Amathillopsis lowry, Lörz & Peart, 2023

Lörz, Anne-Nina & Peart, Rachael A., 2023, Amathillopsidae (Crustacea: Amphipoda) from New Zealand, Including the Description of a New Species, Records of the Australian Museum (Rec. Aust. Mus.) 75 (4), pp. 459-470 : 461-465

Amathillopsis lowry sp. nov.

urn:lsid:zoobank.org:act:D19DD89F-C49F-4649-9701-784667C96619

Figs 2–8

Holotype: NIWA 127043 , male, 34.5 mm, abyssal basin between Three Kings and Colville Ridges, Pacific Ocean, 30°59.448396'S 177°30.059508'W, depth 4159.4 m, SO254_10ROV03, 01 February 2017 . Paratype: NIWA 156301 , female, 29.5 mm, collected with holotype .

Diagnosis. Pereonite 3 without mid-dorsal projection, pereonite 4 with small, rounded mid-dorsal projections. Pereonites 5–7 with large mid-dorsal projections, increasing in size. Pleonites 1–3 mid-dorsal projections large and angular. Urosomite 1 mid-dorsal projection small and rounded, urosomites 2 without obvious carination and urosomite 3 with slight rounded hump distally. Male gnathopod 1–2 posterodistal basis lobe reduced, female gnathopods 1 and 2 strongly developed. Small, acute tooth on posterodistal corner of epimeron 3. Telson elongated (longer than wide), developed into a weakly trifid apex.

Description of holotype (male, 34.5 mm, NIWA127043). Head slightly shorter than pereonites 1 and 2 combined, rostrum very short, pointed, lateral cephalic lobe strongly quadrate, eyes present, pigmented, white in fresh specimen. Pereonites 1–3 indistinctly keeled dorsally; pereonite 4–7 with mid-dorsal curved processes, increasing in length. Pleonites 1–3 each with posteriorly curved mid-dorsal process. Epimeral plate 1 with ventral margin rounded, posteroventral corner rounded; epimeral plates 2 with ventral margin rounded, posteroventral corner toothed; epimeral plate 3 with ventral margin curved and posteroventral corner produced into a small acute tooth. Urosomite 1 weakly carinated with rounded process, urosomite 2 lacking dorsal armature, urosomite 3 weakly dorsally carinate with small, rounded mid-dorsal process. Antenna 1 as long as body length, with peduncular articles 1, 2, and 3 in length ratio of 1.0: 1.1: 0.4, respectively; peduncular 1 article 1 longer than head length; accessory flagellum uniarticulate, spine-like; primary flagellum consisting of more than 60 articles. Antenna 2 0.8 times as long as antenna 1; peduncular article 3 reaching to one-third length of peduncular article 1 of antenna 1; peduncular article 4 long, 1.7 times as long as peduncular article 5, flagellum slightly longer than peduncle, 54-articulate.

Mouthparts. Upper lip with slight depression in apical margin, bearing 2 groups of setae. Lower lip with outer lobes broad, setulose; inner lobes indistinct, fused. Mandibles with left incisor bearing 9 teeth, left lacinia mobilis with 4 teeth; accessory setal row with 12 setae, some bearing row of minute protuberances. Right mandible incisor with 6 teeth, lacinia mobilis with 4 teeth, and accessory setal row with 12 setae. Molar developed, triturative. Palp articles 1, 2, and 3 in length ratio of 1: 3: 3, respectively (for both left and right sides), article 1 with setae on distal corners, article 2 with marginal and submarginal setae, and article 3 with marginal and terminal setae. Maxilla 1 with inner plate ovoid and bearing 3 short, and 4 long slender plumose setae; outer plate rectangular, with 10 large robust setae (5 toothed); palp 2-articulate, longer than outer plate, terminally with 10 long robust setae, outer lateral margin lined with 7 slightly plumose slender setae. Maxilla 2 inner plate slightly broader than outer plate, bearing row of long plumose setae. Maxilliped inner plate reaching base of palp, with 3 robust nodular setae on distomedial margin, distolateral margin with apical robust setae; outer plate exceeding distal margin of palp article 1. Maxilliped palp long, raptorial, broken off; articles 2 and 3 heavily setose.

Pereon. Coxae 1 rounded, coxae 2–4 produced angularly anteroventrally. Coxae 5 and 6 wider than long, bilobate. Coxa 7 small and rounded. Gnathopod 1 subchelate, basis posterior margin without robust setae, posterodistal lobe vestigial; ischium about half length of merus; merus produced posterodistally to form narrow rounded lobe; carpus slightly shorter than propodus, posteroventral lobe broadly rounded, allowing propodus to fold over distally; propodus 2 times longer than wide, ovoid, with 5 medial rows of 4–12 slender simple setae, anterior margin with 3 long rows of 5–15 long slender simple setae and 3 tufts of 2 or 3 separate small slender setae; palm not differentiated from posterior margin, lined with tufts of slender setae and 5 short robust setae along convex palm. Propodus with row of 12 long slender simple setae distally. Dactylus long, slender and gently curved, reaching length of propodus. Gnathopod 2 subchelate, basis with posterodistal lobe reduced; ischium half length of merus. Merus produced posterodistally to form acute lobe lined with long slender simple setae. Carpus twice as long as merus and 0.75 times as long as propodus; ventral lobe broadly rounded, slightly directed distally, positioned allowing propodus to fold over; propodus narrow (twice as long as broad), ovoid. Anterior margin lined with 5 rows of slender simple setae containing 2–10 setae; medial surface with 6 rows of 4–7. Palm not differentiated from posterior margin, convex and lined with long slender simple setae and 12 short robust setae. Dactylus long, slender, gently curved, reaching length of propodus. 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, anteroventral lobe; propodus wider and longer than merus; dactylus half-length of propodus, rounded. 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; proportions of carpus: propodus: dactylus is 18: 22: 17.

Uropods. Uropod 1 long, peduncle as long as inner ramus, medial margin of peduncle with robust setae, inner and outer ramus lateral and medial margins with robust setae, outer ramus 0.9 times as long as inner. Uropod 2 with peduncle length 0.6 times inner ramus, lateral margin with robust setae; outer ramus same length as peduncle, lateral and medial margins with robust setae; outer ramus 0.6 times inner, lateral and medial margins with robust setae. Uropod 3 peduncle length nearly half length of inner ramus; dorsomedial margin of peduncle with 2 robust setae distally; inner ramus with lateral and medial margins bearing robust setae, outer ramus 0.8 times as long as inner, lateral and medial margins with robust setae. Telson length 1.5 times width, each side bearing 2 short robust setae apically plus a number of small slender setae medially. Apically having appearance of being trifid, however, but appearing slightly uneven, possibly owing to damage.

Variation. Paratype female, 29.5 mm, in situ photographed ( Fig. 5B ) and photographed on board ( Figs 7 , 8 ). Antenna 1 peduncular articles of different proportion from male. Spine-like accessory flagellum short. Gnathopod 1 basis expanded to form large posterodistal lobe lined on both sides by many short robust setae reaching almost to junction with coxa; basis medial face lined with rows of long slender setae. Merus weakly produced to form small rounded strongly setose posterodistal lobe. Carpus expanded to form large broadly rounded lobe. Carpus medial surface with 12 long rows of 4–12 long slender simple setae. Carpus anterior margin without slender setae but defined distally by row of 8 long slender simple setae. Posterior and distal carpal margins densely lined with long slender simple setae. Carpus similar length to propodus. Propodus narrow (2.2 times as long as wide). Anterior margin of propodus lined with 3 rows of 10–12 slender, simple setae, and 2 tufts of 2 or 3 small setae. Medial face of propodus with 4 rows of 6–12 long slender setae. Gnathopod 2 basis expanded to form large posterodistal lobe lined with many short robust setae on both sides reaching up to near junction with coxa. Carpus posterior margin densely lined with rows of slender simple setae. Telson long, narrow, emarginate at apex (possibly damaged).

Etymology. The species is named for Dr Jim Lowry, our amphipod colleague who dedicated his scientific expertise to Amphipoda . Used as a noun in apposition.

Colour. In live specimens, Amathillopsis lowry sp. nov. has a white body and antennae; the last three segments of both gnathopods as well as the mouthparts are red. The eyes are clearly visible, solid white, in live and fresh condition, but faded when preserved.

Depth range. 4159.4 m.

Distribution. Only known from the southwest Pacific, from the abyssal basin between Three Kings and Colville Ridges, 4159.4 m.

Remarks. Amathillopsis lowry sp. nov. differs from all other known species of Amathillopsis by the combination of the following characters: pereonites 1–3 mid-dorsally smooth, pereonites 5–7 strong, acute, progressively increasing in size; urosomite 1 mid-dorsal projection reduced to a small rounded hump; gnathopod 1 and 2 posterodistal basis lobe greatly reduced and weakly setose in male but strongly present and covered in robust setae in female; telson shape entire, and longer than wide, but produced in the centre to give a tridentate appearance.

Amathillopsis lowry sp. nov. is most similar to A. charlottae , ( Table 1), collected from the Antarctic Peninsula at 607 m, and A. grevei from 3580 m in the Tasman Sea. The new species has a similar development of the dorsal processes and smooth urosomite 1, but no posterodistal lobes on the basis of male gnathopod 2 as in A. charlottae . The telson of A. lowry sp. nov. differs from all other species of Amathillopsis in the elongated shape and pseudo-trifid apical shape.

LÖrz & Peart: Amathillopsidae New Zealand 465

Figures

Figure 2. Amathilliopsis lowry sp. nov., holotype male, 34.5 mm, NIWA 127043. Scale: Hb 5 mm, U1–3 1 mm, T 0.75 mm.

Figure 3. Amathilliopsis lowry sp. nov.: holotype male, 34.5 mm, NIWA 127043; paratype female, 29.5 mm, NIWA 156301 (A1 only). Scale 1 mm.

Figure 4. Amathilliopsis lowry sp. nov., holotype male, 34.5 mm, NIWA 127043. Scale: G1, G2 0.5 mm; all others 1 mm.

Figure 5. Amathilliopsis lowry sp. nov., paratype, NIWA 156301, female, 29.5 mm, gnathopods 1 and 2. Scale 1 mm.

Figure 6. Amathilliopsis lowry sp. nov.: (A) holotype male 34.5 mm, NIWA 127043; (B) paratype female, 29.5 mm, NIWA 156301. Photographed immediately after capture. Scale 5 mm.

Figure 7. In situ image of three specimens of Amathillopsis lowry sp. nov. on sponge tubes, ROV Kiel 6000, Geomar, 4159 m depth, abyssal basin between Three Kings Ridge and Colville Ridge, Pacific Ocean.

Figure 8. In situ image of paratype Amathillopsis lowry sp. nov., NIWA 156301, 4159 m abyssal basin between Three Kings Ridge and Colville Ridge, Pacific Ocean.