Munida pubescens, Dong & Gan & Li, 2021

Dong, Dong, Gan, Zhibin & Li, Xinzheng, 2021, Descriptions of eleven new species of squat lobsters (Crustacea: Anomura) from seamounts around the Yap and Mariana Trenches with notes on DNA barcodes and phylogeny, Zoological Journal of the Linnean Society 192 : -

MUNIDA PUBESCENS SP. NOV.

( FIGS 15, 16; SUPPORTING INFORMATION, FIG. S5A)

Zoobank registration: urn:lsid:zoobank.org:act:5B1096CD-861F-47C6-B49F-6CDDF11354D7 Material examined: Holotype, MBM189190 , one male (16.3 PCL mm), stn. FX-DIVE 19, Y3 seamount near Yap Trench , West Pacific, 8°51’N, 137°47’E, 255–311 m, coll. Faxian ROV on R / V Kexue, 22 December 2014.

Description: Carapace (excluding rostrum) slightly longer than broad, approximately 1.1 times longer than broad. Front margin slightly oblique. Lateral margins nearly parallel; anterolateral spines strong, anteriorly directed, reaching proximal 0.3 of supraocular spine; hepatic margin armed with distinct spine smaller than anteriolateral one; branchial margin armed with five spines; posterior branchial margin with oblique ridges extending on to dorsal surface; posterior margin weakly concave medially. Dorsal surface gently convex transversely; cervical grooves clear; main transverse ridges present on gastric, cardiac, intestinal and posterior branchial regions bearing fine setae anteriorly; short scale-like secondary striae present among main ridges and on hepatic and anterior branchial regions; paired parahepatic spines, anterior branchial dorsal spines and postcervical spines well developed; gastric region slightly elevated, with five pairs of epigastric spines medially separated by row of three scale-like ridges, mesial second pair of epigastric spines longest and lateralmost pair smallest. Rostral spine spiniform, smoothly carinate, approximately 0.4 times remaining carapace length, horizontal in lateral view; supraocular spines spiniform and parallel, smoothly carinate, approximately 0.4 times of rostral spine length, hardly reaching proximal end of cornea. Pterygostomial flaps with short and long oblique ridges on lateral surface, anterior end blunt.

Sternal plastron broader than long; sternites 4–7 deeply grooved along midline, separated with each other by elevated, transverse ridges. Sternite 3 approximately 3.4 times as broad as long, anterior margin bilobated and faintly denticulate; posterior margin contacting sternite 4 on median 0.3 part. Sternite 4 with anterior margin broadly curved, bearing several scale-like ridges on ventral surface. Sternite 6 with pair of scale-like ridges on lateral ventral surface.

Abdominal tergites smooth. Tergite 2 with eight spines evenly along anterior ridge. Dorsal surfaces of tergites 2–5 each with three transverse main ridges (median ridge much shallower) bearing faint setae anteriorly; median ridge on tergite 4 interrupted medially.

Telson broader than long; dorsal surface with scalelike tubercles.

Eyes large, cornea dilated, diameter approximately 2.9 times wider than sinus between rostral spine and supraocular spine, and third of distance between bases of anterolateral spines. Eyestalk reaching proximal 0.6 of rostral spine; eyelash dense.

Antennular peduncle with basal article (excluding distal spines) approximately 2.4 times longer than broad, reaching distal third of rostral spine. Distolateral spine slightly longer than distomesial spine. Lateral margin with two median spines. Ventral surface with scale-like rugae.

Antennal peduncle falling short of distal cornea margin. Article 1 immovable, with strong distomesial spine reaching midlength of article 2. Article 2 armed with strong distomesial spine reaching distal end of article 3, and distolateral spine hardly reaching distal end of article 3; mesial and lateral margins with small median tubercles. Article 3 and article 4 short and unarmed.

Third maxilliped slender. Ischium slight longer than merus, with acute distoflexor spine; ventral surface with short rugae. Merus with three spines on flexor margin: proximal and distal spines strong, median spine small; extensor margin slightly rugose, unarmed; ventral surface with short rugae. Carpus unarmed.

P1 subequal, 2.6 times PCL; surfaces and margins of each segment covered in thick and soft plumose setae concealing numerous scale-like ridges; scalelike ridges much more elevated as pointed tubercles on ventral surfaces and lateral margins of each segment; mesial margins of each segment bearing sparse iridescent setae. Merus approximately 0.9 times PCL, 2.6 times as long as broad; distal margin with strong dorsal, dorsomesial, ventromesial spines and small lateral spine; distal dorsal spine followed by row of spines descreasing in size proximally on dorsal surface extending to proximal end of merus; distal dorsomesial spine followed by two dorsal spines and another prominent spine ventrally; distal ventromesial spine followed by strong median spine. Carpus subcylinderical, approximately 0.6 times of merus length, 1.7 times longer than broad; distal margin with distinct dorsal, dorsomesial, lateral and ventrolateral spines, each distal spine (except distal ventrolateral spine) followed by longitudinal row of two or three spines, spines on dorsomesial row stronger; dorsal surface with scattered small spines or pointed tubercles on mesial part; ventral surface with strong median spine. Palm compressed, 0.7 times merus length, 1.9 times as long as broad; surface with a row of five or six spines along dorsal midline, row of five spines along dorsomesial margin accompanied with small dorsal spines, row of three spines along ventromesial margin, row of six spines along dorsolateral margin extending distally on to base of fixed finger, and small scattered spines on lateral part of dorsal surface; dorsodistal and ventrodistal margins each with small spines adjacent to base of dactylus. Fingers approximately 0.9 times palm length, tips hooked; occlusal margins nearly straight, denticulate; lateral margin of fixed finger with small paired subterminal spines followed by row of three or four spines; mesial margin of dactylus with elevated scale-like ridges and single strong basal spine.

P2–4 relatively stout, P2 approximately 1.9 times PCL, reaching midlength of P1 palm; surfaces of meri, carpi and propodi with scale-like rugae; extensor margins of meri and carpi with dense plumose setae and row of iridescent setae. Meri compressed, decreasing in length posteriorly from P2 to P4; P2 merus approximately 0.8 times of PCL, P3 merus 0.8 times P2 merus length, P4 merus 0.6 times P2 merus length; length–width ratio of P2–4 meri being 5.4, 4.4 and 3.8, respectively; P2 and P3 meri extensor margin with a row of slender spines, disto-extensor spine strongest; flexor margin with elevated scale-like ridges, bearing prominent distoflexor spine followed with pointed tubercle. Carpi short, P2 and P3 carpi subequal in length, approximately 0.3 times P2 merus length, P4 carpus 0.9 times P2 carpus length; extensor margin with two longitudinal ridges, mesial ridge with one to four spines, distalmost spine strongest, lateral ridge low and with scale-like ridges; flexor margin rugose, with prominent distoflexor spine. Propodi slender; P2 and P3 propodi subequal in length, approximately 0.8 times P2 merus length, 5.7 times as long as broad, P4 propodus approximately 0.9 times P2 propodus length; extensor margin rugose; flexor margin with seven to nine corneous spines, distalmost spine based on acute tooth; additional small spine present on mesial distoflexor corner. Dactyli short, hairy, approximately half of P2 propodus length, 3.4 times as long as broad, terminating in slightly hooked claw; extensor margin rugose and straight; flexor margin slightly convex proximally, armed with 10–12 movable corneous spines on entire length, including distal spine closely appressed to claw.

Pereopods without epipod.

Habitat: Unknown.

Distribution: West Pacific, seamount near the Yap Trench; depth 255– 311 m.

Etymology: From the Latin, pubescens , meaning becoming hairy (litterally to reach puberty), referring to the hairy chelipeds of this species.

Remarks: The new species is morphologically similar to M. eclepsis and M. thoe Macpherson, 1994 from the southern and western Pacific in having a combination of the following characters: carapace with five branchial marginal spines; eyes relatively large (diameter at least one-third of distance between the bases of the anterolateral spines); P1 movable finger with only a basal spine on the mesial margin; P1 fixed finger with a row of spines on the lateral margin; P2–4 meri without a row of spines on the flexor margin. The new species can be readily distinguished from the other two in having P1 covered in thick plumose setae, three spines on the flexor margin of the third maxilliped merus, and the distomesial spine of antennal peduncle article 2 reaching the distal end of article 3. In contrast, the other two species have P1 hairless on the surface, two spines present on the flexor margin of the third maxiliped merus, and the distomesial spine of antennal peduncle article 2 distinctly over-reaching the end of article 3 ( Macpherson, 1994; Macpherson, pers. comm., 2019). Munida pubescens further differs from M. eclepsis in having numerous secondary striae on the dorsal surface of the carapace, whereas the latter has few secondary striae. Munida pubescens further differs from M. thoe in having stout P1–4 (e.g. P1 carpus 1.7 times as long as broad, P2 merus 5.4 times as long as broad), whereas M. thoe has much more slender P1–4 (e.g. P1 carpus 2.9 times as long as broad, P2 merus 8.2 times as long as broad).

The characters of thick plumose setae on P1, relatively large eyes and similar spination pattern on the carapace, abdominal segments, antennular and antennal peduncles link the new species to M.militaris , M. rubella Macpherson & de Saint Laurent, 1991 and M. koyo Komai, 2011b . The new species, however, can be distinguished from the latter three in having three instead of two spines on the flexor margin of the third maxilliped merus, relatively stouter P2–4 (e.g. the P2 merus is 5.4 times longer than broad; in contrast, the values are 7.4 in M. militaris , 7.0 in M. rubella and 7.9 in M. koyo ) (Baba & Macpherson, 1991; Macpherson & de Saint Laurent, 1991; Komai, 2011b). The new species further differs from M. militaris and M. rubella in having a row of spines instead of only one or two proximal spines on the lateral margin of the fixed finger, and P2–4 meri armed with only single distal spine instead of a row of spines (including projecting scales) on the flexor margin. The new species further differs from M. koyo in having subparallel supraocular spines, prominent anterolateral spines (distinctly exceeding the bases of supraocular spines), and the mesial margin of antennal article 2 unarmed; whereas M. koyo has distally divergent supraocular spines, short anterolateral spines (falling short of bases of the supraocular spines) and a distinct median spine on the mesial margin of antennal article 2.

No DNA information for M. rubella and M. koyo is available for comparative analysis. The genetic distances between the new species and M. eclepsis from New Caledonia ( Machordom & Macpherson, 2004) are 8.3% for COI and 2.4% for 16S. The genetic distances between the new species and M. thoe from New Caledonia ( Machordom & Macpherson, 2004; Samadi et al., 2006) are 14.8–15.2% for COI and 5.3% for 16S. The genetic distances between the new species and M. militaris are 12.3–12.7% for COI and 2.3–2.5% for 16S.