Amblyops arianii, Wittmann, 2024

Wittmann, Karl J., 2024, The Mysidae (Crustacea, Mysida) of the ANDEEP I-III expeditions to the Antarctic deep sea with the description of twelve new species, establishment of four new genera and with world-wide keys to the species of Erythropinae and Mysidellinae, European Journal of Taxonomy 940, pp. 1-180 : 32-41

Amblyops arianii sp. nov.

urn:lsid:zoobank.org:act:255ECB18-09AF-4B64-9C92-1CD618131C02

Figs 14–19

Diagnosis

Based on adult and subadult females. Fitting within ranges of generic diagnosis. Carapace with broadly rounded, obtuse-angled, uptilted anterior margin. Uptilted portion half as long as terminal segment of antennular trunk, covering part of eye rudiments. Eye rudiments without visual elements, subovate, converging at mesial third; all around hispid by scales. Ocular papilla with ⅕–¼ of antero-posterior extension of eye rudiments. Antennal sympod disto-laterally with large dorsal and large ventral tooth, plus distally blunt, triangular projection. Antennal scale with short apical segment, total scale length 2.6–2.8 times maximum width. Scale extends 0.5–0.6 times its length beyond antennular trunk. Setose terminal lobe of scale very short, not reaching tip of disto-lateral tooth; no accessory spines beneath this tooth. Mouthparts normal, labrum rostrally rounded. Female with three pairs of oostegites contributing to outer wall of marsupium. Endopod of uropods with one minute spine on mesial margin below statocyst. Telson about trapeziform with transversely flattened, convex terminal margin; length 1.9 times maximum width. Telson proximally with bare lateral margins, distal ⅖–⅗ of each lateral margin with dense series of 9–11 normal-shaped spines distally gradually increasing in size; terminal margin with pair of paramedian setae flanked by 2–3 pairs of large spines with mesially increasing size, innermost large spines only ≈ 1/17 of telson length, no minute median spines. Telson with total of 22–28 spines and two setae.

Etymology

The species name is a noun with Latinized masculine ending in genitive singular, dedicated to Antonio P. Ariani (Univ. Naples) in recognition of his important contributions to the taxonomy, biogeography and biomineralogy of mysids.

Material examined

Holotype SOUTHERN OCEAN • 1 ♀ ad. ( BL = 25.8 mm); Drake Passage , N of South Shetland Islands, ANDEEP-I station 046-7; 60°38.35ʹ S, 53°57.36ʹ W to 60°38.12ʹ S, 53°57.49ʹ W; depth 2893.6– 2893.2 m; 30 Jan. 2002; EBS supranet; ZMH 64653 .

Paratypes SOUTHERN OCEAN • 1 ♀ subad. ( BL = 24.2 mm, on slides); same collection data as for holotype; ZMH 64655 • 1 ♀ imm. (damaged, BL = 20.7 mm), 1 juv. (damaged, BL = 7.1 mm); Drake Passage , NW of Elephant Island, ANDEEP-I station 042-2; 59°40.29ʹ S, 57°35.43ʹ W to 59°40.42ʹ S, 57°35.27ʹ W; depth 3683– 3680 m; 27 Jan. 2002; EBS supranet; ZMH 64654 • 1 imm. ( BL = 16.5 mm, in 2 parts); eastern Weddell Abyssal Plain , S of Maud Rise and E of Sanae Canyon, ANDEEP-III station 059-5; 67°29.74ʹ S, 0°01.93ʹ W to 67°29.61ʹ S, 00°02.19ʹ W; depth 4655– 4655 m; 14 Feb. 2005; EBS supranet; ZMH 64657 • 1 imm. ( BL = 18.0 mm, in 2 parts); Weddell Abyssal Plain , ANDEEP-III station 110-8; 65°00.52ʹ S, 43°02.09ʹ W to 65°00.68ʹ S, 43°02.16ʹ W; depth 4698– 4696 m; 10 Mar. 2005; EBS supranet; ZMH 64658 • 1 ♀ ad. (damaged, BL = 21.8 mm); South Sandwich Trench , E of Montagu Island, ANDEEP-II station 139-6; 58°14.10ʹ S, 24°21.22ʹ W to 58°14.18ʹ S, 24°20.94ʹ W; depth 3941.7– 3926.8 m; 20 Mar. 2002; EBS supranet; ZMH 64656 .

Other material

SE ATLANTIC • 1 imm. ( BL = 8.6 mm); Cape Basin , ANDEEP-III station 016-10; 41°07.06ʹ S, 9°54.88ʹ E to 41°06.99ʹ S, 9°54.75ʹ E; depth 4687– 4669 m; 26 Jan. 2005; EBS epinet .

SOUTHERN OCEAN • 1 ♀ subad. (damaged, BL ≈ 13.9 mm); SE Weddell Sea, ANDEEP-III station 074-6; 71°18.35ʹ S, 13°57.71ʹ W to 71°18.28ʹ S, 13°57.31ʹ W; depth 1030–1040 m; 20 Feb. 2005; EBS epinet.

Type locality and distribution

The type locality is ANDEEP I station 046-7: Drake Passage, South Shetland area, NE of Elephant Island, 60°38.35ʹ S, 53°57.36ʹ W to 60°38.12ʹ S, 53°57.49ʹ W, depth 2893.6– 2893.2 m. This species is widely distributed in the western Southern Ocean: Bellingshausen Sea, Drake Passage, South Sandwich Trench and Weddell Sea. It was also found in the single sample from the SE Atlantic: Cape Basin. Total range 41– 63° S, 9° E anticlockwise to 64° W, depth 2092–4698 m.

Description

Holotype (♀)

All features visible without dissection are within limits of specific diagnosis. Adult female with BL 25.8 mm. Cephalothorax contributes 45%, pleon (without telson) 40% and telson 14% to total BL.

CARAPACE ( Fig. 14C, G ). Normal, length 44% of BL, cervical sulcus strong, cardial sulcus weak. Disto-lateral edges about rectangular, distally narrowly rounded. Concave posterior margin of carapace leaving ultimate thoracomere only marginally dorsally exposed.

EYES ( Fig. 15 ). Eye rudiments dorsoventrally compressed by a factor of 1.7–1.8. Rostral projection ending in a single triangular ocular papilla at one third of eye width from mesial margin ( Fig. 15C ). Antero-posterior extension of eyes 0.7 of maximum width (= transverse extension) and 1.2 times length of terminal segment of antennular trunk. Spiniform scales covering eyes also extend over papilla ( Fig. 15D ). Papilla ends in a toroid with pore in center. Organ of Bellonci near mesio-basal edge of eye.

ANTENNULA ( Fig. 16A ). Trunk measures 9% of BL. It extends ⅘ of its length beyond eyes. Roughly transverse articulations between three segments of trunk. Measured along dorsal midline, basal segment 0.4 of trunk length, median 0.2 and terminal 0.4. Length of basal segment 0.7 times width; segment dorsally with antennular bursa, no ventral carina. This segment produced into a short lobe at disto-lateral edge, lobe apically with five setae. Two setose dorsal apophyses (dashed lines in Fig. 16A ) shortly extending beyond its rostral margin. Median segment also with two setose dorsal apophyses. Length of terminal segment 0.8 times width in dorsal view, 0.7 in ventral view. Terminal segment without female lobe. Disto-median lobe of terminal segment armed with three small teeth increasing in size laterally, lobe disto-laterally with four barbed setae (as in Fig. 4B ). Width of outer antennular flagellum measured near basis 1.2 times width of inner flagellum.

ANTENNA ( Fig. 16C ). Sympod 2-segmented, caudally in addition with large end sac of antennal gland. Segments 1–4 of peduncle contribute 26%, 13%, 25% and 36% to total length in dorsal view, vs 27%, 31%, 18% and 24% in ventral view, respectively. Differences between dorsal and ventral views mainly due to lengthwise oblique border between second segment and dorsally overlapping third segment.

CEPHALOTHORAX. Clypeus ( Fig. 16B ) with low longitudinal ridge marginally extending beyond frontal lobe. Mouthparts essentially as in other species of Amblyops treated here. Thoracic endopods 1–2 with six segments ( Fig. 18A, C ), dactylus with slender nail ( Fig. 18B, D ). Dactylus of endopod 2 not reflexed ( Fig. 18C–D ). Thoracic exopod 1 with nine segments, exopod 2 with 9–10 and exopods 3–8 with ten.

PLEON AND TAIL FAN ( Fig. 19 ). Length of pleomeres 1–5 is 0.6, 0.5, 0.5, 0.5 and 0.6 times length of pleomere 6, respectively. Pleopods increase in length caudally. Scutellum paracaudale large, sinusoid. Uropods with smooth cuticle, not considering setae and single spine of endopod. Exopod with convex mesial margin; its terminus broadly rounded, convex. Exopod 1.2–1.4 times as long as endopod and 1.6–1.8 times as long as telson; endopod 1.2–1.4 times as long as telson. Margins of endopod converge in narrow V-shaped manner up to blunt apex. Telson length 1.2 times as long as ultimate pleomere; width at terminus (measured between lateral margins of latero-terminal spines) is 23% of maximum width and 12% of telson length.

Paratypes

Covers features requiring dissection. Uptilted portion of carapace ( Fig. 14C ) on each side with transverse field of about 80–90 pores (only few pores visualized in Fig. 14D ). No pores detected (though not excluded) near posterior margin of carapace.

MANDIBLES ( Fig. 16D–F ). Basal segment of palp contributes 14–16%, median segment 61–64% and apical segment 21–23% to total palp length. Median segment 2.3–2.6 times as long as wide, mesial and lateral margins convex, lateral margin folded mesially. Length of apical segment 2.6–2.9 times maximum width. Palp not hispid, its basal segment without setae, median segment strongly setose along mesial margin and less strongly along lateral margin, apical segment densely setose along mesial margin and with only few short setae along lateral margin. Distal half of median segment in addition with linear series of setae along midline of caudal face. Masticatory part of right mandible ( Fig. 16E ): pars incisiva with four large plus one medium-sized tooth; digitus mobilis with two large teeth, each serrated by series of small secondary teeth. Pars centralis with ten acute spines in dense series, continuously decreasing in size proximally: two largest, most ventral (= aboral) spines serrated by small denticles, remaining spines armed with stiff bristles. Processus molaris of right mandible and complete masticatory part of more normal left mandible ( Fig. 16F ) as in A. bipapillatus sp. nov. ( Fig. 21C–E ).

GUT ( Fig. 17 ). Foregut with normal gross structure. Anterior part of lateralia with many distally all around strongly dentate spines ( Fig. 17B ). Long slender spines cactus-like along distal 6–10% ( Fig. 17B 2 ), shorter, less slender spines prickly along distal ¼–½ ( Fig. 17B 1 ). Anterior part of lateralia in addition with fewer slender, proximally smooth, subapically sparsely dentate and apically coronate spines ( Fig. 17B 3 ). Central part of lateralia with slender, apically pronged spines ( Fig. 17C ) densely coated with minute teeth along about distal half of shaft. Posterior part of lateralia on each side with dense cluster of ten strongly dentate spines ( Fig. 17D ). Dorsolateral infoldings on each side with cluster of five spines increasing in size laterally, these spines unilaterally serrated along most of distal third to half ( Fig. 17E ). All setae of superomedianum slender and distally microserrated; lateral setae ( Fig. 17F ) longer than caudal setae. Storage volume almost empty in dissected specimen. Sparse presence of unidentifiable organic materials (detritus) and small mineral particles in both foregut and midgut. Anal lobe caudally strongly cuticularized (dashed lines in Fig. 19D ).

MAXILLULA ( Fig. 16G ). Distal segment with eleven strong spines on transverse terminal margin, these spines unilaterally serrated mostly along median portions. This segment subterminally with four setae bearing long stiff barbs; no nearby pores detected. Endite of maxillula terminally with six large, distally spiny setae, on both sides accompanied by numerous less strongly barbed setae. Most proximal seta backward curved.

MAXILLA ( Figs 14F , 16H ). Sympod with three mesial lobes, densely setose along disto-mesial margins. Convex mesial portion of sympod may be interpreted as additional lobe bearing large, dense fan of setae. One large seta extends shortly beyond this fan, on caudal face, at margin near distally neighboring lobe; this seta apically and subapically with series of short, stiff barbs. Exopod of maxilla reaches to terminal margin of basal segment of palp. Exopod with dense series of plumose setae all along lateral margin; largest seta (dashed line in Fig. 16H ) at tip of exopod. Mesial margin bare except for one subapical seta. Ribbon of triangular scales all along lateral margin, on distal half constituted by series of about 5–10 µm long scales, each accompanied by mostly only one small, 2–5 µm long scale, on proximal half with higher incidence of small triangular scales. Basal sinus of exopod with triangular scales together with slender, bristle-like scales ( Fig. 14F ). The smaller and more slender scales are, the more they tend to occur in clusters of 3–8 scales. Maxillary palp with distal segment contributing ⅗ of palp length. This segment two times as long as maximum width, densely setose all along distal ⅘, no spines. Mesial margin of proximal segment with three normal-shaped barbed setae (partly below drawing plane in Fig. 16H ).

THORAX ( Fig. 18 ). Sternite 1 with distally rounded median lobe as normal in Mysidae . One large, basally thick barbed seta closely accompanied by 6–8 smaller such setae ( Fig. 18C ) on intersegmental joint between sympod 2 and its sternite. Basal plate of exopods with smooth cuticle, length 1.8–2.0 times maximum width, plates with minute tooth-like projection on disto-lateral edge, projection unapparent in Fig. 18C due to its small size. Flagellum of exopod 2 with only nine segments in dissected subadult female ( Fig. 18C ) vs ten in adult holotype. Epipod 1 leaf-like, longer than combined ischium, merus and carpus of endopod 1; no seta ( Fig. 18A ). Endopods 1–2 and 8 available in subadults and immatures, remaining endopods broken. Endopods 1–2 with six segments ( Fig. 18A, C ), endopod 8 with eight segments counting from basis to dactylus ( Fig. 18F ). Thoracic endopod 8 with its three carpopropodus segments separated from each other by oblique articulations ( Fig. 18F ). Available endopods with smooth cuticle not counting setae; no pores detected. Coxa of endopod 1 ( Fig. 18A ) with small mesial lobe apically bearing one small barbed seta; basis with large, setose endite, remaining segments without clear endite. All available dactyli with slender, weakly curved acute nail; nail 8 short ( Fig. 18G ), nail 1 normal-sized ( Fig. 18B ), nail 2 longest ( Fig. 18D ); nails 1–2 microserrated along median to subapical portions of weakly concave mesial (= inner) margin ( Fig. 18B, D–E ), nail 8 smooth ( Fig. 18G ).

TAIL FAN ( Figs 14E , 19C–E ). Exopod of uropods extends 0.3–0.4 times its length beyond endopod and 0.4–0.6 times beyond telson. Statoliths composed of fluorite, diameter 0.12–0.28 mm (n = 4). Telson near basal margin with a pair of transverse pore fields flanking midline; each field with ≈100 pores with diameter <2 µm as in Fig. 14D (<100 pores visualized as dots in Fig. 19D ). Telson with about 2 µm long triangular scales along most of its lateral margins. Scales organized in clusters of up to thirty ( Fig. 14E ). Together, clusters form narrow longitudinal ribbon (shaded areas in Fig. 19D ) proceeding close to each lateral margin along 1/12–11/12 telson length from basis.

Figures

Fig. 14. Amblyops arianii sp. nov., holotype, adult female with BL of 25.8 mm (A–C, G: ZMH 64653) and paratype, subadult female 24.2 mm (D–F: ZMH 64655). A–B. Cephalon, dorsal (A) and ventral (B) views. C. Detail of A, showing rostrum and disto-mesial portion of eye rudiments. D. Detail of C, showing part of pore field sublaterally on rostrum in another specimen. E. Scale field close to lateral margin of telson, dorsal view. F. Scales near proximal margin of exopod of maxilla, caudal view. G. Cephalic region, latero-ventral view. Abbreviations: ca = carapace; er = eye rudiment; op = ocular papilla. A–B, G. Objects artificially separated from background.

Fig. 15. Eyes in Amblyops arianii sp. nov., holotype, adult female with BL of 25.8 mm (A–B: ZMH 64653) and paratype, subadult female 24.2 mm (C–E: ZMH 64655). A. Anterior margin of cephalon in loco, lateral view. B. Detail of A showing left ocular papilla with focus on nerve cord, dorsal view. C. Eye rudiments expanded on slide, dorsal view. D. Detail of C showing left ocular papilla, focus on dorsal face. E. Detail of C showing hair-like scales covering surface of eye rudiments. Abbreviations: at = antennular trunk; ca = carapace; er = eye rudiment; op = ocular papilla. A, C. Objects artificially separated from background.

Fig. 16. Amblyops arianii sp. nov., paratype, subadult female with BL of 24.2 mm (ZMH 64655). A. Right antennula, ventral view. B. Clypeus, ventral view. C. Antenna, its sympod with end sac of antennal gland, dorsal view, setae of antennal scale omitted. D. Right mandible with palpus, rostral view. E–F. Masticatory part of right (E) and left (F) mandibles, rostral view. G. Maxillula, caudal view. H. Maxilla, caudal view.

Fig. 17. Foregut and midgut in Amblyops arianii sp. nov., paratype, subadult female with BL of 24.2 mm (ZMH 64655). A. Foregut expanded on slide, dorsal view. B–F. Details of A, arrows point to modified spines (B–E) and seta (F) of foregut. Abbreviations: di = dorsolateral infolding; la = lateralia; mg = midgut; pf = primary cardiac filter; sf = secondary pyloric filter; sm = superomedianum; sp = storage space. A. Figure composed from small photos. A, B1–B3. Objects artificially separated from background. B1, B3. The transverse stripes are phase-contrast artefacts from other objects out of focus.

Fig. 18. Thoracopods in Amblyops arianii sp. nov., paratypes, immature female with BL of 20.7 mm (A–B: ZMH 64654), subadult female 24.2 mm (C–E: ZMH 64655) and immature 8.6 mm (F–G). A. Thoracic endopod 1 with epipod 1, caudal view (exopod broken). B. Detail of A, showing dactylus 1 with nail, setae omitted. C. Thoracopod 2, caudal view. D. Detail of C, showing dactylus 2 with nail, setae omitted. E. Detail of D, showing serrated mesial margin of nail. F. Thoracic endopod 8, caudal view. G. Detail of F, showing dactylus 8 with nail, setae omitted.

Fig. 19. Pleopods and tail fan in Amblyops arianii sp. nov., holotype, adult female with BL of 25.8 mm (C: ZMH 64653) and paratype, subadult female 24.2 mm (A–B, D–E: ZMH 64655).A. Pleopod 4, mesial (= caudal) view, most setae broken. B. Pleopod 5, lateral (= rostral) view, most setae broken. C. Uropods, dorsal view, setae omitted. D. Telson, dorsal view. E. Detail of D, showing terminus of telson.

Fig. 4. Dactylamblyops benthophilus sp. nov., paratypes, adult males with BL of 20.3 mm (A–D, G: ZMH 64670), 17.0 mm (F, H: ZMH 64674) and adult female 21.8 mm (E: ZMH 64676). A. Male antennula, obliquely dorsal. B. Detail of A, showing disto-median lobe of antennular trunk. C. Antenna, dorsal view, setae of antennal scale omitted. D. Eyes and carapace expanded on slide, dorsal view. E. Labrum, ventral = aboral. F. Mandibles with right palpus, rostral view. G. Labium, caudal view; right lobe (visualized to the left) inclined with respect to the observation plane. H. Maxillula, caudal view.

Fig. 21. Amblyops bipapillatus sp. nov., holotype, adult female with BL of 16.7 mm (ZMH 64659). A. Cephalic region, dorsal view; right antennula, left antenna and setae of antennal scale omitted. B. Right antennal peduncle, ventral view. C. Left mandible with palpus, rostral view; broken setae on lower third of mesial margin of median segment were restored based on right palpus and visualized by dashed lines. D–E. Masticatory part of left (D) and right (E) mandibles, rostral view. F. Maxillula, caudal view. G. Maxilla, caudal view.

Fig. 2. Dactylamblyops murrayi W.M. Tattersall, 1939, adult female with BL of 15.6 mm. A. Oostegite 1, inner face. B. Detail of A, showing flagellate seta. C. Oostegite 2, inner face. D. Uropods, ventral view, setae omitted.

Fig. 1. Dactylamblyops murrayi W.M. Tattersall, 1939, adult female with BL of 15.6 mm. A. Distal ⅔ of right eye, dorsal view. B. Ommatidia, ventral view. C. Tip of ocular papilla, dorsal view. D. Right eye, lateral view. E. Antennal peduncle, ventral view. F. Telson, dorsal view.

Fig. 3. Dactylamblyops benthophilus sp. nov. A–B. Cephalon of paratype, adult male with BL of 19.9 mm, dorsal (A) and ventral (B) views (ZMH 64673). C. Paratype, adult female 25.4 mm long, lateral view (ZMH 64672). D. Holotype, adult male 22.6 mm long, lateral view (ZMH 64669). A–D. Objects artificially separated from background.