Trichopagurus trichophthalmus ( Forest, 1954 )

Komai, Tomoyuki & Osawa, Masayuki, 2005, Decapoda: Anomura: Paguridae) from the Ryukyu and Yap Islands, and redescription of T. trichophthalmus (Forest), Zootaxa 801, pp. 1-20 : 11-18

Trichopagurus trichophthalmus ( Forest, 1954) ( Figs. 4–6 )

Catapaguroides ? trichophthalmus Forest, 1954: 74 , figs. 20–24; 1956: 1069.

Trichopagurus trichophthalmus .— de Saint Laurent, 1968: 927; 1970: 212, figs. 1–16; Baba, 1982: 68 (part); Poupin, 1996: 19; Hogarth et al., 1998: 168; Asakura 2004: 460, fig. 3.

Type material. HOLOTYPE: male SL 1.7 mm, Tahiti, French Polynesia, 1953, coll. Ranson, MNHN­Pg 602.

Other material examined. Marshall Islands: 1 male SL 1.4 mm, Bikini, 16 August 1947, coll. USNM, MNHN­Pg 603; 1 female SL 1.6 mm, same locality, April 1946, coll. USNM, MNHN­Pg 604; 1 male SL 2.2 mm, similar locality, 17 August 1947, coll. USNM, MNHN­Pg 606. Palau Islands: 1 male SL 1.1mm, Northeast coast of Kayangel, 8 July 1980, coll. K. Baba, NSMT­Cr 14558. Ryukyu Islands: 1 ovigerous female SL 1.7 mm, Near Sesoko Station of the University of the Ryukyus, Sesoko Island, 1 m, 16 July 2003, coll. M. Osawa and Y. Fujita, NSMT­Cr 15987; 1 male SL 1.7 mm, Ahra, Kumejima Island, outer reef flat, intertidal, 13 June 1995, coll. M. Osawa, NSMT­Cr 15233; 1 female SL 1.6 mm, same locality, moat, intertidal, 14 June 1995, coll. M. Osawa, NSMT­ Cr 15234; 1 male SL 1.7 mm, Shimajiri, Kume­jima Island, 1 m, 30 June 2000, coll. M. Osawa, NSMT­Cr 15988; 1 female SL 1.6 mm, Hizushihama, Aka­shima Island, moat, subtidal, 23 April 1993, coll. M. Osawa, NSMT­Cr 15989; 1 male SL 1.8 mm, in front of the Yaeyama Marine Park Research Station, Kuro­shima Island, moat, subtidal, 7 September 1992, coll. M. Osawa, NSMT­Cr 15990; 1 male SL 1.7 mm, same locality, moat, subtidal, 9 September 1992, coll. M. Osawa, NSMT­Cr 15991. Maldives: 1 female SL 1.5 mm, South coast of Vadoo, 10 m, 19 April 1996, SCUBA diving, coll. K. Nomura, CBM­ ZC 7802; 1 male SL 1.7 mm, Helmut Reef, South Male Atoll, 3 m, 30 August 2003, on SCUBA, coll. K. Nomura, CBM­ZC 7803.

Redescription. Eleven pairs of biserial phyllobranchiae including 1 pleurobranch above third pereopod (sixth thoracic somite) and 2 arthrobranchs on each third maxilliped to fourth pereopods; gill lamellae ( Fig. 4 A) narrowed distally with concave distolateral margins.

Shield ( Fig. 4 B, C) slightly longer or as long as broad; anterior margin between rostrum and lateral projections concave; anterolateral margins sloping; posterior margin truncate; dorsal surface weakly convex, with 1 or 2 median and 5–7 lateral tufts of setae; paragastric grooves indistinct. Rostrum narrowly rounded, distinctly overreaching lateral projections, abruptly tapering and terminating in spinule. Lateral projections low, broadly triangular, with prominent submarginal spine. Carapace lateral lobes narrow, moderately calcified. Posterior carapace ( Fig. 4 C) with few short setae, generally membranous except for weakly calcified anterior parts of posteromedian and posterolateral plates; cardiac sulci short, indistinct; posterolateral plates each with 1 or 2 tufts of setae on median part; sulci cardiobranchialis appearing as opaque lines, extending posterolaterally.

Ocular peduncles (including cornea) ( Fig. 4 B) stout, 0.5–0.6 times of shield length; not inflated basally; cornea slightly dilated; dorsal surfaces with tufts of long setae along distal half of dorsomesial margin and near dorsolateral base of cornea. Ocular acicles subovate, separated basally by width of one acicle, with small submarginal spine terminally; dorsal surface concave; mesial margins with short and moderately long setae.

Antennular peduncles ( Fig. 4 B), when fully extended, overreaching ocular peduncles (including cornea) by full length of ultimate segment. Ultimate segment approximately 1.5 times longer than penultimate segment, widened distally in lateral view, with tuft of long setae at dorsodistal margin; dorsomesial margin with few setae medially. Penultimate segment apparently naked. Basal segment with distolateral margin distinctly produced, terminating acutely; statocyst lobe weakly inflated, with minute spinule laterally.

Antennal peduncles ( Fig. 4 B) overreaching ocular peduncles by 0.2–0.5 length of fifth segment, with supernumerary segmentation. Fifth and fourth segments with tufts of short and long setae. Third segment with small spine on ventromesial distal margin and few tufts of setae. Second segment with dorsolateral distal angle produced, reaching midlength of fourth segment, terminating in simple, acute spine, with tuft of long setae; dorsomesial distal angle with small spine; mesial margin with short setae. First segment with minute spine at dorsolateral distal angle; ventromesial distal margin strongly produced anteriorly, with 1 minute spinule laterally. Antennal acicle overreaching distal margin of cornea by 0.3 length, weakly arcuate, distal part abruptly tapering and terminating in spinule; dorsomesial margin with tufts of long setae. Antennal flagellum approximately 4.0 times as long as shield, with articles each bearing 4 or 5 short and long setae on distal margin.

Maxillule ( Fig. 4 D) with subquadrate coxal endite; endopod with outer lobe moderately produced, inner lobe slightly produced, with 1 apical seta. Third maxilliped ( Fig. 4 E) moderately stout; carpus unarmed on dorsodistal margin; merus with dorsodistal spine; ischium ( Fig. 4 F) with well­developed crista dentata composed of small corneous teeth and 1 accessory tooth; basis­ischium fusion incomplete; basis with 1 spinules on ventromesial margin; exopod reaching half length of carpus.

Chelipeds strongly unequal in both sexes. Right cheliped ( Figs. 5 A, B, 6A, B) large, occasionally strongly elongate; rotation of propodal­carpal articulation 30–45º counterclockwise from perpendicular. Chela subovate in dorsal view, 2.5 times as long as broad (greatest width at about midlength of palm). Dactylus 0.5–0.6 length of palm in male, 0.8 times in female, weakly curved ventrally; articulation with palm strongly oblique; dorsal surface convex, dorsomesial and ventromesial margins not delimited; all surfaces with tufts of short to moderately short setae; cutting edge with 2 large and some smaller calcareous teeth in proximal half and small, calcareous or corneous teeth in distal half, terminating in small calcareous claw. Palm 0.7–0.8 times length of carpus in males, subequal in females; dorsomesial and dorsolateral margin weakly delimited; dorsal surface convex, apparently smooth, with numerous tufts of short to moderately long setae; lateral and mesial surfaces also smooth, with scattered tufts of setae; ventral surface convex, smooth, with scattered tufts of short and long setae extending onto fixed finger. Fixed finger with scattered tufts of moderately long setae on dorsal surface; cutting edge with 1 or 2 large, blunt teeth in proximal half and small rounded calcareous teeth in distal half, terminating in small calcareous claw. Carpus subcylindrical or slightly flattened dorsoventrally, longer than merus; dorsal surface flattish or slightly convex, with numerous tufts of short to long setae, dorsodistal margin unarmed; dorsomesial margin not delimited or slightly delineated, unarmed in holotype, but armed with 1–3 small spines on proximal half in other specimens, dorsolateral margin not delimited or weakly delineated, unarmed; mesial and lateral surfaces also with scattered tufts of short to long setae; ventromesial and ventrolateral margins unarmed; ventral surface smooth, concave in proximal and distal parts and convex in median part, with scattered tufts of short and long setae. Merus nearly smooth on dorsal, mesial and lateral surfaces; dorsodistal margin unarmed but with moderately long setae; ventrolateral margin with 1–3 small spines on distal half and tufts of long setae, ventromesial margin with 2 small spines on distal half and tufts of short and long setae; ventral surface flat, mostly smooth. Ischium with short to moderately long setae on surfaces, ventromesial margin with small, low protuberances. Coxa unarmed but with short setae on ventrodistal margin.

Left cheliped ( Figs. 5 C, D, 6C, D) slender; rotation of propodal­carpal articulation 20– 45º clockwise from perpendicular. Chela 3.5–3.6 times as long as broad (greatest width at about midlength of palm). Dactylus 0.9–1.0 length of palm; articulation with palm strongly oblique; surfaces smooth, with tufts of short to long setae; dorsal surface slightly convex, dorsomesial margin not delimited; cutting edge with row of small, slender corneous teeth, terminating in small corneous claw. Palm 0.5–0.6 times longer than carpus, surfaces smooth, with scattered tufts of short to long setae; dorsal surface slightly convex; dorsomesial and dorsolateral margins slightly delimited proximally; ventral surface convex. Cutting edge of fixed finger with row of small, blunt calcareous teeth, terminating in small corneous claw. Carpus elongate, as long as or slightly longer than merus; dorsomesial margin delimited, with 2–4 small spines and short, faint transverse ridges; dorsolateral margin delimited by short, faint transverse ridges, unarmed or armed with 1 or 2 small spines; dorsal surface flattish, with scattered tufts of long or moderately long setae; mesial and lateral surfaces with short, indistinct, low transverse ridges each bearing tuft of short to long setae; ventral surface slightly convex, scattered long or moderately long setae. Merus with row of low, very short transverse ridges and few tufts of moderately long setae on dorsal surface, dorsodistal margin unarmed but with long or moderately long setae; lateral surface with row of few tufts of short to moderately long setae on midline and row of longer setae ventrally, ventrolateral margin with 1–4 small spines on distal half and small low protuberances; mesial surface with tufts of short to moderately long setae ventrally, ventromesial margin with 1 or 2 small spines on distal half; ventral surface nearly smooth. Ischium with short to moderately long setae on dorsal and ventral surfaces, ventromesial margin with small, low protuberances. Coxa unarmed but with short setae on ventrodistal margin.

Ambulatory legs ( Fig. 6 E, G) generally similar from right to left, right slightly longer than left, slender, elongate, overreaching anterior tip of extended right cheliped by approximately half length of dactylus. Dactyli ( Fig. 6 F) slender, in dorsal view slightly curved, in lateral view almost straight with curved slender claw, approximately equal in length to propodi; dorsal margins with row of tufts of short to moderately long setae; lateral and mesial faces unarmed but with few short to moderately long setae; ventral margins each with 7–9 (second) and 8–10 (third) slender corneous spines, decreasing in size proximally. Propodi 1.2–1.4 times length of carpi, somewhat tapering distally in lateral and dorsal views; dorsal surfaces with numerous tufts of short to long setae; lateral faces with weak or very weak, rounded crest on midline and row of tufts of short to long setae each along dorsal and ventral margins; mesial faces also each with short to long setae along dorsal and ventral margins; ventral surfaces each with 4­6 widely­spaced, slender corneous spines, including 1 or 2 longer spines on ventrodistal margin. Carpi moderately long, 0.7–0.8 length of meri; dorsal surfaces unarmed but with moderately long or long setae; lateral faces each with row of tufts of setae on midline; mesial faces nearly naked; ventral surfaces with few short to long setae. Meri with row of short transverse ridges bearing short to long setae on dorsal surfaces; lateral faces with tufts of setae on proximoventral and distal parts, more numerous in third; mesial faces with few short setae; ventral surfaces smooth or with row of low protuberances, and with long to moderately long setae, ventrolateral distal margins unarmed. Ischium with short to long setae on dorsal and ventral margins; lateral and mesial faces naked. Female with only left gonopore.

Fourth pereopods ( Fig. 6 H) semichelate. Dactyli each with row of minute corneous teeth on distal half of ventral margin, terminating in tiny corneous claw; no preungual process. Propodal rasp composed of single row of small corneous scales on distal 0.7 of ventral margin. Carpi with tufts of long setae on dorsal surface, dorsodistal margin unarmed. Meri with tuft of long setae on dorsodistal margin.

Fifth pereopods chelate. Coxae of male and female slightly asymmetrical ( Fig. 4 H, I), with short and long setae on anterior and posterior margins in males but only on anterior margin in females. Male with moderately long (about 4 times longer than coxa of fifth pereopod measured on ventral surface) right sexual tube ( Fig. 4 H, J) directed toward exterior and upward along lateral side of body, distal part transparent and slightly to somewhat coiled. Right sexual tube ( Fig. 4 H) very short, papilla­like.

Third thoracic sternite with anterior margin slightly produced medially, with pair of spinules. Anterior lobe of sixth thoracic sternite ( Fig. 4 G) transversely oblong, with row of long setae on anterior margin. Eighth thoracic sternite ( Fig. 4 H, I) composed of 2 rounded, contiguous lobes, with few setae on anterior surface.

Abdomen twisted. Male with 3 left unpaired, uniramous pleopods (third to fifth pleopods); fifth pleopod shorter than others. Female with 4 unpaired left pleopods, second to fourth pleopods uniramous or biramous with endopods about half­length of exopods; fifth shorter than others, uniramous. Uropods markedly asymmetrical; protopods unarmed. Telson ( Fig. 4 K) with distinct lateral indentations; dorsal surface with short setae; posterior lobes rounded, terminal margins oblique, each with row of 3–7 small spines, posterolateral margins each with fringe of long setae.

Color in life. Carapace, antennae, chelipeds and ambulatory legs yellowish orange, with no conspicuous markings.

Ecology. Found living among branches of dead corals; intertidal to 10 m. Shells carried by crabs were small compared with the body size, and thus the cephalothorax and thoracic appendages were not completely retracted in shell. The animals were observed to move very rapidly like some Pagurixus species when disturbed.

Distribution. Previously known from Tahiti, Bikini, Palau, Ponape, the Sulu Archipelago of the Philippines, and Sanguinisiapo Archipelago of Indonesia and Japan in the West Pacific Ocean (de Saint Laurent 1970, Baba 1982, Asakura 2004), and the Maldives in the Indian Ocean ( Hogarth et al. 1998).

Remarks. The present specimens are very similar, although they came from widely distant locations in the Indian and Pacific oceans. Two females from the Ryukyu Islands (SL 1.6 mm, NSMT­Cr 15234; SL 1.6 mm, NSMT­Cr 15989) have uniramous pleopods (the former possesses second to fourth pleopods, but the latter lacks the fourth pleopod), although other females all have biramous second to fourth pleopods. This seems to be due to immaturity since these two specimens each have a left gonopore, which is distinctly smaller than that of other females.

De Saint Laurent (1970) tentatively referred two small specimens collected from Indonesia and the Philippines by the Siboga Expedition to T. trichophthalmus because of slightly longer ocular peduncles, slightly more slender chelipeds, and less setose ocular peduncles and chelipeds. Although the Siboga specimens were not available for study, examination of the present material suggests that these differences are size­related.

Asakura (2004) reported examining the holotype of T. trichophthalmus , with the registration number MNHN­Pg 3403. In fact, the holotype of T. trichophthalmus , from Tahiti, French Polynesia, bears the registration number MNHN–Pg 602. Régis Cleva of MNHN kindly informed us that the lot, MNHN­Pg 3403, contains a non­type specimen of T. trichophthalmus collected from Tuléar, Madagascar (personal communication).

Figures

FIGURE 4. Trichopagurus trichophthalmus (Forest, 1954). A – H, J, K, male (SL 1.7 mm), NSMT­ Cr 15233; I, female (SL 1.6 mm), NSMT­Cr 15234. A, gill lamella; B, shield and cephalic appendages, dorsal view (setae omitted from left side); C, carapace, dorsal view (setae omitted from shield); D, left maxillule, ventral view; E, left third maxilliped, ventral view; F, same, basis and ischium, dorsal view; G, sixth thoracic sternite, ventral view; H, I, coxae of fifth pereopods and eighth thoracic sternite, ventral view; J, coxa of right fifth pereopod, lateral view; K, telson, dorsal view.

FIGURE 5. Trichopagurus trichophthalmus (Forest, 1954). Male (SL 1.7 mm), NSMT­Cr 15233. A, right cheliped, mesial view; B, same, lateral view; C, left cheliped, mesial view; D, same, lateral view.

FIGURE 6. Trichopagurus trichophthalmus (Forest, 1954). Male (SL 1.7 mm), NSMT­Cr 15233. A, chela of right cheliped, dorsal view (setae omitted); B, carpus of right cheliped (setae omitted); C, chela of left cheliped, dorsal view (setae omitted); D, carpus of left cheliped (setae omitted); E, right second pereopod, lateral view; F, same, dactylus, mesial view; G, left third pereopod, lateral view; H, left fourth pereopod, lateral view.