Uroptychodes yapensis, 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 : -

UROPTYCHODES YAPENSIS SP. NOV.

( FIGS 3, 4; SUPPORTING INFORMATION, FIG. S1A)

Zoobank registration: urn:lsid:zoobank.org:act:D880EDC1-BEDA-4ECC-8A18-CDB8DAA52239

Material examined: Holotype, MBM189186 , one female ( PCL 6.3 mm), stn. FX-DIVE18, Y3 seamount near Yap Trench , West Pacific, 8°54’N, 137°48’E, 870–1129 m, coll. Faxian ROV on R / V Kexue, 18 December 2014.

Description: Carapace (excluding rostrum) broader than long. Outer orbital angle produced into triangular spine. Lateral margins divergent posteriorly; anterolateral spine slender, over-reaching outer orbital angle; hepatic margin with one or two small spines; anterior branchial margin with one well-developed spine followed with additional small spine; posterior branchial margin armed with five prominent spines decreasing in size posteriorly. Dorsal surface smooth, bearing fine and short setae, especially dense on lateral margins and lateral branchial regions. Rostrum broad, dagger-shaped, approximately 0.8 times of remaining carapace length, twice as long as broad; dorsal surface with fine setae; lateral margin straight, bearing three or four spinules on distal half. Pterygostomial flap with strong spine at anterior end over-reaching anterolateral spine.

Sternal plastron slightly broader than long. Sternite 3 with surface depressed; anterior margin concave, with pair of small submedian spines separated by V-shaped notch; anterior ends triangular; lateral margin with one or two denticles. Sternite 4 with anterolateral margin approximately as long as posterolateral margin, anterolateral corner bearing short spines, anteriorly reaching level of submedian spines of sternite 3. Sternites 5–7 with transverse ridges interrupted by midline groove.

Abdominal tergites smooth, bearing fine and short setae.

Telson approximately 1.8 times broader than long; distal portion 1.9 times proximal portion length.

Eyestalk short, reaching distal 0.8 of rostrum; cornea not dilated, partly concealed by rostrum in dorsal view; longer than half of remaining peduncle length.

Antennal peduncle reaching distal 0.6 of rostrum. Article 2 with small distolateral spine. Article 4 (penultimate article) bearing distal ventromesial spine. Article 5 (ultimate article) unarmed, 1.7 times longer than article 4. Antennal scale subtriangular, 3.2 times longer than broad, slightly broader than article 4, anteriorly reaching midlength of article 5; lateral margin weakly serrated (right) or with minute median spine (left), bearing plumose setae.

Third maxilliped slender. Basis unarmed. Ischium with crista dentata with fine denticles. Merus 1.3 times longer than ischium length; flexor margin with two minute denticles on median part; distal margin bearing small acute spine near lateral end. Carpus having extensor margin proximally tuberculate, with minute distal spine.

P1 long and subequal, approximately 4.5 times PCL; bearing fine setae on surfaces of each segment. Ischium armed with acute dorsodistal spine; ventromesial margin bearing row of spinules and strong subterminal spine. Merus approximately as long as PCL, subcylindrical, surface with rows of rugae sometimes bearing tiny acute spines; distal margin with two dorsal spines (each on mesial and lateral sides), small lateral spine (absent on right P1), strong ventromesial spine and small ventrolateral spine. Carpus longer than meri, subcylindrical, approximately 1.5 times PCL; surface with rows of rugae usually bearing tiny spines; dorsoproximal end with two distinct spines; distal margin with two strong dorsal spines (each on mesial and lateral sides), small lateral spine, strong ventromesial spine and minute ventrolateral spine. Chela relatively compressed; approximately 9.0 times longer than broad, 1.9 times PCL, proximally rugose and bearing two spines on dorsal surface. Fingers much more setose, 0.3 times of palm length; tips acute; occlusal margins minutely denticulate, with low, broad tooth near base of dactylus.

P2 and P4 (P3 missing) subequal, covered with short rugae bearing fine setae on surfaces and margins of each segment. P2 much more slender. P2 merus 6.1 times longer than broad; extensor margin with a row of spines and bearing dense and long setae. P2 carpus relatively long, 3.9 times longer than broad, half of P2 merus length; extensor margin with several spines. P2 propodus slightly curving, 4.9 times longer than broad, 0.6 times P2 merus length; flexor margin with small median cornea spine and pair of distal cornea spines. P2 dactylus curving, approximately 0.6 times P2 propodus length; flexor margin unarmed except slender terminal spine and short and broad penultimate spine obscured in thick stiff setae on distal half. P4 relatively stout. P4 merus 3.7 times longer than broad, 0.8 times P2 merus length; extensor margin with a row of spines; flexor margin rugose, with acute distal spine. P4 carpus relatively short, 1.6 times longer than broad, half of P4 merus length; extensor margin with a row of spines, distalmost one strongest. P4 propodus straight, five times longer than broad, 1.1 times P4 merus length; flexor margin with three corneous spines including distal pair. P4 dactylus moderately curving, 0.4 times of P4 propodus length; flexor margin with 11 corneous spines evenly arranged along entire length, ultimate spine slender and short, close to broad penultimate spine.

Habitat: Unknown.

Distribution: West Pacific, seamount near the Yap Trench; depth 870–1129 m.

Etymology: The specific name refers to the type locality, which is close to the Yap Trench.

Remarks: The new species is morphologically similar to U. spinimarginatus in having a smooth dorsal surface of carapace, minute spines on the distal portion of the rostral lateral margin and five strong spines on the lateral branchial margin. The new species can be readily distinguished from U. spinimarginatus in having strong spines on the distal margins of the P1 merus and carpus, and the P2, P4 (P3 missing) propodi with three corneous spines on the flexor margin including the distal pair. In contrast, U. spinimarginatus lacks distinct spines on P1 ( Baba, 1988, 2004) or at most has small distal spines on the P1 merus ( Schnabel, 2009), and the P2–4 propodi only have the distal pair spines on the flexor margin ( Baba, 2004; Schnabel, 2009). In addition, the P2 merus extensor margin of the new species is armed with a row of distinct spines, while there are no distinct spines on the lectotype of U. spinimarginatus ( Baba, 2004) , but these spines were present in paralectotypes and specimens from Havre volcano ( Schnabel, 2009, 2020). Schnabel (2009) noted the variations in spines on the appendages, maxilliped and pterygostomial flap based on the type material and other specimens of U. spinimarginatus and suggested that these were intraspecific characters that varied with size and sex. However, in our specimen, the spines on the distal margins of the P1 merus and carpus are significantly pronounced; this is different from U. spinimarginatus , which is nearly unarmed on these segments, especially on the dorsodistal margin of the carpus. Moreover, the genetic distances between our specimen and U. spinimarginatus are significantly high (see below). Based on the morphological and molecular analyses, the present material can be accepted as new to science.

The genetic distances between the new species and U. spinimarginatus from this study are 13.5–13.8% for COI and 2.6% for 16S, showing distinct genetic divergence.