JOURNAL OF CRUSTACEAN BIOLOGY, 21(2): 506Ð520, 2001

HETEROPOLYONYX BIFORMA, NEW GENUS AND SPECIES, FROM JAPAN, AND REDESCRIPTION OF POLYONYX UTINOMII (DECAPODA: PORCELLANIDAE)

Masayuki Osawa

Department of Zoology, National Science Museum, 3Ð23Ð1, Hyakunincho, Shinjuku-ku, Tokyo 169Ð0073, Japan (e-mail: [email protected])

ABSTRACT Heteropolyonyx, new genus (type species: H. biforma, new species), is established on the basis of the presence of transverse ridges on the cervical regions of the carapace and the telson being di- vided into five plates, characters quite different from its related genera Polyonyx Stimpson, 1858, and Eulenaios Ng and Nakasone, 1993. The male/female pair of H. biforma was found in a tube of an unidentified polychaete of the genus Chaetopterus. Polyonyx utinomii Miyake, 1943, is re- described from the holotype specimen and recently obtained material from Japan and the Mal- dives. This species is readily distinguishable from the other Indo-West Pacific species of Polyonyx by the carapace and chelipeds covered with numerous transverse and oblique striae on the dorsal surface and the meri of the chelipeds having a very large, broadly rounded lobe on the dorsoflexor margin. The present record of P. utinomii from the Maldives is the first report outside Japan and greatly extends its geographical distribution westwards into the Indian Ocean.

The Polyonyx sinensis group, as recognized tified species of Chaetopterus. Through his by Johnson (1958), may be defined by a suite kind cooperation, I could examine the spec- of characters of the carapace, chelipeds, and imens and found that they belong to an un- dactyli of ambulatory legs, and is currently described species. This species resembles represented by 10 Indo-West Pacific species: members of the Polyonyx sinensis group in P. sinensis Stimpson, 1858; P. transversus general appearance, but differs from all (Haswell, 1882); P. pedalis Nobili, 1905; P. species of Polyonyx Stimpson, 1858, and its utinomii Miyake, 1943; P. loimicola Sankolli, relative Eulenaios Ng and Nakasone, 1993, 1965; P. maccullochi Haig, 1965; P. haigae in the structures of the cervical regions of the McNeil, 1968; P. vermicola Ng and Saseku- carapace and the telson. I herein describe the mar, 1993; P. plumatus Yang and Xu, 1994; specimens as a new genus and species. and P. bella Hsueh and Huang, 1998 (Ng and In addition, I include here a redescription Sasekumar, 1993; Yang and Xu, 1994; Hsueh of Polyonyx utinomii, a rarely recorded and Huang, 1998). Six members of the P. species of the P. sinensis group. This species sinensis group are known to be associated was originally described by Miyake (1943) with tube-dwelling polychaete worms be- based on a single specimen from Tanosaki longing to the genera Chaetopterus, Meso- (Tanabe Bay, Shirahama, Wakayama Prefec- chaetopterus, and Sasekumaria of the family ture, Japan) and the records are restricted to Chaetopteridae and Loimia of the Terebelli- just a few localities in Japan (Miyake, 1943; dae (see Miyake, 1965; Ng and Sasekumar, Miyake et al., 1962; Nakasone, 1978). Al- 1993; Hsueh and Huang, 1998). Of these host though the original description and figures re- genera, Sasekumaria was recently found to be vealed that the species was quite different a junior synonym of Mesochaetopterus by from the other Indo-West Pacific species of Nishi (1999). Polyonyx, a more detailed examination of the During a faunal research of cryptic deca- type specimen and additional material is pod crustaceans from Kushimoto, southern needed for evaluating the intraspecific varia- part of Wakayama Prefecture, Japan, by Mr. tions and more precise systematic relation- K. Nomura of the Yeayama Marine Park Re- ships with the allied species. I examined the search Station, a pair of unusual porcellanid holotype and recently obtained material from crabs was collected from a tube of an uniden- Japan and the Maldives and redescribe P.

506 OSAWA: HETEROPOLYONYX BIFORMA AND POLYONYX UTINOMII 507 utinomii in detail. The presence of this species tro-extensor margin; propodus elongate; ex- in the Maldives is the first record outside opod robust, without distal flagellum. Che- Japan and greatly extends its geographical lipeds unequal, subcylindrical, not showing distribution westwards into the Indian Ocean. distinct sexual dimorphism in shape; carpus The carapace length (CL) was measured unarmed; chela narrow; dactyl opening at from the anteromedian apex of the rostrum strongly oblique angle, not twisted. Ambula- to the posteromedian end of the carapace, and tory legs short, subcylindrical; merus without the carapace width (CW) at the broadest distinct decalcified region on mesial surface; point. Measurements of chelipeds and ambu- dactyl with bifurcate claw, flexor claw much latory legs follow those of Osawa (1998a). larger than extensor. Male with pair of de- The description presented includes the de- veloped pleopods on second abdominal tailed morphology of the ocular peduncle, somite; endopod with broadly rounded apex; thoracic sternites, antennular and antennal pe- no exopod; pleopods of female present only duncles, third maxilliped, and male pleopods. on fourth and fifth abdominal somites. Telson These structures have not been frequently de- composed of 5 plates; proximal lateral plates scribed for porcelain crabs in general, but can each with very shallow suture on proximal prove useful in systematic studies of the Por- part; distal plates of female much more cellanidae (see Kropp, 1986; Ng and Naka- strongly elongated than those of male. sone, 1994; Osawa, 1998b; Harvey, 1999). The holotype specimen of P. utinomii was Etymology.—This name is derived from the borrowed from the Seto Marine Biological Greek, heteros, meaning different, in combi- Laboratory, Kyoto University, Japan (SMBL), nation with the generic name Polyonyx. The and the additional material of that species and gender is masculine. the type specimens of the present new species are deposited in the Natural History Museum Type species.—Heteropolyonyx biforma, new and Institute, Chiba, Japan (CBM). species.

SYSTEMATIC ACCOUNT Remarks.—Heteropolyonyx agrees with the Polyonyx sinensis species group of Johnson Family Porcellanidae Haworth, 1825 (1958) based on the morphological structures, Heteropolyonyx, new genus but is distinguished from this group and all Diagnosis.—Carapace, chelipeds, and ambu- other members of Polyonyx and its relative latory legs fringed with short and long Eulenaios by the following characters: (1) the plumose setae marginally. Carapace trans- carapace has a pair of transverse ridges along versely ovate; dorsal surface convex, regions the cervical regions; and (2) the telson is di- not well defined; protogastric ridges weakly vided into five plates, the distal two plates marked; cervical regions with no grooves, but of female are much more strongly elongated each with transverse ridge. Rostrum broad, than those of male. All the known porcellanid slightly bent ventrally, weakly produced and genera, including Polyonyx and Eulenaios, trilobate anteriorly; median lobe without lon- lack cervical transverse ridges on the cara- gitudinal groove. Pterygostomian flaps entire. pace. Polyonyx and Eulenaios have the telson Third thoracic sternite strongly depressed, composed of seven plates; the distal plates trilobate anteriorly; median lobe flattened, of female are rather short. In addition to the with longitudinal sulcus. Ocular peduncles two distinctions, Heteropolyonyx is distin- small. Basal segment of antennular peduncles guished from Eulenaios by the following fea- unarmed, slightly concave on anterior face. tures: (1) the regions on the carapace are not Antennal peduncles slender; first segment im- well defined in Heteropolyonyx, whereas they movable, strongly produced forward in lateral are very well defined and clearly demarcated view, broadly in contact with anterior mar- by the pattern of shallow and deep grooves in gin of carapace; second to fourth segments Eulenaios; and (2) the rostrum is broad and movable, excluded from orbit; third segment weakly produced anteriorly in Heteropoly- longest. Third maxillipeds with coxa bearing onyx, but it is rather narrow and strongly pro- distomedian projection incompletely articu- duced in Eulenaios. lated; basis articulated with ischium; ischium The proximal lateral plates of the telson of short, without longitudinal ridge along ven- Heteropolyonyx have a very shallow suture 508 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. 21, NO. 2, 2001 on the proximal part, which is rather diffi- ridge extending to mesobranchial region; pos- cult to observe, especially on the male. Paul terior regions with short and long oblique ru- et al. (1993) described the juvenile morphol- gae bearing plumose setae anteriorly. Ros- ogy of two porcellanids, Petrolisthes trum (Fig. 1D) not produced beyond eyes; rufescens (Heller, 1861) and Pisidia gordoni median lobe broadly rounded, slightly ex- (Johnson, 1970), and revealed that the divi- ceeding and broader than laterals; lateral sion of the telson plates started in the juve- lobes each with broadly rounded apex. Orbits nile phase and developed from proximal to (Fig. 1J, K) very shallow; supraorbital mar- distal (see their Fig. 2p for Petrolisthes gins oblique, unarmed; outer orbital angles rufescens, Fig. 4q for Pisidia gordoni). Fol- rounded. Frontal region slightly depressed, lowing their results, the division of the prox- with very short striae or small pit and minute imal lateral plates of the telson of Het- setae as in hepatic regions. Protogastric ridges eropolyonyx must be completed because that weakly marked. Gastric and cardiac regions of the distal plates has already occurred. In a slightly striate and elevated in male but developmental sense, the presence of a rudi- smooth in female. Cervical regions without mentary suture on the proximal lateral plates marked grooves, but each with strong (male) should be treated as not an incomplete con- or weak (female) transverse ridge. Median dition but a constant character in the adult parts of branchial regions each with trans- phase. The well-developed pleopods showing verse ridge weaker than that on cervical re- sexual dimorphism indicate that the present gions (ridge of female indistinct). specimens of H. biforma are fully mature. Al- Pterygostomian flaps (Fig. 1C) with strong though Heteropolyonyx is assigned to a genus longitudinal ridges, weakly narrow posteri- having a five-plated telson as a constant adult orly; anterior angle acutely pointed; an- character, the telson may actually represent terodorsal margin unarmed. a rudimentary condition of seven plates in a Third thoracic sternite (Fig. 1E, F) with phylogenetic sense. median lobe broad and indistinct; lateral lobes The absence of a flagellum on the exopod narrow, distinctly exceeding median, each of the third maxilliped also seems to be a with rounded apex. Fourth thoracic sternite generic character of Heteropolyonyx because with series of short striae (male) or small pits this is unusual in other species of the Por- (female) bearing plumose setae along concave cellanidae, as far as I know, except for anterior margin. Petrolisthes coccineus (Owen, 1839) (per- Ocular peduncles (Fig. 1J, K) smooth on sonal observation). dorsal surface; dorsal extension onto cornea weakly developed, broadly rounded. Heteropolyonyx biforma, new species Basal segment of antennular peduncles Figs. 1Ð3, 7B (Fig. 1I) with no lobes on anterodorsal mar- Type Material.—Holotype, CBM–ZC 5158; ovigerous f gin, anteroventral margin minutely tubercu- (CL 3.3 mm, CW 5.0 mm); Andonohana, Shionomisaki, lated, ventral surface smooth, mesial and lat- Kushimoto, Wakayama Prefecture, Japan; 20 m; in tube of Chaetopterus sp.; November 1995; coll. K. Nomura. eral margins fringed with plumose setae. Allotype (paratype), CBMÐZC 5159; m (CL 2.5 mm, CW Antennal peduncles (Fig. 1J, K) unarmed. 3.5 mm); data as in holotype. First segment largest, with strong longitudi- Diagnosis.—See “Diagnosis” for the genus. nal ridge along ventral margin; anterior an- gle narrowly pointed in lateral view. Second Description.—Carapace (Fig. 1A–C) moder- segment short. Third segment elongate, slen- ately (male) or strongly (female) convex dor- der. Fourth segment small, rounded. sally, 1.4 (male) or 1.5 (female) times as Third maxillipeds (Fig. 2A) with coxa broad as long, broadest on median branchial bearing small, rounded distoflexor projection. margin, fringed with soft or delicate plumose Basis small, subtriangular. Ischium broad, setae marginally, setae on anterior margin of ovate; ventral surface slightly rugose on dis- rostrum longer; dorsal surface with scattered, tomesial region; disto-extensor projection short delicate plumose setae, more densely weakly developed, broadly rounded. Merus distributed in male than female. Branchial with laminate, broad, rounded subrectangular margins strongly convex, female much more lobe bearing small tubercles on ventroflexor inflated on median margins than male; lat- margin, slightly rugose on ventral surface. eral faces each with distinct, longitudinal Carpus with triangular projection on proxi- OSAWA: HETEROPOLYONYX BIFORMA AND POLYONYX UTINOMII 509

Fig. 1. Heteropolyonyx biforma, new genus and species. A, CÐE, G, IÐK, holotype, ovigerous female (CL 3.3 mm, CBMÐZC 5158); B, F, H, allotype, male (CL 2.5 mm, CBMÐZC 5159). A, B, carapace, dorsal; C, carapace and left pterygostomian flap, lateral; D, rostrum, frontal; E, F, anterior thoracic sternites, ventral; G, H, telson, exposed; I, left basal segment of antennular peduncle, ventral; J, left anterior lateral part of carapace, eye, and antennal pedun- cle, dorsal; K, same, lateral. Scales equal 1.0 mm. 510 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. 21, NO. 2, 2001

Fig. 2. Heteropolyonyx biforma, new genus and species. AÐF, holotype, ovigerous female (CL 3.3 mm, CBMÐZC 5158); G, H, allotype, male (CL 2.5 mm, CBMÐZC 5159). A, left third maxilliped; B, larger cheliped, left, dorsal; C, G, same, chela, dorso-extensor, setae omitted; D, same, ventral; E, same, distal part of chela, ventroflexor; F, H, smaller cheliped, chela, right, dorso-extensor, setae omitted. Scales equal 1.0 mm. OSAWA: HETEROPOLYONYX BIFORMA AND POLYONYX UTINOMII 511 mal region of flexor margin, no longitudinal onto dactyl; cutting edge with small, rounded rows of short rugae along extensor margin or subtriangular teeth, no distinct large teeth on ventral surface. Propodus elongate sub- or projections; ventral surface with short ru- rectangular, smooth except for several short gae bearing plumose setae along extensor rugae along extensor margin. Dactyl small, margin, and fringe of plumose setae on prox- ovate, tapering distally; ventral surface imal flexor part and along cutting edge. smooth. Ventral rugae and disto-extensor pro- Dactyl 0.4 (female) or 0.5 (male) length of jection of ischium, and flexor margin of chela, slightly longer than fixed finger, with merus to dactyl with long plumose setae (se- strongly curved distal claw; dorsal surface tae on merus to dactyl not illustrated). Exo- with longitudinal ridge composed of minute pod laminate, robust, inflated and bearing tubercles along flexor margin and numerous long plumose setae on proximal region. plumose setae along cutting region; concave Chelipeds (Fig. 2B–H) moderately inflated, cutting edge minutely granulated and with slender, without distinct spines or teeth. low, broadly rounded projection on proximal Larger cheliped (Fig. 2BÐE, G) with merus part in male, but with small, rounded or sub- 2 having distinct transverse ridge submedially triangular teeth on distal ⁄3 and large, rounded on transversely rugose dorsal surface and tooth on proximal part in female; ventral sur- scattered plumose setae marginally; dor- face with plumose setae along cutting edge soflexor margin with broad subrectangular more densely than that of fixed finger. lobe slightly crenulated, distal corner rounded Smaller cheliped (Fig. 2F, H) almost iden- in male but weakly pointed in female; ventral tical to larger, especially in male, except for: surface with short transverse rugae, flexor chela slightly narrower, 3.1 (female) or 3.3 corner unarmed. Carpus 2.0 (female) or 2.3 (male) times as long as high, extensor mar- 1 (male) times as long as broad; dorsal surface gin slightly concave on distal ⁄3; fingers with with numerous short transverse rugae in male more sharply pointed and more strongly but nearly smooth except for short rugae and curved distal claw, cutting edge of dactyl with small pits along flexor and extensor margins low, broadly rounded projection on proximal in female; dorsoflexor margin with inflated part; dactyl as long as fixed finger. lobe, transverse, slightly crenulated in male Ambulatory legs (Fig. 3AÐE) marginally but nearly smooth in female, bearing plumose with long and short plumose setae on ischium setae densely; dorsodistal margin with to large part of propodus and with short rounded lobe with fringe of plumose setae simple setae on distal end of propodus and on extensor part; ventral surface with short dactyl; lateral surface with short rugae along rugae along margins, flexor margin trans- extensor margin on meri but nearly smooth verse, slightly crenulated. Chela rather elon- on carpus and propodus. Ischium without de- gate, 1.8 (male) or 1.9 (female) times as long calcified region. Merus elongated ovate, with as carpus, 2.9 (female) or 3.2 (male) times lengths decreasing as first > second > third as long as high, lying on extensor side; fin- legs; extensor margin unarmed but slightly 1 gers crossed distally; narrower and more crenulated, slightly inflated in proximal ⁄3 1 sharply pointed distally in male than in fe- (first leg) to distal ⁄3 (third leg); distoflexor male; extensor margin thin, transverse (male) margins of lateral and mesial surfaces with- or weakly convex (female), crenulated or ser- out spines, minutely granulated; mesial sur- 4 rated on distal ⁄5. Palm with dorsal surface face weakly decalcified on proximal region in convex, covered with short and long plumose first and second legs of female, but not de- setae on extensor half; dorsomedian longitu- calcified in third leg of female and all legs dinal ridge indistinct; dorsoflexor margin with of male. Carpus elongate, with lengths de- longitudinal rugose ridge; ventral surface creasing as first > second > third legs; disto- nearly smooth except for short rugae and extensor corner unarmed; distoflexor corner small pits on flexor region, distal extexor part with minutely pointed apex. Propodus 1.1 with few short rugae bearing plumose setae. (first and second legs)–1.3 (third leg) times Fixed finger with moderately curved distal as long as carpus, 3.7 (second leg)–3.8 (first claw; dorsal surface with numerous plumose and third legs) times as long as high; flexor setae as in extensor half of palm; dorsoflexor margin with 3 small movable spines, distal proximal part with broad (female) or narrow pair slightly smaller than subdistal. Dactyl (male) subtriangular projection extending terminating in strongly curved, bifurcate 512 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. 21, NO. 2, 2001

Fig. 3. Heteropolyonyx biforma, new genus and species. AÐE, holotype, ovigerous female (CL 3.3 mm, CBMÐZC 5158); F, allotype, male (CL 2.5 mm, CBMÐZC 5159). A, left first ambulatory leg, lateral; B, same, merus, mesial; C, same, distal part, lateral; D, left second ambulatory leg, lateral; E, left third ambulatory leg, lateral; F, left male pleopod, internal. Scales equal 1.0 mm.

claw; flexor margin with 2 or 3 small cor- pleopods on fourth and fifth abdominal neous, fixed spines, proximal spine very somites. small, distal spine largest. Telson (Fig. 1G, H) weakly calcified; plates Fifth pereiopod small, slender, chelate; weakly marked, approximately same size in propodus with numerous short simple setae male, but distal 2 plates larger and more and 1 or 2 hooked setae. strongly elongated than proximal 3 plates in Male with pair of developed pleopods on female; proximal lateral plates each with very second abdominal somite (Fig. 3F); protopod shallow suture on proximal part, suture of naked; endopod elongated ovate, not taper- male shorter than that of female and indis- ing, with numerous marginal setae except for tinct; distal plates each with short faint suture proximal part. No trace of pleopods (includ- on median part. ing small pore) on third to fifth abdominal somites. Female with no pleopods on third Etymology.—The specific name is a noun in abdominal somite, but with well-developed apposition from the combination of the Latin, OSAWA: HETEROPOLYONYX BIFORMA AND POLYONYX UTINOMII 513

“bis”, meaning two and “forma”, meaning troflexor margin. Chelipeds unequal, sub- shape, in reference to the sexually dimorphic cylindrical, not showing distinct sexual di- structure on the carapace and telson. morphism in shape; dorsal surface covered with short delicate striae; merus with very Color in Life (Fig. 7B).—Carapace light large, broadly rounded lobe on dorsoflexor brown, with white ovate markings on proto- margin; carpus with strongly inflated lobe on gastric, anteromedian branchial, and cardiac dorsoflexor margin; chela narrow, fringed regions; markings on posterior regions irreg- with short and long simple setae on extensor ularly distributed. Chelipeds with mottled pat- margin. Ambulatory legs short, with scattered tern of white, and light and dark brown. Am- simple setae marginally; dactyl with strongly bulatory legs with white background, meri curved, bifurcate claws, flexor claw much with irregular shaped spots of light brown, larger than extensor. Male with pair of de- propodi with transverse band of dark brown veloped pleopods on second abdominal on distal part. somite; exopod present; pleopods of female The characteristic pattern on the body im- present only on fourth and fifth abdominal mediately sets this species apart from all other somites. known commensal porcellanids. Habit.—This species inhabits the tube of a Redescription.—Carapace (Fig. 4A–D) trans- polychaete, Chaetopterus sp., and occurs as versely ovate, 1.2Ð1.3 times as broad as long a male/female pair. The habit agrees with in both male and female, broadest on median those of Eulenaios cometes (Walker, 1887) branchial margin. Dorsal surface weakly con- and species of the Polyonyx sinensis group vex, entirely covered with very shallow, del- (see Ng and Nakasone, 1993; Ng and Saseku- icate transverse striae bearing minute setae on mar, 1993). anterior margin; striae on frontal, inner pos- terobranchial and cardiac regions usually Remarks.—See “Remarks” for the genus. short, those on other regions long and usually interrupted (several striae sometimes unin- Polyonyx utinomii Miyake, 1943 terrupted). Branchial margins strongly con- Figs. 4Ð6, 7A vex, median margins subparallel in male but Polyonyx asiaticus: Miyake, 1937: 216. [not P. asiaticus inflated in female; lateral faces each with dis- Shen, 1936] Polyonyx utinomii Miyake, 1943: 141, figs. 58, 59; 1960: tinct longitudinal ridge; posterior regions with 97, pl. 48, fig. 1; 1982: 204 (list); Johnson, 1958: 99 long oblique rugae. Rostrum (Fig. 4E) rather (key), 114; Miyake et al., 1962: 125 (list); Nakasone, narrow, bent ventrally, very weakly or not 1978: 29 (list). produced beyond eyes, trilobate, bearing short Material Examined.—Japan: Holotype, SMBL 61; m (CL setae on anterior margin; median lobe 4.2 mm, CW 5.6 mm); Tanosaki (Tanabe Bay, Shirahama, rounded, approximately as broad as and dis- Wakayama Prefecture); in tube of Chaetopterus variope- tinctly or slightly extending laterals, without datus; 12 May 1937; coll. H. Utinomi. CBMÐZC 5155; 1 m (CL 2.9 mm, CW 3.6 mm); off Sumizaki, Shio- median longitudinal groove; lateral lobes each nomisaki, Kushimoto, Wakayama Prefecture; 25 m; host with rounded apex. Orbits (Fig. 4I, J) shal- unrecorded; 20 December 1988; coll. K. Nomura. low; supraorbital margins oblique, unarmed; CBMÐZC 5156; 1 m (CL 2.5 mm, CW 3.2 mm), 1 oviger- outer orbital angles rounded. Protogastric ous f (CL 3.0 mm, CW 4.0 mm); Futo, Ito, Shizuoka Prefecture; 12 m; in tube of Chaetopterus sp.; 15 De- ridges and cervical grooves unmarked. cember 1995; coll. E. Nishi. Maldives: CBMÐZC 5157; Pterygostomian flaps (Fig. 4B) entire, with 1 m (CL 1.7 mm, CW 2.0 mm), 1 ovigerous f (CL 2.1 strong oblique and longitudinal ridges, mm, CW 2.7 mm); Vadoo; outer side of eastern reef; 20 weakly narrow posteriorly; anterior angle m; in tube of Chaetopterus sp.; 22 April 1996; coll. K. rather sharply pointed; anterodorsal margin Nomura. unarmed. Diagnosis.—Carapace transversely ovate; Third thoracic sternite (Fig. 4F) strongly dorsal surface weakly convex, entirely cov- depressed, trilobate anteriorly; median lobe ered with delicate, short and long transverse much broader than laterals, with broadly striae; cervical grooves unmarked. Rostrum rounded anterior margin; lateral lobes narrow, rather narrow, trilobate anteriorly. Ocular pe- distinctly exceeding median, each with duncles small. Third thoracic sternite strongly rounded apex. Fourth thoracic sternite with- depressed, median lobe with broadly rounded out distinct series of short striae but bearing anterior margin. Third maxillipeds with merus several short or minute setae along concave provided with broad subovate lobe on ven- anterior margin incompletely marked. 514 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. 21, NO. 2, 2001

Fig. 4. Polyonyx utinomii Miyake, 1943. A, B, EÐJ, holotype, male (CL 4.2 mm, SMBL 61); C, male (CL 2.5 mm, CBMÐZC 5156); D, ovigerous female (CL 3.0 mm, CBMÐZC 5156); K, male (CL 2.9 mm, CBMÐZC 5155). A, C, D, carapace, dorsal; B, carapace and left pterygostomian flap, lateral; E, rostrum, frontal; F, anterior thoracic stern- ites, ventral; G, telson, exposed; H, left basal segment of antennular peduncle, ventral; I, left anterior lateral part of carapace, eye, and antennal peduncle, dorsal; J, same, lateral; K, left male pleopod, internal. Scales equal 1.0 mm. OSAWA: HETEROPOLYONYX BIFORMA AND POLYONYX UTINOMII 515

Fig. 5. Polyonyx utinomii Miyake, 1943. AÐF, holotype, male (CL 4.2 mm, SMBL 61); GÐJ, male (CL 2.9 mm, CBMÐZC 5155); K, ovigerous female (CL 3.0 mm, CBMÐZC 5156). A, larger cheliped, right, dorsal; B, same, chela, dorso-extensor; C, same, ventral; D, same, distal part of chela, ventroflexor; E, smaller cheliped, left, dorsal; F, same, chela, dorso-extensor; G, larger cheliped, merus and carpus, left, dorsal; H, same, chela, dorso-extensor, se- tae omitted; I, same, ventral; J, smaller cheliped, chela, left, dorso-extensor, setae omitted; K, larger cheliped, chela, dorso-extensor, setae omitted. Scales equal 1.0 mm. 516 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. 21, NO. 2, 2001

Ocular peduncles (Fig. 4I, J) small, with 1 having distinct transverse ridge submedially or 2 transverse striae on dorsal surface; dor- on dorsal surface; dorsoflexor margin with sal extension onto cornea weakly developed, very large, broadly rounded lobe, slightly broadly triangular with rounded apex. crenulated; ventral surface with distoflexor Basal segment of antennular peduncles corner unarmed (mesial margin near its cor- (Fig. 4H) unarmed; anterior face slightly con- ner bearing small low projection). Carpus cave, with 2 weakly developed, broadly 1.3Ð1.5 times as long as broad; dorso-exten- rounded lobes on dorsomesial margin, minutely sor margin strongly rugose; dorsoflexor mar- tuberculated on ventral margin; ventral sur- gin with strongly inflated lobe, transverse or face smooth except for 1 or 2 short, oblique slightly convex, occasionally slightly crenu- rugae; lateral margin fringed with plumose lated; dorsodistal margin with broad rounded setae. lobe on extensor part and tuft of short simple Antennal peduncles (Fig. 4I, J) slender, setae at extensor end; ventral surface with slightly rugose; first segment immovable; fol- flexor margin slightly concave. Chela narrow, lowing 3 segments movable, excluded from elongate, 1.9Ð2.0 times as long as carpus, ap- orbit, unarmed. First segment largest, strongly proximately 3.3 times as long as high, lying produced forward in lateral view, broadly in on extensor side; fingers crossed distally, cut- contact with anterior margin of carapace, with ting edges nearly transverse; dactyl opening longitudinal ridge along ventral margin; an- at moderately or strongly oblique angle; ex- terior angle narrowly rounded. Second seg- tensor margin thin, weakly convex, granu- 2 ment short. Third segment elongate, slender. lated or minutely serrated on distal ⁄3, fringed Fourth segment small, rounded. with soft or moderately stiff, short and long, Third maxillipeds (Fig. 6A) with coxa with simple setae entirely. Palm with dorsal sur- broadly (holotype) or narrowly (other speci- face convex; dorsomedian longitudinal ridge mens examined) pointed distoflexor projec- indistinct; dorsoflexor margin with longitu- tion, distomedian projection incompletely ar- dinal rugose ridge; ventral surface with ticulated. Basis articulated with ischium, sub- weakly or moderately developed longitudinal triangular with rounded edges. Ischium broad, ridge along midline, distal flexor part usually ovate, slightly rugose on ventral surface, with with several simple setae (no setae in holo- longitudinal ridge along extensor margin; type). Fixed finger with moderately or disto-extensor angle rather weakly produced, strongly curved distal claw; dorsal surface rounded. Merus with laminate, broad sub- with short simple setae; dorsoflexor proximal ovate lobe on ventroflexor margin, moder- part with broad, weakly developed, subtrian- ately rugose on ventral surface. Carpus with gular projection extending onto dactyl; cut- triangular projection on proximal region of ting edge with small, rounded or subtriangu- flexor margin and weakly developed longi- lar teeth, submedian teeth forming broad, sub- tudinal rows of short and minute rugae along triangular projection in both male and female; extensor margin on ventral surface. Propo- ventral surface usually with fringes of several dus rather elongated, subrectangular (taper- simple setae on proximoflexor part and along ing distally in holotype), nearly smooth ex- cutting edge (no setae in holotype). Dactyl cept for short rugae along extensor margin. 0.3Ð0.4 length of chela, as long as or slightly Dactyl small, subtriangular; ventral surface shorter than fixed finger, with strongly curved smooth. Merus to dactyl with long plumose distal claw; dorsal surface with longitudinal setae on flexor margin (not illustrated). Exo- ridge composed of minute tubercles along pod laminate, robust, inflated proximally, flexor margin (distal part serrated in female) with distal flagellum. and simple setae along cutting edge; cutting Chelipeds (Fig. 5BÐK) unequal, subcylin- edge usually with small, rounded or subtri- 2 drical, inflated, without distinct spines or angular teeth on distal ⁄3, proximal part with teeth, not showing distinct sexual dimorphism weakly or strongly developed, large rounded in shape; dorsal surface covered with short tooth in both male and female; ventral sur- delicate, oblique and transverse striae; ven- face with simple setae along cutting edge (no tral surface nearly smooth except for rugae setae in holotype). along flexor margins of ischium, merus and Smaller cheliped (Fig. 5E, F, J) almost palm, and extensor margin of carpus. Larger identical to larger, except for: chela narrower, cheliped (Fig. 5BÐD, GÐI, K) with merus 3.6 times as long as high, granulated or OSAWA: HETEROPOLYONYX BIFORMA AND POLYONYX UTINOMII 517

Fig. 6. Polyonyx utinomii Miyake, 1943. AÐF, holotype, male (CL 4.2 mm, SMBL 61); GÐJ, male (CL 2.9 mm, CBMÐZC 5155). A, left third maxilliped, ventral; B, right probable second ambulatory leg, lateral; C, same, merus, mesial; D, right probable third ambulatory leg, lateral; E, distal part of right probable second ambulatory leg, lateral; F, distal part of right probable third ambulatory leg, lateral; G, left first ambulatory leg, lateral; H, left second am- bulatory leg, lateral; I, left third ambulatory leg, lateral; J, distal part of left first ambulatory leg, lateral. Scales equal 1.0 mm.

3 minutely serrated on distal ⁄4 of extensor mar- as or slightly longer than fixed finger, with gin, with dactyl opening at nearly vertical an- more strongly developed, longitudinal ridge gle; fingers with more sharply pointed, distal along flexor margin, distal part usually ser- claw, cutting edges usually concave (nearly rated (minutely tuberculated in holotype). transverse in holotype), without large tooth or Ambulatory legs (Fig. 6BÐJ) short, sub- projection on fixed finger side; dactyl as long cylindrical, with scattered simple setae mar- 518 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. 21, NO. 2, 2001

Fig. 7 Entire animal, dorsal. A, Polyonyx utinomii Miyake, 1943; left, male (CL 2.5 mm); right, ovigerous female (CL 3.0 mm); CBMÐZC 5156. B, Heteropolyonyx biforma, new genus and species; upper, holotype, ovigerous fe- male (CL 3.3 mm, CBMÐZC 5158); lower, allotype, male (CL 2.5 mm, CBMÐZC 5159). ginally; lateral surface nearly smooth except Fifth pereiopod small, slender, chelate; for short rugae on meri (especially along ex- propodus with numerous short simple setae tensor margin). Ischium decalcified on distal and 0Ð2 hooked setae. region of mesial surface. Merus elongated Male with pair of developed pleopods on ovate, with lengths decreasing as first > sec- second abdominal somite (Fig. 4K); protopod ond > third legs; extensor margin unarmed naked; endopod elongated ovate with nar- but slightly crenulated, inflated in proximal rowly rounded apex (not tapering, with 1 ⁄3 (second leg) to half (first and third legs); broadly rounded apex in holotype), bearing distoflexor margins of lateral and mesial sur- numerous marginal setae except for proximal faces without spines, latter minutely granu- part; exopod small, ovate, naked. No trace of lated; mesial surface nearly transparent, de- pleopods (including small pore) on third to calcified on proximo-extensor region (in fifth abdominal somites. Female with no smaller specimens, decalcified region reduced pleopods on third abdominal somite, but with in size). Carpus elongate, with lengths de- well-developed pleopods on fourth and fifth creasing as first > second > third legs; disto- abdominal somites. extensor and distoflexor corners unarmed. Telson (Fig. 4G) composed of 7 plates; Propodus 0.8 (right probable second leg of proximolateral plates much smaller than oth- holotype)Ð1.3 (third leg of Wakayama speci- ers; distal plates moderately broad and short. men, CBMÐZC 5155) times as long as car- pus, 2.7 (right probable third leg of holo- Color (Fig. 7A).—The fresh specimens col- type)–3.8 (first and third legs of Wakayama lected from Futo (CBMÐZC 5156) had a specimen, CBMÐZC 5155) times as long as characteristic pattern, although the other ma- high; flexor margin usually with 3 small mov- terial examined was entirely faded into white able spines, distal pair larger than subdistal color because of preservation in ethanol. The (4 spines on right probable second leg and 5 color and spot pattern generally agrees with spines on right probable third leg in holo- that of the figure of male specimen of P. uti- type). Dactyl terminating in strongly curved, nomii shown by Miyake (1960: pl. 48, fig. 1). bifurcate claws, flexor claw sharply pointed, Carapace and pereiopods semitransparent much larger than extensor; flexor margin with white in ground color. Carapace with orange- 2 small corneous, fixed spines, proximal spine brown transverse lines, in the male most lines much smaller than distal and sometimes in- along cervical grooves and lateral margins are distinct (these spines broken in holotype). fused to each other; such lines are absent on OSAWA: HETEROPOLYONYX BIFORMA AND POLYONYX UTINOMII 519 cardiac and inner branchial regions. Che- 1), and two eastern Atlantic species, P. bou- lipeds with reddish-brown spots and indistinct vieri de Saint-Joseph, 1900 and P. sene- transverse lines on carpus; chela with few galensis Chace, 1956 (see Chace, 1956: figs. scattered, orange-brown spots on distal half. 13A, 14A), but those striae of P. utinomii are Ambulatory legs with reddish- or orange- distinctly longer. brown transverse bands on propodi, carpi, and As pointed out by Miyake (1943), Miyake distal parts of meri. (1937) had reported the holotype specimen of P. utinomii as P. asiaticus Shen, 1936. Poly- Habit.—The specimens examined inhabit onyx asiaticus is currently regarded as a ju- tubes of polychaetes of the genus Chaetop- nior subjective synonym of P. sinensis, as dis- terus. Polyonyx utinomii probably occurs as cussed by Johnson (1958). In addition to the a male/female pair in normal case. two distinguishing characters of P. utinomii from the other Polyonyx species of the Indo- Distribution.—Only known from Japan (cen- West Pacific mentioned above, P. utinomii tral Pacific coast of Honshu mainland and differs from P. sinensis in the following fea- western coast of Kyushu) and the Maldives. tures: (1) the rostrum has short setae on the The present record of this species from the anterior margin (no setae in P. sinensis); (2) Maldives greatly extends its geographical dis- the merus of the third maxilliped is provided tribution westwards into the Indian Ocean. with a broad lobe on the ventroflexor margin (narrow and smaller lobe in P. sinensis); and Remarks.—The holotype specimen differs (3) the carpus of the cheliped has a more somewhat from the other specimens exam- strongly inflated dorsoflexor lobe, and the ined in the form of the ambulatory legs. The margin of the lobe is transverse or slightly relative lengths of the propodus against the convex (the dorsoflexor margin is moderately carpus and its height are shorter, and there are or strongly convex in P. sinensis) (see Shen, more spines on the flexor margin of propodus 1936: figs. 1a, 2a, as P. asiaticus; Miyake, in the holotype (see above description and 1943: figs. 56, 57C). Fig. 6B, D, GÐI). These may be due to the holotype being older and considerably larger ACKNOWLEDGEMENTS than the rest of the specimens (see “Material I thank K. Nomura of the Yaeyama Marine Park Re- Examined”). Minor morphological differ- search Station and Dr. E. Nishi of the Manazuru Marine Laboratory for Science Education, Yokohama National Uni- ences between the holotype and the other versity, for providing the porcellanid material. K. Nomura specimens examined are also found in the also kindly provided me with a photograph of Hetero- forms of the coxa and propodus of the third polyonyx biforma for publication. I am indebted to Dr. S. maxilliped and the fingers of the smaller che- Kubota of the Seto Marine Biological Laboratory, Kyoto liped, and the setation on the ventral surface University, for arranging the loan of the holotype speci- men of Polyonyx utinomii. Dr. P. K. L. Ng of the National of the chelae. Although the form of chelipeds University of Singapore and Dr. C. B. Boyko of the Ameri- does not show a distinct sexual dimorphism, can Museum of Natural History kindly offered valuable the median branchial margins of the carapace comments on the manuscript. This study was supported are different in a male/female pair. They are in part by a research fellowship of the Japan Society for subparallel in male but are inflated in female the Promotion of Science for young scientists. (see Fig. 4C, D). LITERATURE CITED Although P. utinomii belongs to the P. Chace, F. A., Jr. 1956. Porcellanid crabs. Expédition sinensis group of Johnson (1958), it is still Océanographique Belge dans les Eaux Côtières very distinct. This species is readily distin- Africaines de l’Atlantique Sud (1948–1949).—Résul- guishable from the other Indo-West Pacific tats Scientiques 3: 1Ð54. Bruxelles. species of Polyonyx by the carapace and che- de Saint-Joseph, B. 1900. Sur quelques invertébrés lipeds having numerous transverse and marins des cotes du Sénégal.—Annales des Sciences naturelles, série 8, Zoologie et paléontologie 12: oblique striae on the entire dorsal surface and 217Ð248. the meri of the chelipeds provided with a very Haig, J. 1960. The Porcellanidae (Crustacea Anomura) large, broadly rounded lobe on the dor- of the eastern Pacific.—Allan Hancock Pacific Expe- soflexor margin. The numerous striae on the dition 24: iÐviii, 1Ð440. ———. 1965. The Porcellanidae (Crustacea, Anomura) transversely ovate carapace may be also ob- of Western Australia with descriptions of four new Aus- served in an eastern Pacific species, P. confi- tralian species.—Journal of the Royal Society of West- nis Haig, 1960 (see Haig, 1960: pl. 17, fig. ern Australia 48: 97Ð118. 520 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. 21, NO. 2, 2001

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