Eutrichopagurus shiarakawai Komai, 2015, n. sp.
Creators: name: Komai, Tomoyuki
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Paguridae
Eutrichopagurus
Eutrichopagurus shiarakawai

description: Eutrichopagurus shiarakawai n. sp.
[New Japanese name: Shirakawa-yadokari] (Figs. 1–5)
Material examined. Holotype: Ginowan, Okinawa Island, 5 m, under large rock, 25 June 2013, SCUBA diving, coll. N. Shirakawa, female (sl 1.85 mm), CBM-ZC 12569.
Paratypes: Nakayukui, Onna Village, Okinawa Island, 3 m, under large rock, 28 July 2013, SCUBA diving, coll. N. Shirakawa, 1 female (sl 1.30 mm), CBM-ZC 12570; Sunabe, Chatan, Okinawa Island, 5 m, under large rock, 3 May 2014, SCUBA diving, coll. N. Shirakawa, 1 ovigerous female (sl 1.93 mm), CBM-ZC 12571; Ginowan, 3 m, under large rock, 18 August 2014, SCUBA diving, coll. N. Shirakawa, 1 female (sl 1.91 mm), CBM-ZC 12572.
Description. Gills deeply quadriserial (Fig. 1 A), 11 pairs in number.
Shield (Fig. 1 B) 1.0–1.1 times longer than wide; anterior margin between rostrum and lateral projections concave; anterolateral margins sloping; posterior margin roundly truncate; dorsal surface slightly convex transversely, with some tufts of short to moderately long setae laterally; no paragastric groove delineated. Rostrum triangular, terminating in acute tip, slightly overreaching lateral projections. Lateral projections triangular, each with small marginal spine slightly directed outward.
Posterior carapace (Fig. 1 C) with lateral lobes very narrow, continuing with hinge between posterior margin of shield and anterior margin of posteromedian and posterolateral plates. Cardiac sulci slightly diverging posteriorly, overreaching midlength of posterior carapace. Sulci cardiobranchiales extending to midlength of posterior carapace, slightly converging posteriorly, followed by whitish line extending posteriorly along posterolateral margin of posterior carapace. Posteromedian and posterolateral plates poorly calcified; branchiostegites membranous, almost glabrous.
Ocular peduncle (including cornea) (Fig. 1 B) moderately stout, about half length of shield, tapering distally to substantially reduced cornea; dorsal surface with prominent tuft of elongate stiff setae near base of cornea, followed by 1 tuft of shorter setae and few very short setae, lateral face with 1 tuft of long setae near base of cornea. Ocular acicles elongate, narrowly triangular, terminating acutely, slightly curved ventrally, directed outward, reaching proximal 0.4 of ocular peduncle; dorsal surface flat. Interocular lobe apparently fused with ocular acicles, overhung by rostrum, but partially visible in dorsal view; anterior surface slightly convex.
Antennular peduncle (Fig. 1 B) moderately stout, when fully extended, overreaching distal corneal margin by approximately full length of ultimate segment. Ultimate segment (Fig. 1 D) about 1.8 length of penultimate segment, slightly widened distally, with tuft of long setae (length exceeding that of ultimate segment) on dorsodistal margin. Basal segment with distolateral margin not markedly produced; statocyst lobe slightly inflated, with small spine on lateral face. Dorsal flagellum subequal in length to ultimate peduncular segment, consisting of very short aesthetasc-bearing portion (4 or 5 articles) and long distal portion (4 elongate articles, more than twice of aesthetasc-bearing portion). Ventral flagellum about half length of ultimate peduncular segment, consisting of 4 articles.
Antennal peduncle (Fig. 1 B) overreaching distal corneal margin by full length of fifth segment. Fifth segment slightly flattened and arcuate, with sparse setae. Fourth segment slightly inflated basally, with few setae mesially. Third segment with spinule at ventromesial distal margin (not visible in dorsal view). Second segment with dorsolateral distal angle produced, reaching midlength of fourth segment, terminating in simple, acute spine partially obscured by subterminal setae; dorsomesial distal angle with small spine; mesial surface with few short setae. First segment with small, anterolaterally directed spine on lateral face; ventromesial distal margin somewhat produced anteriorly, with small, mesially curved spine just lateral to green gland opening. Antennal acicle overreaching distal corneal margin by half length and reaching midlength of fifth peduncular segment, terminating in small spine partially obscured by tuft of setae; dorsomesial margin with row of sparse moderately long setae. Antennal flagellum (Fig. 1 E) more than 4 times of shield length, overreaching extended right cheliped; each article with 3–5 short to long setae on distal margin, making flagellum somewhat setose.
Mouthparts not dissected. Third maxilliped (Fig. 1 F) moderately slender; carpus unarmed on dorsodistal margin; merus with strong dorsodistal spine and ventromesial spine arising proximal to midlength; ischium with well-developed crista dentata composed of small, closely set corneous teeth and 1 or 2 accessory teeth (Fig. 1 G); basis-ischium fusion incomplete; basis with few denticles on ventromesial margin; exopod reaching distal margin of carpus.
Chelipeds unequal in length, dissimilar with right much more robust than left. Right cheliped (Figs. 2 A–D) large. Chela suboval in dorsal view, about 2.0 times as long as wide (greatest width at midlength of palm); surfaces of chela and carpus microscopically finely granulate. Dactylus about 0.8 length of palm, nearly straight; no conspicuous spines or tubercles on surfaces, dorsomesial margin not delimited, all surfaces with sparse tufts of
(setae on ventral surface particularly long; cutting edge with some small, rounded calcareous teeth in proximal 0.8 and row of minute corneous teeth in distal 0.2, terminating in small corneous claw. Palm shorter than carpus, with sparse setae on surfaces (ventral setae longest); dorsomesial margin not delimited, dorsolateral margin bluntly ridged, with single or double row of tiny tubercles extending onto fixed finger; dorsal surface slightly elevated medially, with tiny tubercles or granules proximomedially, dorsomesial part with scattered tiny tubercles; ventral surface slightly convex. Fixed finger with row of calcareous teeth, decreasing in size distally, on cutting edge, terminating in minute corneous claw. Carpus not particularly flattened dorsoventrally, slightly widened distally, subequal in length to merus; dorsomesial margin not clearly delimited, but with row of small spines and row of long setae; dorsolateral margin also not clearly delimited, with row of tiny spines or tubercles; dorsal surface without conspicuous armature, but with few very short setae; lateral surface with scattered tiny, tubercles and few moderately long setae, ventrolateral distal angle unarmed; mesial surface with longitudinal row of small spines or tubercles adjacent to dorsomesial margin and few low, tiny protuberances or tubercles and sparse long setae, distomesial angle unarmed; ventral surface gently convex, with scattered long setae. Merus with very low, short transverse ridges on dorsal surface, dorsodistal margin unarmed; lateral surface mostly smooth, but with minute granules ventrally, ventrolateral margin with row of 5 small spines; mesial surface with scattered low, tiny tubercles or very low, short transverse ridges, ventromesial margin with 2 or 3 small spines proximal to midlength; ventral surface nearly flat, unarmed, with long setae laterally and mesially. Ischium with sparse short setae on surfaces; ventral surface with 1 small spine laterally; ventromesial margin with row of minute denticles. Coxa unarmed.
Left cheliped (Fig. 3 A–C) moderately slender; surfaces of chela and carpus microscopically finely granular. Chela about 3.0 times longer than wide (greatest width at slightly proximal to base of dactylus). Dactylus about 0.9 times as long as palm, without conspicuous armature on surfaces; dorsomesial margin not delimited; surfaces with sparse short to moderately long setae; cutting edge with widely spaced, minute, broadly triangular calcareous teeth in proximal 0.8, distal 0.2 bordered by corneous plate fused in terminal claw. Palm about 0.8 times as long as carpus; median part of dorsal surface slightly elevated, with 2 irregular longitudinal rows of tiny tubercles, dorsal surface either side of elevated median part shallowly sulcate or concave; dorsomesial part not delimited in distinct margin, but with scattered tiny tubercles or granules; dorsolateral margin slightly delimited by double or triple row of tiny tubercles or granules extending onto fixed finger; ventral surface gently convex; surfaces with sparse short to long setae (setae on ventral surface longest). Cutting edge of fixed finger with row of minute, broadly triangular calcareous teeth (teeth more closely spaced toward distal), terminating in bifid corneous claw. Carpus about half length of merus; dorsolateral margin with 4 tiny spines, dorsomesial margin with 7 small spines arranged in double row, both margins with sparse moderately long setae; dorsal surface without conspicuous armature; lateral surface with scattered minute tubercles, distolateral angle unarmed; mesial surface with few small, low protuberances and long setae, distomesial angle unarmed; ventral surface gently convex, with sparse long setae. Merus with short, very low transverse ridges on dorsal surface, dorsodistal margin unarmed; lateral surface with scattered minute, low granules or tubercles, ventrolateral margin with 2 or 3 widely spaced small spines in distal half, followed by few minute tubercles in proximal half, and few long setae; mesial surface with scattered very short, low transverse ridges, ventromesial margin with 2 widely spaced spines and row of stiff long setae; ventral surface nearly flat. Ischium with small spine on lateral surface ventrally; ventromesial margin with row of minute denticles; surfaces with sparse short to long setae. Coxa unarmed.
Ambulatory legs (Fig. 4 A, C) moderately long and slender, right second overreaching tip of right cheliped by half length of dactylus; third pereopods slightly longer than second pereopods; entire surfaces of dactyli to carpi, and ventral parts of lateral surfaces of meri minutely finely granular. Dactyli subequal in length to (second) or 1.1–1.2 (third) times as long as propodi, in dorsal view straight, in lateral slightly curved; dorsal margins each with row of sparse individual setae becoming shorter distally; lateral and mesial faces non-sulcate, each with row of sparse long setae adjacent to ventral margin; mesial faces unarmed (second; Fig. 4 B) or armed with few corneous spinules dorsodistally (third; Fig. 4 D); ventral margins each with 6–9 moderately short corneous spines. Propodi distinctly longer than carpi, slightly narrowing distally; dorsal surfaces each with sparse short to long stiff setae; lateral and mesial faces glabrous; ventral surfaces each with 1small corneous spinule, distal margin with 1 or 2 corneous spines. Carpi armed each with 1 minute spine on dorsal surface mesially at proximal 0.2 or unarmed (second) or always unarmed (third), no dorsodistal spine; dorsal surfaces with sparse short to long setae, ventral surfaces only with few setae. Meri with sparse individual setae on dorsal and ventral margins; ventral margins each with 1 minute spine at distal 0.3 or unarmed (second) or always unarmed (third), ventrolateral distal margin all unarmed; mesial surfaces smooth. Ischia unarmed, with sparse setae on dorsal and ventral margins. Female with unpaired left gonopore (Fig. 1 H).
Fourth pereopods (Fig. 1 I) semichelate. Dactyli nearly straight, each with row of minute corneous teeth on ventral margin, terminating in tiny corneous claw; no preungual process. Propodal rasp consisting of single row of small corneous scales.
Fifth pereopods chelate.
Third thoracic sternite with anterior margin slightly produced medially, unarmed, with prominent tuft of stiff setae medially. Sixth thoracic sternite (Fig. 1 H) with anterior lobe transversely oblong, with row of moderately short setae on anterior margin. Eighth thoracic sternite composed of 2 rounded, narrowly separated lobes, each lobe with numerous moderately short setae.
Pleon (Fig. 5) dextrally twisted. Female with 4 unpaired pleopods; second to fourth pleopods slightly unequally biramous, fifth much smaller than preceding pleopods, uniramous. Uropods markedly asymmetrical, left about twice of right in length; protopods unarmed.
Ovigerous female paratype carrying about 15 eggs.
Male unknown.
Variation. The number of accessory teeth of the third maxilliped is variable in the specimens examined, one on either side (non-ovigerous female paratype, CBM-ZC 12570) or two (holotype, CBM-ZC 12569; and two paratypes, CBM-ZC 12571, 12572). Spination on the carpi and meri of second pereopods is also variable. In the holotype (CBM-ZC 12569) and the two non-ovigerous paratypes (CBM-ZC 12570, 12572, carpi of the second pereopods each bears a minute spine on the dorsal surface proximal to the midlength, whereas in the ovigerous paratype (CBM-ZC 12571), such a spine is absent. Similarly, the meri of the second pereopods has a minute spine on the ventral surface in the holotype (CBM-ZC 12569) and two non-ovigerous paratypes (CBM-ZC 12570, 12572), while unarmed in the ovigerous paratype (CBM-ZC 12571).
Coloration in life. Shield, ocular peduncles, antennal peduncles, chelipeds and ambulatory legs generally white, without conspicuous markings; cornea gray; posterior carapace and pleon transparent (Fig. 5 A, B). Eggs orange-yellow.
Distribution and habitat. At present, known only from Okinawa Island (Ginowan, Chatan and Onna), Ryukyu Islands; shallow subtidal, 3– 5 m. All the four specimens examined were found under large coral rocks on sand substrates (N. Shirakawa, pers. com.). Found to use gastropod shells for housing (Fig. 5 B).
Etymology. The new species is dedicated to Mr. Naoki Shirakawa, a SCUBA diving instructor at Naha, Okinawa. He has much contributed to accumulate material of marine invertebrates from subtidal shallow waters in the Ryukyu Islands for taxonomic studies.
description: Published as part of Komai, Tomoyuki, 2015, A new genus and new species of Paguridae (Crustacea: Decapoda: Anomura) from shallow subtidal waters in Okinawa Island, the Ryukyu Islands, Japan, pp. 250-260 in Zootaxa 3918 (2) on pages 251-259, DOI: 10.11646/zootaxa.3918.2.6, http://zenodo.org/record/236870