Raphidopus brevipes, Osawa & Ng, 2018

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 : 119-124

publication ID	https://doi.org/ 10.11646/zootaxa.4433.1.6
publication LSID	lsid:zoobank.org:pub:4D532EFF-7063-4772-AF77-58F5A8213B44
DOI	https://doi.org/10.5281/zenodo.5967591
persistent identifier	https://treatment.plazi.org/id/03B787EB-FFD7-0514-D4F8-0AC1FE09F844
treatment provided by	Plazi
scientific name	Raphidopus brevipes
status	sp. nov.

Treatment

Raphidopus brevipes View in CoL n. sp.

( Figs. 6–8 View FIGURE 6 View FIGURE 7 View FIGURE 8 , 9D–F View FIGURE 9 )

Raphidopus indicus View in CoL .— Ng & Nakasone 1994: 7, fig. 3 (not R. indicus Henderson, 1893 View in CoL ).

Type material. Holotype: ZRC 1992.10521 View Materials , male (cl 5.8 mm), Tanjong Tokong , Penang, Malaysia, among terebellid worm tubes, 10 March 1966, coll. J. A. Bullock.

Paratypes: ZRC 1992.10522–10526, 1 male (cl 5.7 mm), 2 females (cl 6.1, 6.2 mm), 2 oVigerous females (cl 6.4, 6.8 mm), collected with holotype .

Other material examined. Malaysia: ZRC 2016.528 View Materials , 7 males (cl 4.1–5.0 mm), 3 females (cl 4.1–5.1 mm), 2 oVigerous females (cl 4.4, 4.5 mm), Jeram, Kuala Selangor, Selangor, Jeram Polychaete Reef , station A, 3°13’27’’N, 101°18’13’’E, lower intertidal, mud, associated with tubes of Loimia verrucosa Caullery, 1944 , July– October 2016, coll. J. J. Eeo. GoogleMaps

Description. Carapace ( Fig. 6A View FIGURE 6 ) 1.3 times as broad as long; dorsal surface slightly conVex from side to side, with scattered, short or Very short striae; pair of protogastric ridges low, obtuse; cerVical grooVes moderately deep; anterior branchial region with small tubercles and short rows of beaded tubercles; posterior branchial and intestinal regions with long, tuberculate ridges; hepatic margin broadly conVex, granular; branchial margins strongly conVex, narrowly laminar, each with row of small, rounded tubercles; epigastric angle blunt, shallowly notched; lateral surfaces below branchial margins with dense, soft plumose setae. Rostrum ( Fig. 6B View FIGURE 6 ) bent Ventrally, trilobate, with all lobes rounded on anterior margins; median lobe reaching or slightly oVerreaching leVel of apices of lateral lobes; anterior margin with row of short plumose setae.

Pterygostomial flap entire, with longitudinal ridges of small tubercles and dense, soft plumose setae; anterior margin terminating in small subacute apex ( Fig. 6C View FIGURE 6 ).

Third thoracic sternite ( Fig. 6D View FIGURE 6 ) 3.9–4.9 times broader than long measured along midline, with surface somewhat depressed medially; anterior margin trilobate, median lobe broad, low, lateral lobes strongly produced anteriorly and each with rounded apex. Fourth thoracic sternite with anterior margin concaVe, anteromedian part transVerse; surface depressed medially, with submarginal row of small tubercles anteriorly.

Telson ( Fig. 6E View FIGURE 6 ) distinctly broader than long, composed of 7 plates; with scattered, Very short striae on extensor surface; each posterior plate broader than long.

Eyes ( Fig. 6A, G View FIGURE 6 ) small, at most slightly exceeding lateral limits of orbits; dorsodistal projection of ocular peduncle low, rounded.

Basal article of antennular peduncle ( Fig. 6F View FIGURE 6 ) approximately as long as broad; Ventral surface with transVerse row of small tubercles on lateromedian part, anterior part slightly concaVe and delimited by transVerse ridges of small tubercles; anterior margin obtuse, with row of small tubercles, but without distinct lobes or teeth; anterior mesiodistal margin blunt.

Antennal peduncle ( Fig. 6G View FIGURE 6 ) slender, weakly striate on surface. First article largest, as long as combined second to fourth articles, produced forward in lateral View, broadly in contact with lower orbital margin; surface slightly concaVe, with row of small tubercles along Ventral margin. Second article short, subrectangular. Third article oblong, about 1.5 times longer than second article. Fourth article short, suboVate.

Third maxilliped ( Fig. 6H View FIGURE 6 ) moderately stout, with short ridges on lateral surfaces of ischium to carpus. Ischium broad; distolateral margin strongly produced, narrowly rounded. Merus with rounded lobe proximal to median part of Ventral margin. Carpus with small subtriangular projection medially on inflated Ventral margin; dorsal margin slightly undulate. Propodus moderately stout, slightly tapering; lateral surface with row of short ridges along dorsal margin. Dactylus short, subtriangular. Merus to dactylus with long plumose setae on Ventral margin. Exopod broad, 0.7 width of ischium, reaching nearly to distal margin of merus, with distal flagellum; lateral surface with small, low tubercles and striae; dorsally margin strongly conVex on distal 0.8.

Chelipeds ( Fig. 7A–H View FIGURE 7 ) unequal in size; Ventral surface of merus to chela with scattered, numerous, short and Very short rows of granules; dense, soft plumose setae on anterior and posterior margins of merus to chela, dorsoanterior and Ventroposterior surfaces of chela, and cutting regions of fixed finger and dactylus. Merus with moderately narrow, rounded lobe on dorsal disto-anterior margin; dorsal surface with short and long, transVerse rows off small tubercles and with transVerse crest medially; Ventro-anterior margin conVex, tuberculate, with strong but short spine medially. Carpus 1.5–1.9 (larger cheliped) and 1.5–1.8 (smaller cheliped) times as long as broad; dorsal surface somewhat conVex, with short and moderately long rows of small tubercles entirely, and with low (sometimes indistinct), blunt ridge on longitudinal midline, shallow sulcus sometimes present posterior along median longitudinal ridge; dorso-anterior margin slightly concaVe medially, with row of small tubercles; dorsoposterior distal lobe broadly rounded or roundly truncate; posterior margin unarmed, rounded entirely (larger) and somewhat bluntly angled on distal part (smaller). Chela 2.3–2.4 (larger) and 2.5–2.6 (smaller) times longer than broad, with curVed claw; dorsal surface conVex, with numerous, coarse, small tubercles and with slightly eleVated ridge of small tubercles along posterior margin; anterior margin nearly straight on posterior half and fixed finger; cutting edge of fixed finger with row of moderately large, blunt teeth (larger, proximal and distal teeth usually largest) or with row of small, low teeth (smaller), proximal tooth prominent. Dactylus 0.4–0.5 (larger) and 0.5–0.6 (smaller) length of chela, opening at oblique angle (more acute angle in smaller cheliped), with curVed claw; dorsal surface with scattered, flattened, small tubercles and with slightly eleVated ridge of small tubercles along posterior margin; cutting edge with 2 distinct, blunt teeth on proximal part (larger) and with row of small, low teeth (smaller); claw distally curVed.

Ambulatory legs ( Fig. 8A–J View FIGURE 8 ) comparatiVely stout, somewhat flattened laterally, decreasing in size posteriorly, second pereopod longest; lateral and mesial surfaces with scattered, Very short, weak striae, small pits, and sparse, soft plumose setae, on fourth pereopod, setae most numerous; margins without spines or teeth; dense, soft plumose setae on anterior and posterior margins of ischium to dactylus. Meri 3.1–3.3, 2.8–3.0, 2.4–2.6 times longer than high on respectiVe second to fourth pereopods, somewhat narrowed distally in lateral View; lateral and mesial surfaces with sparse, short plumose setae; anterior and posterior margins somewhat conVex; posterolateral and posteromesial margins rounded; posterodistal margin rounded. Carpi relatiVely slender. Propodi 2.6–2.8, 2.4–2.6, 2.2–2.4 times longer than high on respectiVe second to fourth pereopods, somewhat narrowed distally in lateral View. Dactyli 0.6–0.8 length of propodi, each with short, distal claw; anterior and posterior margins nearly straight; lateral and mesial surfaces each with blunt, median, longitudinal ridge flanked by rows of short stiff setae.

Fifth pereopod slender, chelate; propodus with numerous short simple setae and 1 or 2 subdistal hooked setae.

Male with pair of gonopods on second abdominal segment; endopod elongate oVate, rounded on distal margin; exopod small, rounded.

Female with well deVeloped pleopods on third to fifth abdominal segments.

Coloration. In freshly preserVed specimens ( Fig. 9D View FIGURE 9 ), the body and pereopods are generally pale brown, and the soft plumose setae are dark brown.

Distribution. At present, known only from the island of Penang and Kuala Selangor, western coast of Peninsular Malaysia.

Habitat. The specimens from Penang were collected together with unidentified terebellids, but the nature of the association with the polychaetes was not specified on the label (cf. Ng & Nakasone 1994). The Jeram (Kuala Selangor) specimens were collected from the lower intertidal region of muddy shore and associated with tubes of the terebellid Loimia verrucosa Caullery, 1944 . Polgar et al. (2015) described and illustrated the enVironments of the Jeram beach from December 2010 to April 2013, and reported that the bottom condition and community composition of polychaetes in the area underwent substantial changes oVer the years.

Etymology. The specific name is deriVed from a combination of the Latin, brevis (short) and pes (leg), in reference to the proportionally stout ambulatory legs of the new species; used as a noun in apposition.

Remarks. As preViously mentioned, the Penang specimens reported as R. indicus by Ng & Nakasone (1994) are referred to the present new species. The largest male from Penang (cl 5.8 mm, ZRC 1992.10521) is designated as the holotype of R. brevipes n. sp., and preserVes only the body, cephalic appendages, and third maxillipeds as noted and illustrated by Ng & Nakasone (1994: 8, fig. 3A–D, J, K). The other Penang specimens including bodies of one male and four females with detached pereopods (ZRC 1992.10522–10526) are all designated as paratypes of the new species. The specimens recently collected from Jeram include intact indiViduals but are excluded from the type series because they were collected from the different locality and are much smaller than the types from Penang (4.1–5.1 mm Versus 5.7–6.8 mm in the carapace length). The Jeram and Penang specimens agree well with each other in all diagnostic characters, and are here regarded as conspecific.

Raphidopus brevipes n. sp. is similar to R. indicus and R. johnsoni in the carapace branchial margins and posterior margins of the carpi of both chelipeds lacking distinct spines, but can be distinguished by the detailed morphology of the carapace, chelipeds, and ambulatory legs. The carapace is proportionally narrower in R. brevipes n. sp. than the two known species; i.e., 1.3 Versus 1.4 times breadth of the length ( Figs. 1A View FIGURE 1 , 3A View FIGURE 3 , 4A View FIGURE 4 , 6A View FIGURE 6 ). On each cheliped, the carpus usually has a low, blunt ridge on the dorsal longitudinal midline and the palm possesses small, closely-set tubercles on the dorsal surface in R. brevipes n. sp. ( Fig. 7A, E View FIGURE 7 ), whereas in R. indicus and R. johnsoni , the dorsomedian ridge on the carpus is absent, and more coarsely distributed tubercles are present on the palm ( Figs. 2A View FIGURE 2 , 5A View FIGURE 5 ). The cutting edge of the dactylus of the larger cheliped possesses two large, blunt teeth on the proximal part in R. brevipes n. sp. ( Fig. 7D, H View FIGURE 7 ), while it is armed with only one distinct, proximal tooth in R. indicus and R. johnsoni ( Figs. 2D View FIGURE 2 , 3H View FIGURE 3 , 5C View FIGURE 5 ). The ambulatory legs are proportionally stouter in R. brevipes n. sp. than in the other two species; particular in the fourth pereopod: 2.4–2.6 Versus 2.8–3.1 times and 2.2–2.4 Versus 2.7–3.0 times longer than high on the merus and propodus, respectiVely ( Figs. 1J View FIGURE 1 , 2K, L View FIGURE 2 , 4N, O View FIGURE 4 , 8F, G, J, K View FIGURE 8 ). Raphidopus brevipes n. sp. can be further separated from R. johnsoni by its comparatiVely narrower third thoracic sternite, 3.9–4.9 Versus 5.3–7.0 times broader than the length measured along the midline ( Figs. 1C View FIGURE 1 , 3C View FIGURE 3 , 4D View FIGURE 4 , 6D View FIGURE 6 ).

Raphidopus johnsoni differs from R. indicus in haVing the relatiVely larger eyes reaching at least to the lateral limits of the orbits ( Figs. 3A View FIGURE 3 , 4A View FIGURE 4 ), the third thoracic sternite being proportionally broader (5.3–7.0 Versus 4.6 times broader than the length measured along the midline; Figs. 1C View FIGURE 1 , 3C View FIGURE 3 , 4D View FIGURE 4 ), and the dactylus of the larger cheliped possessing a distinct blunt tooth on the median part of the cutting edge ( Figs. 3H View FIGURE 3 , 5C View FIGURE 5 ). In R. indicus , the eyes do not reach the lateral limits of the orbits ( Fig. 1A View FIGURE 1 ) and the dactylus of the larger cheliped has no prominent median tooth on the cutting edge ( Fig. 2D View FIGURE 2 ).