Munida rosea, 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 ROSEA SP. NOV.

( FIGS 17, 18; SUPPORTING INFORMATION, FIG. S5B)

Zoobank registration: urn:lsid:zoobank.org:act:6DDF79B6-6574-4502-B547-E475653E4736

Material examined: Holotype, MBM189193 , one male ( PCL 13.7 mm), stn. FX-DIVE 61, M2 seamount near the Mariana Trench , West Pacific, 11°21.01’N, 139°20.41’E, 865 m, coll. Faxian ROV on R / V Kexue, 18 March 2016.

Description: Carapace (excluding rostrum) approximately 1.2 times longer than broad. Front margin oblique. Lateral margins slightly convergent posteriorly; anterolateral spines strong, weakly anteriolaterally directed, reaching base of rostral spine; hepatic margin armed with distinct spine smaller than anteriolateral spine; branchial margin armed with five distinct spines decreasing in size posteriorly; posterior branchial margin with oblique ridges extending on to dorsal surface; posterior margin nearly straight. Dorsal surface gently convex transversely; cervical grooves clear; main transverse ridges present on gastric, cardiac, intestinal and posterior branchial regions bearing fine setae anteriorly; paired parahepatic spines, anterior branchial dorsal spines and postcervical spines well developed; gastric region slightly elevated, with four pairs of epigastric spines, mesial second pair longest and lateralmost pair smallest; hepatic and anterior branchial regions with short, scale-like ridges. Cardiac region well delineated. Rostral spine spiniform, smoothly carinate dorsally, approximately half of remaining carapace length, slightly upturning distally; supraocular spines spiniform and slightly divergent distally, approximately 0.4 times rostral spine length, slightly over-reaching distal margin of cornea. Pterygostomial flaps with short and long ridges on lateral surface, anterior end blunt.

Sternal plastron broader than long; sternites 4–7 shallowly grooved along midline, separated with each other by elevated, transverse ridges. Sternite 3 approximately 3.6 times as broad as long, anterior margin faintly denticulate, medially concave; posterior margin contacting sternite 4 on median third. Sternite 4 with anterior margin broadly curved, several short and scale-like ridges present on ventral surface.

Abdominal tergites smooth. Tergite 2 with eight spines evenly along anterior ridge. Dorsal surfaces of tergites 2–5 each with two uninterrupted transverse main ridges bearing faint setae anteriorly; tergite 4 with two secondary striae between main ridges.

Telson broader than long; dorsal surface with scalelike tubercles.

Eyes moderate size, cornea hemispheric, slightly dilated, diameter approximately 1.6 times as wide as sinus between rostral spine and supraocular spine, and slightly more than quarter of distance between bases of anterolateral spines. Eyestalk short, reaching proximal third of rostral spine; eyelash scarce.

Antennular peduncle with basal article approximately 2.2 times longer than broad, barely reaching midlength of rostral spine. Distolateral spine slightly longer than distomesial spine. Lateral margin with two median spines. Ventral surface with scale-like rugae.

Antennal peduncle slightly over-reaching distal cornea margin. Article 1 immovable, with strong distomesial spine reaching midlength of article 2. Article 2 armed with strong distomesial spine nearly reaching distal end of article 4, and distolateral spine hardly reaching distal end of article 3; additional small spine present on midlength of mesial margin. Article 3 and 4 unarmed.

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

P1 subequal, 2.8 times PCL; surfaces of each segment with scale-like rugae (especially on ventral surfaces), bearing fine setae; mesial and lateral margins with stiff non-iridescent setae and plumose setae. Merus approximately 1.1 times PCL, 4.2 times as long as broad; distal margin with strong dorsal, lateral, dorsomesial spines and moderate-sized ventromesial spine; dorsodistal spine followed by a row of spines diminishing in size proximally and extending to proximal end of merus; distal dorsomesial spine followed by prominent ventral spine and another two dorsal spines; distal ventromesial spine followed by two median spines. Carpus subcylinderical, half of merus length, 2.2 times longer than broad; disal margin with distinct dorsal, lateral, dorsomesial and ventrolateral spines, each (except ventrolateral spine) followed with longitudinal row of two or three spines, spines on dorsomesial row stronger; ventral surface with strong median spine and small spine near ventrodistal margin. Palm compressed, 0.6 times merus length, 2.6 times as long as broad; surface with a row of five spines on dorsal midline, row of three dorsomesial spines with several small affiliated dorsal spines, row of four or five dorsolateral spines and row of three ventromesial spines; dorsodistal and ventrodistal margins each with small spines adjacent to base of dactylus. Fingers approximately 1.1 times palm length, tips hooked; occlusal margins nearly straight, minutely denticulate, with soft setae; lateral margin of fixed finger rugose, with strong base spine and two small subterminal spines; mesial margin of dactylus rugose, with only strong basal spine.

P2–4 slender, P2 approximately 2.3 times PCL, reaching bases of P1 fingers; surfaces of meri, carpi and propodi covered with scale-like rugae bearing fine setae on edges; extensor margin of each segment with dense fine plumose setae and row of stiff setae. Meri compressed, decreasing in length posteriorly; P2 merus approximately as long as PCL, P3 merus 0.9 times P2 merus length, P4 merus 0.6 times P2 merus length; length–width ratio of P2–4 meri being 9.8, 7.7 and 5.2, respectively; extensor margin with a row of slender spines, disto-extensor spine strongest; flexor margin with a row of two to six spines, distoflexor spine strongest. Carpi short, subequal in length from P2 to P4, approximately 0.2 times P2 merus length; extensor margin with two longitudinal ridges, mesial ridge with two spines (distalmost spine strongest) and additional small spines on proximal part, lateral ridge granulate; flexor margin with prominent distoflexor spine. Propodi slender; P2 and P3 propodi subequal in length, approximately 0.7 times P2 merus length, eight or nine times as long as broad, P4 propodus relatively shorter, approximately 0.9 times P2 propodus length; extensor margin rugose, with a row of two to four slender spines (unarmed on P4); flexor margin with 8–12 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, 5.2 times as long as broad, terminating in slightly hooked claw; extensor margin rugose, straight; flexor margin nearly straight, armed with 10–14 movable corneous spines on entire length.

Pereopods without epipod.

Coloration: Carapace and pereopods pinkish white; rostral spine, anterolateral spines and tips of dactyli on P1–4 orange; cornea grey-black.

Habitat: On rocky substrate of seamount.

Distribution: West Pacific, seamount near the Mariana Trench; depth 865 m.

Etymology: From the Latin roseus, rosy or pink, referring to the basic colour of the species.

Remarks: The new species can be readily discriminated from the known congeners in having row of slender spines (at least two) on the extensor margin of the P2 and P3 propodi. Munida rosea is morphologically similar to M. amathea Macpherson & de Saint Laurent, 1991 , M. rubella and M. militaris in having a combination of the following characters: carapace with five branchial marginal spines; third maxilliped merus with two flexor spines; lateral portions of sternites 6 and 7 smooth; P1 movable finger only with basal spine on the mesial margin; P1 fixed finger only with strong basal spine and two subterminal spines on the lateral margin; P2 and P3 dactyli at most half of the propodi length and with movable spines on the entire flexor margin. In addition to the spinose P2 and P3 propodi, the new species is also different from the three species in having relatively small corneas (diameter slightly more than a quarter of the distance between the bases of the anterolateral spines), and the dorsal surfaces of the carapace (except the hepatic and anterior branchial regions) and abdominal tergites 2 and 3 are devoid of secondary striae among the main ridges. In contrast, the three species have relatively large corneas (diameter one-third of the distance between the bases of the anterolateral spines), and the dorsal surfaces of the carapace and abdominal tergites 2 and 3 have short secondary striae among the main ridges (at least on the gastric region and the abdominal tergites, see remarks under Munida pubescens for more details) ( Macpherson & de Saint Laurent, 1991; Baba, 2005). The new species further differs from M. amathea and M. rubella in having four pairs of epigastric spines and the distomesial spine of the antennal peduncle article 2 reaching the end of peduncle, whereas the latter two have five or six pairs of epigastric spines, and the distomesial spine of the antennal peduncle article 2 falls short of the end of the peduncle. The new species further differs from M. militaris in having sparse setae on the dorsal surface of P1; M.militaris , by comparison, has P1 densely covered in plumose setae concealing the surfaces.

Munida rosea also resembles M.eclepsis in having the similar spination pattern on the carapace, abdominal segments, antennular and antennal peduncles. In addition to the spinose P2 and P3 propodi, the new species differs from M. eclepsis in having smaller eyes with cornea slightly more than a quarter, instead of half, of the distance between bases of anterolateral spines; P1 fixed finger only armed with basal spine (excluding distal spines) instead of a row of spines on the lateral margin; and much more slender P2–4 (e.g. P2 merus is 9.8 times instead of 5.5 times longer than broad; P2 dactylus 5.2 times instead of 4.5 times longer than broad) ( Macpherson, 1994).

No DNA information for M. amathea or M. rubella is available for comparative analysis. The genetic distances between the new species and M. militaris are 8.0–8.2% for COI and 2.5% for 16S. The genetic distances between the new species and M. eclepsis from New Caledonia ( Machordom & Macpherson, 2004) are 6.8% for COI and 2.5% for 16S.