Pagurus tabataorum, Osawa, 2012

Osawa, Masayuki, 2012, A new species of the genus Pagurus Fabricius, 1775 (Crustacea: Decapoda: Anomura: Paguridae) from the Ryukyu Islands, southwestern Japan *, Zootaxa 3367 (1), pp. 155-164 : 155-162

publication ID	https://doi.org/ 10.11646/zootaxa.3367.1.15
persistent identifier	https://treatment.plazi.org/id/03FE87E1-FFA0-E055-FF49-8AB8FB7DFC5E
treatment provided by	Felipe
scientific name	Pagurus tabataorum
status	sp. nov.

Treatment

Pagurus tabataorum n. sp.

[New Japanese name: Chura-honyadokari]

( Figs. 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

Type material. Holotype: KUMEJIMA 2009, St. Dredge 11, 26° 22.670 –22.806 ʹN, 126° 48.035 –48.327 ʹE, 68 m, 10 November 2009, male (sl 4.0 mm), RUMF-ZC-1508. GoogleMaps

Description. Eleven pairs of biserial, phyllobranchiate gills.

Shield ( Fig. 1A View FIGURE 1 ) 1.1 times as long as broad; anterior margins between rostrum and lateral projections concave; anterolateral margins sloping, posterior margin roundly truncate; dorsal surface with few tufts of short setae anterolaterally. Rostrum roundly triangular, terminating bluntly. Lateral projections obtusely triangular, not reaching level of rostral tip, each with marginal spinule. Posterior carapace membranous, with pair of tufts of short setae on anteromedian part; posteromedian plate narrow, with subparallel lateral margins; sulci cardiobranchiales slightly sinuous, extending to midlength between cervical groove and posteromedian margin of carapace.

Ocular peduncles ( Fig. 1A View FIGURE 1 ) about 0.7 times as long as shield, moderately stout, not inflated basally, each with row of tufts of short setae on dorsal midline and few short setae on mesial surface; corneas slightly dilated, corneal width 0.4 times peduncular length. Ocular acicles narrowly subtrianbular, terminating bluntly and with submarginal spine, separated by basal width of more than one acicle; dorsal surface slightly grooved. Interocular lobe small, visible in dorsal view.

Antennular peduncles ( Fig. 1A View FIGURE 1 ), when fully extended, overreaching ocular peduncles by half-lengths of ultimate segments. Basal segment with small spine on lateral margin located slightly distal to midlength; distolateral angle produced in small rounded lobe. Penultimate segment with few short setae on dorsodistal margin. Ultimate segment relatively short, 0.4 times as long as shield, broadened distally in lateral view, with row of 3 setae dorsolaterally, distal seta longest. Dorsal flagellum with distal portion 1.3 times longer than proximal, aesthetascbearing portion.

Antennal peduncles ( Fig. 1A View FIGURE 1 ) moderately long, slightly overreaching distal corneal margins. First segment with spinule on lateral face, ventromesial distal margin produced, with small spine just lateral to antennal gland opening. Second segment with dorsolateral distal angle produced, reaching nearly to midlength of third segment, terminating in bifid spine; dorsomesial distal angle with small spine; tufts of sparse setae present. Third segment with small spine on ventrodistal margin and tufts of sparse setae. Fourth and fifth segments with few marginal setae, fifth segment about 2.2 times as long as fourth segment. Antennal acicle slender, weakly arcuate, reaching distal corneal margin and to half-length of fifth peduncular segment, terminating bluntly, with 2 irregular rows of tufts of sparse setae mesially. Antennal flagellum moderately long, each article with few short setae distally.

Third maxilliped ( Fig. 1B, C View FIGURE 1 ) with endopod moderately long and slender; carpus and merus unarmed; ischium and basis incompletely fused; ischium with row of 15 closely spaced teeth on crista dentata, 3 accessory teeth present; basis with 1 tiny tooth on mesial margin.

Chelipeds ( Figs. 2 View FIGURE 2 , 3 View FIGURE 3 ) grossly unequal. Right cheliped ( Figs. 2A–C View FIGURE 2 , 3A, B View FIGURE 3 ) massive. Chela suboval, 1.5 times longer than wide and 1.9 times longer than carpus; transverse scutes each with row of short plumose setae. Dactylus 0.7 length of palm; dorsal surface strongly convex, with interrupted arcuate scutes; dorsomesial margin with shallow sulcus between 2 rows of arcuate scutes; mesial surface with short scutes; ventral surface with short transverse ridges laterally on proximal part and some tufts of short setae; cutting ridge with 4 blunt calcareous teeth, terminating in blunt calcareous claw. Palm 1.2 times longer than carpus; dorsal surface strongly convex, slightly elevated on midline, covered with sinuous, transverse scutes, distal scutes arcuate and with single oblique row of short soft, somewhat flask-shaped capsules, distolateral part also with 2 irregularly arranged longitudinal rows of short capsules extending onto half length of fixed finger; dorsal surface of fixed finger also convex, with short and long, arcuate scutes; dorsolateral margin slightly arched on palm and strongly convex on fixed finger, delimited by blunt crest of short arcuate scutes extending onto tip of fixed finger; dorsomesial margin nearly straight, delimited by 2 irregular rows of short arcuate ridges; ventral surface convex, with short arcuate ridges bearing tufts of setae on lateral and mesial part; ventral surface of fixed finger with scattered tufts of setae; cutting edge with 8 blunt, proximally diminishing calcareous teeth, terminating in blunt calcareous claw. Carpus subequal in length to merus, widened distally in dorsal view; dorsal surface weakly convex, with row of 3 small spines on distal half of midline, 2 median spinules laterally on midline, 2 somewhat remote spines distally adjacent to dorsomesial margin, and scattered short ridges, ridges on distal half bearing short plumose setae and those on proximal half with sparse, long simple setae; dorsolateral margin not delimited; dorsomesial margin delimited by blunt carina, with row of 4 spines and sparse long setae on distal half; lateral surface dorsally with short transverse ridges; mesial surface with sparse long setae dorsally and distally; ventral surface strongly convex, with row of short setae on distal margin. Merus strongly convex and smooth on dorsal surface, dorsodistal margin with row of setae; lateral surface smooth, with some short setae ventrally; ventrolateral margin strongly convex in lateral view, with 3 small spines and moderately long setae on distal half; ventromesial margin strongly convex in mesial view, with 2 small rounded tubercles and moderately long setae on distal half; ventral surface flattish, with low, blisterlike protuberances adjacent to ventrolateral margin. Ischium unarmed, with few tufts of short setae.

Left cheliped ( Figs. 2D, E View FIGURE 2 , 3C, D View FIGURE 3 ) moderately slender, nearly reaching to half-length of right dactylus, moderately compressed laterally. Chela elongate suboval, 2.8 times longer than wide and 1.2 times longer than carpus; dactylus and fixed finger not curved ventrally, without hiatus; transverse scutes each with row of short plumose setae. Dactylus approximately as long as palm; surfaces with sparse tufts of short to moderately long setae; dorsal surface weakly convex, with small blunt tubercle proximally; dorsomesial margin not delimited; cutting edge with row of closely set corneous teeth on entire length, terminating in small corneous claw. Palm 0.6 length of carpus; dorsal surface convex, bluntly but distinctly elevated on midline, with short arcuate scutes on lateral half, row of short soft, somewhat flask-shaped capsules adjacent to distal dorsolateral margin extending onto proximal 0.3 of fixed finger, 3 capsules also present on distolateral part; dorsal surface of fixed finger with sparse, short arcuate ridges and tufts of setae; dorsolateral margin delimited by row of short arcuate scutes extending onto distal 0.3 of fixed finger; lateral surface also with short arcuate scutes; dorsomesial margin not distinctly delimited; mesial surface almost smooth, but with some tufts of setae; ventral surface convex, with longitudinal row of short arcuate ridges laterally and sparse tufts of moderately long setae on mesial half; cutting edge with row of closely set corneous teeth on entire length, terminating in relatively large corneous claw. Carpus widened distally in dorsal view, slightly shorter than merus; dorsolateral and dorsomesial margins each with row of small spines, dorsomesial spines stronger than dorsolateral, spines of each row bearing short plumose setae on distal half and moderately long simple setae on proximal half; dorsal surface narrow, flat; lateral surface with slightly arcuate ridges bearing short plumose setae; mesial surface with sparse tufts of moderately long setae; ventral surface slightly convex, with sparse setae. Merus with sparse short setae on dorsal surface, dorsodistal margin with row of moderately long setae; lateral surface with short ridges; ventrolateral margin with row of small distal spines, proximal protuberances, and sparse setae; mesial surface nearly smooth, with few short setae; ventromesial margin with small subproximal spine and moderately long setae; ventral surface flattish, with some blister-like protuberances adjacent to ventrolateral and ventromesial margins. Ischium with scattered setae.

Ambulatory legs ( Fig. 4 View FIGURE 4 ) similar from right to left, moderately slender, right second pereopod overreaching tip of right cheliped by half length of dactylus. Dactyli 1.1–1.3 length of propodi, 6.3–6.7 (second) or 7.3–8.1 (third) longer than proximal wide, slightly curved ventrally in lateral view, weakly curved mesially in dorsal view, terminating in moderately long corneous claws; dorsal margins each with row of 7–9 corneous spines and sparse setae; lateral faces each with shallow longitudinal sulcus dorsoproximally and rows of sparse setae along dorsal and ventral margins; mesial faces each with very shallow longitudinal sulcus dorsoproximally and row of 4 (second) or 6–7 (third) corneous spinules and few short setae adjacent to dorsal margin, additional short row of 2– 4 spinules present on proximal midline in third pereopod; ventral margins each with 8 or 9 slender corneous spines increasing in size distally. Propodi slightly tapering distally in lateral view, 4.1–4.3 (second) or 3.7–4.1 (third) times longer than distal wide, right third pereopod stouter than left third pereopod; dorsal and ventral surfaces each with row of sparse setae; lateral and mesial faces smooth; ventral surfaces slightly convex, each with row of 5 or 6 small corneous spines including 2 spines on distal margin. Carpi with tufts of sparse setae on dorsal, lateral, and mesial surfaces; dorsal surfaces each with small spine at dorsodistal angle, additional median small spine present mesially on second pereopod but absent on third pereopod. Meri compressed laterally, unarmed, with sparse setae on dorsal and ventral surfaces; lateral and mesial surfaces with few short setae; ventrolateral distal margins nearly straight.

Fourth pereopods ( Fig. 1D, E View FIGURE 1 ) semichelate, subequal in size, right slightly larger than left. Dactyli each with row of small corneous teeth on ventral margin; dorsal margin with row of tufts of short setae; preungual process slightly shorter than distal corneous claw, tube-like. Propodi each with prominent tuft of setae distally on dorsal margin; rasp consisting of 5 irregularly arranged rows of subovate corneous scales. Carpi and meri unarmed but bearing tufts of sparse setae on dorsal and ventral margins.

Fifth pereopods chelate; coxae equal in size, male gonopores partially obscured by tuft of short setae.

Anterior lobe of sixth thoracic sternite ( Fig. 1F View FIGURE 1 ) subsemicircular, with row of setae on anterior margin, setae longest in medial portion. Eighth thoracic sternite developed anteriorly as 2 compressed, rounded lobes separated by shallow median depression, anterior margin with row of setae.

Pleon dextrally twisted. Male with unequally biramous second to fifth left pleopods, endopods much smaller than exopods. Female unknown.

Telson ( Fig. 1G View FIGURE 1 ) with transverse indentations weakly delimited, each with tuft of sparse setae; posterior lobes slightly asymmetrical, separated by very small median cleft; terminal margins strongly oblique, each with row of 14 (right) or 19 (left) small spines extending onto lateral margins.

Colouration in life ( Fig. 5 View FIGURE 5 ). Shield with various sized light red markings on white ground colour. Posterior carapace pale red, with scattered small red spots. Ocular peduncles white, each with broad red ring at midlength. Antennular peduncles light red, ultimate segment with distal white ring. Antennal peduncles also light red, with irregular white marks. Chelipeds reddish brown; palms with some small red spots, ventromesial surface of right palm with moderately large red blotch; carpi and meri with white reticular pattern. Ambulatory legs light red; dactyli with white marks on median part and adjacent to distal brown corneous claw; propodi with irregular white marks on proximal and distal parts; meri with white reticular pattern.

Etymology. The new species is named in honor of Captain Eizo Tabata and his two sons, Atsushi and Yuji Tabata, of the fishing boat that operated dredging and trawling in the period of the KUMEJIMA 2009 Expedition. Their skillful efforts resulted in many new findings of coastal invertebrates around Kume Island, including the present new hermit crab.

Distribution. Only known from the type locality, Kume Island, Ryukyu Islands, at the depth of 68 m.

Remarks. Pagurus tabataorum n. sp. is unique for the genus in having many arcuate or sinuous, transverse scutes on the dorsal surface of the chelae. Such scutes are not known in other Pagurus species.

The new species appears close to the following seven Indo-West Pacific species: P. capsularis McLaughlin, 1997 ; P. hirtimanus ( Miers, 1880) ; P. japonicus ( Stimpson, 1858) ; P. pergranulatus ( Henderson, 1896) ; P. rubrior Komai, 2003 ; P. similis ( Ortmann, 1892) ; and P. sinuatus ( Stimpson, 1858) in having small slender capsules on the dorsal surface of the chelae, although the number of the capsules seems to be much fewer in P. tabataorum n. sp. (cf. Komai 2003a; McLaughlin 1997; de Saint Laurent & McLaughlin 2000). This character represents a possible synapomorphy, and thus the eight species can be assumed to be phylogenetically related.

Pagurus tabataorum n. sp. may be closest to P. capsularis known from Tanimbar Islands, Indonesia, in having the following characters: shield slightly longer than broad, with an obtusely triangular rostrum; ocular peduncles relatively robust, each with slightly dilated cornea; carpi of the chelipeds comparatively less spinose or tuberculate, without small slender capsules on the dorsal surface; slender dactyli and propodi of the ambulatory legs; and telson with strongly oblique, terminal margins. However, aside from the possession of transverse scutes on the dorsal surface of the chelae, P. tabataorum n. sp. is distinguished from P. capsularis by the absence of rows of distinct spines on the dorsolateral margin and dorsomidline of each chela and on the dorsomesial margin of the right chela. Pagurus pergranulatus somewhat resembles P. tabataorum n. sp. in general appearance, but differs in the right chela with a distinctly produced, subacute lobe at the dorsomesial distal angle (cf. Alcock & Anderson 1897: pl. 31, fig. 1) and the merus of the right cheliped with a distinct, somewhat wing-like ventrally produced lobe on the ventromesial margin (cf. McLaughlin 1997). The strongly oblique terminal margins of the telson discriminates P. tabataorum n. sp. from P. hirtimanus , P. japonicus , P. rubrior , P. similis , and P. sinuatus . In the latter five species, the mentioned margins are weakly oblique or nearly transverse. Pagurus tabataorum n. sp. is further distinguished from P. japonicus , P. rubrior , P. similis , and P. sinuatus in the absence of tubercles each with a small slender capsule on the dorsal surface of the carpi of the chelipeds. Pagurus similis is similar to P. tabataorum n. sp. in having relatively slender propodi and dactyli of the ambulatory legs, but different in that the ocular peduncles are much more slender, the right chela is armed with rows of distinct spines on the dorsolateral and dorsomesial margins, and the left chela has rows of distinct spines on the dorsolateral margin and dorsomidline. Pagurus hirtimanus is distinguishable from P. tabataorum n. sp. in that the rostrum terminates in an acute spine, the ocular peduncles are strongly concave on the lateral and mesial margins, the right chela has rows of spines on the dorsolateral and dorsomesial margins and dorsomidline, and the left chela is provided with rows of spines on the dorsolateral margin and dorsomidline.

Alcock (1905) noted that “A variety (of P. pergranulatus ) from the south coast of Ceylon is characterized by the sculpture of the outer surface of the palm and fingers of both chelipeds, where depressed squamiform granules form an unbroken mosaic”. This suggests that the Alcock’s specimen might represent the present new species, although reexamination of his specimen is necessary to finally determine the specific identity.