Pagurixus maorus ( Nobili, 1906 )

Komai, Tomoyuki & Osawa, Masayuki, 2006, A review of the Pagurixus boninensis species group, with descriptions of six new species (Crustacea: Decapoda: Anomura: Paguridae), Zootaxa 1214 (1), pp. 1-107 : 17-25

Pagurixus maorus ( Nobili, 1906)

( Figs. 4–7 , 44A , 47 )

Eupagurus maorus Nobili, 1906: 259 [type locality: Rikitea, Mangareva, Gambier Islands].—1907:

371, pl. 1, fig. 9.— Forest, 1954: 73; 1956: 52. Pagurus maorus .— Gordan, 1956: 331. Pagurus (Pagurixus) maorus .— Dechancé, 1964: 37.— Ball & Haig, 1972: 103.— Lewinsohn,

1982: 58. Pagurixus maorus .— McLaughlin & Haig, 1984: 127, fig. 2.— Komai & Asakura, 1995: 347, figs.

4–6.— Paulay et al., 2003: 490.

Type material

(Not examined). HOLOTYPE: MNHN, ovigerous female, Rikitea , Mangareva, Gambier, French Polynesia .

Other material. Ryukyu Islands: CBM­ZC 381, 1 male (SL 3.4 mm), 1 ovigerous female (SL 3.1 mm), Hiyajo, Kume­jima Island , Okinawa Islands , coll. S. Hirayama, 13 August 1993 ; CBM­ZC 382, 2 males (SL 3.3, 4.0 mm), 1 ovigerous female (SL 3.0 mm), Madomari Port, Kume­jima Island , coll. S. Hirayama, 28 August 1993 ; CBM­ZC 3114, 2 ovigerous females (SL 2.4, 3.1 mm), Madomari Port, Kume­jima Island , 8–10 m, SCUBA diving, coll. K. Nomura, 11 June 1995 ; CBM­ZC 5853, 1 female (SL 2.6 mm), Ahra Beach, Kume­jima Island , intertidal, coll. T. Komai, June 1995 ; CBM­ZC 8173, 1 ovigerous female (SL 2.7 mm), Uehara Beach, Iriomote Island, Yaeyama Islands , subtidal, Acropora sp. , coll. T. Komai, 16 July 2000 ; CBM­ZC 8471, 1 male (SL 2.8 m), Ahra Beach, Kume­jima Island , 2 July 2000 , coll. M. Osawa. Guam: UF 343 , 1 ovigerous female (SL 2.6 mm), Orote Peninsula , 10–20 m, coll. G. Paulay, 22 February 2000 ; UF 602 , 1 female (CL 2.6 mm), Gun Beach , fore reef, 3–20 m, coll. J. Starmer & L. Kirkendale, 17 January 1997 . Indonesia: UF 5629 , 1 ovigerous female (SL 4.3 mm), Nusa Penida, off Lembongan flat, Bali, 10–15 m, coll. L. Kirkendale, 20 December 1999 . Samoa: UF 3280 , 1 female (SL 2.3 mm), Pagopago main harbor dock, Tuituilia Island, American Samoa , 14°16.59’S, 170°41.26’W, 1–8 m, coll. V. Bonito, 15 October 2002 . Tuamotu Archipelago: UF 1816 , 3 ovigerous females (SL 2.6–3.6 mm), Tikehau Atoll , 1–5 m, coll. G. Paulay, 10 January 2001 .

Description

Shield ( Fig. 4A ) 1.0–1.1 times as long as broad; anterior margin between rostrum and lateral projections concave; anterolateral margins sloping; dorsal surface slightly convex. Rostrum triangular, distinctly overreaching lateral projections. Lateral projections triangular, weakly produced, with small submarginal spine.

Ocular peduncle ( Fig. 4A ) moderately long, stout, 0.6–0.7 length of shield, with row of tufts of short setae on dorsal surface mesially; cornea somewhat dilated, corneal width 0.4–0.5 of peduncular length; basal part slightly inflated, narrower than corneal width. Ocular acicles subovate or subtriangular, each with very small submarginal spine.

Antennular peduncle ( Fig. 4A ) overreaching distal margin of cornea by 0.2–0.3 length of ultimate segments. Ultimate segment with short seta at dorsolateral distal angle; 2 longitudinal rows of comparatively long setae present on ventral surface (setae directed posterolaterally) ( Fig. 4C ). Basal segment with small lateral spine on statocyst lobe. Ventral flagellum with numerous long setae on lateral and mesial margins.

Antennal peduncle ( Fig. 4A ) overreaching distal margin of cornea by 0.2–0.3 length of fifth segment. Second segment with small spine at dorsomesial distal angle; laterodistal projection not reaching midlength of fourth segment, terminating in simple or bifid spine. Antennal acicles moderately long, overreaching base, but not reaching distal margin of cornea; mesial margin with row of tufts of short to moderately long, stiff setae. Antennal flagellum very long, exceeding 9.0 times of shield length.

Right cheliped of adult males ( Fig. 5 ) greatly elongate. Chela subrectangularly lengthened in dorsal view, 2.6–3.7 times longer than wide. Dactylus about 0.4–0.8 length of palm, strongly curved ventrally, terminating in small calcareous claw; dorsomesial margin not delimited; surfaces minutely granular, ventral surface with numerous tufts of long setae; cutting edge with 1 or 2 very low calcareous teeth. Palm greatly elongate, longer than carpus; convex dorsal surface covered with fine granules, dorsolateral margin faintly delimited in distal half, not delimited in posterior half, dorsomesial margin not delimited; lateral, mesial and ventral surfaces also finely granular, with scattered tufts of long setae on ventral surface. Fixed finger with dorsolateral margin weakly delimited; cutting edge with 1 large, low tooth, terminating in calcareous claw. Carpus 1.9–2.2 times longer than distal width, slightly longer than merus; dorsomesial and dorsolateral margins not clearly delimited, but with dorsomesial row of 2–5 moderately small spines in proximal half; all surfaces finely granular, lateral surface smooth or with faint longitudinal ridge of small granules on midline. Meral­carpal articulation with about 10–15° of clockwise rotation; dorsal surface of merus with row of low transverse ridges, dorsodistal margin with 0–3 small spines; lateral face with short vertical ridges dorsally and minute ridges ventrally, ventrolateral margin with 2 or 3 small spines distally and remainder unarmed; mesial face with small granules ventrally, ventromesial margin with row of closely set small spines in distal half, unarmed in proximal half; ventral surface slightly convex, covered with coarse granules and with scattered long setae. Ischium with smooth ventromesial margin; surfaces unarmed.

Right cheliped of female ( Fig. 6A–C ) moderately long, slender for genus. Chela subovate in dorsal view, about 2.4–2.6 times longer than broad. Dactylus subequal to or slightly longer than palm; dorsomesial margin delimited by row of granules; mesial face with row of granules on midline; surfaces with sparse tufts of setae; cutting edge with 1 or 2 low calcareous teeth in proximal half and row of small corneous teeth in distal half, terminating in small corneous claw. Palm shorter than carpus; midline of dorsal surface with slight elevation bearing row of small granules; dorsolateral margin delimited by granular ridge extending nearly to tip of fixed finger; dorsomesial margin also delimited by row of small granules; dorsal surface with scattered small granules; lateral, mesial and ventral surfaces with scattered low granules; scattered long setae on ventral surface. Carpus 2.0–2.4 times longer than distal width, slightly shorter than merus; dorsolateral and dorsomesial margins each weakly delimited by row of moderately small spines (spines of dorsomesial row larger than those of dorsolateral row); all surfaces with scattered small granules, lateral surface divided into two sections (oblique dorsal and perpendicular ventral sections) by distinct, granular median ridge. Merus with 1 or 2 low transverse ridges subdistally on dorsal surface, dorsodistal margin unarmed; lateral face with numerous minute vertical ridges, ventrolateral margin with 1 small subdistal spine followed by row of small spinulose tubercles extending to midlength; mesial face with short vertical ridges ventrally, ventromesial margin weakly tuberculate, but without distinct spines. Ischium with faintly denticulate ventromesial margin; surfaces unarmed.

Left cheliped ( Fig. 6D–F ) similar between male and female, elongate, slender. Chela 2.8–3.0 times longer than broad. Dactylus slightly longer than palm, with sparse tufts of setae on surfaces (setae on ventral surface longest); dorsal surface nearly smooth, dorsomesial margin not delimited; cutting edge with fine row of long corneous teeth in distal half, terminating in small corneous claw. Palm about half length of carpus; dorsal surface weakly elevated in mid­line and armed with row of small granules extending onto base of fixed finger, sloping mesial part with scattered small granules; dorsomesial margin delimited by row of small granules; lateral part of dorsal surface also sloping, dorsolateral margin delimited by granular ridge; lateral, mesial, ventral surfaces each with scattered low granules and tufts of short to long setae. Carpus elongate, subcylindrical, 0.9–1.0 length of chela and subequal in length to merus; length 2.7–3.0 of distal width and 3.3–3.6 of greatest height; dorsolateral and dorsomesial margins each delimited by row of small spines decreasing in size proximally and tufts of long setae; lateral surface divided into oblique dorsal and perpendicular ventral sections by row of granules or granular ridge on midline; mesial surface with several scattered small granules dorsally; ventral surface smooth, with scattered long setae. Merus with smooth dorsal surface bearing row of tufts of short setae; dorsodistal margin unarmed, but with several long bristles; lateral surface with scattered low granules, ventrolateral margin with 1 or 2 small spines distally, otherwise smooth; mesial face smooth, ventromesial margin unarmed. Ischium with smooth ventromesial margin; surfaces unarmed.

Ambulatory legs ( Fig. 7A, B ) comparatively long and slender, similar from right to left. Dactyli ( Fig. 7C, D ) 0.8–0.9 length of propodi in second, 1.0–1.1 length in third, 7.6–9.9 times longer than high, terminating in large corneous claws; dorsal surfaces each with sparse row of short setae; lateral and mesial faces each with few tufts of short setae, mesial faces each also with row of corneous spinules adjacent to dorsal margin, spines on third more numerous than those on second; ventral margins each with 8–10 long corneous spines notably increasing in size distally. Propodi slightly tapering distally, 5.0–6.0 times longer than high; dorsal surfaces smooth (second) or with row of low protuberances (third), each with row of tufts of moderately short setae; lateral faces nearly smooth; ventral margins each with row of 3–5 corneous spinules, ventrodistal margins with paired corneous spines. Carpi each with small dorsodistal spine; dorsal surfaces smooth, with tufts of moderately short to long setae; lateral faces nearly smooth. Meri each with row of low protuberances (second) or smooth (third) on dorsal surface, and with dorsal row of tufts of short setae; lateral surfaces slightly granular (second) or smooth (third); ventrolateral distal margins each with small subdistal spine (second) or unarmed (third), ventral surfaces with row of low protuberances (second) or smooth (third), and with tufts of moderately short setae.

Fourth pereopods ( Fig. 4D–F ) similar from right to left in both male and female. Dactyli terminating in small corneous claws, each with row of moderately long setae on dorsal margin. Propodi each with longitudinal row of tufts of short setae on nearly flat mesial face.

Anterior lobe of sixth thoracic sternite ( Fig. 4G ) subrectangular, anterolateral angles rounded; anterior margin with row of moderately short setae. Eighth thoracic sternite ( Fig. 4H ) composed of 2 subequal, closely set, rounded lobes.

Males with coxae of fifth pereopods ( Fig. 4H ) slightly unequal. Right coxa with tuft of long stiff setae directed toward left and reaching to left coxa; posteromesial protrusion absent, no papilla­like sexual tube apparent. Left coxa with gonopore partially masked by tuft of short setae directed anteriorly. Female with paired gonopores.

Telson ( Fig. 4I ) with terminal margins slightly oblique, each bearing 3–5 large spines.

Variation. Variation exhibited in the present material clearly suggests that the right cheliped in males of this species is considerably lengthened with increasing animal size. Furthermore, the armature of the right cheliped varies with increasing body size. In the smallest male examined here (SL 2.8 mm), the dorsomesial and dorsomesial margins of the carpus are weakly delimited by a row of small spines, with two median spines on the dorsomesial margins being larger than others. In large specimens, the armature on the carpus is considerably reduced.

Colour in life. ( Fig. 44A ) Ultimate segment of antennular peduncle generally transparent, with red stripe on dorsolateral and dorsomesial margins. Fifth segment of antennal peduncle with each margin edged with red; flagellum with alternating red (2 or 3 articles) and white (1 article). Chelipeds with several red and white or pale brown longitudinal stripes; dactylus of right cheliped whitish. Ambulatory legs also with narrow red and white or pale brown stripes; distal parts of propodi whitish.

Distribution

French Polynesia, Enewetak Atoll, Marshall Islands, Indonesia (new record), and Ryukyu Islands ( Fig. 47 ); intertidal to 20 m.

Remarks

Nobili’s (1906) original description is brief and preliminary. His subsequent description of the holotype of P. maorus ( Nobili 1907) was relatively detailed, and provides some important species specific features, including the striped color of the chelipeds and ambulatory legs, which made recognition of this species easy.

As summarized in Table 1, P. maorus can be distinguished from the other species in subgroup A by a suite of characters, including the setation of the ultimate segment of the antennular peduncle, greatly elongate palm of the male right cheliped, slender carpus of the left cheliped, being subequal or slightly shorter than the chela, comparatively slender ambulatory legs, relatively broad, subrectangular anterior lobe of the sixth thoracic somite with rounded anterolateral angles, and large spines on the terminal margins of the telson. Although the male right cheliped may be subject to size­related variation, the unusually elongate palm is still useful in recognizing adult males of P. maorus . The striped color of the chelipeds and ambulatory legs is also characteristic of this species, and therefore, if the color pattern is still preserved, this species will be immediately recognizable. In the structure of the setal rows on the ultimate segment of the antennular peduncle and the general shape of the sixth thoracic sternite, P. maorus appears most similar to P. concolor n. sp.

As P. maorus was described from a single female specimen and P. laevimanus from a single male, and the illustrations and brief descriptions of each bore some resemblance to one another; Forest (1954, 1956) suggested that the differences between the two taxa might be a result of sexual dimorphism. As shown in this study, there is no doubt that the two species are distinct.

Figures

FIGURE 4. Pagurixus maorus (Nobili, 1906). Male (SL 3.4 mm) from Kume­jima Island (CBM­ ZC 381). A, shield and cephalic appendages, dorsal view; B, left antennule, lateral view; C, ultimate segment of left antennular peduncle, ventral view; D, dactylus and propodus of left fourth pereopod, lateral view; E, same, mesial view; F, dactylus and propodus of right fourth pereopod, lateral view; G, sixth thoracic sternite, ventral view; H, coxae of fifth pereopods and eighth thoracic sternite, ventral view; I, telson, dorsal view. Scale bars: 1 mm for A, H; 0.5 mm for B, C–G, I.

FIGURE 5. Pagurixus maorus (Nobili, 1906). Male (SL 3.4 mm) from Kume­jima Island (CBM­ ZC 381). Right cheliped. A, chela of right cheliped, dorsal view; B, entire right cheliped, mesial view; C, same, lateral view; D, carpus, dorsal view. Scale bar: 2 mm.

FIGURE 6. Pagurixus maorus (Nobili, 1906). A–C, ovigerous female (SL 2.7 mm) from Iriomote Island (CBM­ZC 8173); D–F, male from Kume­jima Island (CBM­ZC 381). A, right cheliped, chela and carpus, dorsal view; B, entire right cheliped, mesial view; C, same, lateral view; D, left cheliped, chela and carpus, dorsal view; E, entire left cheliped, mesial view; F, same, lateral view. Scale bar: 1mm.

FIGURE 7. Pagurixus maorus (Nobili, 1906). Male (SL 3.4 mm) from Kume­jima Island. A, right second pereopod, lateral view; B, left third pereopod, lateral view; C, right second pereopod, dactylus and distal part of propodus, mesial view; D, left third pereopod, dactylus and distal part of propodus, mesial view. Scale bars: 1 mm.

FIGURE 44. A, Pagurixus maorus (Nobili, 1906), male (SL 3.9 mm) from Kume­jima Island, Ryukyu Islands, photo taken by M. Osawa; B, Pagurixus tweediei (Forest, 1956), male (SL 3.9 mm) from Tahiti, Society Islands, French Polynesia (UF 1731), photo taken by G. Paulay; C, Pagurixus nomurai Komai & Asakura, 1995, ovigerous female from Guam, Mariana Islands (UF), photo taken by G. Paulay; D, Pagurixus concolor n. sp., paratype female (SL 3.2 mm) from Tokashiki Island, Kerama Islands (CBM­ZC 8484), photo taken by M. Osawa.

FIGURE 47. Geographic distribution of Pagurixus laevimanus (), P. maorus (), P. tweediei (), P.nomurai (), P. pulcher () and P. concolor n. sp. ().