Epimeria liui, Wang & Zhu & Sha & Ren, 2020

Wang, Yanrong, Zhu, Chaodong, Sha, Zhongli & Ren, Xianqiu, 2020, Epimeria liui sp. nov., a new calcified amphipod (Amphipoda, Amphilochidea, Epimeriidae) from a seamount of the Caroline Plate, NW Pacific, ZooKeys 922, pp. 1-11 : 1

Epimeria liui sp. nov. Figs 1 , 2 , 3 , 4

Material examined.

Holotype. Ovigerous ♀ (17.8 mm) (MBM 286613), dissected, unnamed seamount on Caroline Plate, NW Pacific, M6089, St. FX-Dive 218, 10°07'N, 140°14'E, depth 813-1242 m, 6 June 2019, collected by team of ROV FAXIAN.

Diagnosis.

Rostrum hardly reaching to distal margin of first peduncular article of antenna 1; eyes present, pigmented, pyriform. Maxilliped palp article 4 with more than two teeth in internal margin. Coxa 5 with posterodistal corner produced. Pereonites 6, 7 and pleonites 1, 2 with size-increasing mid-dorsal teeth, the one on pereonite 6 blunt and small.

Description.

Body calcified. Head. Rostrum nearly as long as head, not reaching to distal margin of first peduncular article of antenna 1; anterior cephalic margin with a small lobe medially, lateral cephalic slightly produced; eyes bulging on head, pigmented, pyriform. Antenna 1 with peduncular article 1 about twice as long as article 2, 3 times as long as article 3, without distal tooth; accessory flagellum scale-like, hardly reaching to half-length of first flagellar article; primary flagellum with 26 articles, sparsely setose. Antenna 2 nearly as long as antenna 1, peduncular article 4 slightly longer than article 5; flagellum with 29 articles.

Mouthparts. Mandible with incisor and lacinia mobilis strongly dentate; molar triturative; palp article 3 densely setose medially, with two long setae distally. Maxilla 1 with inner plate subtriangular, obliquely convex inner margin with 10 stout plumose setae; outer plate distal margin oblique, with 11 lobate robust setae; palp exceeding outer plate; palp 2-articulate, article 2 with 3 robust setae and 5 long setae distally, inner margin bearing row of dense setae. Maxilla 2 with long, slender setae distally on lateral and medial plates. Maxilliped with outer plate broadly rounded distally, bearing short setae, hardly reaching to distal margin of palp article 3; inner plate with row of short setae medially and anteriorly; palp medial margin strongly setose, article 3 with groups of long setae reaching distal end of dactylus, dactylus with serrate medial margin.

Pereonites. Pereonites 1-7 lacking lateral projection; pereonite 1 subequal in length to head (excluding rostrum), pereonite 2 shorter than pereonite 1; pereonites 1-5 lacking mid-dorsal tooth; pereonite 6 with slight blunt mid-dorsal protrusion; pereonite 7 with acute triangular mid-dorsal tooth.

Pleosome. Pleonites 1 and 2 with size-increasing, acute triangular mid-dorsal tooth, and inconspicuous posterolateral protrusions; dorsal margin of pleonite 3 sinuous. Epimeral plates 1-3 with posteroventral angle produced into small subacute tooth.

Urosome. Urosomite 1 with blunt triangular mid-dorsal tooth; urosomite 2 shortest; urosomite 3 dorsal margin slightly sinuous.

Pereopods. Gnathopod 1 coxa long and slender, posterior margin bearing row of small robust setae; basis linear, both margins with numerous slender setae; merus nearly as long as ischium, anterior margin very short, distal margin oblique, posterodistal angle acute, setose; carpus linear, longer than propodus, posterior margin strong setose, anterior margin bearing group of setae distally; propodus slightly expanded distally, posterior margin and palm with robust setae, faces bearing groups of robust setae; dactylus slender, slightly curved, posterior margin minutely serrated. Gnathopod 2 coxa wider and longer than coxa 1, posterior margin bearing row of small robust setae; basis linear, ischium and merus similar to that of gnathopod 1; carpus linear, posterior margin setose; propodus and dactylus of similar appearance to gnathopod 1. Pereopod 3 coxa wider and longer than coxa 2, posterior margin bearing small robust setae and blunt protrusion on proximal half; basis linear, both margins setose; merus longer than carpus, margins bearing small setae; carpus shorter than propodus, margins setose; propodus with posterior margin bearing robust setae; dactylus stout, curved, without setae. Pereopod 4 coxa longer than coxa 3, anterior margin nearly straight, ventral tooth slightly curved, apically subacute and oriented backwards, lateral carina without tooth, not projecting laterally, carina very distant from margin of coxa at its deepest point; basis to dactylus as for pereopod 3. Pereopod 5 coxa subrectangular, posterodistal corner produced, drawn out to pointed wing in dorsal view; basis wider than that of pereopod 4, posterodistal corner rounded, setose; ischium bearing posterodistal lobe; merus nearly as long as carpus, posterior margin produced, anterior margin bearing small setae; carpus shorter than propodus, with anterior margin bearing robust setae; propodus with anterior margin setose; dactylus stout, curved. Pereopod 6 coxa bearing carinate, lateral tooth forming a small triangular wing in dorsal view; basis wider in pereopod 5, bearing carina, setose; ischium to dactylus as for pereopod 5. Pereopod 7 coxa subrectangular; basis larger than that of pereopod 6, expanded mid-posteriorly; ischium to dactylus similar to that of pereopods 5 and 6.

Uropods and telson. Uropod 1 peduncle subequal in length to rami, outer margin setose; rami subequal in length, margins bearing small robust setae. Uropod 2 peduncle subequal to outer ramus, outer margin setose; outer ramus shorter than inner ramus, both rami outer and inner margins setose. Uropod 3 peduncle much shorter than rami, inner margin with robust setae; rami subequal in length, inner and outer margins of both rami bearing short robust setae. Telson nearly as long as wide, posterior margin notched medially.

Coloration. Freshly captured specimen of Epimeria liui sp. nov. show distinct orange eyes and rose- to ivory-colored body.

Etymology. The species is named in honor of the late Prof. Dr. Ruiyu Liu (J.Y. Liu), the Institute of Oceanology, Chinese Academy of Sciences, for his great contribution to the carcinology of China.

Distribution. NW Pacific, unnamed seamount on Caroline Plate at a depth of 813-1242 m.

Remarks. Eight Epimeria species have been reported from the northern Pacific, including E. abyssalis Shimomura & Tomikawa, 2016, E. cora J.L. Barnard, 1971, E. morronei Winfield et al., 2012, E. ortizi Varela & García-Gómez, 2015, E. pacifica Gurjanova, 1955, E. pelagica Birstein & Vinogradov, 1958, E. subcarinata Nagata, 1963 and E. yaquinae McCain, 1971. Epimeria liui sp. nov. can be distinguished from above species by the following characters: rostrum hardly reaching to the distal margin of first peduncular article of antenna 1; the presence of pyriform pigmented eyes; the projection of coxa 5 not reaching to epimeral plate 1. Actually, E. liui sp. nov. more closely resembles E. bruuni Barnard, 1961 and E. horsti Lörz, 2008, which occur in the southern Pacific, by the produced mid-dorsal carinae starting from pereonite 5 or 6 and having the process on coxa 5 not extending to pleonite 1. The new species differs from E. bruuni by the mid-dorsal teeth starting on pereonite 6 and the pleonite 3 not having a large acute mid-dorsal tooth. Epimeria liui sp. nov. is especially similar to E. horsti for the coloration of the animal body. But it morphologically differs from E. horsti by the rostrum not extending to the distal margin of first peduncular article of antenna 1, the anterior cephalic margin having a semicircular lobe, the coxa 5 having a ridge whereas this part in E. horsti appears to be smooth ( Lörz 2008, figs 1, 5), the mid-dorsal blunt tooth of pereonite 6 not forming a triangular acute tooth as in E. horsti ( Lörz 2008, fig. 1), the pleonite 3 not having a mid-dorsal tooth, the posteroventral angle of the epimeron 3 not being produced, and by the telson being notched medially. The key to the species of Epimeria based on Lörz and Coleman (2014) and Shimomura and Tomikawa (2016) is presented below.

Figures

Figure 1. Epimeria liui sp. nov., female holotype (17.8 mm) (MBM 286613), photographed immediately after capture by Shao-qing Wang.

Figure 2. Epimeria liui sp. nov., female holotype (17.8 mm) (MBM 286613), G 1 R, right gnathopod 1; G 2 R, right gnathopod 2.

Figure 3. Epimeria liui sp. nov., female holotype (17.8 mm) (MBM 286613), P 3 R, right pereopod 3; P 4 R, right pereopod 4; P 5 R, right pereopod 5; P 6 R, right pereopod 6; P 7 R, right pereopod 7; A 1, antenna 1; A 2, antenna 2; U 1 R, right uropod 1; U 2 R, right uropod 2; U 3 R, right uropod 3; T, telson.

Figure 4. Epimeria liui sp. nov., female holotype (17.8 mm) (MBM 286613), H, head; UL, upper lip; LL, lower lip; Md L, left mandible; Mx 1 L, left maxilla 1; Mx 2 L, left maxilla 2; Mxp, maxilliped.