Amathillopsis inkenae, Lörz & Horton, 2021

Loerz, Anne-Nina & Horton, Tammy, 2021, Investigation of the Amathillopsidae (Amphipoda, Crustacea), including the description of a new species, reveals a clinging lifestyle in the deep sea worldwide, ZooKeys 1031, pp. 19-39 : 19

Amathillopsis inkenae sp. nov. Figures 1 , 2 , 3 , 4 , 5

Type material.

Holotype: North East Atlantic • Male, 9.4 mm; Porcupine Abyssal Plain; 49°47.969'N, 015°12.975'E, 4622 m; 20 July 2020; RV ‘Sonne’ cruise 267, station 133-4, gear ROV KIEL 6000; ZMH K-60236. Paratype: North East Atlantic • Male, 14 mm; Porcupine Abyssal Plain; 48°58.201'N, 016°53.297'W to 48°55.316'N, 016°49.452'W, 4834-4844 m; 06 June 2018; RRS 'James Cook’ Cruise 165, station JC165#064, Otter Trawl Semi-Balloon 14; NHMUK 2021.66.

Type locality.

Porcupine Abyssal Plain, 4622 m, 49°47.969'N, 015°12.975'E, RV ‘Sonne’ cruise 267, station 133-4, gear ROV KIEL 6000.

Diagnosis.

Pereonites 3 and 4 with small, rounded mid-dorsal projections. Pereonites 5-7 mid-dorsal projections, small, rounded, increasing in size. Pleonites 1 and 2 mid-dorsal projections small, rounded, reduced to dorsal hump on pleonite 3. Urosomite 1 mid-dorsal projection absent, urosomites 2 and 3 carinate, urosomite 3 with a small mid-dorsal process. Gnathopod 2 posterodistal basis lobe developed. Strong, acute tooth on posterodistal corner of epimeron 3. Telson cleft.

Description.

Male holotype 9.4 mm: Head slightly shorter than pereonites 1 and 2 combined, rostrum very short, pointed, lateral cephalic lobe quadrate, eyes present, pigmented, strongly white in fresh specimen. Pereonites 1 and 2 indistinctly keeled dorsally; pereonite 3-5 with short mid-dorsal processes; pereonites 6 and 7 each with short, weakly posteriorly curved mid-dorsal process. Pleonites 1 and 2 each with short weakly posteriorly curved mid-dorsal process; pleonite 3 with low, mid-dorsal rounded process. Epimeral plates 1 and 2 with ventral margin rounded, posteroventral corner rounded; epimeral plate 3 with ventral margin curved and posteroventral corner produced into an acute tooth. Urosomite 1 lacking dorsal armature, urosomites 2-3 dorsally carinate, each with short weakly posteriorly curved mid-dorsal process, urosomite 3 with a small mid-dorsal process. Antenna 1 long, as long as body length, with peduncular articles 1, 2, and 3 in length ratio of 1.0: 1.1: 0.4. Article 1 longer than head length; accessory flagellum uni-articulate, not spine-like; primary flagellum consisting of 64 articles, article 1 long, as long as articles 2-7 combined. Antenna 2 0.8 × as long as antenna 1; peduncular article 3 reaching to mid length of peduncular article 1 of antenna 1; peduncular article 4 long, 1.7 × as long as peduncular article 5, flagellum approximately the same length, as long as peduncle, 54-articulate.

Mouthparts. Upper lip with weakly convex apical margin, bearing two groups of setae. Lower lip with outer lobes broad, setulose; inner lobes indistinct, fused. Mandibles with left incisors bearing eight teeth, left lacinia mobilis with four teeth; accessory setal row with nine setae, some bearing a row of minute protuberances. Molar developed, triturative. Palp articles 1, 2, and 3 in length ratio of 1.0: 5.0: 7.1, article 1 lacking setae, article 2 with marginal and submarginal setae, and article 3 with six marginal and three terminal setae. Maxilla 1 with inner plate ovate and bearing four plumose setae; outer plate rectangular, with 11 serrate, robust setae; palp two-articulate, longer than outer plate, terminally with seven long robust setae. Maxilla 2 inner plate slightly broader than outer plate, bearing row of long plumose setae. Maxilliped, inner plate reaching base of palp, with three robust nodular setae on the distomedial margin, distolateral margin with apical robust setae; outer plate exceeding distal margin of palp article 1. Maxillipedal palp long, raptorial, four-articulate; article 2 and 3 heavily setose and widened medially; dactylus as long as article 3.

Pereon. Coxae 1 and 2 with acute processes projecting anteroventrally. Coxa 3 subtriangular, Coxa 4 rhomboid, both with acute processes projecting anteroventrally. Coxae 5 and 6 wider than long, bilobate. Coxa 7 small, rounded. Gnathopod 1 subchelate, basis posterior margin with row of robust setae, posterodistal lobe absent; ischium and merus short; carpus 0.68 × as long as propodus, ventral lobe broad, concave, allowing propodus to retract; propodus stout, tapering distally, with four groups of robust setae, palmar margin with long and short robust setae; dactylus as long as palmar margin, sickle-like. Gnathopod 2 subchelate, basis with posterodistal lobe present, posterior margin with row of robust setae; carpus 0.67 × as long as propodus, ventral lobe broad, concave, allowing propodus to retract; propodus stout, tapering distally, with four groups of robust setae, palmar margin with long and short robust setae; dactylus as long as palmar margin, sickle-like. Pereopod 3 basis with row of robust setae along weakly convex posterior margin, ischium short, as long as wide; merus margins subparallel with slight anterior curvature. Pereopod 4 similar to pereopod 3. Pereopods 5-7 anterior and posterior margins of basis sub-parallel, linear, posterior lobe lacking; ischium short, as long as wide; merus margins subparallel with slight anterior curvature. Carpus, propodus and dactylus missing from pereopods 3-7.

Uropods. Uropod 1 long, peduncle length 0.88 × inner ramus; medial margin of peduncle with robust setae, inner ramus, lateral and medial margins with robust setae, outer ramus 0.88 × as long as inner, lateral and medial margins with robust setae. Uropod 2 with peduncle length 0.57 × inner ramus, lateral margin with robust setae, dorsomedial margin with one robust seta distally; inner ramus, lateral and medial margins with robust setae; outer ramus 0.64 × inner, lateral and medial margins with robust setae. Uropod 3 peduncle length 0.74 × inner ramus; dorsomedial margin of peduncle with three robust setae distally; inner ramus with lateral and medial margins bearing robust setae, outer ramus 0.64 × as long as inner, lateral, and medial margins with robust setae. Telson length 1.44 × width, cleft 22%. Each lobe bearing terminal setae.

Paratype male, 14 mm: As for holotype except the dorsal processes are more pronounced and acute on pereonites 5-7 and pleonites 1 and 2 (Fig. 5c ).

Etymology.

The name is dedicated to Dr. Inken Suck, the pilot who flew the ROV and sampled the specimen, to honour her dedication to deep-sea biology.

Remarks.

In live condition, Amathillopsis inkenae sp. nov. has a white coloured body and antennae, the last three segments of both gnathopods as well as the mouthparts are red. Eyes are clearly visible, solid white, in live and fresh condition, but fade after a few days of fixation. Care should be taken in use of the relative sizes of the dorsal processes as these are likely to vary ontogenetically, as for the two specimens available here, where the larger male paratype has more pronounced, acute processes than the smaller male holotype. This is also likely to occur in other species in the genus. The specimens reported by Wakabara and Serejo (1999) as A. atlantica are likely to belong to a new species, and the authors point out that the mid-dorsal processes and the telson show some variation. Other characters, such as the reduced lobes on the basis of the gnathopods, also indicate that this is probably a new taxon.

Amathillopsis inkenae sp. nov. differs from known species of Amathillopsis by the characters listed in Table 2 . Amathillopsis inkenae sp. nov. is most similar to Amathillopsis comorensis Ledoyer, 1986, which was collected in the Indian Ocean near the Comoros Islands at 2500 m. The new species has a similarly cleft telson, and a similar development of the dorsal processes and of the lobe on the basis of gnathopod 2 only. Amathillopsis inkenae differs from A. comorensis in having carination on urosomites 2 and 3, with posteriorly directed dorsal processes (lacking in A. comorensis ), the stronger acute tooth on epimeron 3 posterodistal corner (smaller on A. comorensis ), the curved article 2 of the mandible palp (straight in A. comorensis ), and the medially widened articles 2 and 3 of the maxilliped palp (subparallel sided in A. comorensis ).

The barcode of Amathillopsis inkenae sp. nov. is deposited in BOLD:AEF9286 and GenBank MW726208.

Depth range.

4622-4844 m.

Distribution.

Only known from the North East Atlantic Ocean, Porcupine Abyssal Plain, between 4622-4844 m.

Figures

Figure 1. Amathillopsis inkenae sp. nov. Holotype: ZMH K- 60236, male, 9.4 mm. Habitus lateral and dorsal views, head, antenna 1, uropods 1 - 3, and telson.

Figure 2. Amathillopsis inkenae sp. nov., Holotype: ZMH K- 60236, male, 9.4 mm. Upper lip, Lower lip, Maxilliped (left palp external rotation is an artefact of the mounting), maxillae 1, 2, and mandible.

Figure 3. Amathillopsis inkenae sp. nov., Holotype: ZMH K- 60236, male, 9.4 mm. Gnathopods 1, 2, and pereopods 3 - 7.

Figure 4. Amathillopsis inkenae sp. nov., Holotype: ZMH K- 60236, male, 9.4 mm A mandible B mandible incisor detail C gnathopod 1 D gnathopod 1 detail E gnathopod 2 F gnathopod 2 palm detail.

Figure 5. Amathillopsis inkenae sp. nov., Holotype: ZMH K- 60236, male, 9.4 mm A habitus, fresh specimen photograph (S. Zankl) B in situ image clinging to a polychaete tube via ROV KIEL 6000. In situ video can be found in Suppl. material 1 C Amathillopsis inkenae sp. nov., paratype NHMUK 2021.66, male, 14 mm. Habitus, preserved specimen (photograph T. Horton).