Trichopagurus macrochela Komai & Osawa, 2005, n. sp.
Creators: name: Komai, Tomoyuki
name: Osawa, Masayuki
Publisher: name: Zenodo
Year: 2005
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Paguridae
Trichopagurus
Trichopagurus macrochela

description: Trichopagurus macrochela, n. sp. (Figs. 1–3)
Trichopagurus trichophthalmus. — Baba, 1982: 68 (part).
Type material. HOLOTYPE: male SL 1.8 mm, Hiyajo, Kume­jima Island, Ryukyu Islands, 10 m, 12 June 1995, SCUBA diving, coll. K. Nomura, CBM­ZC 7853.
PARATYPES: 2 males SL 1.6, 2.0 mm, 1 ovigerous female SL 2.5 mm, Ahra Beach, Kume­jima Island, Ryukyu Islands, subtidal, 15 June 1995, hand, coll. T. Komai, CBM­ ZC 7854; 1 male SL 1.5 mm, 1 female SL 1.3 mm, Urabishi, Kuroshima Island, Ryukyu Islands, 3–4 m, 10 July 1998, skin diving, coll. K. Nomura and T. Komai, CBM­ZC 7855.
Other material examined. 1 ovigerous female SL 1.7mm, Off Inuf, Yap Islands, lagoon, 29 June 1980, coll. K. Baba, NSMT­Cr 14559.
Description. Gill lamellae narrowed distally with concave distolateral margins (Fig. 1 A).
Shield (Fig. 1 B, C) approximately as long as broad; anterior margin between rostrum and lateral projections concave; anterolateral margins sloping; posterior margin truncate; dorsal surface weakly convex, with 1 median and 2–5 dorsolateral tufts of setae. Rostrum triangular or roundly subacute, distinctly overreaching lateral projections, terminating bluntly or subacutely. Lateral projections obsolete, with prominent marginal or submarginal spine. Carapace lateral lobes (Fig. 1 C) narrow, moderately calcified. Posterior carapace (Fig. 1 C) generally membranous except for weakly calcified anterior part of posteromedian plate; posteromedian plate with 1 pair of tufts of setae; cardiac sulci obsolescent; sulci cardiobranchialis appearing as opaque lines on either side of posteromedian plate, extending posterolaterally; branchial region with few short setae.
Ocular peduncles (including cornea) (Fig. 1 B) stout, about 0.7 times of shield length; not inflated basally; cornea slightly dilated; dorsal surface with tuft of long setae near base of cornea. Ocular acicles subtriangular or subovate, separated basally by width of one acicle, with small submarginal spine terminally; dorsal surface concave.
Antennular peduncles (Fig. 1 B), when fully extended, overreaching ocular peduncles (including cornea) by 0.5–0.7 length of ultimate segment. Ultimate segment approximately twice length of penultimate segment, somewhat widened distally in lateral view, with tuft of long setae at dorsodistal lateral angle. Penultimate segment short, without setae. Basal segment with distolateral margin distinctly produced as short process, statocyst lobe weakly inflated, unarmed laterally.
Antennal peduncles (Fig. 1 B) overreaching ocular peduncles by 0.2–0.3 length of fifth segment, with supernumerary segmentation. Fifth and fourth segments with few setae distally. Third segment with spinule at ventromesial distal margin. Second segment with dorsolateral distal angle produced, not reaching midlength of fourth segment, terminating in simple, acute spine; dorsomesial distal angle with small spine; mesial and lateral faces with few setae. First segment with small spine at dorsolateral distal angle; ventromesial distal margin strongly produced anteriorly, with 1 minute spinule laterally. Antennal acicle reaching or slightly overreaching distal margin of cornea, weakly arcuate, distal part abruptly tapering and terminating in small spine; dorsomesial margin with sparse setae. Antennal flagellum (missing in holotype) 4.0–5.0 length of shield; each article with 3–5 very short to moderately long setae on distal margin.
Mandible without distinctive features. Maxillule (Fig. 2 A) with subquadrate coxal endite; endopod with outer lobe obsolete, inner lobe slightly produced, with 1 apical seta. Maxilla (Fig. 2 B) with broad proximal lobe of coxal endite; endopod overreaching anterior margin of moderately broad scaphognathite. First maxilliped (Fig. 2 C) with moderately broad exopod; endopod distinctly overreaching anterior margin of basial endite. Second maxilliped (Fig. 2 D) with basis­ischium fusion incomplete; dactylus and carpus stout. Third maxilliped (Fig. 2 E) moderately stout; carpus unarmed on dorsodistal margin; merus with strong dorsodistal spine and small ventromesial spine; ischium (Fig. 2 F) with welldeveloped crista dentata composed of very small corneous teeth and 1 accessory tooth; basis­ischium fusion incomplete; basis apparently unarmed on ventromesial margin; exopod slightly falling short of carpus.
Chelipeds strongly unequal in both sexes. Right cheliped (Fig. 3 A–C) very large, moderately stout. Chela elongate, subovate in dorsal view, 2.0–2.1 times as long as broad (greatest width at about midlength of palm). Dactyl about 0.7 length of palm, weakly curved ventrally; dorsal surface minutely granular proximally, dorsomesial margin not delimited; all surfaces with scattered tufts of short to moderately short setae; cutting edge with 2 or 3 large calcareous teeth and very small corneous teeth interspersed, terminating in small calcareous claw. Palm equal in length to carpus; dorsomesial margin not delimited, dorsolateral margin slightly delimited by multiple rows of small granules; dorsal surface weakly convex, nearly smooth medially and granular laterally and mesially, and with few short to moderately short setae; lateral and mesial surfaces minutely granular; ventral surface convex, smooth or microscopically granular, with scattered tufts of long setae extending onto fixed finger. Fixed finger with scattered tufts of short setae on dorsal surface; cutting edge with 1 large tooth proximally and row of small calcareous claw, terminating in small calcareous claw. Carpus flattened dorsoventrally, approximately equal to merus in length; dorsomesial margin clearly delimited by row of moderately large spines and some distal tubercles, dorsodistal margin unarmed, dorsolateral margin weakly delimited by row of low tubercles or protuberances; dorsal surface with some small, low tubercles laterally and scattered tufts of moderately long setae; lateral surface granular, ventrolateral margin with row of small, low protuberances; mesial surface shallowly concave, microscopically granular; distal part of ventral surface concave, bordered by distinct tuberculate ridge bearing tufts of long setae, posterior part convex, with few small tubercles and tufts of long setae. Merus with subdistal transverse ridge extending onto mesial face and few tufts of setae on dorsal surface, dorsodistal margin unarmed; lateral and mesial faces smooth, ventrolateral margin with row of small spines becoming smaller and blunt proximally and tufts of long setae, ventromesial margin with large, blunt tooth proximally and row of long stiff setae; ventral surface with tufts of long setae distally. Ischium with short spiniform setae and moderately short setae on surfaces, ventromesial margin nearly smooth. Coxa unarmed.
Left cheliped (Fig. 3 D–F) slender. Chela about 3.5 times as long as broad (greatest breadth at about base of fingers). Dactylus slightly longer than palm; dorsomesial margin not delimited, surfaces nearly smooth, with tufts of short to long setae; cutting edge with row of small, slender corneous teeth, terminating in small corneous claw. Palm with dorsal surface weakly elevated in midline, bearing several very small tubercles and scattered short setae; dorsolateral margin of palm and proximal half of fixed finger weakly delimited by row of small, low protuberances, dorsomesial margin not delimited; lateral face with scattered low tubercles; mesial face with low protuberances and long setae; ventral surface convex, with few low protuberances and long setae. Cutting edge of fixed finger with row of small, blunt corneous teeth, terminating in small corneous claw. Carpus equal to or slightly shorter than merus; dorsolateral and dorsomesial margins each with row of small, low protuberances accompanied by spiniform setae; lateral and mesial faces with scattered low protuberances, and short to long setae; ventral surface slightly convex, with low protuberances and scattered long setae. Merus with row of low transverse ridges and few tufts of short setae on dorsal surface, dorsodistal margin unarmed; lateral face with scattered very small, low tubercles and short stiff setae, ventrolateral margin with 2 or 3 small spines distally and row of long stiff setae; mesial face with short, low transverse ridges bearing long stiff setae adjacent to ventromesial margin, ventromesial margin also with row of long stiff setae; ventral surface without distinct spines or tubercles, but with short oblique rows of long stiff setae. Ischium with short to long setae on dorsal and ventral surfaces and cluster of short spiniform setae at ventrolateral angle. Coxa unarmed.
Ambulatory legs (Fig. 2 G, H) elongate, overreaching tip of extended left cheliped, but not reaching tip of right cheliped. Dactyli slender, in dorsal view straight, in lateral view almost straight with slightly curved claw, 1.1–1.3 times longer than propodi (third pair slightly longer than second); dorsal margins with row of tufts of short to moderately short setae; lateral faces with few short setae; mesial faces (Fig. 2 I, J) also with few short setae, unarmed on second, but armed with corneous spinules dorsally on third; ventral margins each with 8–10 long corneous spines. Propodi 1.75–2.00 times length of carpi; dorsal surfaces each with widely­spaced tufts of moderately long stiff setae; lateral and mesial faces with few setae; ventral surface with 3 or 4 widely­spaced, long corneous spines, including 2 or 3 spines on ventrodistal margin. Carpi short, 0.50–0.70 length of meri; dorsal surfaces unarmed but with moderately short to long stiff setae; lateral faces each with row of tufts of setae on midline; ventral surfaces with few short to long, stiff setae. Meri with row of short transverse ridges and stiff setae on dorsal surfaces; lateral and mesial faces mostly naked; ventral surfaces smooth or with row of low protuberances and tufts of moderately long setae, ventrolateral distal margins unarmed. Ischia with short to long setae on dorsal and ventral margins.
Fourth pereopods (Fig. 1 D) 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 (Fig. 1 E) chelate. Male coxae (Fig. 1 H) slightly asymmetrical, both with short stiff setae on anterior and posterior margins. Female coxae (Fig. 1 I) asymmetrical, left larger, with oblique transverse row of numerous long setae on ventral surface.
Third thoracic sternite with anterior margin slightly produced medially, unarmed. Anterior lobe of sixth thoracic sternite (Fig. 1 F, G) transversely oblong or subrectangular, with row of short setae on anterior margin. Eighth thoracic sternite (Fig. 1 H, I) composed of 2 rounded, contiguous lobes.
Male with moderately long (3–4 times of coxal length) right sexual tube directed toward exterior and upward along lateral side of body, distal part transparent and coiled (Fig. 1 E, H). Right sexual tube (Fig. 1 H) very short. Female with only left gonopore.
Abdomen twisted. Male with 3 unpaired, very unequally biramous left pleopods (third to fifth pleopods). Female with 4 unpaired left pleopods, second to fourth subequally biramous; fifth pleopod very small, uniramous. Uropods markedly asymmetrical; protopods unarmed.
Telson (Fig. 1 J) with only slight lateral indentations; posterior lobes triangular or rounded, terminal margins oblique, each with row of 4–7 very small spinules, lateral margins with fringe of long setae (Fig. 1 K).
Color in life. Carapace, antennae, chelipeds and ambulatory legs generally pale reddish brown, without conspicuous markings; setae at base of cornea accentuated with dark reddish brown.
Ecology. Found to inhabit small crevices or holes on dead coral. Various gastropod shells were used as housing.
Distribution. Presently known only from Ryukyu and Yap Islands; subtidal to 10 m.
Etymology. From the Latin macro meaning large and chela meaning cheliped and referring to the very large right cheliped.
Remarks. This new species is characterized by the very large right cheliped with a dorsoventrally flattened carpus and markedly asymmetrical coxae of the female fifth pereopods, of which the left is the largest and is provided with numerous long setae on the ventral surface. Furthermore, the following notable differences are found between T. macrochela and T. trichophthalmus. The dorsomesial margin of the carpus of the right cheliped is distinctly delimited by a row of spines in T. macrochela, while in T. trichophthalmus, the carpus is subcylindrical or slightly flattened, without distinct delineation of the dorsomesial margin. The surfaces of the right cheliped are granular or tuberculate in A. macrochela, rather than smooth and polished in T. trichophthalmus. The chelipeds and ambulatory legs are distinctly less setose in T. macrochela than in T. trichophthalmus. In addition, males of T. macrochela possess unpaired, unequally biramous pleopods, but those of T. trichophthalmus have uniramous pleopods.
Baba (1982) recorded T. trichophthalmus from the Palau and Yap Islands based on four specimens. Two of the four specimens are now deposited in the collection of the National Science Museum, Tokyo, although other two were not located. Reexamination of these two specimens revealed that the male (NSMT­Cr 14558) from Palau is referable to true T. trichophthalmus, but an ovigerous female (NSMT­Cr 14559) from the Yap Islands represents T. macrochela.
description: Published as part of Komai, Tomoyuki & Osawa, Masayuki, 2005, Decapoda: Anomura: Paguridae) from the Ryukyu and Yap Islands, and redescription of T. trichophthalmus (Forest), pp. 1-20 in Zootaxa 801 on pages 3-10, DOI: 10.5281/zenodo.170561