Uroptychus inaequipes, Wang, 2017

Wang, Chunsheng, 2017, Three squat lobsters (Crustacea: Decapoda: Anomura) from tropical West Pacific seamounts, with description of a new species of Uroptychus Henderson, 1888, Zootaxa 4311 (3), pp. 389-398 : 390-393

Uroptychus inaequipes n. sp.

( Figs. 1 , 2 , 4 A)

Material examined. Holotype: oVig. female (PCL 9.1 mm), St. DV 83, slope of the Lamont Guyot , East Mariana Basin, 159.24°E, 21.61°N, depth 2000 m, commensal with gorgonian coral, coll. Dr. Bo Lu in Jiaolong manned submersible, R/ V Xiangyanghong 9, 29 July 2014.

Description of holotype. Carapace ( Fig. 1 A) (eXcluding rostrum) distinctly longer than broad. Lateral margins slightly diVergent posteriorly, ridged at posterior part, anterolateral spine slightly eXceeding lateral limit of orbital margin, dorsally accompanying tiny affiliated spine; posterior margin strongly concaVe. Dorsal surface glabrous, strongly conVeX from side to side; cerVical grooVes weakly defined. Rostrum narrowly triangular, 0.4 remaining carapace length, 1.2 times as long as broad (distance between bases of posterior orbital margin); apeX acute, weakly upturned; lateral margins unarmed, nearly straight. Pterygostomial flap ( Fig. 1 B) medially concaVe, with blunt anterior end.

Sternal plastron ( Fig. 1 C) broader than long, widening posteriorly. Sternite 3 approXimately twice broader than long; surface greatly depressed; anterior margin concaVe, with pair of submedian spines separated by narrow Ushaped notch; lateral lobes each with stout distolateral spine. Sternite 4 with anterior part depressed, separated from posterior part by transVerse ridges; anterolateral corner shallowly ridged but not produced; anterolateral margins unarmed, 1.2 posterolateral margins length. Sternites 5–7 with transVerse ridges interrupted by median longitudinal grooVe on surface.

Abdominal tergites ( Fig. 1 A) glabrous and unarmed on dorsal surface.

Telson ( Fig. 1 D) 1.8 times broader than long; distal part 1.7 times proXimal part length, distal margin subdiVided by median, broad V-shaped notch.

Eyestalk reaching distal 0.4 of rostrum, medially dilated; cornea small, narrower than and 0.6 of remaining peduncle length.

Antennular peduncle with basal article longitudinally oVate; Ventral surface glabrous, unarmed.

Antennal peduncle ( Fig. 1 E) reaching distal 0.14 of rostrum. Article 2 with produced distolateral angle. Article 4 and 5 unarmed; article 5 twice as long as article 4. Antennal scale subtriangular, 2.8 times as long as broad, almost reaching distal margin of article 4. Flagellum short, 1.5 times peduncle length.

Third maXilliped ( Fig. 1 F) slender. Ischium subcylindrical, relatiVely short, with moderately deVeloped crista dentata ( Fig. 1 G) on proXimal half (teeth irregularly arranged). Merus and carpus subcylindrical, unarmed. Propodus elongate, with broad, triangular lobe on fleXor margin. Dactylus oVate. EXopod straight, reaching midlength of endopod merus, flagellum deVeloped.

Pereopod 1 (P1, cheliped) ( Fig. 1 H) slender, subequal, glabrous, unarmed eXcept for fingers; surfaces with scattered small pits; meri and carpi subcylindrical, strongly broadened distally; right P1 4.8 times PCL, 1.1 times longer than left P1; right carpus and palm slightly longer than those of left. Ischium ( Fig. 1 I) armed with strong distolateral spine. Meri 1.1 times PCL, 0.6 right carpus length. Carpi relatiVely long; right carpus 1.5 times PCL, 1.1 left carpus length. Palms compressed; right palm 3.5 times longer than broad, 1.1 times left palm length, 0.8 right merus length. Fingers (dactylus and fiXed finger) setose, half of palm length; tips acute and bent Ventrally, slightly crossing oVer each other; occlusal margins straight and minutely denticulate on fiXed finger, and with broad, subrectangular tooth at base of dactylus.

Pereopods 2–4 (P2–4, ambulatory legs 1–3) ( Fig. 2 A–C) slender, each segment laterally compressed. Meri subrectangular, unarmed; P2 merus 0.9 to 1.0 PCL and 7 times longer than broad, P3 merus 0.9 PCL and P4 merus 0.8 PCL. Carpi unarmed, bearing few setae on distal eXtensor margins, subequal in length on P2–4, 0.6 P2 merus length. Propodi moderately setose on distal parts; subequal in length on P2–4, 0.7 P2 merus length; eXtensor margin straight; distal 0.6 part of fleXor margin weakly broadened but not conVeX, with row of moVable, corneous spines (7 spines on P2–3, 6 spines on P4), distalmost spine unpaired, adjacent to distofleXor end. Dactyli ( Fig. 2 D– F) setose, 0.3 of P2 merus length, strongly bent on proXimal one-third, fleXor spines differently arranged among P2–4; P2 dactylus with pair of fiXed, corneous terminal spines, eXtensor spine relatiVely stronger, fleXor margin eVenly with row of 8 moVable corneous spines increasing in size distally, distal first spine located relatiVely remote from terminal paired spines (twice of distance between distal first and distal second); P3–4 dactyli with strong single, corneous terminal spine, fleXor margin with row of 9 or 10 corneous spines, P3 fleXor distal first spine relatiVely closer to terminal spine than to distal second spine, P4 fleXor distal first spine equally close to terminal spine and distal second spine.

OVum with diameter 1.7 mm.

Coloration. Carapace reddish purple on hepatic and anterior gastric regions, base of rostrum and eyestalks; light purplish on cardiac, intestinal, posterior gastric and anterior branchial regions; white to light orange on posterior branchial regions. Abdomen tergites 1–4 orange-yellow to transparent, remaining tergites reddish-orange. Cornea bright orange. Pereopods orange yellow. Sternal plastron white. Third maXilliped red. Eggs orange.

Habitat. Commensal with gorgonian coral, Guyot slope; 2000 m.

Distribution. Only known in the type location, Lamont Guyot, tropical West Pacific.

Etymology. The specific name is deriVed from the Latin inaequalis meaning unequal, and Latin pes meaning foot, referring to the different arrangement of fleXor spines among the P2–4 dactyli.

Remarks. The new species has the fleXor spines on P2–4 dactyli differently arranged, which is morphologically unusual in most Uroptychus species. This character, howeVer, can also be obserVed in some specimens of U. remotispinatus Baba & Tirmizi, 1979 , U. longioculus Baba, 1990 and U. fenneri Baba & Wicksten, 2017 .

The new species belongs to a group of species characterized by the following morphological features: the carapace and chelipeds are glabrous and unarmed eXcept for the carapace anterolateral spines, the rostrum is narrow and longer than the eyestalks, and the P2–4 propodi are not strongly conVeX distally and each with an unpaired distalmost spine. The most closely allied species in this group include U. brevisquamatus Baba, 1988 , U. remotispinatus and U. vandamae Baba, 1988 . The new species is different from its relatiVes chiefly in haVing short antennal scales (just reaching the distal margin of the penultimate article), and unproduced anterolateral corners of sternite 4; whereas, in the latter three, the antennal scales generally either reach or oVerreach the middle of the ultimate article, and the anterolateral corners of the sternite 4 are distinctly produced. The new species can also be distinguished from U. brevisquamatus by the relatiVely longer chelipeds (more than four times PCL, instead of three times PCL on U. brevisquamatus ), antennal scales equally as broad as the peduncles instead of broader than the peduncles, and the fleXor marginal spines on P2–4 dactyli slender and slightly inclined instead of tiny and directed almost parallel to the fleXor margin. Uroptychus inaequipes n. sp. further differs from U. remotispinatus and U. vandamae in that the moVable spines of P2–4 dactyli are relatiVely eVenly arranged on fleXor margin, instead of being distributed almost on proXimal half (at least on P2).

We haVe no in-situ photo to Verify the new species directly associated with the gorgonian corals. HoweVer, the holotype was collected together with gorgonian corals and sponge samples. We therefore inferred the commensal relationships based on preVious studies ( Baba 2005; Baba et al. 2009).

Figures

FIGURE 1. Uroptychus inaequipes n. sp., holotype, ovig. female, PCL 9.1 mm. A, carapace and abdominal tergiteS 1 – 3, dorSal vieW; B, left pterygoStomian, lateral vieW; C, Sternal plaStron, ventral vieW; D, telSon, extenSor vieW; E, left antennal peduncle, ventral vieW; F, left third maxilliped, ventral vieW; G, left criSta dentata, ventral vieW; H, right cheliped, dorSal vieW; I, right cheliped iSchium and baSiS, ventrolateral vieW. ScaleS equal 1.0 mm.

FIGURE 2. Uroptychus inaequipes n. sp., holotype, ovig. female, PCL 9.1 mm. A, right pereopod 2, lateral vieW; B, right pereopod 3, lateral vieW; C, right pereopod 4, lateral vieW; D, dactyluS and diStal part of right pereopod 2 propoduS, lateral vieW; E, dactyluS of right pereopod 3, lateral vieW; F, dactyluS of right pereopod 4, lateral vieW. Setae omitted on B – F. ScaleS equal 1.0 mm.

FIGURE 4. SpecimenS examined, dorSal vieW. A, Uroptychus inaequipes n. sp., holotype, ovig. female, PCL 9.1 mm, freSh colour; B, Munidopsis bairdii (Smith, 1884), male, PCL 8.4 mm, conServed in ethanol; C, Munidopsis kensmithi JoneS & MacpherSon, 2007, male, PCL 8.5 mm, conServed in ethanol.