Pagurixus pulcher Osawa, Fujita & Okuno, 2006, n. sp.
Creators: name: Osawa, Masayuki
name: Fujita, Yoshihisa
name: Okuno, Junji
Publisher: name: Zenodo
Year: 2006
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Paguridae
Pagurixus
Pagurixus pulcher

description: Pagurixus pulcher n. sp. (Figs. 1–3, 7 A,B)
[new Japanse name: Seiryu­hime­hon­yadokari]
Pagurixus sp.: Kawamoto & Okuno, 2003: 89, unnumbered fig.
Type material. HOLOTYPE: CMNH­ZC 783, female (SL 2.4 mm), “Shadow Cave”, Kume­jima Island, Ryukyu Islands, 20 m, 24 November 2001, coll. T. Kawamoto. PARATYPE: CMNH­ZC 1820, 1 male (SL 2.7 mm), Maeda­misaki, Onna, Okinawa­jima Island, Ryukyu Islands, submarine cave, 3 m, 8 November 2003, coll. Y. Fujita.
Description. Eleven pairs of biserial phyllobranchiae.
Shield (Fig. 1 A) slightly longer than broad; anterior margin between rostrum and lateral projections concave; anterolateral margins sloping; posterior margin truncate; dorsal surface with few pairs of tufts of short setae. Rostrum triangular, distinctly overreaching lateral projections and slightly overreaching base of ocular acicles, terminating in small spine. Lateral projections obtusely triangular, with small submarginal spine.
Ocular peduncles (Fig. 1 A) moderately long, approximately 0.7–0.8 length of shield, each with row of tufts of short setae on dorsal mesial surface; corneas slightly dilated, corneal width about 0.3 of peduncular length; basal part inflated, slightly broader than corneas. Ocular acicles subtriangular, with small submarginal spine, separated basally by basal width of 1 acicle; mesial margin with row of setae.
Antennular peduncle (Fig. 1 A, D–F) overreaching distal margin of cornea by 0.7–0.8 length of ultimate segment. Ultimate segment with 4 or 5 short and long setae at dorsolateral distal angle; distal half of ventral surface with 2 longitudinal lines each consisting of irregular rows of sparse or moderately dense, short setae directed ventrolaterally. Basal segment with small spine on lateral face of statocyst lobe.
Antennal peduncle (Fig. 1 A) overreaching distal margin of cornea by 0.5–0.7 length of fifth segment. Fifth and fourth segments with scattered setae. Third segment apparently unarmed but with tuft of short setae at ventromesial distal angle. Second segment with small spine at dorsomesial distal angle; dorsolateral distal projection moderately elongate, slightly overreaching proximal margin of fourth segment, terminating in bifid spine. First segment unarmed at distolateral angle; ventromesial distal margin produced, with 3 small spines lateral to antennal gland opening. Antennal acicle moderately long, arcuate, overreaching base of corneas but not reaching its distal margin; mesial margin with row of tufts of setae. Flagellum long, approximately 6.8 length of shield (missing in holotype).
Third maxilliped moderately stout; ischium with well developed crista dentata composed of row of small corneous teeth and 1 accessory tooth; merus and carpus unarmed; exopod reaching midlength of carpus.
Right cheliped of male (Fig. 2 E–G) elongate. Chela subovate in dorsal view, approximately 2.5 times longer than wide measured along base of fingers. Dactylus 0.7 length of palm, weakly curved ventrally; dorsomesial margin weakly delimited by ridge of small granules; surfaces closely granular, with scattered tufts of setae; dorsal surface with longitudinal elevated ridge; cutting edge with unequal calcareous teeth on proximal 0.7 and row of small, closely set corneous teeth in distal 0.3, terminating in small corneous claw. Palm approximately 0.7 times as long as carpus; convex dorsal surface covered with coarse granules, dorsolateral margin delimited by ridge of small granules, dorsomesial margin not clearly delimited; lateral, mesial and ventral surfaces with numerous small granules and scattered short setae, ventral face convex. Cutting edge of fixed finger with row of unequal calcareous teeth, terminating in small corneous claw. Carpus approximately 1.1 times as long as merus; dorsolateral margin delimited by row of small and moderately large spines; dorsomesial margin weakly delimited by irregular row of spines (proximal 0.3 margin crested), strongest proximally; all surfaces with numerous small granules and scattered short setae, lateral surface divided in oblique dorsal and perpendicular ventral sections by distinct, longitudinal ridge of small tubercles. Merus with row of low transverse ridges bearing short stiff setae on dorsal surface; dorsodistal margin with small spine medially and row of short stiff setae; lateral surface with small, flattened granules; mesial surface with short vertical ridges; ventrolateral margin with 1 subdistal spine; ventromesial margin unarmed; ventral surface flattish, with small granules. Ischium with row of small granules on ventromesial margin.
Right cheliped of female (Fig. 2 A–D) comparatively long, slender. Chela subovate in dorsal view, 2.7 times longer than wide measured in base of fingers. Dactylus approximately 0.9 length of palm, slightly curved ventrally; surfaces nearly smooth, with scattered tufts of setae; dorsal surface with ridge of small granules on dorsal midline; dorsomesial margin weakly delimited by low ridge; cutting edge with unequal calcareous teeth on proximal 0.7 and row of small, closely set corneous teeth in distal 0.3, terminating in small corneous claw. Palm approximately 0.5 times as long as carpus; all surfaces with numerous small granules and scattered short and moderately long setae, dorsal surface convex, covered with coarse granules, low longitudinal ridge present on midline and short ridge present adjacent to dorsomesial margin proximally; dorsolateral margin clearly delimited by granular ridge; dorsomesial margin weakly delimited by ridge of small granules; ventral surface convex. Cutting edge of fixed finger with row of calcareous teeth, terminating in small corneous claw. Carpus approximately as long as merus, length approximately 2.9 of distal width and 3.6 of greatest height; dorsolateral margin delimited by row of small spines; dorsomesial margin weakly delimited by irregular row of small and moderately large spines; all surfaces with numerous small granules, lateral surface divided in oblique dorsal and perpendicular ventral sections by distinct, longitudinal ridge of small tubercles. Merus with row of low transverse ridges bearing short stiff setae on dorsal surface; dorsodistal margin unarmed but with row of short and moderately long stiff setae; lateral and mesial surfaces with short vertical ridges; ventrolateral margin with 1 distal spine; ventromesial margin unarmed; ventral surface flattish, with small granules. Ischium with small granules on ventromesial margin.
Left cheliped (Fig. 3 A–D) elongate, slender, similar in male and female. Chela 3.3–3.4 times longer than broad measured along base of fingers. Dactylus 0.8–1.0 times longer than palm, with scattered tufts of short and moderately long setae on surfaces; surfaces nearly smooth; cutting edge with minute calcareous teeth on proximal 0.3 and fine row of small corneous teeth on distal 0.7, terminating in small corneous claw. Palm 0.4 length of carpus; dorsal surface slightly convex, with sparse, small granules and slightly elevated longitudinal ridges of small tubercles on midline and adjacent to dorsomesial margin (tubercles on midline replaced by small spines in paratype), dorsolateral margin delimited by row of small, low protuberances or subacute tubercles; dorsomesial margin weakly delimited by row of small granules; mesial and ventral surfaces with sparse small granules and moderately long setae. Cutting edge of fixed finger with row of obsolete calcareous teeth on proximal 0.5–0.8 and row of closely set small corneous teeth on distal 0.2–0.5, terminating in small corneous claw. Carpus elongate, very slender, subcylindrical, 1.2 times longer than chela, approximately as long as merus; length 4.6–4.8 of distal width and 4.5–4.7 of greatest height; dorsal surface smooth, dorsolateral and dorsomesial margins each delimited by row of small spines and subacute protuberances and moderately long setae (spines of dorsomesial row stronger than those of dorsolateral row); lateral surface divided in oblique dorsal section and perpendicular ventral section by longitudinal ridge of small granules or protuberances, dorsal section with sparse small granules, ventral section with short, low, oblique ridges; mesial and ventral surfaces also with short, low, oblique ridges and sparse, moderately long setae. Merus with row of short transverse ridges on dorsal surface; dorsodistal margin unarmed but with row of short stiff setae; lateral surface with short, low, vertical ridges dorsally and small tubercles ventrally, ventrolateral margin with 1 small subdistal spine; mesial face with short vertical or oblique ridges, ventromesial margin unarmed; ventral surface slightly concave, with small granules and sparse, short and moderately long setae. Ischium with row of minute granules on ventromesial margin, otherwise apparently unarmed.
Ambulatory pereopods (Fig. 3 E–H) long and slender, generally similar from right to left. Dactyli weakly curved ventrally and mesially, 1.1–1.2 length of propodi (measured along dorsal surface, excluding distal rounded projection), 8.1–9.6 (second) or 9.8–9.9 (third) times longer than proximal height, terminating in large corneous claws; dorsal surfaces each with row of sparse, short and moderately long setae, distal part with row of dense short setae; lateral and mesial faces with few tufts of short setae near dorsal and ventral margins, mesial faces unarmed in second but with row of corneous spinules adjacent to dorsal margin in third; ventral margins each with 7 or 8 slender corneous spines increasing in size distally. Propodi somewhat tapering distally, not curved, 5.1–5.6 (second) or 5.4–5.7 (third) times longer than distal height; dorsal surfaces each with row of short, low, transverse ridges bearing short and moderately long setae; lateral and mesial surfaces nearly smooth; ventral surface slightly protuberant, each with row of 2–4 short corneous spines, ventrodistal margins each with paired long corneous spines. Carpi with low protuberances and sparse setae on dorsal surface, dorsodistal margins unarmed; lateral and mesial faces with few short setae. Meri somewhat tapering distally; dorsal surfaces each with irregular row of short, low, transverse ridges bearing few short stiff setae; lateral surfaces with scattered granules in second but nearly smooth in third; mesial faces smooth; ventral margins crenulated but unarmed in second, smooth or slightly crenulated in third, with row sparse short and moderately long setae; ventrolateral distal margins with small denticles or protuberances in second but nearly smooth in third, right second with small subdistal spine. Female with paired gonopores.
Fourth pereopods (Fig. 1 G, H) semichelate, form similar from right to left in both male and female, though slightly unequal (left larger). Dactyli moderately broad, terminating in small corneous claw; dorsal margins with few short setae; ventral margin with row of small corneous teeth; no preungual process. Propodi with tufts of setae on dorsal margin, distal tuft long, mesial face slightly convex, each with row of short setae ventrally; propodal rasp consisting of 1 row of corneous scales. Carpi with small dorsodistal spine; mesial face with some short and long setae near ventrodistal margin.
Coxae of fifth pereopods of male (Fig. 1 I) subequal in size; right coxa with short but clearly demarcated posteromesial protrusion; long setae comprising tuft arising from posteroventral surface of protrusion, directed toward left and nearly reaching left coxa; vas deferens papilla­like; left coxa also with papilla­like protrusion of vas deferens arising from gonopore, partially masked by tuft of moderately long setae directed ventrally.
Third thoracic sternite with pair of small spines on anterior median margin. Anterior lobe of sixth thoracic sternite (Fig. 1 B) transversely oval, anterolateral angles rounded, anterior margin with row of moderately long setae. Eighth thoracic sternite (Fig. 1 I) composed of 2 subequal, closely set, rounded lobes.
Male with 3 unpaired, unequally biramous left pleopods; female lacking paired pleopods, but with 4 unpaired left pleopods, second, fourth and fifth unequally biramous, third subequally biramous.
Telson (Fig. 1 C) with transverse indentations; posterior lobes subequal in size, terminal margins oblique, with 2 or 3 small spines; chitinous plates present along terminal margins. Telson of holotype broken.
Coloration. See Fig. 7 A, B. Shield white. Ocular peduncles mostly white, with pale brown blotch medially. Antennular peduncles brown. Antennal peduncles generally white; fifth segment with brown lateral and mesial stripes; fourth and third segments with brown blotches. Right chela pale brown entirely; carpus also pale brown, lateral and mesial surface pale brown or indigo; merus whitish semitransparent, with 3 narrow brown bands on distal margin and median and proximal parts, median and proximal bands interrupted or uninterrupted. Left chela pale brown with 2 indistinct dark brown longitudinal lines; carpus pale brown, lateral and mesial surface indigo; merus whitish semitransparent, with 3 dark brown bands on distal margin and median and proximal parts. Ambulatory pereopods white in ground color; dactyli with indigo blotch on dorsoproximal part; propodi and carpi indigo on dorsal surface; meri with 3 indigo blotches on dorsal face (on distal margin, and median and subproximal parts).
Etymology. The specific name is derived from the Latin, pulcher meaning beautiful, referring to the pretty coloration in life of the species.
Remarks. McLaughlin & Haig (1984) divided the genus Pagurixus into two species groups on the basis of the presence or absence of row(s) of setae on the ventral surface of the ultimate segment of the antennular peduncle. Pagurixus pulcher n. sp. has two longitudinal rows of short setae on the ultimate segment, although the setal rows are restricted only to the distal half. Thus the new species is compared with species belonging to the informal species group characterized by the possession of two longitudinal rows or series of setae on the antennular ultimate segment. This informal species group will be named the P. boninensis group, and the other species group, characterized by the absence of the setal rows on the ventral surface of the antennular ultimate segment, will be named the P. anceps group. (Komai & Osawa, in preparation).
Among the P. boninensis group, P. pulcher, P. maorus (Nobili, 1906), and P. nomurai Komai & Asakura, 1995 share the elongate chelipeds and ambulatory pereopods, especially the slender carpus of the left cheliped and the dactyli of the ambulatory pereopods, and carpus of the left cheliped with a longitudinal ridge on the lateral surface. Pagurixus pulcher and P. nomurai further share the right cheliped with generally similar armature between male and female, carpus of the male right cheliped with a distinct, tuberculate longitudinal ridge on the lateral surface, and terminal margins of the telson with comparatively small spines. The new species, however, differs from both P. maorus and P. nomurai by the more slender ocular peduncles and shape of the anterior lobe of the sixth thoracic sternite. The ocular peduncle is approximately 3.3 times longer than the width of the cornea in P. pulcher, whereas it is 2.1–2.4 times in P. maorus and P. nomurai. The anterior lobe of the sixth thoracic sternite is oval in P. pulcher, whereas it is transversely subrectangular in P. maorus and P. nomurai. The setation on the ventral surface of the ultimate segment of the antennular peduncle also distinguishes P. pulcher from P. nomurai. The setae of the ventral rows of P. pulcher are longer but much fewer than those of P. nomurai (see Komai & Asakura 1995: fig. 1C, D).
The live coloration of Pagurixus pulcher is characteristic. The carpus of the left cheliped is indigo­colored on the lateral and mesial surfaces, and the propodi and carpi of the ambulatory pereopods are also indigo­colored dorsally. The new species can be easily recognized on the basis of color pattern in life.
description: Published as part of Osawa, Masayuki, Fujita, Yoshihisa & Okuno, Junji, 2006, Two new species of Pagurixus (Crustacea: Decapoda: Anomura: Paguridae) from submarine caves of the Ryukyu Islands, southwestern Japan, pp. 27-45 in Zootaxa 1148 on pages 29-36, DOI: 10.5281/zenodo.172116