Hexaplax saudade, Rahayu & Ng, 2014

Rahayu, Dwi Listyo & Ng, Peter K. L., 2014, New genera and new species of Hexapodidae (Crustacea, Brachyura) from the Indo-West Pacific and east Atlantic, Raffles Bulletin of Zoology 62, pp. 396-483 : 474-478

Hexaplax saudade , new species

( Figs. 2G, H , 56D , 57D , 58D , 59G, H , 60C , 61B , 65 , 66 )

Hexaplax megalops – Serène, 1964: 270, text fig. 21, pl. 24A; Sakai, 1965: 40, 45, pl. 6 fig. 8; Sakai, 1976: 556, pl. 196 fig. 4; Ng et al., 2008: 86 (part), fig. 78. (not Hexaplax megalops Doflein, 1904 )

Material examined. Holotype: male (16.4 × 12.1 mm) ( NMCR), station CP 2660, 15°52.2'N 121°48.8'E, 542 m, Philippines, coll. AURORA 2007 Expedition , 20 May 2007 . Paratypes: Philippines: 3 males (11.6 × 8.2 mm, 14.8 × 10.5 mm, 18.2 × 13.2 mm) , 3 females (14.3 × 10.8 mm, 14.6 × 10.6 mm, 16.9 × 9.8 mm, 18.6 × 13.6 mm) ( ZRC 2013.1692 ) , 3 males (13.6 × 9.7 mm, 15.3 × 11.2 mm, 17.2 × 12.0 mm), 2 females (15.2 × 11.1 mm, 15.8 × 11.7 mm) ( MNHN), station CP 2658, 15°58.03'N 121°49.11'E, 422 m, coll. AURORA 2007 Expedition , 20 May 2007 ; 1 male (16.4 × 12.1 mm), 1 female (11.4 × 8.0 mm) ( ZRC 2013.1693 ), station CP 2660, 15°52.2'N 121°48.8'E, 542 m, coll. AURORA 2007 Expedition , 20 May 2007 ; 1 male (17.9 × 12.7 mm), 2 females (16.6 × 12.3 mm, 13.1 × 9.7 mm) ( ZRC 2013.1694 ), station CP 2735, 15°59.52'N 121°50.93'E, 431 m, coll. AURORA 2007 Expedition , 1 June 2007 . Others: Taiwan: 1 male (15.9 × 11.1 mm) ( ZRC 2008.1456 ), Su- Ao fish port, Ilan province , trawled, deep-sea, coll. C.-W. Lin, 29 July 2004 . Japan: 1 male (15.1 × 11.6 mm) (NSMT-Cr 13586), Tosa Bay , 400 m, coll. Kotaka Maru, M. Takeda, 9 May 2000 .

Diagnosis. Carapace subquadrate ( Fig. 65A ), about 1.4 times as broad as long, dorsal surface very finely granulated; regions indistinct, median H-shaped depression shallow. Anterolateral margin arcuate; posterolateral corner with small angle over base of posterior pereopods. Front not deflexed (Fig. and 56D), divided into 2 lobes, not projecting beyond distal edge of orbits. Orbit distinct, transverse; eye movable, large, corneas dilated, pigmented, much wider than peduncle ( Fig. 56D ). Pterygostomial region with oblique stridulatory ridge consist of long row of 24 short, widely-spaced striae, including ca. 14 shorter, less produced striae adjacent to epistome ( Fig. 60C ); shallow oblique groove above ridge. Third maxillipeds broad ( Fig. 66A ), not covering buccal cavity, with gap when closed; ischium longer than broad, longer than merus, with scattered granules, dilated distally, mesial margin rounded; merus squarish, as long as broad; dactylus longer than propodus; exopod relatively narrow, less than 0.3 width of ischium; flagellum well developed. Chelipeds subequal ( Fig. 57D ); major chela with slight gap when fingers closed; with large teeth at cutting edge of dactylus and fixed finger; outer surface of dactylus with 2 longitudinal ridges; inner surface near upper margin with longitudinal ridge; palm longer than wide, outer surface finely granulated; fixed finger with 2 longitudinal ridges; lower margin with row small teeth continuing to lower margin of palm; carpus finely granulated on outer surface, inner angle blunt, upper margin with row of small tubercles obscured by short setae, long setae on outer angle; merus short, row of denticles on outer and inner lower margins, fringe of setae dorsomesially. Minor chela without gap when fingers closed; ornamentation similar to that of major chela. P2–P4 long, slender ( Fig. 65 ); outer surface finely granulated; merus of P4 about 7 times as long as broad ( Fig. 59G, H ). Male thoracic sternum broad ( Fig. 58D ), surface finely granular; sternites 1 and 2 fused, separated from sternite 3 by distinct ridge; sternite 3 not separated from sternite 4, sternites 4–7 well developed, separated by distinct sutures; sternoabdominal cavity reaching middle of sternite 4, no thoracic sternal groove; sternite 8 exposed, triangular, reaching half length of male abdominal somite 2. Male abdomen relatively narrow ( Figs. 58D , 66B ); somite 1 hidden under carapace; somite 2 free, somites 3–5 fused, lateral margin sinuous; somite 6 wider than long, lateral margin slightly expanded subproximally; telson rounded, as long as somite 6. Female abdomen not much wider than male ( Fig. 66E ), 6 free somites and telson, first somite hidden under carapace. G1 ( Fig. 66C, D ) concealed under abdomen, straight, distal part tapered, sparse short setae present in proximal half, small spinules on mesial margin medially.

Colour. In life, the carapace is light brown with a tinge of orange or orangish-brown medially. The cheliped transparent white with an orange line at the articulation of the dactylus and palm; P2–P4 transparent are whitish on the dactylus, propodus and carpus; with the merus light brown tinged of orange distally ( Fig. 2G, H ).

Etymology. The species name is derived from the Portuguese word “saudade” which means a melancholic longing for something that cannot exist or be realised; alluding to the long-held belief that Hexaplax was a monotypic genus. The name is used as a Latin noun in apposition.

Remarks. See remarks for H. megalops s. str. for differences with congeners.

The records of “ Hexaplax megalops ” from Philippines ( Serène, 1964; Ng et al., 2008) and Tosa Bay in Japan ( Sakai, 1965; Sakai, 1976) are clearly Hexaplax saudade , new species. The figure of a fresh specimen in Sakai (1965, 1976) agrees well with those of the new species from Philippines ( Fig. 2E ) and Taiwan ( Fig. 2F ). We have also examined a male specimen from Tosa Bay specimen (NSMT-Cr 13586) which agrees with our definition of H. saudade .

Type locality. Philippine Sea , Philippines .

Distribution. Philippines, Taiwan and Japan. Deep water, 422– 542 m.

Figures

Fig. 2. Colours in life. A, Mariaplax ourabay, new species, holotype male (7.6 × 5.4 mm) (RUMF-ZC-2114), Oura Bay, Okinawa Island, Japan; B, Mariaplax ourabay, new species, paratype female (9.2 × 7.0 mm) (ZRC 2012.1032), Oura Bay, Okinawa Island, Japan; C, Mariaplax narusei, new species, holotype male (9.6 × 5.8 mm) (RUMF-ZC-2112), Funaura Bay, Iriomote Island, Japan; D, Rayapinus maenosonoi, new species, holotype male (6.6 × 4.9 mm) (RUMF-ZC-2115) Sesoko, Okinawa, Japan; E, Hexaplax megalops Doflein, 1904, male, (13.5 × 9.0 mm) (MNHN-IU-2011-1026), west of New Hanover; F, Hexaplax aurantium, new species, paratype male (12.1 × 8.4 mm) (MNHN-IU-2011-1527), south of Lae, Gulf of Huon; G, Hexaplax saudade, new species, paratype male (16.9 × 9.8 mm) (ZRC 2013.1692), AURORA, 2007, station CP2658, Philippines; H, Hexaplax saudade, new species, male (15.9 × 11.1 mm) (ZRC 2008.1456), Su-Ao fish port, Ilan province, Taiwan.

Fig. 56. Frontal view of cephalothorax. A. Hexaplax megalops Doflein, 1904, holotype male (15.0 × 10.0 mm) (ZMB); B, Hexaplax megalops Doflein, 1904, male (18.7 × 12.1 mm) (MNHN-IU-2011-2251); C. Hexaplax aurantium, new species, holotype male (15.3 × 10.8 mm) (MNHN-IU-2011-2158); D. Hexaplax saudade, new species, holotype male (16.4 × 12.1 mm) (NMCR).

Fig. 57. Chelae. A. Hexaplax megalops Doflein, 1904, male (18.7 × 12.1 mm) (MNHN-IU-2011-2251); B, Hexaplax aurantium, new species, holotype male (15.3 × 10.8 mm) (MNHN-IU-2011-2158); C, Hexaplax aurantium, new species, paratype female (13.2 × 9.5 mm) (ZRC 2013.1696); D, Hexaplax saudade, new species, holotype male (16.4 × 12.1 mm) (NMCR).

Fig. 58. Ventral view of carapace showing abdomen and telson and third maxillipeds. A, Hexaplax megalops Doflein, 1904, holotype male (15.0 × 10.0 mm) (ZMB); B, Hexaplax megalops Doflein, 1904, male (18.7 × 12.1 mm) (MNHN-IU-2011-2251); C, Hexaplax aurantium, new species, holotype male (15.3 × 10.8 mm) (MNHN-IU-2011-2158); D, Hexaplax saudade, new species, paratype male (17.9 × 12.7 mm) (ZRC 2013.1694)

Fig. 59. Right P4, outer surface. A, Hexaplax megalops Doflein, 1904, holotype male (15.0 × 10.0 mm); B, Hexaplax megalops Doflein, 1904, female (17.7 × 12.2 mm) (MNHN-IU-2011-2251); C, Hexaplax megalops Doflein, 1904, male (18.7 × 12.1 mm) (MNHN- IU-2011-2251); D, Hexaplax aurantium, new species, holotype male (15.3 × 10.8 mm)(MNHN-IU-2011-2158); E, Hexaplax aurantium, new species, paratype female (17.6 × 12.4 mm) (MNHN-IU-2011-2158); F, Hexaplax aurantium, new species, paratype female (13.2 × 9.5 mm) (MNHN); G, Hexaplax saudade, new species, holotype male (16.4 × 12.1 mm); H, Hexaplax saudade, new species, paratype female (13.1 × 9.7 mm).

Fig. 60. Pterygostomial region showing row of stridulatory striae. A, Hexaplax megalops Doflein, 1904, male (18.7 × 12.1 mm) (MNHN- IU-2011-2251); B, Hexaplax aurantium, new species, holotype male (15.3 × 10.8 mm)(MNHN-IU-2011-2158); C, Hexaplax saudade, new species, holotype male (16.4 × 12.1 mm) (NMCR).

Fig. 61. A, Hexaplax aurantium, new species, paratype female (13.2 × 9.5 mm); B, Hexaplax saudade, new species, paratype male (17.9 × 12.7 mm) (ZRC 2013.1694); C, Hexaplax megalops Doflein, 1904, male (18.7 × 12.1 mm) (MNHN-IU-2011-2251). A, front showing eyes in orbit; B, anteroventral view of cephalothorax showing abdomen and telson, third maxillipeds and stridulatory ridge on pterygostomial regions; C, inner surface of palm.

Fig. 65. Hexaplax saudade, new species, overall view of carapace, chelipeds and P2–P4. A, holotype male (16.4 × 12.1 mm) (NMCR); B, paratype male (17.9 × 12.7 mm); C, paratype male (18.2 × 13.2 mm); D, paratype female (13.1 × 9.7 mm).

Fig. 66. Hexaplax saudade, new species. A–D, holotype male (16.4 × 12.1 mm) (NMCR); E, paratype female (13.1 × 9.7 mm). A, left third maxilliped; B, male abdomen and telson; C, D, G1; E, female abdomen and telson. Scale bars = 1.0 mm.