Amblyopsoides lepidophthalma, 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 : 70-77

Amblyopsoides lepidophthalma sp. nov.

urn:lsid:zoobank.org:act:830B8838-C5F9-4C1B-AF7E-D2489C265D2E

Figs 37–40

Diagnosis

Based on subadults of both sexes. All features within limits of generic diagnosis. Frontal margin of carapace obtuse-angled. Carapace covers less than a third of rostral extension of eyes, its antero-lateral edges broadly rounded. Eye rudiments separate, dorsoventrally compressed, reduced to roughly trapeziform, almost triangular pads without visual elements. Eyes dorsally hispid all over, mid-rostrally with ocular papilla projecting one-tenth of antero-posterior extension of eye. Transverse articulations between three antennular trunk segments. Antennal peduncle with three segments lined in a single plane. Antennal scale extends half its length beyond antennular trunk. Scale with minute apical segment separated by a transverse suture. Lateral margin bare up to a tooth at half length of scale, remaining distal portion densely setose. Mouthparts normal, labrum rostrally angular with rounded tip. Thoracic exopod 1 with 9-segmented flagellum, exopods 2–8 with 10-segmented flagellum. Endopods 3–8 with unsegmented carpus separated from 2-segmented propodus by an oblique articulation; both segments of propodus again separated by an oblique articulation from each other. Subadult male with pleopods 1–5 biramous, no spines; sympod without setae, exopod and endopod with setae. Endopod of uropods with one slender spine near mesial margin below statocyst. Telson trapezoid with distally continuously converging margins, length 5/3 times maximum width near basis, five times width at terminus, and about 11/10 length of ultimate pleomere. Terminal margin with very shallow (1–3% of telson length) median indentation bearing a pair of small laminae. A pair of barbed setae may be present between laminae in some specimens. Indentation flanked by 2–3 pairs of large spines in all specimens. Lateral margins of telson proximally bare, distal ⅗ with 20–26 spines discontinuously increasing in length distally, proximal 11–15 spines organized in groups of large spines with 1–2 small spines in between. Telson with total of 45–58 spines, always with pair of paramedian laminae, pair of setae not always present.

Etymology

The species name is an adjective with Latinized feminine ending, formed by fusion of the Classic Greek adjective ‘λεπιδωτός’ (‘scaly’) with the noun ‘ὀφθαλμός’ (‘eye’), related to the scaly ( Fig. 38D ) eye rudiments. The adjectivation of the noun has precedence in the moth Elachista ophthalma Kaila, 2011 .

Material examined

Holotype SOUTHERN OCEAN • 1 ♂ subad. (BL = 21.4 mm); South Sandwich Trench , E of Montagu Island, ANDEEP-II station 141-10; 58°25.08ʹ S, 25°00.77ʹ W to 58°24.93ʹ S, 25°00.95ʹ W; depth 2313– 2281 m; 23 Mar. 2002; EBS supranet; ZMH 64662 .

Paratypes SOUTHERN OCEAN • 1 ♀ subad. (BL = 18.9 mm), 7 imm., 14 juv.; same collection data as for holotype; ZMH 64666 • 1 ♀ imm. (BL = 11.0 mm); same collection data as for holotype except for occurrence in epinet; ZMH 64664 • 1 imm. (BL = 8.1 mm); same collection data as for preceding; ZMH 64665 • 1 ♀ subad. (BL = 24.4 mm at premolt stage, ovarian tubes full with large eggs, on slides); Drake Passage , NW of Elephant Island, ANDEEP-I station 041-3; 59°22.24ʹ S, 60°04.06ʹ W to 59°22.40ʹ S, 60°03.99ʹ W; depth 2375– 2372 m; 26 Jan. 2002; EBS epinet; ZMH 64663 .

Type locality and distribution

The type locality is South Sandwich Trench, east of Montagu Island, 58°25.08ʹ S, 25°00.77ʹ W to 58°24.93ʹ S, 25°00.95ʹ W, depth 2313– 2281 m. Also found in the Drake Passage, NW of Elephant Island. The resulting total ranges are 58– 59° S, 25– 60° W, depth 2281–2375 m.

Description

Holotype (♂)

Subadult male not dissected ( Figs 37 , 38G , 39K ). Fig. 39A–J, L of a paratype serves to illustrate situation in non-dissected holotype. All features of holotype within ranges of specific diagnosis. Body length 21.4 mm. Rostrum measures 3% of BL, carapace without rostrum 29%, cephalothorax 35%, pleon without telson 50% and telson 12%. Clypeus with short, spear-like mid-rostral process (visible only in ventral view: Fig. 37E ) nearly as long as proximal segment of antennular trunk.

CARAPACE ( Fig. 37A–B ). Normal, anterior margin uptilted ( Fig. 37C ), forming a short obtuse-angled rostrum ⅕ of length of terminal segment of antennular trunk. Cervical sulcus strong, cardial sulcus distinct; posterior margin concave, broadly rounded. Carapace leaves only ultimate thoracomere mid-dorsally exposed.

EYES ( Fig. 37D ). Eye rudiments large, their antero-posterior extension 0.8–0.9 times maximum width and 1.2 times length of terminal segment of antennular trunk. Eyes dorsoventrally flattened by a factor of 3.0. Cuticle hispid over most of dorsal, lateral and frontal faces. Ocular papilla emerges dorsally closely behind rostral margin. Papilla small, proximally hispid due to smaller scales compared to those of main body of eye rudiments.

ANTENNULA ( Fig. 39C ). Trunk measures 10% of BL, extending ¾ of its length beyond eyes. Measured along dorsal midline, basal segment is 0.4 of trunk length, median 0.2 and terminal 0.4. Length of basal segment 0.6 times width. Basal segment produced in a short lobe at disto-lateral edge, lobe distally with four setae. Terminal segment of antennular trunk 1.1 times as long as wide ( Fig. 37D ). Terminal segment with disto-median lobe armed disto-laterally with four barbed setae (for teeth see paratypes below). Appendix masculina inserts ventrally near terminal margin of antennular trunk; appendix conical, apically rounded, still small at this stage of maturity. Flagella large, width of outer flagellum measured near basis 1.1 times width of inner flagellum.

ANTENNA ( Fig. 37C–E ). Antennal scale measures 18% of BL. Scale length 3.5 times maximum width, 1.7 times length of antennular trunk and 2.0 times length of antennal peduncle. Sympod 2-segmented, caudally in addition with large end sac of antennal gland. Sympod with slightly produced disto-lateral edge forming small tooth-like projection. Scale well setose along mesial margin and on distal lobe. Peduncle 3-segmented, its basal segment contributes 25%, median segment 40% and terminal segment 35% to total length.

CEPHALOTHORAX ( Fig. 37 ). Rostral half of labrum right-angled triangular with blunt apex ( Fig. 37E ; dorsoventrally inclined in Fig. 39E ). Basal plate of exopods 1–8 twice as long as maximum width. Plates increase by total of ⅖ of length from plate 1 to plate 5 and then decrease by ⅕ down to plate 8. Plates 1–8 with smooth cuticle, disto-lateral edge with tooth-like projection (less tooth-like in Fig. 40F for a paratype). Endopods very slender (as in Fig. 40K ), endopod 3 measures one-fourth of BL, endopod 4 one-third (endopods 5–8 broken in holotype). Endopod 3 extending to distal end of antennular trunk when stretched anteriorly and to pleomere 2 when stretched posteriorly. Endopods 1–2 with six segments, endopods 3–4 with eight segments counting from basis to dactylus. Endopods with smooth cuticle, not counting setae and pores. Dactyli 1–2 large as in most Mysidae , in contrast to tiny dactyli 3–4 (as in Fig. 40K–L ). Dactylus 2 not reflexed. Dactyli 1–4 with smooth, weakly curved claws. Claws 1–2 strong; claws 3–4 small, needle-like. Penes small, already longer than wide at this stage of maturity.

PLEON ( Figs 37A–B , 39K ). Length of pleomeres 1–5 is 0.6, 0.6, 0.5, 0.5 and 0.6 times length of pleomere 6, respectively. Endopod of pleopods 1–5 with large pseudobranchial lobe. Endopods 3 and 5 ninesegmented and exopods unsegmented at this stage of male maturity ( Fig. 39K ). Endopods well setose, exopods with only few setae on and near apex. Scutellum paracaudale triangular with slightly convex flanks and with narrowly blunt, almost acute apex.

TAIL FAN ( Figs 37A–B , 38E, G ). Endopod and exopod of uropods 1.2 and 1.8 times as long as sixth pleomere, respectively. Exopod 1.7 times telson length; endopod 1.2 times telson length and 0.6 times exopod length. Exopod extends 0.3 times its length beyond endopod, 0.4 times beyond telson and endopod 0.2 times its length beyond telson. Exopod with slightly concave, almost straight lateral margin and with well convex mesial margin; its terminus broadly rounded, convex. Margins of endopod converge in narrow V-shaped manner up to blunt apex. Uropods with smooth cuticle, not considering setae and single spine. Lateral margins of telson armed with 25–26 spines; telson with total of 57 spines and a pair of paramedian setae flanked by a pair of laminae ( Fig. 38G ).

Paratypes

CARAPACE ( Fig. 39A–B ). Median pore group located 5% of carapace length in front of posterior margin of carapace, constituted by ten pores flanking a larger pore-like structure ( Fig. 39B ) on top of a low bulge.

EYES ( Figs 38B–D , 39A ). Expanded on slide. Papilla ends in a toroid with central pore ( Fig. 38B ). Completely internal, ovoid cell mass proximally close to papilla interpreted as organ of Bellonci; this organ drawn as tiny dashed ellipsoid in Fig. 39A . Dorsal face of (mounted) eyes covered with minute, acutely-tipped triangular scales laterally and frontally increasing in size by a factor of ≈2–3 ( Fig. 38C vs 38D).

ANTENNAE S. LAT.. ( Fig. 39C–D ). Basal segment of antennular trunk with well-developed antennular bursa. Terminal segment of trunk with disto-median lobe armed with four barbed setae and with 3–4 minute teeth increasing in size laterally as in Fig. 33C ; no female lobe, no callynophore. Position of tooth at outer margin of antennal scale varies with body size: arising at one-third of scale length from basis in juveniles with BL 7–10 mm (n = 10) vs at half scale length in subadults with BL 19–24 mm (n = 3).

MANDIBLES ( Fig. 39F–H ). Palp of both mandibles and processus molaris of right mandible as in A. fenestragothica sp. nov. (33E–G), but left processus molaris ( Fig. 39H ) less strongly cuticularized. Right mandible ( Fig. 39G ) in A. lepidophthalma sp. nov.: pars incisiva with three large and two intermediate-sized teeth; digitus mobilis with one large and about five small teeth; pars centralis with series of nine tooth-like spines increasing in size distally, four large, distal-most spines armed with small secondary humps (worn-out toothlets?). Left mandible ( Fig. 39H ): pars incisiva with three large and a cluster of five small teeth; digitus mobilis with four large teeth; pars centralis with six slender spines distally increasing in size (smaller spines covered by trunk, not visualized in Fig. 39H ), all along armed with stiff bristles.

GUT ( Fig. 40B–E ). Foregut most similar to that of A. fenestragothica sp. nov. ( Fig. 34 ). As a notable difference, posterior part of lateralia on each side with dense cluster of five rather than eleven subequal spines. Storage volume empty. Anal lobe moderately cuticularized.

MAXILLULA ( Fig. 39I ). Only minor differences from that of A. fenestragothica sp. nov. ( Fig. 33H ). Distal segment with seven dorsal (= oral) spines serrated along aboral margin, 3–4 ventral (= aboral) spines along oral margin and two large ventral spines not serrated. Endite of maxillula terminally with 3–4 large, distally spiny setae. Only one (most proximal) seta backward curved in A. lepidophthalma sp. nov. MAXILLA ( Fig. 39J ).Almost identical to that of A. fenestragothica sp. nov. ( Fig. 33I ).As almost negligible differences, length of distal segment of palp 1.8–1.9 times maximum width and 59–60% of total palp length in A. lepidophthalma sp. nov.

THORAX ( Fig. 40F–L ). Sternite 1 with smooth, distally rounded median lobe. A median lobe on this sternite is normal in Mysidae . Closely set, basally thick, barbed setae on intersegmental joint between sternites 2–8 and their respective sympods ( Fig. 40F, K ), no such setae on sternite 1. Sternites 2–8 each with acutely triangular median process. Processes on sternites 2–3 clearly larger than subequal processes on 4–8 ( Fig. 40F ). Only process on sternite 8 covered all around with triangular, mostly slender scales ( Fig. 40F, H ). Epipod 1 leaf-like, about as long as combined ischium, merus and carpus of endopod 1, no seta ( Fig. 40F ). Basal plate of exopods 2–8 with tooth-like projection from disto-lateral edge; small projection not always present in exopod 1. Coxa of endopod 1 mesially with one small barbed seta; basis with large, setose endite on rostral face (endite indicated by dashed line in Fig. 40F ), remaining segments without endite. Propodus of endopod 1 with about 16–20 loosely scattered pores ( Fig. 40G ) with diameter ≤3 µm on caudal face. Endopods 3–8 each with eight segments counting from basis to dactylus ( Fig. 40K ); these endopods 30–40% of BL; small dactylus with tiny, needle-like claw ( Fig. 40L ). Endopod 8 extends to mandibles when stretched anteriorly and to basal third of telson when stretched posteriorly.

TAIL FAN ( Figs 38E–F , 40M ). Statoliths composed of fluorite, diameter 0.26–0.27 mm (n = 2). Telson with pair of subbasal pore fields ( Fig. 38E ) flanking midline; each field with about 40 pores with diameter <3 µm (only part of pores in focus in Fig. 38F ). Two barbed setae visible between disto-paramedian laminae ( Fig. 38E ) in ten out of 21 telsons inspected. No scales such as otherwise found along lateral telson margins detected in Amblyopsoides fenestragothica sp. nov., Amblyops arianii sp. nov., A. bipapillatus sp. nov., A. tattersalli , Dactylamblyops benthophilus sp. nov. or Desmocornea subchelata gen. et sp. nov. These species share a pair of paramedian pore fields near basis of telson with Amblyopsoides lepidophthalma sp. nov.

Figures

Fig. 37. Amblyopsoides lepidophthalma sp. nov., holotype, subadult male with BL of 21.4 mm (ZMH 64662). A–B. Holotype in toto, lateral (A) and dorsal (B) views. C–E. Cephalon, lateral (C), dorsal (D) and ventral (E) views. Abbreviations: cp = clypeus with rostral process; la = labrum; le = left eye rudiment; ro = rostrum. Objects artificially separated from background.

Fig. 38. Amblyopsoides lepidophthalma sp. nov., paratype, subadult female with BL of 24.4 mm (A–F: ZMH 64663) and holotype, subadult male 21.4 mm (G: ZMH 64662). A. Left eye rudiment with ocular papilla (op), dorsal view. B. Detail of A, showing tip of ocular papilla with toroidal bulge (tb). C. Detail of A, showing scales on anterior margin of eye, tangential view. D. Detail of A, showing scales on dorsal face of eye rudiment. E. Telson, dorsal view. F. Detail of E, showing left pore field and mid-longitudinal fold. G. Terminus of telson in another specimen, dorsal view. Abbreviations: lf = mid-longitudinal fold; pf = pore field. A–F. Objects expanded on slide with dorsal face upwards. G. Object photographed in loco. A–B, E, G. Objects artificially separated from background.

Fig. 39. Amblyopsoides lepidophthalma sp. nov., paratype, subadult female with BL of 24.4 mm (A–J, L: ZMH 64663) and holotype, subadult male 21.4 mm (K: ZMH 64662). A. Carapace with right eye expanded on slide, dorsal view. B. Detail of A, showing minute pore group. C. Antennula, dorsal view. D. Antenna with antennal gland, dorsal view, setae omitted from antennal scale. E. Labrum, aboral view, dorsoventrally somewhat inclined. F. Mandible with right palpus, caudal view. G–H. Masticatory part of right (G) and left (H) mandibles, caudal view. I. Maxillula, caudal view. J. Maxilla, caudal view. K. Pleopod 3 of subadult male, rostral = lateral. L. Pleopod 4 of subadult female, caudal = mesial.

Fig. 40. Amblyopsoides lepidophthalma sp. nov., paratype, subadult female with BL of 24.4 mm (ZMH 64663). A. Labium. B–E. Modified spines of foregut, from anterior (B), median (C) and posterior (D) parts of lateralia and from dorsolateral infolding (E). F. Thoracopod 1 with epipod and sternites 1–8, ventral view, setae omitted from right endopod (drawn to the left). G. Detail of F showing dactylus with nail, setae omitted, pore diameters not to scale. H. Detail of F showing median process of sternite 8. I. Thoracic endopod 2, caudal view. J. Detail of I showing dactylus with nail, setae omitted. K. Thoracic endopod 8, caudal view. L. Detail of K showing dactylus with nail, setae omitted. M. Uropods, ventral view, setae omitted.

Fig. 33. Amblyopsoides fenestragothica sp. nov., holotype, immature male with BL of 16.2 mm (ZMH 64660). A. Carapace with eyes expanded on slide, dorsal view, arrows point to minute pore group (detail in Fig. 31D). B. Antennula, dorsal view. C. Detail of B, showing disto-median lobe of antennular trunk. D. Antenna with antennal gland, ventral view, setae omitted from antennal scale. E. Mandible with right palpus, caudal view. F. Masticatory part of right mandible, caudal view. G. Masticatory part of left mandible, rostral view. H. Maxillula, caudal view. I. Maxilla, caudal view.

Fig. 34. Foregut in Amblyopsoides fenestragothica sp. nov., holotype, immature male with BL of 16.2 mm (ZMH 64660). A. Foregut expanded on slide, dorsal view. B–E. Details of A, arrows point to modified spines of foregut. Abbreviations: di = dorsolateral infolding; la = lateralia; mg = midgut; sp = storage space. A. Object artificially separated from background.