Manaxius aurantiaca, Komai, 2020

Komai, Tomoyuki, 2020, First record of Bouvieraxius keiensis Sakai, 1992 and Manaxius aurantiaca n. sp (Decapoda: Axiidea) from the waters around the Ogasawara Islands, Japan, Zootaxa 4869 (3), pp. 369-386 : 378-385

Manaxius aurantiaca n. sp.

[New Japanese name: Suzaku-ana-ebi]

( Figs. 6–9 )

Material examined. Holotype: CBM-ZC 16168, female (cl 5.3 mm), RV “Tansei-maru”, KT-09-2 cruise, stn KK-1-1(2), Kaikata Seamount, Izu-Ogasawara Arc, 26°40.00’N, 140°55.26’E, 335– 299 m, 16 March 2009, chain bag dredge, coll. T. Komai.

Diagnosis. Rostrum narrowly triangular in dorsal view, reaching distal margin of article 2 of antennular peduncle, each lateral margin bearing 2 spines. Carapace surface glabrous on lateral sides; gastric median carina bearing 1 small anterior spine followed by 1 small tubercle; submedian gastric carinae each consisting of 2 widely spaced spines; lateral carinae each divided in 2 parts, anterior part with 1 conspicuous spine (supraocular spine), posterior part ending anteriorly in 1 small spine; no additional intercarinal tubercles or spines; no trace of postcervical median carina. Pleura 2–5 all rounded. Telson lateral margins each with 1 conspicuous proximal lobe and 2 pairs of tiny spines; posterolateral angles each with 2 unequal submarginal spiniform setae just mesial to tiny spine. Eyestalks reaching mid-length of rostrum, cornea pigmented. Chelipeds subequal in length, dissimilar in stoutness; each ischium with 1 prominent subdistal spine followed by few small tubercles on lower margin, upper margin unarmed; each merus with 2 small subdistal spines on upper margin, lower mesial margin armed with 3 spines, becoming noticeably strong toward distal; each carpus unarmed; palm upper margins without conspicuous spines except for distal spine, but weakly crenulate, bearing sparse short setae; lateral surfaces almost glabrous except for few tufts of setae, no spine near bases of fingers; dactylus subequal in length to palm on major cheliped side, slightly longer than palm on minor cheliped side.

Description. Holotype female. Body ( Fig. 6 ) moderately robust; integument firm.

Rostrum ( Fig. 7A, B ) narrowly triangular in dorsal view, reaching distal margin of article 2 of antennular peduncle, 0.4 times as long as distance between rostral base and cervical groove or 0.2 times as long as carapace, tapering into acute tip; lateral margins elevated, each with 2 small, evenly spaced, asymmetrically arranged spines and supraocular spine at rostral base, continuous with lateral gastric carina on carapace; dorsal surface shallowly concave. Carapace ( Fig. 7A, B ) with smooth surface, with tufts of short to long, erect setae arranged in longitudinal rows on gastric region, postcervical dorsum almost glabrous; dorsal profile in lateral view nearly straight, anterior gastric region slightly sloping down to rostrum; median gastric carina distinct, extending from anterior to level of supraocular spines to midway of anterior carapace (anterior to cervical groove), with 1 small spine followed by 1 small tubercle; submedian carinae consisting of 2 widely separated spines; lateral gastric carinae falling far short of midway between rostral base and cervical groove, divided into 2 widely separated parts, anterior part extending from base of supraocular spine, posterior part represented by 1 small spine; intercarinal spaces without armature; no trace of postcervical carina; cervical groove distinct, but restricted to dorsum; suborbital lobe obtusely angular; pterygostomial margin slightly produced, rounded; cardiac notch deep.

Thoracic sternite 7 shield ( Fig. 7C ) divided by deep median groove, lateral margins strongly elevated, subtriangular with bluntly pointed tip.

Pleon ( Fig. 7D ) with few paired tufts of short or long setae on pleomeres 1, 4–6. Pleomere 1 widening posteriorly in dorsal view, anterodorsal margin excavate; pleuron triangular with subacute tip, produced as far as ventral margin of pleuron 2. Pleomere 2 with pleuron slightly asymmetrical; ventral margin unarmed, rounded at either angle. Pleomeres 3–5 with all pleura unarmed, rounded. Pleomere 6 with pleuron rounded ventrally; posterolateral projection blunt.

Telson ( Fig. 7E ) subrectangular, 1.5 times as long as maximal width at anterolateral lobes; lateral margins faintly convex and subparallel, with conspicuous, unarmed anterolateral lobe, and 2 pairs of tiny, widely spaced spines; posterior margin convex, without posteromedian spine, fringed with numerous long setae, each posterolateral area with 2 unequal spiniform setae (lateral seta much smaller than mesial) just mesial to tiny spine; dorsal face shallowly sulcate medially, armed with 2 pairs of small spines, anterior spine located slightly anterior to mid-length and posterior spine at about midlength of telson; long setae arising at bases of dorsal spines.

Eyestalk ( Fig. 7A, B ) reaching mid-length of rostrum, inflated basally; cornea hemispherical, subequal in length and width to eyestalk, darkly pigmented.

Antennular peduncle ( Fig. 7A, B ) reaching level of distal margin of article 4 of antennal peduncle, subcylindrical; statocyst lobe on article 1 unarmed. Articles 2 and 3 combined shorter than article 1. Flagella slightly longer than carapace.

Antennal peduncle ( Fig. 7A, B ) with article 1 bearing 1 small spine at ventromesial distal angle. Article 2 with straight dorsolateral distal spine reaching beyond mid-length of scaphocerite; scaphocerite simple, acuminate, falling slightly short of distal end of article 4. Article 3 with 1 small spine at ventromesial distal angle. Article 4 slightly longer than article 2 (except for dorsolateral distal spine). Article 5 about 0.6 length of article 4. Flagellum with each article distally having some setae of various length (longest setae about twice length of 1 article).

Mouthparts not dissected. Maxilliped 3 ( Fig. 8A, B ) moderately slender. Coxa with 2 small distal spines. Basis with 1 lower distal spine. Ischium with distomesial angle produced into strong, acutely pointed projection; crista dentata consisting of row of 13 sharp teeth diminishing in size proximally (Fig.); lower margin with 2 small spines in proximal half. Merus bearing 3 spines on lower margin, noticeably becoming larger distally. Carpus with 1 small spine at lower distal angle. Dactylus shorter than propodus. Exopod falling slightly short of distal margin of merus, its distal half with multiple subdivisions.

Chelipeds ( Figs. 6 , 9 ) subequal in length, right somewhat stouter than left; mero-carpal articulation with about 30° of torsion (left with clockwise torsion, right with counter-clockwise torsion).

Right (major) cheliped ( Fig. 9 A–D) with coxa bearing 1 small spine on lower mesial margin. Basis unarmed. Ischium short, unarmed on upper margin; lower margin with 1 prominent subdistal spine followed by 3 small tubercles. Merus widened distally; upper margin gently arcuate, sharply carinate, with 2 unequal subdistal spines and row of setae in distal half; lateral face glabrous, generally convex, lower distal part deeply excavated and fitting lower margin of carpus, when cheliped flexed; distolateral angle with prominent articular condyle; mesial face smooth, somewhat flattened; lower mesial margin sharply carinate, bearing 3 spines, becoming noticeably strong toward distal, in distal half. Carpus short, as long as high, upper margin sharply carinate, unarmed but with row of short setae; lateral face almost glabrous, with sharp keel along ventral margin; mesial and lower surfaces glabrous; mesial surface deeply excavated proximally to accommodate lower distal margin of merus when cheliped is flexed. Palm 1.2 times as long as high; upper margin sharply carinate and crenulate, armed only with small distal spine and sparse short setae; lateral surface flattened, almost glabrous except for few short setae; finger base unarmed; lower lateral margin sharply keeled, this keel extending onto mid-length of fixed finger; mesial face gently convex, almost glabrous except for some tufts of short setae adjacent to ventral margin. Fingers crossing, each terminating in subacute tip; leaving narrow hiatus proximally when closed. Fixed finger with slightly convex lower margin; occlusal margin with 2 small principal teeth, otherwise faintly denticulate; lateral surface with 2 rows of tufts of moderately short setae; mesial face also with 2 rows of tufts of setae. Dactylus subequal in length to palm, slightly curved, with row of several tufts of moderately long setae on non-carinate, spineless upper margin; lateral surface with rows of tufts of setae adjacent to dorsal and occlusal margins, midline glabrous; both lateral and mesial surfaces slightly elevated in midline, appearing as blunt ridge in proximal half; occlusal margin with small, triangular tooth at about midlength.

Left (minor) cheliped ( Fig. 9 E–G) with coxa to carpus generally similar to those of major cheliped; ischium with unarmed upper margin, lower margin with 1 prominent subdistal spine followed by 3 small tubercles. Merus with 2 subdistal spines on upper margin; lower margin with 1 large subdistal spine followed by 2 much smaller spines. Carpus upper margin sharply carinate, unarmed. Palm and fingers slightly narrower than those of major cheliped, otherwise generally similar; palm 1.2 times as long as high, upper margin sharply carinate and crenulate as in major cheliped, only with 1 distal spine; lateral surface unarmed. Fixed finger with 2 small principal teeth on occlusal margin, interspersed by row of minute denticles. Dactylus 1.2 times as long as palm; occlusal margin slightly sinuous, without conspicuous tooth.

Pereopod 2 ( Fig. 8C ) moderately slender. Ischium unarmed. Merus with 2 small spines on lower margin, located distally to mid-length. Chela 1.1 times as long as carpus; fixed finger nearly straight, slightly deflexed, occlusal margin with row of minute spiniform setae in distal half; dactylus 0.7 times as long as palm, slightly curved, terminating in slender corneous claw.

Pereopod 3 ( Fig 8D, E ) moderately slender. Ischium unarmed. Merus with 2 minute spines on lower margin in distal half. Propodus with 5 transverse rows of spiniform setae (each consisting of 2–4 unequal spiniform setae) on flexor lateral surface; distal margin with row of 4 spiniform setae, longest seta on flexor side reaching proximal 0.25 of dactylus. Dactylus about half-length of propodus, slightly curving, terminating in acute tip; lateral surface with longitudinal row of 4 small spiniform setae adjacent to extensor margin and row of minute spiniform setae adjacent to flexor margin; mesial face unarmed.

Pereopod 4 ( Fig.8F, G ) as slender as pereopod 3. Ischium to carpus unarmed. Propodus with 6 transverse rows of spiniform setae on flexor lateral face (each consisting of 2–4 unequal spiniform setae) and grooming setae on distal 0.25 of flexor margin; distal margin with row of 4 spiniform setae, longest seta on flexor side not reaching proximal 0.2 of dactylus. Dactylus about half-length of propodus, gently arcuate, terminating in acute tip; lateral surface with row of 9 spiniform setae, increasing in length distally, adjacent to extensor margin and row of minute spiniform setae on distal half of flexor margin; mesial face unarmed.

Pereopod 5 ( Fig. 8H, I ) most slender and shortest, neither chelate nor semichelate. Ischium to carpus unarmed. Propodus with grooming apparatus consisting of 3 terminal spiniform setae and field of setae extending to midlength of propodus. Dactylus lanceolate, slightly twisted, terminating in basally demarcate, acute unguis; extensor and outer surface without spiniform setae; inner surface with some spiniform setae arranged in double row adjacent to extensor margin and short distal row of minute spiniform setae on flexor margin.

Pleopod 1 ( Fig. 7D ) consisting of 2 articles, uniramous. Pleopods 2–5 narrow, each with well-developed, rodlike appendix interna, 0.3–0.4 length of endopod.

Uropod ( Fig. 7F ) with endopod about twice as long as wide, lateral margin with row of 3 small spines on posterior half of outer margin (posterolateral spine largest); median ridge on dorsal surface with row of 3 spines, posterior submarginal spine largest. Exopod subequal in length to endopod; lateral margin slightly convex, with 2 small spines on posterior 0.7 of exopod length (including posterolateral spine) and with 1 strong spiniform seta mesial to posterolateral spine; mid-dorsal ridge unarmed; transverse suture serrate with row of 6 spinules.

Colour in life. Carapace generally orange-red, whitish along mid-dorsal line, including rostrum; gastric spines white; pleon and telson also generally orange-red, whitish along dorsal mid-line; eyestalk orange-red, cornea dark gray; antennae pale orange, semitransparent; cheliped meri orange, carpi whitish; palm lateral surface whitish in dorsal part and orange-red in ventral part, fixed finger orange-red, tip whitish, dactylus orange with whitish tip; pereopods 2–5 pale orange; uropods semitransparent ( Fig. 6 ).

Type locality. Kaikata Seamount, at a depth of 299–335 m.

Distribution. Presently known only from the type locality.

Remarks. The new species is assigned to Manaxius as rediagnosed by Poore (2020). The genus is currently represented by 18 species worldwide ( Poore 2020; updated by Komai & Anker 2020). Manaxius aurantiaca n. sp. has rounded pleura of pleomeres 2–5 and is notable in the lack of spines on the upper margin of the cheliped palms. In this regard, it is most similar to M. iro known from Papua New Guinea and Vanuatu ( Poore 2020). Manaxius aurantiaca n. sp. is readily distinguished from M. iro by the rostrum having two pairs of lateral spines (versus having only one pair of lateral spines in M. iro ), the gastric median carina bearing one spine and one denticle (versus unarmed in M. iro ), the bi-spined submedian gastric carinae (versus bearing 2–8 small teeth in M. iro ), the possession of two spines on the ventral margin of the maxilliped 3 ischium (versus unarmed in M. iro ), the cheliped ischia being armed with one prominent subdistal spine on the lower margins (versus unarmed in M. iro ), and the palms of the chelipeds each having a upper distal spine (versus no distal spine present in M. iro ) (cf. Poore 2020).

Etymology. From the Latin adjective, “ aurantiaca ”, meaning “orange-coloured”, in reference to the living coloration of the new species.

Figures

FIGURE 6. Manaxius aurantiaca n. sp., holotype, female (cl 5.3 mm), CBM-ZC 16168, habitus, lateral (A) and dorsal (B) views, showing colouration in fresh.

FIGURE 7. Manaxius aurantiaca n. sp., holotype, female (cl 5.3 mm), CBM-ZC 16168, habitus, lateral (A) and dorsal (B) views, showing colouration in fresh. A, carapace and cephalic appendages, lateral view; B, same, dorsal view; C, thoracic sternites 6 and 7 and coxae of pereopods 3 and 4, ventral view; D, thoracic sternite 8, pleon, telson, coxa of pereopod 5, pleopod 1 and uropod, left lateral view; E, telson, dorsal view (setae omitted); F, left uropod, dorsal view perpendicular to horizontal plane (setae omitted).

FIGURE 8. Manaxius aurantiaca n. sp., holotype, female (cl 5.3 mm), CBM-ZC 16168. A, left maxilliped 3, lateral view; B, ischium of left maxilliped 3, upper view; C, left pereopod 2, lateral view; D, left pereopod 3, lateral view; E, distal part of propodus and dactylus of left pereopod 3, lateral view; F, left pereopod 4, lateral view; G, distal part of propodus and dactylus of left pereopod 4, lateral view; H, right pereopod 5, lateral view; I, distal part of propodus and dactylus of right pereopod 5, mesial view.

FIGURE 9. Manaxius aurantiaca n. sp., holotype, female (cl 5.3 mm), CBM-ZC 16168, chelipeds (pereopod 1). A, ischium and merus of right (major) cheliped, lateral view; B, same, mesial view (setae omitted); C, carpus and chela of right (major) cheliped, lateral view; D, same, mesial view (setae omitted); E, ischium and merus of left (minor) cheliped, lateral view; F, carpus and chela of left (minor) cheliped; G, same, mesial view (setae omitted).