Catapaguroides rubromaculatus, Komai, 2017

Komai, Tomoyuki, 2017, Redescription of the pagurid hermit crab Catapaguroides fragilis (Melin, 1939) and descriptions of two new species from deep-sea off the Ryukyu Islands, Japan (Crustacea: Decapoda: Anomura), Zootaxa 4273 (2), pp. 235-257 : 243-250

Catapaguroides rubromaculatus sp. n.

[New Japanese name: Akahoshi-hime-yadokari] ( Figs 5–9 )

Catapaguroides sp.— McLaughlin et al. 2010: fig. 12E.

Material examined. Holotype. TRV “ Toyoshio-maru ”, 2005-04 cruise, stn 4, E of Amami-ohshima Island, 28°08.44’N 129°31.01’E to 28°08.63’N 129°31.33’E, 348–353 m, 24 May 2005, beam trawl, coll. T. Komai, male (sl 1.34 mm), CBM-ZC 13701.

Paratypes. TRV “ Toyoshio-maru ”, 1994-25 cruise, stn 11, E of Kakeroma Island, Amami Islands, 28°04.71’N, 129°27.38’E, 310 m, 10 November 1994, sledge net, coll. Eiji Tsuchida, 2 males (sl 1.3, 1.4 mm), CBM-ZC 13702 ; 2001-06 cruise, stn 7, W of Amami-ohshima Island, 28°21.23’N 129°13.60’E to 28°21.41’N 129°14.10’E, 290 – 285 m, 27 May 2001, beam trawl, coll. T. Komai, 1 male (sl 1.4 mm), CBM-ZC 13703; same data as holotype , 2 males (sl 1.3, 1.4 mm), 2 ovigerous females (sl 1.11, 1.2 mm), CBM-ZC 13704.

Description. Eight pairs of biserial phyllobranchiate gills; no arthrobranchs on maxilliped 3; no pleurobranch on either wall of thoracomere 7 (above base of pereopod 4).

Shield ( Fig. 5 A) as long as wide; anterior margins between rostral lobe and lateral projections concave; anterolateral margins not terraced, posterior margin roundly truncate; dorsal surface almost glabrous, with few tufts of short setae on anterior part. Rostrum roundly triangular, with 1 pair of long individual setae. Lateral projections broadly triangular, produced to level of rostrum, with submarginal spinule.

Ocular peduncle ( Fig. 5 A) long, slender, subequal in length to shield, subcylindrical; dorsal surface mesially with row of 4 tufts of stiff setae increasing in length distally; cornea somewhat elongate (lateral length distinctly greater than width), rounded, slightly inflated, corneal width 0.25–0.27 of peduncular length. Ocular acicle triangular, terminating in small marginal or submarginal spine, separated to each other basally by basal width of 2 acicles. Interocular lobe with slightly convex anterior surface.

Antennular peduncle ( Fig. 5 A), when fully extended, overreaching distal corneal margin by 0.8 to full length of ultimate article. Basal article with spinule on lateral face of statocyst lobe. Ultimate article 0.8 length of shield, slightly broadened distally, with 2 long plumose setae at dorsolateral distal portion; dorsal surface with row of some widely spaced setae. Dorsal flagellum longer than ultimate peduncular segment; distal portion more than 3 times as long as proximal aesthetasc-bearing portion, consisting of 6 or 7 articles; ventral flagellum consisting of 8 articles.

Antennal peduncle ( Fig. 5 A, B) not reaching distal corneal margin. Articles 5 and 4 with few short setae. Article 3 with 1 small spine at ventromesial distal angle. Article 2 with dorsolateral distal angle produced into simple spine far falling short of midlength of article 4; dorsomesial distal angle with tiny spine. Article 1 unarmed. Antennal acicle moderately slender, slightly arcuate, overreaching corneal base but not reaching distal corneal margin, terminating in slender spine, with row of short to long stiff setae over entire length. Antennal flagellum exceeding 6.0 times of shield length; articles each principally with 2 or 3 setae on distal margin, those in proximal half of flagellum each with setae of 2 or more length of 1 article.

Maxilliped 3 ( Fig. 5 C) moderately slender, with crista dentata on ischium consisting of 1–3 acute, triangular teeth ( Fig. 5 D); no accessory tooth. Carpus without dorsodistal spine. Merus also unarmed.

Chelipeds greatly unequal in length, dissimilar. Male right cheliped ( Fig. 6 A–D) elongate; propodal-carpal articulation without pronounced rotation. Chela about 2.7 times longer than wide, widest at base of dactylus. Dactylus articulating obliquely with palm, about 0.6 length of palm, gently curved ventrally; dorsal surface convex, unarmed, dorsomesial margin not delimited; cutting edge with 3 blunt, triangular calcareous teeth, terminating in minute corneous claw; scattered tufts of short to moderately long setae on surfaces. Palm 1.9 times as long as wide, 0.9 times as long as carpus, with scattered tufts of short to long setae on surfaces (ventral setae longest); dorsal surface gently convex, with dorsomesial row of 3–5 very small spine, otherwise unarmed; dorsolateral and dorsomesial margins not delimited; ventral surface slightly convex. Fixed finger with 2 blunt calcareous teeth on cutting edge, terminating in calcareous claw. Carpus subcylindrical, about 1.3 length of merus, not broadened distally, about 3 times longer than distal width; surfaces microscopically granular, with scattered tufts of long setae (setae on dorsolateral part thickened, bristle-like); dorsal surface with row of 7–10 small spines or tubercles on midline, otherwise unarmed; ventrolateral distal angle and distomesial angle each with very small spine. Merus with transverse rows of stiff bristle-like setae on dorsal surface; dorsodistal margin with small spine mesially, obscured by stiff setae; lateral surface with few tufts of setae, ventrolateral margin generally convex, with 1 small distal spine and 1 larger subdistal spine; mesial surface with several setae ventrally, ventromesial margin with 2 small spines distally; ventral surface gently convex, without conspicuous armature. Ischium unarmed, but bearing long thick, bristle-like setae on dorsal margin.

Female right cheliped ( Fig. 7 A–C) less elongate and stouter than in males; setation less developed. Chela about 2 times longer than wide, ovate in general outline. Dactylus 0.7 length of palm, gently curved ventrally; dorsal surface unarmed, dorsomesial margin not delimited; cutting edge with 3 blunt, triangular calcareous teeth, terminating in tiny corneous claw. Palm 1.3 times as long as wide, 1.1 times as long as carpus; dorsal surface gently convex, with dorsomesial row of 3–5 very small spines and 1 small spine proximally on dorsal midline; dorsolateral and dorsomesial margins not delimited; ventral surface gently convex. Fixed finger with 2 blunt calcareous teeth on cutting edge, terminating in calcareous claw. Carpus subequal in length to merus, somewhat broadened distally, about 1.5 times longer than distal width; surfaces microscopically granular; dorsal surface with row of 6 or 7 small spines or tubercles on midline; ventrolateral distal angle unarmed, distomesial angle with tiny spine. Merus with 2 distal spines on ventrolateral margin; ventromesial margin somewhat expanded, with 3 spines distally; ventral surface concave, without conspicuous armature. Ischium unarmed.

Left cheliped ( Fig. 7 D–F) moderately slender, reaching midlength of right chela in males; propodal-carpal articulation without noticeable rotation. Chela not arched, 3.2 times longer than wide. Dactylus subequal in length to palm, unarmed, with scattered tufts of short to long setae on surfaces; dorsomesial margin not delimited; cutting edge with row of minute corneous teeth in distal half, terminating in small corneous claw. Palm approximately half length of carpus, with scattered long setae on surfaces; dorsal surface gently convex, with 1 or 2 tiny dorsomesial spines in distal half, otherwise spineless. Fixed finger with row of minute corneous teeth at least on distal half of cutting edge, terminating in small corneous claw. Carpus elongate, slightly widened distally, about 3.4 times longer than distal width, with small spine at dorsomesial distal angle; dorsal surface with 0–3 small spines on midline and 1 or 2 small spines mesially, and with numerous tufts of long setae (proximal setae thick, bristle-like); lateral, mesial and ventral surfaces also with scattered tufts of long setae, ventrolateral distal angle with small spine; ventral surface slightly convex. Merus with some tufts of short to long setae on dorsal surface, dorsodistal margin unarmed; ventrolateral margin generally convex, with 2 small spines distally; ventromesial margin also convex, with 1 small spine subdistally; ventral surface with numerous long setae. Ischium with long setae on ventral surface.

Ambulatory legs (pereopods 2 and 3) ( Fig. 8 A, B) long and slender, right second reaching extended right cheliped in males. Dactyli (Fig.) 1.2 (second) or 1.5 (third) as long as propodi, about 16 times longer than wide, straight in dorsal view, weakly curved ventrally in lateral view, terminating in long, slender corneous claws; dorsal margins each with row of stiff setae becoming longer and bristle-like distally; mesial faces ( Fig. 8 C, D) each with row of stiff setae on midline; ventral margin unarmed. Propodi each with long, slender spiniform setae flanked by 3 or 4 shorter spiniform or bristle-like setae (male second) or 1 small spiniform setae (female second and third in both sexes) on ventrodistal margin; dorsal margins each with sparse, short stiff setae; ventral surface almost glabrous. Carpi each with tiny dorsodistal spine; sparse setae on dorsal margin. Meri each with 1 tiny distal spine on ventrolateral margin (second) or unarmed (third); dorsal margins each with row of tufts of moderately long setae; ventral margins with sparse long setae (second) or glabrous (third), those of second each with tiny or minute spine located at distal one-fifth. Ischia with sparse tufts of setae on dorsal and ventral margins. Second pereopods with conspicuous notch on ventral margin at articulation between merus and ischium. Female with unpaired left gonopore.

Pereopod 4 ( Fig. 5 E) semichelate; dactylus with several minute corneous teeth on ventral margin; propodal rasp consisting of single row of several corneous scales. Pereopod 5 semichelate.

Anterior lobe of thoracic sternite 6 ( Fig. 5 F) subtrapezoidal, no conspicuous armature, slightly skewed to left, bearing short setae on anterior margin.

Male with long sexual tube emanating from coxa of right pereopod 5 ( Fig. 5 G), directed from right to left across ventral body surface and then strongly curved anteriorly, not tapering distally; right coxa with tuft of setae at base of sexual tube. Coxa of left without gonopore. Thoracic sternite 8 ( Fig. 5 G) with broad, faintly divided lobe bearing numerous setae.

Telson ( Fig. 5 H) longer than wide, narrowed posteriorly; no trace of lateral indentations; posterior lobes strongly asymmetrical, separated by deep median cleft; left terminal margin with 2 or 3 small spines and laterally directed, spinose outer angle; right terminal margin strongly oblique, with 1 or 2 small spine and spinose outer angle.

Eggs about 0.6 × 0.5 mm.

Coloration in life. Body and appendages generally semitransparent. Corneas yellowish brown. Carpi and meri of chelipeds each with 1 red spot on dorsal surface distal to midlength. Propodi and carpi of ambulatory legs each with 1 red spot distal to midlength; meri each with 1 or 2 red spots. See Fig. 9 .

Variation. Eight specimens are available for study, all generally very similar. As in the vast majority of congeners, the armature of the ventrodistal margin of the propodi of the second pereopods is sexually dimorphic in this new species. In males, the margin is armed with a prominent set of spiniform setae. In females, there is one small spiniform setae on that margin. The dorsomesial spines on the right palm are three to five; the dorsal spines or tubercles on the right cheliped carpus are six to ten.

Distribution and habitat. Presently known only from off Amami Islands, Ryukyu Islands, at depths of 285– 353 m; sand and mud bottoms. Found to use gastropod shells for housing; no association with other invertebrates was observed.

Remarks. Catapaguroides rubromaculatus n. sp. is most similar to C. fragilis in the general configuration of the ocular, antennular and antennal peduncles, the abundance of the setation of the male chelipeds, and the general armature of the right cheliped. However, the new species is readily distinguished from C. fragilis by the following particulars: (1) there are no arthrobranch gills on the maxilliped 3 in C. rubromaculatus n. sp., whereas two very small arthrobranchs are present in C. fragilis ; (2) the cornea is somewhat elongate longitudinally with its diameter being greater than the basal width of the ocular peduncle in C. rubromaculatus n. sp. ( Fig. 5 A), whereas it is normal in the shape with its width being subequal to the basal width of the ocular peduncle in C. fragilis ( Fig. 1 A); (3) the dactylus of the right cheliped is unarmed in C. rubromaculatus n. sp. ( Figs 6 C, 7C), while armed with a small proximal spine on the dorsomesial margin in C. fragilis ( Figs 2 C, 3C); (4) dorsomesial spines of the right chela are much weaker in C. rubromaculatus n. sp. than in C. fragilis (cf. Fig. 6 A, C and Fig. 1 A, C); (5) the carpus of the left cheliped bears one or two dorsomesial spines and at most three middorsal spines in C. rubromaculatus n. sp. ( Fig. 7 D–F)), whereas having only three to five middorsal spines in C. fragilis ( Fig. 3 D–F); (6) the ambulatory dactyli have no or at most one ventral spiniform seta on the mesial face in C. rubromaculatus n. sp. ( Fig. 8 C, D), rather than having two to four (second) or four to seven (third) ventral spiniform setae on the mesial face in C. fragilis ( Fig. 4 C, D); (7) the right sexual tube of C. rubromaculatus n. sp. is long (exceeding 6 times of the coxal length), directed from right to left across the ventral body surface and then strongly curved anteriorly ( Fig. 5 G), whereas it is of medium length (3–4 times of the coxal length) without an anteriorly directed portion in C. fragilis ( Fig. 1 G).

Catapaguroides hirsutus also resembles C. rubromaculatus n. sp. in the general configuration of the cephalic appendages, the elongate right cheliped and the abundance of the setation of both chelipeds, but the new species is easily distinguished from C. hirsutus by the shape of the ocular peduncle (see above), the presence of dorsomesial spines on the right cheliped palm (dorsomesial spines are absent in C. hirsutus ), the presence of a middorsal row of spines on the right cheliped carpus (no middorsal spines in C. hirsutus ) and the much longer right sexual tube (cf. Komai & Rahayu 2013).

Etymology. From the combination of the Latin ruber (red) and maculatus (spotted), referring to the characteristic color pattern of the chelipeds and ambulatory legs of the new species.

Figures

FIGURE 1. Catapaguroides fragilis (Melin, 1939), male (sl 1.54 mm), CBM-ZC 13594. A, shield (including carapace lateral lobes) and cephalic appendages, dorsal view; B, left antennal peduncle, ventral view; C, left maxilliped 3, lateral view; D, same, ischium, ventral view; E, left pereopod 4, lateral view; F, thoracic sternite 6, ventral view; G, coxae of pereopods 5 and thoracic sternite 8, ventral view; H, telson, outer view.

FIGURE 2. Catapaguroides fragilis (Melin, 1939), male (sl 1.54 mm), CBM-ZC 13594. A, right cheliped, mesial view; B, same, lateral view, setae omitted; C, same, chela, dorsal view; D, same, carpus, dorsal view.

FIGURE 3. Catapaguroides fragilis (Melin, 1939), A – C, female (sl 1.18 mm), CBM-ZC 9018; C – E, male (sl 1.54 mm), CBM-ZC 13594. A, right cheliped, mesial view; B, same, lateral view, setae omitted; C, same, chela and carpus, dorsal view; D, left cheliped, mesial view; E, same, lateral view, setae omitted; F, same, chela and carpus, dorsal view, setae omitted.

FIGURE 4. Catapaguroides fragilis (Melin, 1939), male (sl 1.54 mm), CBM-ZC 13594. A, right pereopod 2, lateral view; B, left pereopod 3, lateral view; C, D, dactyli of right pereopod 2 and left pereopod 3, mesial view.

FIGURE 5. Catapaguroides rubromaculatus n. sp., holotype, male (sl 1.34 mm), CBM-ZC 13701. A, shield (including carapace lateral lobes) and cephalic appendages, dorsal view; B, left antennal peduncle, ventral view; C, left maxilliped 3, lateral view; D, same, ischium, ventral view; E, left pereopod 4, lateral view; F, thoracic sternite 6, ventral view; G, coxae of pereopods 5 and thoracic sternite 8, ventral view; H, telson, outer view.

FIGURE 6. Catapaguroides rubromaculatus n. sp., holotype, male (sl 1.34 mm), CBM-ZC 13701. A, right cheliped, mesial view; B, same, lateral view, setae omitted; C, same, chela, dorsal view; D, same, carpus, dorsal view.

FIGURE 7. Catapaguroides rubromaculatus n. sp. A – C, paratype, female (sl 1.11 mm), CBM-ZC 13704; D – F, holotype, male (sl 1.34 mm), CBM-ZC 13701. A, right cheliped, mesial view; B, same, mesial view, setae omitted; C, same, chela and carpus, dorsal view; D, left cheliped, mesial view; E, same, lateral view, setae omitted; F, same, chela and carpus, dorsal view, setae omitted.

FIGURE 8. Catapaguroides rubromaculatus n. sp., holotype, male (sl 1.34 mm), CBM-ZC 13701. A, right pereopod 2, lateral view; B, left pereopod 3, lateral view; C, D, dactyli of right pereopod 2 and left pereopod 3, mesial view.

FIGURE 9. Catapaguroides rubromaculatus n. sp., paratype, male (sl 1.3 mm), CBM-ZC 13704, showing colouration in life.