Munidopsis dispar, 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 : -

MUNIDOPSIS DISPAR SP. NOV.

( FIGS 19, 20; SUPPORTING INFORMATION, FIG. S6A)

Zoobank registration: urn:lsid:zoobank.org:act:AE49D1A4-AB91-444A-82F4-7ED52B0FB058

Material examined: Holotype, MBM189200 , one ovig. female ( PCL 7.2 mm), stn. FX-DIVE 70, M2 seamount near the Mariana Trench , West Pacific, 11°16.25’N, 139°25.51’E, 1458 m, coll. Faxian ROV on R / V Kexue, 27 March 2016 . Paratypes: MBM286629 , one female ( PCL 6.8 mm), stn. FX-DIVE 137, M4 seamount located on the Caroline Plate , West Pacific, associated with Schizopathidae gorgonian coral, 10°35.20’N, 140°07.54’E, 1282 m, coll. Faxian ROV on R / V Kexue , 21 August 2017 . MBM286630 , one male ( PCL 8.2 mm), stn. FX-DIVE 137, M4 seamount located on the Caroline Plate , West Pacific, 10°35.18’N, 140°07.50’E, 1246 m, coll. Faxian ROV on R / V Kexue , 21 August 2017 .

Description: Carapace (excluding rostrum) approximately as long as broad. Frontal margins concave, outer orbital angle produced into blunt lobe above antennal peduncle. Lateral margins slightly convex, with numerous tooth-like tubercles. Anterolateral corners subrectangular. Posterior margin ridged, covered with tubercles. Dorsal surface covered with numerous toothlike tubercles with triangular tips and bearing curved, weakly plumose setae anteriorly. Gastric region slightly elevated, with two pairs of prominent epigastric processes much more acute than surrounding tubercles. Cervical groove distinct. Rostrum flat and horizontal, 0.4 times as long as remaining carapace length, 1.1 times longer than broad (measured between posterior orbital margins), and covered with tubercles on dorsal surface and lateral margins; lateral margins straight; dorsal surface longitudinally carinate along midline. Pterygostomial flaps with flat and elongate tubercles on lateral surface.

Sternal plastron slightly longer than broad. Sternite 3 broader than anterior margin of sternite 4, divided into two parts by median groove; anterior margin with four lobes. Sternite 4 with narrow anterior margin contacting median third part of sternite 3; lateral margin straight on anterior half, distinctly tuberculate and rugose; ventral surface with short rugae and shallow, longitudinal median groove in anterior part, and depressed in posterior part. Sternites 4–7 with shallow median groove, seperated with one another with elevated, transverse ridges.

Abdominal tergites unarmed; tergites 2–4 each with two transverse uninterrupted ridges; lateral part of dorsal surfaces with numerous scale-like rugae.

Telson composed of eight (or seven in one paratype) distinct plates.

Eyestalk immovable. Cornea hemispheric, globular and cupped in ocular peduncle. Ocular peduncle short and fixed, without eyespine. Epistomial spine well developed immediately lateral to eyestalk and ventral to frontal margin.

Antennular peduncle with basal article longer than broad; distal margin armed with strong ventrolateral (rarely with affiliated spine) spine and two dorsolateral spines; lateral face slightly inflated; ventral surface with short rugae.

Antennal peduncle reaching to distal third length of rostrum. Article 1 immovable, with stout distolateral tooth; ventral distomesial corner blunt. Article 2 armed with distinct distolateral spine. Article 3 unarmed, with concave mesial margin. Article 4 unarmed.

Third maxilliped stout. Ischium longer than broad, approximately 0.8 times merus length; disto-extensor and distoflexor corners each with small acute spine; crista dentata well developed, extending on to basis. Merus longer than broad, extensor margin rugose, with small distal spine; flexor margin with four spines increasing in size posteriorly (sometimes serrated distally). Carpus short, extensor margin with tubercles and rugae. Propodus with distoflexor margin slightly convex.

P1 subequal(subequal in paratypes;right P1 of holotype larger than left P1), 2.2 times PCL; each segment covered with numerous tooth-like and scale-like tubercles on surfaces and margins bearing weakly plumose setae (usually curved) anteriorly; tubercles on ventral surfaces and palm somewhat compressed. Ischium short, dorsal distal margin with distinct spine; ventrodistal margin anteriorly produced. Merus approximately 0.7 times PCL; dorsal surface armed with longitudinal row of spines (or pointed tubercles) successively decreasing in size; distal margin with strong dorsomesial, ventromesial and ventrolateral spines. Carpus approximately half of merus length; distal margin with strong dorsomesial and lateral spines and additional pointed tubercles; dorsal surface with a row of tubercles. Palm relatively compressed, unarmed, approximately 0.8 times merus length, 2.2 times as long as broad; lateral margin at base of fixed finger slightly concave. Fingers 0.7 times palm length, opposable margins distally spooned and crenulated; occlusal margins serrated, with low, triangular tooth near base of movable finger.

P2–4 stout; P2 approximately 1.6 times PCL, reaching midlength of P1 palm; lateral surfaces of ischia, meri, carpi and propodi covered with tooth-like and scaleliketubercles; extensor margin of each segment, as well as anterior margins of tubercles, bearing weakly plumose setae. Meri somewhat compressed, subequal in breadth but decreasing in length posteriorly; P2 merus approximately half of PCL and 3.8 times as long as broad, P3 merus 0.9 times P2 merus length, P4 merus 0.8 times P2 merus length; extensor margin armed with a row of spines accompanied by pointed tubercles; flexor margin with a row of pointed tubercles. Carpi subequal in length, approximately half of P2 merus length; extensor surface with two longitudinal ridges, each armed with a row of spines, spines on lateral ridge relatively short and degenerated; flexor margin unarmed. Propodi subcylindrical, subequal in length and breadth, approximately 0.9 times P2 merus length and 5.6 times as long as broad; lateral surface with a row of spines or pointed tubercles (degenerated on P4); extensor margin indistinctly with two rows of spines or pointed tubercles on proximal 0.6 part; flexor margin with distal pair of movable corneous spines. Dactyli approximately half of propodi length, narrowing distally; extensor margin slightly rugose; flexor margin straight, with 10 or 11 movable corneous spines (increasing in size distally) on entire length including distal spine closely appressed to claw; each corneous spine based on low, triangular tooth.

Pereopods without epipod.

Coloration: In fresh condition, body entirely light orange.

Habitats: One ovig. female from M2 seamount was associated with golden coral Chrysogorgia sp. , and one female from the Caroline plate was associated with Schizopathidae coral Bathypathes sp.

Distribution: A seamount near the Mariana Trench and a seamount located on the Caroline Plate, West Pacific; depth 1246–1458 m.

Etymology: From the Latin dispar , unlike, in reference to the clear difference between the new species and the closely related species M. sonne Baba, 1995 .

Remarks: Munidopsis dispar is morphologically similar to its sister-species M. sonne from the West Pacific in having numerous tooth-like tubercles on the carapace and pereopods, lateral margins of carapace unarmed, triangular rostrum, cornea hemispheric and eyestalks without eye spines. The new species, however, can be distinguished from M. sonne by having two pairs of highly protruding triangular epigastric processes, a row of corneous spines on nearly the entire length of the P2–4 dactyli flexor margin and pereopods without epipods. In contrast, M. sonne has a pair of ‘broad, anteroposteriorly compressed, truncate’ epigastric processes, a row of setae (probably setae-like spines) on the distal twothirds of the P2–4 dactyli flexor margin and epipods on P1–3 ( Baba, 1995).

The numerous tubercles on the carapace and pereopods also link the new species to M. laevisquama Lin & Chan, 2011 . The new species is different from the latter in having tooth-like tubercles on the carapace, a triangular rostrum, the flexor margin of P2–4 dactyli with corneous spines nearly on entire length, and pereopods without epipods. In contrast, M. laevisquama has squama-like tubercles on the carapace (and without pairs of prominent epigastric processes), the base of the rostrum is distinctly constricted, flexor margin of P2–4 dactyli with small corneous spines only on distal half and epipods present on P1–3.

No DNA information for M.sonne and M.laevisquama is available for comparative analysis. The intraspecific genetic distances among the type specimens, although they were collected from two different seamounts, are 0.5–1.1% for COI and 0.2–2.6% for 16S.