Raphidopus johnsoni Ng & Nakasone, 1994

Osawa, Masayuki & Ng, Peter K. L., 2018, A new species of the genus Raphidopus Stimpson, 1858 (Crustacea: Decapoda: Anomura: Porcellanidae) from Peninsular Malaysia, with additional records of R. johnsoni Ng & Nakasone, 1994 from Southeast Asia, and a key to species in the genus, Zootaxa 4433 (1), pp. 111-126 : 115-118

Raphidopus johnsoni Ng & Nakasone, 1994

( Figs. 3–5 , 9B, C )

Raphidopus indicus .— Haig 1981: 275 (not R. indicUs Henderson, 1893 ).

Raphidopus Johnsoni Ng & Nakasone, 1994: 9 , fig. 4.— OsaWa & McLaUghlin 2010: 115 (list).—Ng et al. 2011: 27, UnnUmbered color fig.

Type material. Holotype: ZRC 1992.10669 , male (cl 3.8 mm), Lim Chu Kang , Singapore, road end, in mangroVe swamp, 4 April 1989, coll. P. K. L. Ng.

Other material examined. “Indo-Chinese Sea” (= probably South China Sea): ZMUC-CRU-20517, 1 female (cl 3.2 mm), coll. Schmidt. Thailand: CBM-ZC 12485, 2 males (cl 4.7, 5.0 mm), 1 female (cl 5.9 mm), Koh Sirae , Phuket, intertidal, sand flat, in burrows, 22 December 2009, yabby pump, coll. T. Komai ; ZRC 2018.256 , 1 male (cl 3.7 mm), 1 female (cl 4.2 mm), same data as CBM-ZC 12485. Singapore : ZRC 2018.247 , 1 male (cl 4.2 mm), sta. 3821 [SEA-7603 ( CMBS Seabed)], West Johor Strait off Tengah ReserVoir , 11.0– 11.5 m, dredge, 9 April 2014. Indonesia: ZMUC-CRU-20518, 3 females (cl 3.4–4.0 mm), Surabaya, JaVa Island, 1870, coll. Andrea.

Description. Carapace ( Figs. 3A , 4A ) 1.4 times as broad as long; dorsal surface with scattered, short or Very short striae; anterior branchial region with small tubercles and short rows of beaded tubercles ( Fig. 4B ); posterior branchial and intestinal regions with long, tuberculate ridges; branchial margins narrowly laminar, each with row of small, rounded and subacute tubercles. Rostrum ( Figs. 3B , 4C ) trilobate, median lobe slightly exceeding leVel of apices of lateral lobes.

Third thoracic sternite ( Figs. 3C , 4D ) 5.3–7.0 times broader than long measured along midline.

Telson ( Fig. 4E ) distinctly broader than long, with each posterior plate broader than long.

Eyes ( Figs. 3A , 4A, G ) moderately small, reaching to distinctly oVerreaching lateral limits of orbits.

Basal article of antennular peduncle ( Figs. 3D , 4F ) as long as broad or slightly longer than broad.

Antennal peduncle slender ( Fig. 4G ). First article slightly shorter than combined second to fourth articles. Third article elongate rectangular, about 1.5 times longer than second.

Third maxilliped ( Figs. 3E , 4H ) moderately stout, with short ridges on lateral surfaces of ischium to carpus. Merus with rounded lobe proximal to median part of Ventral margin. Propodus comparatiVely stout. Exopod broad, 0.7–0.8 width of ischium.

Chelipeds ( Figs. 3F–J , 5A–G ) unequal in size. Merus with strong slender spine on Ventro-anterior margin. Carpus 1.5–2.0 (larger cheliped) and 1.6–1.9 (smaller cheliped) times as long as broad; dorsal surface with short and moderately long rows of small tubercles entirely and with single, flattened tubercles distally, no blunt ridge on longitudinal midline; posterior margin unarmed, rounded entirely (larger) and somewhat bluntly angled on distal part (smaller). Chela 2.5–2.6 (larger) and 2.5–2.8 (smaller) times longer than broad; dorsal surface with coarse, small and relatiVely larger tubercles; cutting edge of fixed finger with row of small and moderately large, rounded or subacute teeth (larger) or with row of small teeth decreasing in size distally (smaller). Dactylus 0.4–0.5 length of chela; cutting edge with some small rounded teeth and distinct, blunt tooth on each of proximal and median parts, proximal tooth larger (larger), and with row of small, rounded teeth (smaller).

Ambulatory legs ( Figs. 3K, L , 4I –O ) comparatiVely slender, lateral surface with short and minute, weak striae. Meri 3.7–3.9, 3.4–3.6, 2.8–3.1 times longer than high on respectiVe second to fourth pereopods. Carpi relatiVely slender. Propodi 3.0–3.5, 2.9–3.3, 2.7–3.0 times longer than high on respectiVe second to fourth pereopods. Dactyli 0.7–0.9 length of propodi.

Coloration. Ng & Nakasone (1994) noted that “The colour of the hairs of the liVe and freshly preserVed specimen is beige brown, the carapace and appendages being white”. In the preserVed specimens ( Fig. 9C ), the body and pereopods are generally whitish or pale brown, and the soft plumose setae are dark brown.

Distribution. PreViously known only from Singapore (Ng & Nakasone 1994). The present specimens from Phuket ( Thailand) (western coast of Peninsular Malaysia) and JaVa Island ( Indonesia), are additional records of R. johnsoni and extend the known range of the species north and southwards.

Habitat. The specimens examined from Phuket were collected from burrows on the tidal sand flat using a stainless-steel suction pump (yabby pump; cf. Dworschak 2015; Ahyong et al. 2017), but the hosts in the burrows could not be collected. Ng & Nakasone (1994) mentioned that the holotype of R. johnsoni was obtained from soft mangroVe mud in the littoral zone and it seemed to be commensal with tubicolous worms that were relatiVely common in the mangroVes of the collection site. Although the substratum from which R. johnsoni was collected is different between Singapore and Phuket, we expect the species is probably commensal with polychaetes such as those in the family Terebellidae , as presumed by Ng & Nakasone (1994), as is also the case for Raphidopus brevipes n. sp. shown below. AVailable specimens indicate that R. johnsoni occurs in the intertidal region to subtidal depth of about 11 m.

Remarks. Re-examination of the specimens reported as R. indicus by Haig (1981) has shown that they belong to R. johnsoni instead. Distinctions among R. indicus , R. johnsoni , and R. brevipes n. sp. are discussed below in the Remarks of the new species.

Four of the fiVe Phuket specimens (cl 4.2–5.9 mm) are larger than the holotype from Singapore (cl 3.8 mm), and the aVailable material shows that females reach larger sizes than males.

Figures

FIGURE 3. Raphidopus Johnsoni Ng & Nakasone, 1994, holotype, male (cl 3.8 mm), ZRC 1992.10669, Singapore. A, carapace and ocUlar and antennal pedUncles, dorsal vieW (transverse striae and ridges not draWn); B, rostrUm, dorso-anterior vieW; C, third and foUrth thoracic sternites, ventral vieW; D, basal article of left antennUlar pedUncle, ventral vieW; E, left third maxilliped, lateral vieW (sUrface strUctUre not draWn); F, larger cheliped, merUs, ventral vieW (sUrface strUctUre not draWn); G, larger cheliped, carpUs, dorsal perpendicUlar vieW (sUrface strUctUre not draWn); H, larger cheliped, chela, dorsal perpendicUlar vieW (sUrface strUctUre not draWn); I, smaller cheliped, carpUs, dorsal perpendicUlar vieW (sUrface strUctUre not draWn); J, smaller cheliped, chela, dorsal perpendicUlar vieW (sUrface strUctUre not draWn); K, left foUrth pereopod, lateral vieW (short striae not draWn); L, same, merUs, lateral perpendicUlar vieW (short striae not draWn). Setae are not draWn on all figUres. Scale bars = 1.0 mm.

FIGURE 4. Raphidopus Johnsoni Ng & Nakasone, 1994, male (cl 5.0 mm), CBM-ZC 12485, PhUket. A, carapace and ocUlar and antennal pedUncles, dorsal vieW (marginal setae not draWn on right side); B, right branchial margin of carapace, dorsomesial vieW; C, rostrUm, dorso-anterior vieW; D, third and foUrth thoracic sternites, ventral vieW (setae not draWn on left side); E, telson, external vieW; F, basal article of left antennUlar pedUncle, ventral vieW; G, left ocUlar and antennal pedUncles, dorsolateral vieW; H, left third maxilliped, lateral vieW; I, left second pereopod, lateral vieW; J, left second pereopod, merUs, mesial vieW (short striae not draWn); K, left second pereopod, dactylUs, lateral vieW (setae not draWn); L, left third pereopod, lateral vieW (setae and short striae not draWn); M, left third pereopod, merUs, mesial vieW (short striae not draWn); N, left foUrth pereopod, lateral vieW (setae and short striae not draWn); O, left foUrth pereopod, merUs, mesial vieW (short striae not draWn). Scale bars = 1.0 mm.

FIGURE 5. Raphidopus Johnsoni Ng & Nakasone, 1994, male (cl 4.7 mm), CBM-ZC 12485, PhUket. A, larger cheliped, dorsal vieW; B, larger cheliped, merUs and carpUs, ventral vieW; C, larger cheliped, chela, dorsal perpendicUlar vieW (sUrface strUctUre on palm and dactylUs not draWn); D, smaller cheliped, dorsal vieW (sUrface strUctUre not draWn); E, smaller cheliped, chela, dorsal perpendicUlar vieW (sUrface strUctUre not draWn). Setae are not draWn on all figUres. Scale bars = 1.0 mm.

FIGURE 9. Preserved specimens of three Raphidopus species. Entire animal, dorsal vieW (A–D); carapace, dorsal vieW (E); larger and smaller chelipeds, dorsal vieW (F). A, Raphidopus indicus Henderson, 1893, holotype, male (cl 6.5 mm), NHM 1892.7.15.246; B, Raphidopus Johnsoni Ng & Nakasone, 1994, holotype, male (cl 3.8 mm), ZRC 1992.10669; C, Raphidopus Johnsoni Ng & Nakasone, 1994, female (cl 5.9 mm), CBM-ZC 12485; D, Raphidopus brevipes n. sp., female (cl 5.1 mm), ZRC 2016.528; E, Raphidopus brevipes n. sp., male, holotype, male (cl 5.8 mm), ZRC 1992.10521; F, Raphidopus brevipes n. sp., paratypes, ZRC 1992.10522–10526.