiff bristles on anterior and posterior margins.

Male abdomen relatively broad ( Figs. 2B , 3E ). Telson semicircular, evenly rounded, slightly longer than somite 6; somite 6 about 2.5 times as long as wide, lateral margins slightly convex. Somites 3–5 progressively more trapezoidal, lateral margins of somites 4, 5 straight, lateral margins

of somite 3 slightly convex, somites 1, 2 very narrow longitudinally.

G1 slender ( Figs. 3A–D ), apical process corneous, long, bent at angle of 45º, tip truncate; long simple setae at base of apical process. G2 very short.

Female chelipeds smaller, pectinated crests on palm replaced by 2 transverse rows of tubercles, dactylar tubercles indistinct. Vulva on anterior edge of sternite 5.

Remarks. — Parasesarma jamelense was described from Luzon, Philippines, as Sesarma (Parasesarma) moluccensis jamelensis , by Rathbun (1914) without any figures provided. Tesch (1917), Serène (1968) and Ng et al. (2008) listed this species, but no new specimens have been reported, and its taxonomy was not discussed. Rathbun (1914) considered this species to be allied to P. moluccensis (De Man, 1896) and noted the differences in the narrower carapace, and the presence of 9 or 10 obliquely transverse dactylar tubercles instead of 8 or 9 longitudinally positioned tubercles. Examination of the holotype of P. jamelense showed that the number of dactylar tubercles is actually 10 or 11, not 9 or 10 as described by Rathbun (1914: 81). Rathbun probably missed the distalmost tubercles which are low and indistinct.

Distribution. — This species is known only from the type locality, “Point Jamelo”, in what is now called Hamilo Cove, near Nasugbu town, Batangas province, southwestern Luzon, 14°10'36"N, 120°35'48"E, Philippines.

Figures

Fig. 2. Parasesarma jamelense (Rathbun, 1914), holotype, male (11.5 × 10.0 mm).A, ventral view showing anterior part of thoracic sternum, abdomen; B, frontal view of carapace; C, cheliped; D, dactylus of cheliped, showing dactylar tubercles.

Fig. 3. Parasesarma jamelense (Rathbun, 1914), holotype, male (11.5 × 10.0 mm). A–D, left G1; E, abdomen. Scale bars =1 mm (A, B, E), 0.5 mm (C, D). Setae omitted.