Micropagurus polynesiensis ( Nobili, 1906 )

Asakura, Akira, 2005, A review of the genus Micropagurus (Crustacea Decapoda Anomura Paguridae), Zootaxa 1090 (1), pp. 1-34 : 21-31

Micropagurus polynesiensis ( Nobili, 1906) ( Figs. 14–18 , 19A–C , 20 )

Anapagurus polynesiensis Nobili, 1906: 260 ; 1907: 372, pl. 1: fig. 10.— Forest, 1956: 1056.— Chevalier et al., 1968: 119.

Micropagurus polynesiensis .— Haig & Ball, 1988: 184.— Poupin, 1996: 18, 78 (checklist).

Micropagurus vexatus Haig & Ball, 1988: 181 , figs 11, 12.

Material Examined. Syntypes: 1♂, SL = 1.5 mm, 2♀, SL = 1.2 mm (1 female damaged, not measured), Rikitea, French Polynesia, coll. M. Seurat, MNHN­Pg 2765. Other material: PACIFIC OCEAN: Loyalty Islands: 1♀, SL = 1.8 mm, stn. 1452, 2­ 25 m, between Cape Mandé and Cape Lefèvre (=Nem), Santal Bay, Lifou Island, 20°54.6'S, 167°02.1' E, 20, 22 Nov. 2000, LIFOU, MNHN­Pg 7251; 2♂, SL = 1.2, 1.8 mm, 1 ov. ♀, SL = 2.0 mm, stn. 1453, 21– 30 m, on gorgonians, underwater cliff, between Cape Mandé and Cape Lefèvre (=Nem), Santal Bay, Lifou Island, 20°54.6'S, 167°02.1' E, 22 Nov. 2000, MNHN­Pg 7252; 1♂, SL = 1.0 mm, stn. 1455, 15– 20 m, underwater cliff, between Cape Wekutr and Cape Wajez, Santal Bay, Lifou Island, 20°56.8'S, 167°02.7' E, 25 Nov. 2000, LIFOU, MNHN­Pg 7253; 1♂, SL = 2.0 mm, stn. 1419, 5 m, mud with fragments and algae, Gaatcha Bay, Santal Bay, Lifou Island, 20°55.6'S, 167°04.5' E, 10 Nov. 2000, LIFOU, MNHN­Pg 7248; 2♂, SL = 0.8, 1.2 mm, 2♀, SL = 1.1, 1.1 mm, stn. 1449, 17 m, north of Cape Aimé Martin (= Acadro), Santal Bay, Lifou Island, 20°45.8'S, 167°01.65' E, 17 Nov. 2000, LIFOU, MNHN­Pg 7249; 1♀, SL = 1.6 mm, stn. 1450, 27­ 31 m, north of Cape Aimé Martin (= Acadro), Santal Bay, Lifou Island, 20°45.8'S, 167°01.65' E, 17­21 Nov. 2000, LIFOU, MNHN­Pg 7250; 1 ov. ♀, SL = 1.7 mm, stn. 1456, 25­ 30 m, underwater cliff, in region of Cila, north east of Santal Bay, Lifou Island, 20°49.3'S, 167°10.4' E, 26 Nov. 2000, LIFOU, MNHN­Pg 7254; 1♀, SL = 1.7 mm, st. 1221, 10 m, d'Ouvéa Lagoon, 20°28.9'S, 166°31.0' E, coll. R. Leborge, 11 Sept. 1992, Campagne PLOUVEAL, MNHN­Pg 7247. New Caledonia: 1♂, SL = 1.0 mm, 10 m, Touho, 8 Sept. 1993, MNHN Pg 7255; 1♂, SL = 1.6 m, Touho, 6 Sept. 1993, MNHN­Pg 7256; 2 ov. ♀, SL = 1.6, 1.6 mm, 5­7 m, Touho­Tié (Toumo­Tié on the label), MNHN­Pg 7257; 1♂, SL = 2.1 mm, st. 395, 31 m, Grand Récif Sud, 22°48'S, 167°08' E, coll. B. Richer ( ORSTOM), 23 Jan. 1985, LAGON, MNHN­Pg 7258; 1♂, SL = 2.4 mm, st. 464, 44 m, Surprise Atoll, 18°21'S, 163°03'E, B. Richer ( ORSTOM), 1 Mar. 1985, LAGON, MNHN­Pg 7259; 1 ov. ♀, SL = 1.2 mm, 1♂, SL = 1.4 mm, 20­30 m, lagoon, Grotte Merlet, coll. J. L. Menou, 19­21 Jan. 1993, MNHN­Pg 7260. Tahiti: 1♀, SL = 0.7 mm, Tiahurá, coll. B. Thomassium, MNHN­Pg. 3404. Philippine Islands: 1♂, SL = 1.7 mm, coll. by diving, 17 Dec. 1980, MNHN­Pg. 2766. Japan: 1♂, SL = 1.6 mm, diving, coll. Tetsuya Kinjyou, Okinawa­hontow, Ryukyus, Feb. 2004, CBM­ZC 8380. INDIAN OCEAN: Indonesia: 1♂, SL = 1.6 mm, Banda stn. 9, Alpha Helix Expedition, LACM­AHF 755 (= paratype of Micropagurus vexatus ); 1 ov. ♀, SL = 1.1 mm, Siboga st. 144, 45 m, coral bottom and Lithothamnion , dredge, Salomakiée (Damar) Island, 1°S, 127°E, 7­9 Aug. 1899, MNHN­ Pg 7278. Seychelles: 1♀, SL = 1.8 mm, st. 4, 32 m, hard bottom, 5°07.7'S, 56°34.0'E, 2 Sept. 1980, Campagne REVES II, coll. R. Cleva, MNHN­Pg 7261; 1♂, SL = 1.3 mm, st. 7, 50­ 55 m, fine sand and algae Halimeda , 4°51.8'S, 55°59.6'E, 3 Sept. 1980, Campagne REVES II, coll. R. Cleva, MNHN­Pg 7262.

Description. Shield ( Fig. 14A, B ) approximately as long as broad; anterior margin between rostral lobe and lateral projections weakly concave; posterior margin rounded or roundly truncate; dorsal surface with rows or tufts of moderately long setae. Rostral lobe slightly produced, broadly rounded. Lateral projections broadly rounded, unarmed.

Ocular peduncles ( Fig. 14A, B ) 0.9–1.0 length of shield; slightly to strongly inflated basally, slightly inflated distally; surfaces sometimes with several low protuberances accompanied distally by few short setae. Corneas dilated. Paired interocular lobes prominent. Ocular acicles each bearing 4–7 spines on distal margin and fringe of setae just proximal to spine row.

Antennular peduncles ( Fig. 14A, B ) shorter than or barely reaching to bases of corneas; ultimate and penultimate segments unarmed; basal segment with strong spine at ventrolateral distal angle.

Antennal peduncles ( Fig. 14A, B, C ) not reaching to bases of corneas; fifth and fourth segments unarmed; third segment with sharp spine at ventrodistal margin; second segment with dorsolateral distal angle produced, terminating in simple or bifid spine; dorsomesial distal angle with small spine; first segment with small, simple or bifid spine on lateral margin distally and acute spine ventrodistally. Antennal acicles moderately short, each terminating in small spine; mesial margin unarmed or with 1 or 2 small spines or tubercles; lateral margin with spine proximally or unarmed.

Third maxilliped with basis bearing 1 or 2 small teeth; ischium with moderately developed crista dentata and accessory tooth; merus and carpus each bearing strong dorsodistal spine.

Right cheliped stout; male cheliped ( Fig. 15 ) much stouter but armature much weaker than female ( Fig. 16 ). Dactyl 0.4–0.6 (male) or 0.7–0.8 (female) length of palm, terminating in small corneous claw not visible in dorsal view; cutting edge ( Fig. 15D ) with 2 calcareous teeth proximally and row of tiny corneous and calcareous teeth distally; dorsomesial margin with few small spines or tubercles (male), or with 2 or 3 strong spines (female). Palm 1.1–1.2 (male) or 1.0–1.1 (female) length of carpus; dorsal surface flat, with 1–3 tubercles (male) or spines (female) proximally in longitudinal row along midline or slightly mesiad of, and with additional longitudinal row of tubercles and/or blunt spines (male) or spines (female) in midline or slightly laterad of, not extending onto fixed finger; dorsomesial margin with row of tubercles and/or blunt spines (male) or spines (female); dorsolateral margin with row of tubercles and/or blunt spines (male) or spines (female) extending onto fixed finger for approximately half length; fixed finger terminating in corneous claw, cutting edge with variously­sized calcareous teeth proximally and row of tiny calcareous teeth distally (male, Fig. 15D ), or with 1–4 comparatively large calcareous teeth proximally and row of small calcareous and sharp corneous teeth distally (female). Carpus 0.9–1.1 (male) or 0.7–0.8 (female) length of merus; mesial and lateral faces unarmed or with scattered tubercles; dorsomesial margin with row of 3–7 spines or tubercles (male), or with 2–4 strong spines (female); dorsolateral margin with row of tubercles or small spines (male), or with row of 3­6 strong spines (female). Merus with lateral and mesial faces unarmed or tuberculate ventrally; ventromesial margin unarmed or tuberculate, and/or with 1 spine (male), or with 2 or 3 strong spines (female). Ischium unarmed or with tubercles on ventromesial margin (male), or with row of protuberances on ventromesial margin and sharp spine on ventrolateral margin (female).

Left cheliped ( Fig. 17 ) slender, armature of chela stronger in females ( Fig. 17E–G ) than in males ( Fig. 17 A­D). Dactyl 0.8–0.9 length of palm, terminating in sharp corneous claw; dorsomesial margin unarmed or with 1–3 spines; cutting edge ( Fig. 17D ) with row of small corneous teeth. Palm 0.6–0.7 length of carpus; dorsal surface with longitudinal row of 2–5 spines or tubercles; dorsomesial margin with row of 3 or 4 spines or tubercles; dorsolateral margin with row of spines extending onto fixed finger proximally; fixed finger terminating in sharp corneous claw, cutting edge ( Fig. 17D ) with row of corneous teeth. Carpus 0.9–1.0 length of merus, basal portion of spines on surface often prominently swollen; dorsomesial margin with row of 4 or 5 strong spines, distalmost very large and sometimes terminally bifid; dorsolateral margin with row of 4 or 5 strong spines. Merus with ventromesial margin bearing 1 or 2 strong spines; ventrolateral margin unarmed or with 1 strong spine. Ischium with 1 or 2 spines on ventromesial margin.

Second ( Fig. 18A–D ) and third ( Fig. 18E–F ) pereopods generally similar; second shorter and carpal armature stronger than third. Dactyls 0.8–0.9 (second) or 1.0–1.1 (third) length of propodi, each terminating in strong corneous claw; slightly curved ventrally in lateral view; ventral margins each generally with 3 (up to 5) corneous spines. Propodi 1.7– 1.8 (second) or 1.9–2.0 (third) length of carpi; ventrodistal margins each with sharp corneous spine. Carpi 0.6–0.7 length of meri; dorsal surfaces each with 3–5 strong spines, basal portions of spines often swollen. Meri with 0–3 spines on ventral margins. In large individuals, lateral, mesial and dorsal surfaces of propodi, carpi and meri often with scattered low protuberances accompanied distally by few long setae.

Sternite of third pereopods with broad, subrectangular anterior lobe ( Fig. 14E ) bearing setae anteriorly.

Fourth pereopod ( Fig. 14D ) with dactyl bearing 0–3 corneous spines on lateral face ventrally; propodal rasp composed of several rows of scales.

Male with coxa of left fifth pereopod ( Fig. 14E ) bearing well­developed sexual tube; no gonopore on right coxa.

Pleon with well­developed columellar muscle near anterior margin ventrally ( Fig. 14E ).

Telson ( Fig. 14G–I ) rounded or subtriangular, unarmed.

Coloration. Two color morphs were reported by Haig & Ball (1988) (as M. vexatus ). The specimens from Saparua and Seram were reported to have the shield mottled gray and cream, or green and white; ocular peduncles transparent, with black mottling, or mottled green and white; corneas salmon pink or off white; antennules transparent but for black stripe or row of black dots dorsally; antennal peduncles with green mottling; flagellum transparent; meri of chelipeds with brownish mottling on white background, carpi and chelae dirty white; second and third pereopods basically transparent, with mottled brown and cream, propodi and dactyls each with narrow brown longitudinal stripe on lateral face. Specimens from Banda were described with the ocular peduncles uniform olive drab; antennules white except for purple stripe dorsally; antennal peduncles mottled red and white; flagellum transparent; right cheliped purplish pink, left with proximal segments mottled olive drab and transparent, palm pink; dactyls and propodi of second and third pereopods each with narrow dark longitudinal stripe on lateral face, carpi with fine red mottling on white/transparent background, meri and ischia purplish pink.

I examined the color in two living specimens of this species from Japan. Although color patterns were sometimes irregular, they were somewhat different from those reported by Haig & Ball (1988). The specimen in Fig. 19A & B has the shield mottled green and white, with a pair of salmon pink areas anteriorly; ocular peduncles with red mottling on salmon pink background; corneas dark salmon pink; antennules salmon pink, with black stripe dorsally; antennal peduncles salmon pink; flagellum transparent; chelipeds generally salmon pink; second and third pereopods basically salmon pink, dactyls each with narrow brown longitudinal stripe on lateral face. The specimen in Fig. 19C has the shield mottled green and white, with pair of darker areas anteriorly; ocular peduncles with distal half green and proximal half salmon pink, with red mottling; corneas dark green; antennules generally transparent, with black stripe dorsally; antennal peduncles generally transparent; flagellum transparent; chelipeds with chelae generally salmon pink, meri and carpi greenish; second and third pereopods basically slightly greenish light brown, dactyls each with narrow brown longitudinal stripe on lateral face.

Despite differences in color patterns in life between individuals, preserved specimens exhibit similar color patterns, viz., numerous brown dots covering the antennular and antennal peduncles as well as the ocular peduncles ( Fig. 14B ).

Remarks. The syntypes of Micropagurus polynesiensis consist of two right chelipeds, three ambulatory pereopods and bodies of two females and one male, in which all chelipeds and ambulatory pereopods are detached. The two chelipeds are morphologically very similar and slender, so they most probably belong to the two female specimens.

Nobili (1906, 1907) made no mention of the number of specimens he examined. Consequently, I could not determine if they were all that Nobili (1906, 1907) used for the description. Nevertheless, morphological features of one of the right chelipeds of the syntypes agree well with that illustrated by Nobili (1907).

Haig & Ball's (1988) description for Micropagurus vexatus was so detailed that I was able to identify specimens very easily. I initially identified the specimens before seeing the syntypes of M. polynesiensis , and, as a result, I recognized many " M. vexatus " specimens from the MNHN collection. Haig & Ball (1988) made no mention of the sexual dimorphism in this species, but I found that the morphology of the chelipeds was sexually dimorphic; the female cheliped was slenderer than the male. However, when I later examined the syntypes of M. polynesiensis , I found that the two chelipeds of the syntypes were quite similar to the female chelipeds of M. vexatus . Additionally, morphological features of the shield, ambulatory pereopods and telson of the syntypes M. polynesiensis agreed very well with those of M. vexatus . Consequently, I concluded that M. vexatus was a junior synonym of M. polynesiensis .

When Haig & Ball (1988) described M. vexatus , they did not examine the types of M. polynesiensis directly, but, instead, asked the late Mme M. de Saint Laurent to examine them. Haig & Ball (1988: 184) stated (in parentheses by AA) "Sketches of the shield, anterior appendages, and chelipeds of M. polynesiensis , provided by M. de Saint Laurent, show that it differs from our new species (= M. vexatus ) in the greater number of spines on the chela and carpus of the chelipeds, and in lacking a fringe of setae on the ocular acicles (= setae arising just proximal to the marginal spines)."

Nine lots of non­type specimens identified as M. polynesiensis are housed in the MNHN. However, my reexamination of these has shown that two lots (MNHN­Pg 3294, 7277) are M. spinimanus , n. sp., and three lots (MNHN­Pg 2766, 3404, 7278) are M. polynesiensis . The identities of the remaining four lots (MNHN­Pg 3295, 3296, 3297, 3298) could not be determined to species because of damage.

Regarding the differences between M. vexatus and M. polynesiensis pointed out by Haig & Ball (1988), viz., spination on the chelipeds, I could not detect any differences between Haig & Ball's (1988) description of the chelipeds of M. vexatus and the chelipeds of the syntypes of M. polynesiensis . However, among the non­type specimens of M. polynesiensis , there are specimens (MNHN­Pg 3294, 7277) with greater numbers of spines on the chelipeds than those of M. vexatus . But these specimens are now reassigned to M. spinimanus , n. sp. It is highly probable that M. Saint Laurent, believing that all the material was conspecific, actually sketched the chelipeds of a specimen of M. spinimanus . Regarding the second difference, viz., the absence of fringe of setae arising just proximal to the marginal spines on the ocular acicles in M. polynesiensis , my reexamination of the syntypes has revealed that the ocular acicles of all three specimens have a fringe of setae.

Spination of the right cheliped in males of this species is the weakest among Micropagurus species ; the midline of the dorsal face of the palm often is provided with only a row of small tubercles ( Fig. 15A ). However, the same surfaces in males of other species are armed with single or multiple rows of sharp spines. If color patterns are preserved on the specimens, this species is easily separated from other species in having numerous brown dots on the antennular and the antennal peduncles as well as the ocular peduncles. None of other species have such color patterns. If the color pattern has faded, however, females of this species are sometimes difficult to separate from females of M. devaneyi .

Distribution. Western Pacific: Loyalty Islands, New Caledonia, Philippine Islands, Japan; 2– 44 m. Indian Ocean: Indonesia, Seychelles; 32– 55 m.

Figures

FIGURE 14. Micropagurus polynesiensis (Nobili, 1906). A, C, F, G: syntype, ♂, SL = 1.5 mm, Rikitea, French Polynesia, MNHN­Pg 2765; H, syntype,♀, SL = 1.2 mm, Rikitea, French Polynesia, MNHN­Pg 2765; D, E, I: ♂, SL = 1.7 mm, Philippines, MNHN Pg­2766; B, ov.♀, SL = 1.7 mm, Loyalty Islands, stn. 1456, LIFOU, MNHN­Pg 7254. Shield and cephalic appendages: A, dorsal; B, same, setae and right antennal peduncle omitted, color pattern indicated; C, ocular peduncle, antennal peduncle, ocular acicle, anterior portion of cephalothorax, left lateral, setae omitted. Left fourth pereopod: D, lateral, setae omitted. Coxae and sternites of third to fifth pereopods and anterior portion of pleon: E, ventral. Coxae and sternites of fifth pereopods: F, ventral. Tergite of sixth pleonal somite and telson: G–I, dorsal. Scales = 1 mm.

FIGURE 15. Micropagurus polynesiensis (Nobili, 1906): ♂, SL = 1.7 mm, Philippines, MNHN­Pg 2766. Male right cheliped: A, dorsal; B, mesial; C, lateral; D, dactyl and fixed finger, dorsal, setae omitted. Scales = 1 mm.

FIGURE 16. Micropagurus polynesiensis (Nobili, 1906): syntype, Rikitea, French Polynesia, MNHN­Pg 2765. Right cheliped (detached from body, most probably of female): A, dorsal; B, lateral; C, mesial. Scales = 1 mm.

FIGURE 17. Micropagurus polynesiensis (Nobili, 1906). A–D: ♂, SL = 1.7 mm, Philippines, MNHN Pg 2766; E­G: ♀, SL = 1.8 mm, Loyalty Islands, stn. 1452, LIFOU, MNHN­Pg 7251. Male left cheliped: A, dorsal; B, lateral; C, mesial; D, dactyl and fixed finger, dorsal, setae omitted. Female left cheliped: E, chela, setae omitted, dorsal; F, same, lateral; G, same, mesial. Scales = 1 mm.

FIGURE 18. Micropagurus polynesiensis (Nobili, 1906): ambulatory pereopods of syntypes (all detached from body), Rikitea, French Polynesia, MNHN­Pg 2765. Left second pereopod: A, lateral; B, dactyl and propodus, mesial. Right second pereopod: C, mesial; D, dactyl and distal portion of propodus, lateral. Right third pereopod: E, mesial; F dactyl, lateral. Scales = 1 mm.

FIGURE 19. Live coloration. A–C: Micropagurus polynesiensis (Nobili, 1906); D: Micropagurus acantholepis (Stimpson, 1858). Photos A–C by © Hiroyuki Shidara and D by ©Michael Marmach and Museum Victoria.

FIGURE 20. Geographical distribution of Micropagurus species., M. devaneyi;, M. spinimanus;, M. propinquus; ♢, M. polynesiensis;, M. acantholepis.