Pisidia streptochiroides Johnson 1970, comb. nov.
Creators: name: Dong, Dong
name: Li, Xinzheng
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Porcellanidae
Pisidia
Pisidia streptochiroides

description: Pisidia streptochiroides (Johnson, 1970) comb. nov.
(Figs. 1–3)
Porcellana (Pisidia) streptochiroides Johnson, 1970: 26, figs. 3j–l [type locality: Singapore].
Lissoporcellana streptochiroides.— Hsieh et al., 1997: 342, fig. 36 (citing original figures and descriptions of syntypes).— Komai, 2000: 362 (list, part).— Davie (2002): 98 (list, part)
Material examined. Syntypes: ZRC 1984.2.21.1, 1 male (CL 5.50 mm), Kampong Mata Ikan, Singapore, beach, about 500 yards NE of village, on washed in sponge, 8 Jan. 1955; ZRC 1984.2.21.2–6, 1 male (CL 4.57 mm), 2 females (CL 3.33 mm, 3.88 mm) and 2 ovig. females (CL 3.26 mm, 5.30 mm). Changi beach, Singapore, in much bored rotten driftwood, 11 Sept. 1953.
Description. Carapace (Fig. 1 A) ovate, approximately as long as broad, broadest at middle of lateral margins; dorsal surface with short and transverse faint striae; posterior branchial regions with strong, oblique rugae; gastric regions slightly elevated; protogastric ridges conspicuous; cervical grooves distinct. Rostrum (Fig. 1 B) relatively broad, trilobate, with anterior margin denticulate; median lobe twice as broad as lateral lobes; produced beyond lateral lobes, with longitudinal median groove. Orbit shallow, supra-ocular margins oblique; outer orbital angles sharp, directed forward. Hepatic margins each armed with 2 or 3 spines, posterior one largest. Median branchial margins slightly convex, armed with 3 spines on each side; anteriormost spine smallest, sometimes undistinguishable. Pterygostomian flaps (Fig. 1 C, D) entire, with longitudinal, wavy ridges; anterior angle acute; dorsal margin anteriorly armed with 6 or 7 triangular, subacute spines, just below second antennal peduncle. Third thoracic sternite (Fig. 1 E) trilobate; median lobe very broad, with anterior margin fringed with fine setae; lateral lobes slender, produced anteriorly. Fourth thoracic sternite (Fig. 1 E) with anterior margin strongly concave.
Telson (Fig. 1 F) composed of seven plates.
Eyes (Fig. 1 G) large; ocular peduncles short; dorsal extensions onto corneas subtriangular.
Basal article of antennular peduncles (Fig. 1 H) longer than broad; ventral surface with transverse rugae and ridges; anterior surface with faint striae; anterior margin armed with triangular tooth ventromesially, and 2 small, subacute spines on lateral corner and dorsomesial corner. Antennal peduncles (Fig. 1 G) slender; first article immovable, strongly produced forward, with projection reaching anterior margin of carapace; second article (first movable article) stout, with small spine on anteriodistal angle; third article rectangular, with anterior margin slightly tuberculate; fourth article short.
Third maxilliped (Fig. 1 I) relatively stout; with long, plumose setae on dorsoflexor (mesial) margins of merus to dactylus. Coxa with median, longitudinal ridge on ventral surface. Basis subtriangular. Ischium broad, distoflexor margin extending as rounded lobe; disto-extensor projection narrow; ventral surface with transverse or oblique striae. Merus with extensor margin nearly straight; flexor lobe subrectangular, distoflexor margin denticulate, often armed with tiny spinules. Carpus with triangular projection on flexor margin, ventral surface with longitudinal striae. Propodus slender, with faint striae on ventral surface. Dactylus short. Exopod with first article relatively small, subtriangular and unarmed; second article laminate, gradually narrowing distally, with extensor margin convex, ventral surface with transverse striae; flagellum well developed.
Chelipeds (Fig. 2 A–D) unequal, showing distinct sexual dimorphism in armature as well as degree of distortion of dactylus.
Smaller cheliped (Fig. 2 A, C, D) relatively slender. Ischium with distinct tubercle or spine dorsally on flexor margin. Merus short, dorsal surface with transverse striae, usually armed with small spine medially near dorsoextensor margin, and occasionally with small median tubercle on dorsodistal margin; flexodistal lobe broad, with margin crenulate or spinulate; ventral surface (Fig. 2 C) with faint striae, ventrodistal margin armed with 1 or 2 prominent spines. Carpus 1.6–1.7 times as long as broad, extensor margin moderately inflated dorsoventrally, obliquely rugose, nearly nake, and unarmed except prominent distal spine; dorsoflexor margin sinuous or with 2 low triangular teeth and occasionally several minute teeth on distal half (teeth more clear in females (Fig. 2 D)), distal flexor angle produced, forming narrow, blunt lobe (males), or armed with small subtriangular tooth (females); dorsodistal margin slightly 2-lobed, bearing plumose setae around disto-extensor spine; dorsal surface with faint, short and transverse striae; ventrodistal margin fringed with plumose setae; ventral surface with faint transverse striae. Chela (Fig. 2 E–G) 3.2–3.3 times as long as broad, relatively compressed dorsoventrally; lying on extensor margin with chela plane twisted nearly vertically to carpus plane; extensor margin strongly denticulate, bearing long plumose (or clubbed) setae (denser in small individuals); row of submarginal spines present along dorso-extensor margin (weaker in males than in females); dorsoflexor margin relatively inflate dorsoventrally, with longitudinal ridge on entire length; dorsal surface smooth, with faint transverse striae, convex medially to form smooth longitudinal crest; ventral surface also with faint striae. Fixed finger (immovable finger) terminally bifurcate (Fig. 2 C); dorsal surface smooth or bearing plumose (or clubbed) setae. Dactylus (movable finger) slender, approximately half length of palm, strongly twisted in males (Fig. 2 F), and moderately twisted in females (Fig. 2 G); dorso-extensor (posterior) margin distinctly ridged, with row of oblique rugae; dorsal surface with shallow, longitudinal groove near extensor margin. Dactylus and fixed finger each curved distally, enclosing narrow, excavated gap (Fig. 2 E) (in small individuals much narrower slit); cutting edges unarmed, grooved, bearing thick plumose (or fluffy) setae.
Larger cheliped (Fig. 2 B) relatively robuster, and morphologically similar to smaller cheliped. Merus with dorsal surface unarmed. Chela (Fig. 2 H) broad, 3.0–3.1 times as long as broad, chela of male relatively more inflated dorsoventrally than that of female; extensor margin hairless or with sparse plumose (or clubbed) setae, submarginal spines on dorsal surface distinct (females) or mostly obsolescent (males). Fixed finger (Fig. 2 I) singleclawed, cutting margin armed with triangular median tooth. Dactylus relatively short (less than 0.4 times length of palm in female, and approximately third length of palm in male), distinctly twisted in males (somewhat less twisted than in smaller cheliped of males), and moderately or slightly twisted in females (similar to that of smaller cheliped of females); cutting margin (Fig. 2 I) with broad and triangular submedian tooth.
Ambulatory legs (first to third legs, second to fourth pereopods) (Fig. 3 A–C) moderately slender, decreasing in size from first to third legs; extensor margins of each segment, except dactyli, bearing sparse simple setae (occasionally slightly clubbed). Meri subrectangular in lateral view, 1.9–2.5 times as long as broad (longest in first legs), compressed laterally; extensor margin unarmed but slightly crenulate; flexor margin smooth; lateral surface with interrupted, transverse rugae, hairless on first and second legs, but with sparse simple setae on rugae of third legs. Carpi short; extensor margin slightly uneven, distally with 2 spines on first leg, 1 spine or acute tubercle on second leg, and unarmed on third leg; lateral surface with longitudinal or oblique rugae bearing few setae and tuft of setae near flexodistal corner. Propodi subcylindrical, slender, 4.2–4.7 times as long as broad; flexor margin with 4 movable corneous spines including distal pair, proximalmost spine located on proximal 0.3–0.4, each spine usually with setae on base; lateral distal margin unarmed, fringed with row of simple setae; lateral surface with faint, oblique rugae bearing tuft of setae. Dactyli terminating in slender claw; flexor margin armed with 3 or 4 corneous spines, decreasing in size proximally, distal spine with base strongly elevated.
Fifth pereopods (Fig. 3 D) short, slender, chelate; propodus bearing numerous stiff simple setae and several curved simple setae on sufaces and margins.
Male with pair of developed pleopods (Fig. 3 E) modified as gonopods on second pleonal segment; endopod spoon-shaped, elongate, with fine marginal setae on distal two-thirds; exopod reduced, naked. Female with pair of pleopods on each of second to fifth pleonal segments.
Habitat. Muddy to sandy bottoms in shallow, offshore habitats (Johnson 1970).
Distribution. Singapore and adjacent waters.
Remarks. Pisidia differs from Lissoporcellana in the dissimilarity of the chelipeds, showing sexual dimorphism. Males of the genus Pisidia have the distortion of the dactyli of chelipeds more pronounced than in females, and females have chelipeds more strongly spinulate than in males (Haig 1965, 1978; Osawa & Chan 2010). The genus further differs from Lissoporcellana in having a relatively more rugose carapace, relatively compressed chelae, and the rostrum without a median notch on the anterior margin. In Lissoporcellana, the carapace is smooth with the regions undefined, the chelae are subcylindrical, and the anterior margin of the rostrum usually has a median notch. The two male syntypes examined are sufficient to define the sexual dimorphic generic characters. In the male syntypes, the distortion of the dactyli of the chelipeds (especially in the smaller cheliped) is much more pronounced than in the females. In the female syntypes, the dorsoflexor margins of carpi are armed with two distinct subacute teeth and several small teeth, and the dorsal submarginal spines on chelae are distinctly strong (stronger in the smaller cheliped). In contrast, the male syntypes have the dorsoflexor margins of the chelipeds carpi sinuous or with one small tooth; the dorsal submarginal spines on smaller chelae somewhat weaker than in females, and those spines on larger chelae are distinctly reduced. In addition, the syntypes each have compressed smaller chelae, slightly defined regions on dorsal surface of the carapace (gastric regions slightly elevated), and anterior margin of median lobe of rostrum without median notch. Therefore, the syntypes should be assigned to Pisidia rather than Lissoporcellana.
Pisidia streptochiroides resembles P. serratifrons (Stimpson, 1858), P. gordoni (Johnson, 1970), P. striata Yang & Sun, 1990, P. streptocheles (Stimpson, 1858) and P. inaequalis (Heller, 1861) in having the rostrum trilobate in dorsal view, and the median lobe of the rostrum twice as broad as the lateral lobes. Pisidia streptochiroides differs from P. serratifrons in having the extensor margins of the carpi of the chelipeds unarmed, and the base of the distalmost corneous spine of each dactylus of the ambulatory legs more elevated. In P. serratifrons, the extensor margins of the carpi of the chelipeds are each armed with a prominent spine on the distal third, and the base of the distalmost corneous spine of each dactylus of the ambulatory legs is less elevated or horizontal (Yang & Sun 1990; Osawa & Chan 2010). Pisidia streptochiroides differs from P. gordoni in having the dorsal surface of the smaller chela unarmed. In P. gordoni, the dorsal surface of the smaller chela is armed with a longitudinal ridge of spines on the midline (Johnson 1970). Pisidia streptochiroides differs from P. striata in having a distally bifurcated fixed finger of the smaller cheliped, and the dorsal surface of carapace is relatively smooth, without distinct scale-like rugae. In P. striata, the fixed finger of the smaller cheliped is not distally bifurcate, and the dorsal surface of the carapace has scale-like rugae on frontal, orbital and hepatic regions (Yang & Sun 1990). Pisidia streptochiroides differs from P. streptocheles in having hepatic spines and the first article of the antennal peduncle unarmed. In P. streptocheles, the hepatic spine is absent, and the first article of the antennal peduncle is armed with 4 strong denticles (Barnard 1950; Osawa 2007). Pisidia streptochiroides differs from P. inaequalis in having the median lobe of rostrum denticulate on the anterior margin, and the carapace as long as broad. In P. inaequalis, the median lobe of the rostrum is not denticulate on the anterior margin, and the carapace is broader than long (Lewinsohn 1969; Osawa 2007). Moreover, P. streptochiroides has the pterygostomian flaps each armed with 6 or 7 spines on the dorsal margin; this character seems to be unique as it has not been reported previously in other Pisidia species.
Haig (1978) assigned P. streptochiroides to the genus Lissoporcellana, probably on the basis of Johnson’s (1970) statement that P. streptochiroides was the same species as De Man’s (1888) specimens reported as of Porcellana (Porcellana) streptochira. However, De Man’s specimens were distinctly different with the former in having a weakly concave anterior margin of the median lobe of the rostrum and converging anterior branchial margins. These special characters agree well with those of our new Lissoporcellana species, described below.
description: Published as part of Dong, Dong & Li, Xinzheng, 2014, Revision of Lissoporcellana streptochiroides (Johnson, 1970) (Crustacea: Decapoda: Anomura: Porcellanidae), with description of a new species of Lissoporcellana Haig, 1978 from Beibu Bay, South China Sea, pp. 419-434 in Zootaxa 3860 (5) on pages 420-425, DOI: 10.11646/zootaxa.3860.5.2, http://zenodo.org/record/227518