Liuiuristis thermalis, Wang & Sha, 2024

Wang, Yan-Rong & Sha, Zhong-Li, 2024, A new genus and one new species of the family Uristidae Hurley, 1963 (Amphipoda, Lysianassoidea) described from hydrothermal vent of the Okinawa Trough, NW pacific, Zootaxa 5447 (3), pp. 413-423 : 417-422

Liuiuristis thermalis sp. nov.

( Figs. 2–5 )

Material examined. Holotype: MBM 286562 , ♀ (6.8 mm), Okinawa Trough, 27°33'N 126°58'E, RY0067, ROV-3, depth 1243 m, coll. Zhongli Sha, 16 April 2014 . Paratype: J (6.3 mm), dissected, same collection data as holotype. Additional material: MBM 286562 , 7 JJ (5.6–6.8 mm), 4♀♀ (6.2–7.0 mm), Okinawa Trough , 27°33'N 126°58'E, RY0067, ROV-3, depth 1243 m, coll. Zhongli Sha, 16 April 2014 . MBM 286561 , 1 J (5.6 mm), Okinawa Trough , 27°33'N 126°58'E, RY0169, ROV-5, depth 1361 m, coll. Zhongli Sha, 20 April 2014 . MBM 286563 , 3♀♀ (5.8–6.1 mm), Okinawa Trough , 27°33'N 126°58'E, RY0051, ROV-3, depth 1243 m, coll. Zhongli Sha, 16 April 2014 . MBM 286564 , 6♀♀ (6.0– 7.3 mm), 2JJ (5.9–6.1 mm), Okinawa Trough , 27°33'N 126°58'E, RY0069, ROV-3, depth 1243 m, coll. Zhongli Sha, 16 April 2014 .

Descriptions. Based on female holotype, 6.8 mm. Body smooth; pleonite 3 with weak dorsal carina. Epimeron 1–3 smooth, posteroventral margin rounded. Head. Eyes no traces visible in ethanol-preserved material; lateral cephalic lobe subtriangular, apically subacute. Antenna 1 longer than antenna 2; peduncular article 1 long, not expanded, length about 1.6 times than width; article 2 slightly less than half-length of article 1; article 3 1/2 length of article 2; primary flagellum 10-articulate, with callynophore, article 1 long, but shorter than peduncular article 1, without calceoli; accessory flagellum 3-articlulate, forming a cap. Antenna 2 peduncular article 4 subequal in length to article 5; flagellum subequal in length to peduncle, 9-articulate.

Mouthparts. Upper lip subtriangular, produced anteriorly. Mandible asymmetrical, incisor smooth; left lacinia mobilis and accessory setal row absent; molar well developed, columnar, triturative; palp 3-articulate, article 2 longer than article 3, bearing 4 marginal setae sub-distally on the right mandible and 4 or 6 on the left. Maxilla 1, inner plate rounded, with two pappose setae apically; outer plate 11 setal-teeth in 7/4 crown arrangement; palp large, 2-articlulated, with 8 terminal robust setae, marginal setose. Maxilla 2 with inner plate narrower and shorter than outer plate, distal margin bearing 9 long robust setae; outer plate bearing several terminal long setae. Maxilliped with inner plate rectangular, bearing 3–4 apical and several mesial setae; outer plate not reaching to distal margin of palp article 2, inner margin with close-set teeth; palp 4-articulate, dactylus much shorter than article 3, bearing three apical setae.

Gills from gnathopod 2 to pereopod 6, not pleated. Coxae 1–4 longer than broad, overlapping.

Pereopods. Gnathopod 1 parachelate, coxa well-developed; basis slender, length 3.6 times than width, anterior margin fringed with slender setae; ischium sub-equal in length to merus, anterior margin produced medially; merus nearly as long as carpus; carpus much shorter than propodus, distally slightly expanded, posterior margin lobate, bearing slender setae; propodus subrectangular, posterior margin bearing slender setae, palm obtuse, mesial and outer sides both with robust setae, defining by two robust setae; dactylus as long as palm. Gnathopod 2 minutely chelate; basis linear, 2.7 times longer than ischium, posterior margin bearing special setae distally; ischium longer than merus, posterior margin bearing rayed setae distally; merus shorter than carpus; carpus longer than propodus, bearing row of slender setae sub-distally; propodus with anterior margin bearing 5 robust setae distally, posterior margin bearing 5 robust in distal half length; dactylus reaching corner of palm. Pereopod 3 basis with posterior margin bearing slender rayed setae distally; merus longer than carpus, posterior margin fringed with slender setae; propodus subequal in length to merus, posterior margin with small robust setae; dactylus slender. Pereopod 4 coxa large, posteroventral lobe acute. Pereopod 5 shorter than pereopod 6, coxa subquadrate, bilobed, lobes subequal; basis expanded. Pereopod 6 coxa deeper than long, posterior lobate; basis expanded, but less broad than that of pereopod 5. Pereopod 7 subequal in length to pereopod 6; coxa small, basis strongly expanded, larger than that of pereopod 5.

Uropods and telson. Uropod 1 peduncle longer than rami, with two distal, 2–5 lateral and 4–5 mesial robust setae; outer ramus subequal in length to inner ramus, with 3–4 robust setae; inner ramus with 3 robust setae. Uropod 2 peduncle nearly as long as rami, with two distal and 7 lateral robust setae; outer ramus longer than inner ramus, with 4 robust setae; inner ramus with three robust setae. Uropod 3 peduncle shorter than outer ramus, with one distal and three lateral robust setae; outer ramus 2-articulate, article 1 with 3 lateral setae, article 2 1/3 length of article 1. Telson entire, a little longer than wide, distal margin rounded.

Sexually dimorphic characters. Based on male paratype, 6.3 mm. Antenna 1 subequal in length to antenna 2; primary flagellum composed of 10 articles. Antenna 2 flagellum 11-articulate. Gnathopod 1 subchelate. Gnathopod 2 basis and ischium without special setae on posterior margin; ischium longer than carpus.

Etymology. From the Latin thermal (=of warm springs), referring to the collection of type material are collected from hydrothermal vents.

Distribution. Presently known only from hydrothermal vents of the Okinawa Trough at a depth of 1243–1361 m.

Figures

FIGURE 2. Liuiuristis thermalis sp. nov., MBM 286562, Holotype, ♀(6.8 mm): G1 R, right gnathopod; G2 R, right gnathopod 2.

FIGURE 3. Liuiuristis thermalis sp. nov., MBM 286562, Holotype, ♀(6.8 mm): LL, lower lip; Md R, right mandible; Md L, left mandible; Mx1 L, left maxilla 1 with SEM picture of outer plate; Mx2 R, right maxilla 2; Mxp, maxilliped; Paratype, J(6.3 mm): UL, upper lip.

FIGURE 4. Liuiuristis thermalis sp. nov., MBM 286562, Holotype, ♀(6.8 mm): P3 R, right pereopod 3; P4 R, right pereopod 4; P5 R, right pereopod 5; P6 R, right pereopod 6; P7 R, right pereopod 7; H, head; U2 L, left uropod 2; U3 L, left uropod 3; T, telson; Paratype, J(6.3 mm): A1, antenna 1; A2, antenna 2; Md L, left mandible, U1 L, left uropod 1.

FIGURE 5. Liuiuristis thermalis sp. nov., MBM 286562, Paratype, J(6.3 mm): G1 L, left gnathopod; G2 L, left gnathopod 2.