Kumepagurus cavernicolus, Komai & Osawa, 2012

Komai, Tomoyuki & Osawa, Masayuki, 2012, A new genus and new species of pagurid hermit crab (Crustacea: Decapoda: Anomura: Paguroidea) from a submarine cave in Kume Island, Ryukyu Islands *, Zootaxa 3367 (1), pp. 145-154 : 146-153

publication ID	https://doi.org/ 10.11646/zootaxa.3367.1.14
persistent identifier	https://treatment.plazi.org/id/F95087D8-FFE0-FFA6-269B-FCA0BD673E1C
treatment provided by	Felipe
scientific name	Kumepagurus cavernicolus
status	sp. nov.

Treatment

Kumepagurus cavernicolus View in CoL n. sp.

[new Japanese name: Kumejima-doukutsu-yadokari]

( Figs. 1–6 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 )

Material examined. Holotype: male (sl 2.4 mm), 50 m from entrance inside a submarine limestone cave, Kume Island , 26°19.964ʹN, 126°43.906ʹE, 38 m, 15 November 2009, bait trap, coll. Y. Fujita & S. Ogawa, RUMF-ZC- 1518. GoogleMaps

Description. Shield ( Fig. 1A, B View FIGURE 1 ) as long as broad; anterior margins between rostrum and lateral projections concave; anterolateral margins slightly terraced, posterior margin roundly truncate; dorsal surface with few tufts of short setae laterally. Rostrum roundly triangular, terminating in tiny sharp spine. Lateral projections obtusely triangular, not reaching level of rostral tip; each with small submarginal spine. Posterior carapace ( Fig. 1B View FIGURE 1 ) membranous; with pair of tufts of short setae at level of midlength; posteromedian plate moderately wide, with slightly convex lateral margins; sulci cardiobranchiales parallel, extending to midlength between cervical groove and posteromedian margin of carapace.

Ocular peduncles ( Fig. 1A View FIGURE 1 ) about 0.6 times as long as shield, moderately stout, not tapering distally or inflated basally, each with prominent tuft of stiff setae at base of cornea and few short setae dorsomesially; corneas not dilated, corneal width about 0.3 times peduncular length. Ocular acicles narrowly subtriangular, directed slightly mesially, terminating in subacute marginal spine. Interocular lobe small, visible in dorsal view.

Antennular peduncles ( Fig. 1A, C View FIGURE 1 ), when fully extended, overreaching ocular peduncles by full lengths of ultimate segments. Basal segment with small spine on lateral margin located slightly distal to midlength; distolateral angle produced in small lobe. Ultimate segment elongate, 0.9 times as long as shield, slightly broadened distally in lateral view, with few short setae dorsally. Dorsal flagellum with distal portion much longer than proximal, aesthetasc-bearing portion.

Antennal peduncles ( Fig. 1A View FIGURE 1 ) relatively long, overreaching distal corneal margins by full lengths of fifth segments. First segment unarmed on lateral face, ventromesial distal margin produced, with bifid spinule just lateral to antennal gland opening. Second segment with dorsolateral distal angle produced, reaching midlength of third segment, terminating in bifid spine; dorsomesial distal angle with small spine. Third segment with 1 small spine at ventrodistal margin. Fourth and fifth segments with few short setae mesially, fourth segment slightly shorter than fifth segment. Antennal acicle slender, elongate, overreaching distal corneal margin by about half own length, not reaching distal end of fifth peduncular segment, terminating in small spine, bearing prominent tuft of long setae distally and row of sparse short setae dorsomesially. Antennal flagellum ( Fig. 1D View FIGURE 1 ) very long, each article with few short to long setae distally.

Mandible ( Fig. 2A View FIGURE 2 ) without distinctive features. Maxillule ( Fig. 2B View FIGURE 2 ) with endopod slender, weakly developed inner lobe with 1 apical spiniform seta, outer lobe elongate, with 1 terminal and 1 basal seta. Maxilla ( Fig. 2C View FIGURE 2 ) with relatively short scaphognathite; endopod slender, gradually tapering distally ( Fig. 2D View FIGURE 2 ). First maxilliped ( Fig. 2E View FIGURE 2 ) with distal endite subovate; endopod reaching beyond distal margin of distal endite; exopod consisting of 2 segments and flagellum, distal segment strongly flexed laterally, proximal segment with slightly expanded lateral margin, flagellum shorter than distal segment. Second maxilliped ( Fig. 2F View FIGURE 2 ) relatively large, with elongate exopod; flagellum well developed, flexed at proximal 0.3. Third maxilliped ( Fig. 1E View FIGURE 1 ) with endopod relatively long and slender; carpus and merus unarmed; ischium and basis incompletely fused; crista dentata on ischium consisting of row of about 10 rather widely separated, acute teeth, accessory tooth absent; basis with 1 tiny denticle on mesial margin ( Fig. 1F View FIGURE 1 ).

Right cheliped ( Fig. 3A–G View FIGURE 3 ) massive. Chela operculate, subrectangular, about 1.2 times longer than wide; propodal-carpal articulation rotated clockwise about 20° from perpendicular. Dactylus subequal in length to palm, articulating obliquely; dorsal surface with scattered blunt granules, dorsomesial margin produced, forming sharp crest with granulated margin; ventral face convex along midline, shallowly concave proximolaterally, with scattered small, blister-like tubercles; cutting edge with 3 bluntly triangular calcareous teeth, terminating in tiny, sharp corneous claw. Palm longer than carpus, widened distally, about 1.2 times wider than long; dorsal surface slightly convex in general, with scattered, occasionally corneous-tipped, granules; dorsolateral margin delimited by row of minute granules not extending onto fixed finger, distal end of dorsolateral margin forming low, but rather prominent short ridge; dorsomesial margin delimited proximally by distinct crest with slightly upturned edge, distal part of dorsomesial portion rounded; lateral, mesial, ventral surfaces (including fixed finger) densely covered with low, rounded granules (granules largest and rather blister-like on ventral surface of fixed finger and distal part of palm), lateral surface with scattered short to long setae dorsally, ventral surface having blunt transverse ridge extending from base of dactylus to ventrolateral distal margin of fixed finger, thus ventral face of fixed finger shallowly concave. Fixed finger with markedly convex lateral face; cutting edge with 3 triangular calcareous teeth (middle tooth strongest), terminating in minute corneous claw; scattered short to moderately long setae present on dorsal surface and dorsal part of mesial face. Carpus subequal in length to merus, widened distally; dorsal surface elevated in midline, with row of small spines, sloping lateral and mesial sides with scattered granules, latter with long stiff setae adjacent to mesial margin; lateral margin faintly delimited, with 1 small distal spine, mesial margin sharply delimited by spinulose carina (spinules strongest distally) bearing long stiff setae; ventrolateral surface with scattered granules; ventromesial face nearly smooth but with scattered stiff setae; ventral surface strongly convex, with scattered granules and stiff setae, proximal part only weakly calcified. Merus with few low, transverse ridges in dorsodistal part, distalmost ridge longest, with row of short stiff setae; lateral face covered with minute granules and with iridescent sheen; ventrolateral margin elevated, strongly convex in lateral view, with row of spinules in distal half; mesial face nearly flat, smooth; ventromesial margin crested, strongly convex in lateral view, with row of spinules and stiff setae; only weakly calcified distal part of ventral surface forming deep concavity to accommodate flexed carpus, proximal part well calcified and almost flat. Ischium unarmed, with iridescent sheen on lateral face. Coxa unarmed.

Left cheliped ( Fig. 4A–C View FIGURE 4 ) moderately slender, reaching nearly to distal end of right cheliped, with slight degree of counterclockwise rotation from perpendicular. Chela about 3.1 times longer than wide and 1.4 times longer than carpus; dactylus and fixed finger only slightly curved ventrally, without hiatus. Dactylus about 1.2 times longer than palm, unarmed but with sparse tufts of short to moderately long setae, terminating in small corneous claw ( Fig. 4D View FIGURE 4 ); dorsomesial margin not delimited; cutting edge with row of closely set corneous teeth over entire length. Palm 0.6 length of carpus; dorsal surface slightly convex, with scattered granules and sparse setae and few low protuberances mesially, without delineation of dorsolateral and dorsomesial margins; mesial and ventral faces generally smooth, with scattered setae. Fixed finger bearing 2 acute corneous spines at tip ( Fig. 2D View FIGURE 2 ); cutting edge with few tiny acute calcareous teeth and row of sparse minute, corneous teeth. Carpus widened distally, length about 3.0 of distal width; dorsal surface sloping to lateral face, having tufts of short to long stiff setae and row of tiny spines mesially; lateral face with scattered granules, distal margin with small spine; mesial face with long stiff setae dorsally; ventral surface slightly convex, with sparse setae. Merus with sparse row of short setae on dorsal surface, dorsodistal margin unarmed; lateral face with scattered granules, ventrolateral margin with row of small spines in distal half; mesial face smooth, with few short setae, ventromesial margin with 1 distal spine, otherwise unarmed; ventral surface with sparse tufts of long setae. Ischium unarmed, with scattered short setae. Coxa unarmed.

Ambulatory legs ( Fig. 5A, C View FIGURE 5 ) relatively slender, slightly overreaching tip of right cheliped. Dactyli about 1.3 (second) or 1.7 (third) length of propodi, about 11.0 times longer than wide, slightly curved ventrally in lateral view, nearly straight in dorsal view, terminating in long, slender corneous claws; dorsal margins each with row of moderately long setae; lateral faces each with very shallow longitudinal sulcus; mesial faces each with very shallow longitudinal sulcus and row of 8 (second) or 9–11 (third) corneous spinules adjacent to dorsal margin; ventral margins each with 10–12 slender corneous spines increasing in size distally ( Fig. 5B, D View FIGURE 5 ). Propodi slightly curved ventrally, those of second longer than those of third; dorsal surfaces each with sparse short and long setae; lateral and mesial faces smooth; ventral surfaces with sparse short setae, ventrodistal margins each armed with 1 or 2 slender corneous spines. Carpi with or without spinule at dorsodistal angle and with few setae on dorsal surface; lateral and mesial faces smooth. Meri unarmed, with sparse setae on dorsal and ventral surfaces; ventrolateral margins shallowly concave in distal 0.2. Ischia unarmed. Distinct concavity on ventral margin around articulation between merus and ischium in second pereopods.

Fourth pereopods ( Fig. 1G View FIGURE 1 ) simple. Dactyli each with row of corneous teeth on ventral margin; dorsal margin with prominent tuft of stiff setae. Propodi each with tuft of setae distally on dorsal margin; rasp consisting of single row of corneous scales increasing in size distally; carpus with tufts of setae in distal half of dorsal margin.

Fifth pereopods semichelate.

Anterior lobe of sixth thoracic sternite ( Fig. 1H View FIGURE 1 ) subsemicircular, with row of setae on anterior margin, setae longest in medial portion.

Right sexual tube ( Fig. 1I View FIGURE 1 ) medium in length, coiled, oriented laterally, tapering distally; tip roundly truncate; basal portion with covering of numerous short setae. Left sexual tube ( Fig. 1I View FIGURE 1 ) short, but distinctly extending beyond posterior margin of coxa, somewhat flattened, directed posterolaterally, tapering distally to acute tip; numerous short setae present on dorsal side. Coxae of fifth pereopods ( Fig. 1I View FIGURE 1 ) unequal (left larger than right), each with transverse row of setae on anterior margin. Eighth thoracic sternite ( Fig. 1I View FIGURE 1 ) with 2 compressed lobes, each lobe bearing marginal setae.

Pleon dextrally twisted ( Fig. 6 View FIGURE 6 ), with relatively long, unequally biramous third to fifth pleopods; fourth pleopod longest, with elongate exopod.

Telson ( Fig. 1J, K View FIGURE 1 ) with slightly asymmetrical posterior lobes separated by very small median cleft; terminal margins strongly oblique, microscopically denticulate; transverse indentations weakly delimited, each with prominent tuft of setae.

Colouration in life ( Fig. 6 View FIGURE 6 ). Shield generally white, reddish gut inside visible; posterior carapace translucent. Ocular peduncle generally white, with reddish-brown longitudinal stripe mesially and laterally on dorsal surface; cornea gray. Antennular peduncle translucent, with tinge of reddish-brown. Antennal peduncle with white first to third segments and reddish-brown fourth and fifth segments; antennal acicle white. Right chela generally pale brown, darker mesially and laterally, mesial crest white; carpus light brown, with white patches laterally and mesially on dorsal surface; merus generally light brown, lateral face with large white patch. Left chela generally light brown, whitish on lateral side of dorsal surface of palm. Dactyli of ambulatory legs white in distal 0.6–0.7, red in proximal 0.3–0.4; propodi and carpi white (on the photo, the area appears blue, but this is due to the lighting), lateral faces with red longitudinal stripes dorsally and ventrally; meri with distal and middle red bands and small proximal red spot, remainder white; ischia generally white. Pleon reddish.

Distribution. Known only from the type locality, submarine cave in Kume Island, at a depth of 38 m.

Remarks. To date, the following 11 hermit crab species have been recorded from marine caves in the Ryukyu Islands: Paguristes jalur Morgan, 1992 ; Catapaguroides foresti McLaughlin, 2002 (= C. kasei Osawa & Takeda, 2004 ); C. iejimensis Osawa & Takeda, 2004 ; C. longior Komai, Yamada & Shirakawa, 2010 ; Catapagurus tuberculosus ( Asakura, 1999) ; Pagurixus longipes Osawa, Fujita & Okuno, 2006 ; P. nomurai Komai & Asakura, 1995 ; P. pulcher Osawa, Fujita & Okuno, 2006 ; Pylopaguropsis bellula Osawa & Okuno, 2007 ; P. fimbriata McLaughlin & Haig, 1989 ; P. speciosa McLaughlin & Haig, 1989 ( Osawa & Takeda 2004; Osawa et al. 2006; Osawa & Okuno 2007; Komai et al. 2010). However, all but Catapaguroides longior occur in cryptic but normal non-cave habitats ( McLaughlin & Haig 1989; Morgan 1992; Komai & Asakura 1995; Asakura 1999; McLaughlin 2002; Osawa & Okuno 2007; unpublished data), and therefore it is considered that the occurrence of these species in cave environments is rather opportunistic. Catapaguroides longior and the present new species have been found only in deep chambers of submarine caves, despite extensive collecting efforts in recent years. It is possible that these two species are restricted to cave environments.