Amblyops tattersalli Zimmer, 1914

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 : 27-32

Amblyops tattersalli Zimmer, 1914

Figs 11–13

Amblyops tattersalli Zimmer, 1914: 390–391 , pl. xxiii figs 13–16 (coast of E Antarctica ).

Amblyops tattersalli – W.M. Tattersall 1923: 275, 277, 285 (short description, record, Ross Sea). — O.S. Tattersall 1965: 15–16, figs 1–4 (description, record, Ross Sea). — Birstein & Tchindonova 1970: 284–285 (in species list). — Ariani et al. 1993: table 1 (mineral composition of statoliths). — Wittmann 1995: fig. 1 (reproductive adaptations). — Brandt et al. 1998: table 1 (biogeography, endemism). — Petryashov 2006: 1409, fig. 5 (distribution, in key). — San Vicente et al. 2006: table 2 (biodiversity, new records, Southern Ocean). — San Vicente 2010: 42, table 4, fig. 35 (distribution, diagnosis, in key). — Murano 2012: 84 (in key). — Petryashov 2014a: 150, map 10 (biogeography). — Wittmann & Ariani 2019: suppl. (fluorite statoliths, biogeography). — Mees & Meland 2024: Aphia-ID 227029 (accepted).

Diagnosis

Based on adults of both sexes. All features within limits of generic diagnosis. Carapace with rounded, obtusely angled anterior margin. Eye rudiments without visual elements, roughly trapeziform with widely rounded lateral margin and with roughly linear, oblique anterior margin. Ocular papilla with ¼–⅓ of antero-posterior extension of eye rudiments. Disto-lateral edge of antennal sympod with only one large tooth. Antennal scale length 2.6–3.2 times maximum width. Scale extends 0.4–0.6 times its length beyond antennular trunk. Scale with small apical segment; bare portion of lateral margin ending at 9/10 of scale length in a large tooth, mesially tightly accompanied by 2–3 small spines. Setose terminal lobe of scale well projecting beyond large tooth. Mouthparts normal, labrum rostrally rounded. Thoracic exopod 1 with 9-segmented flagellum, exopods 2–8 with 10-segmented flagellum. Endopods 3–8 with unsegmented carpus separated from propodus by a strongly oblique articulation, two segments of propodus separated by a less oblique articulation. Female with three pairs of oostegites contributing to wall of marsupium. Male pleopods 1–5 biramous; endopods with 1, 18, 16–17, 16 and 15–16 segments, exopods with 17, 17, 17–18, 18 and 18 segments, respectively. Pleopods of both sexes with normal setae only. Both rami of uropods undivided, setose all around, endopod with one spine on mesial margin below statocyst. Telson linguiform, distal ⅔ with weakly converging, slightly sigmoid lateral margins and with broad, slightly flattened, convex terminal margin, disto-lateral edges rounded; length 1.7–1.9 times maximum width. Proximal ⅖ of telson with bare lateral margins, distal ⅗ of each lateral margin with dense series of 18–23 normal-shaped spines discontinuously increasing in length distally. Terminal margin with pair of paramedian setae tightly flanked by a pair of small spines, in turn flanked by 2–3 pairs of large spines, the latter forming a continuous series and gradually changing in length with proximally adjoining lateral spines; innermost large spine ⅑–⅙ of telson length. Telson with total of 42–54 spines plus two barbed setae.

Material examined

SE ATLANTIC • 1 ♂ subad. ( BL = 16.4 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 juv. ( BL = 7.7 mm); NW Weddell Sea, ANDEEP-II station 131-3; 65°19.83ʹ S, 51°31.62ʹ W to 65°19.95ʹ S, 51°31.41ʹ W; depth 3049–3050 m; 5 Mar. 2002; EBS supranet • 1 ♀ ad. (fragmented, BL ≈ 27.3 mm, bearing nauplioid larvae), 1 ♂ ad. ( BL = 22.7 mm), 3 juv.; NW Weddell Sea, ANDEEP-II station 133-3; 65°20.15ʹ S, 54°14.35ʹ W to 65°20.06ʹ S, 54°14.51ʹ W; depth 1122– 1119 m; 7 Mar. 2002; EBS epinet • 1 imm. ( BL = 8.7 mm); Weddell Abyssal Plain , ANDEEP-III station 088-8; 68°03.66ʹ S, 20°27.90ʹ W to 68°03.61ʹ S, 20°27.52ʹ W; depth 4929–4931 m; 27 Feb. 2005; EBS supranet • 1 juv. ( BL = 6.2 mm); Weddell Abyssal Plain, ANDEEP-III station 102-13; 65°34.32ʹ S, 36°31.32ʹ W to 65°34.40ʹ S, 36°31.07ʹ W; depth 4805– 4803 m; 6 Mar. 2005; EBS supranet • 2 ♂♂ ad. ( BL = 24.6, 27.7 mm), 1 ♀ subad. ( BL = 17.4 mm); Powell Basin , ANDEEP-III station 133-2; 62°46.49ʹ S, 53°03.50ʹ W to 62°46.38ʹ S, 53°03.98ʹ W; depth 1584– 1579 m; 16 Mar. 2005; EBS epinet • 1 ♂ ad. ( BL = 22.8 mm, on slides); same collection data as for preceding • 1 ♀ subad. (BL = 11.1 mm); Powell Basin , SW continental slope of South Orkney Islands, ANDEEP-III station 151-7; 61°45.52ʹ S, 47°07.68ʹ W to 61°45.42ʹ S, 47°08.04ʹ W; depth 1182–1185 m; 21 Mar. 2005; EBS epinet • 1 imm. ( BL = 6.5 mm); Drake Passage , N of South Shetland Islands, ANDEEP-I station 114-4; 61°43.54ʹ S, 60°44.20ʹ W to 61°43.54ʹ S, 60°44.55ʹ W; depth 2914–2920 m; 18 Feb. 2002; EBS epinet • 1 ♀ ad. ( BL = 20.9 mm), 1 imm., 1 juv.; same collection data as for preceding except for occurrence in supranet • 1 juv. ( BL = 4.6 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 .

Supplementary description

All features within the limits of the above diagnosis.

CARAPACE ( Figs 11A–B , 13B ). Anterior margin convex, posterior margin weakly concave. Median pore group 6% of carapace length in front of posterior margin. This group is constituted by eight (2 ×4) pores flanking a larger pore-like structure, together in M-like arrangement ( Fig. 13B ).

EYES ( Fig. 11A–E ). Eye rudiments dorsoventrally compressed by a factor of 1.5–1.9 measured near center. Eye surface mostly hispid by minute, slender triangular scales ( Fig. 11C–D ); on average largest scales ( Fig. 11C ) in median portions of anterior margin. Dorsal face covered only partly by somewhat shorter scales ( Fig. 11D ) scattered over surface, for methodological reasons best visible along accidental folds produced by forcing eye rudiments into a plane. Each eye with large, distally broadly rounded ocular papilla ( Fig. 11B, E ) closely behind anterior margin at ⅓ of eye width from mesial margin. Papilla ends in a toroid with central pore. Organ of Bellonci near papilla.

ANTENNAE S. LAT. ( Figs 11F–G , 13A ). Basal segment of antennula dorsally with striated sensory cushion well visible at bottom of an almost empty antennular bursa ( Fig. 11F ); such striation not visible in a bursa filled with extraneous material ( Fig. 11G ). Terminal segment of antennular trunk without female lobe. Disto-median lobe of trunk armed with four teeth increasing in size laterally, lobe disto-laterally with four barbed setae. The 2–3 tooth-like structures mesially adjoining disto-lateral tooth of antennal scale show a clear basal articulation ( Fig. 13A ) and thus represent true spines (or spiniform setae), as already concluded by W.M. Tattersall (1923), but not representing the “secondary denticles” [translation] indicated by Zimmer (1914) in the original description of this species.

MANDIBLES. Compared with left mandible (as in Fig. 21C–D ), right mandible (as in Fig. 21E ) bears smaller, serrate digitus mobilis and more strongly tooth-like spines of pars centralis.

GUT ( Fig. 12 ). Similar to that of A. bipapillatus sp. nov. ( Fig. 22 ). Dissected adult male of A. tattersalli differs from this species by presence of small denticles on distal fourth of apically coronate spines ( Fig. 12B ), posterior part of lateralia on each side with cluster of fewer (eight vs eleven) unilaterally serrated spines rather than with stiff bristles ( Fig. 12D ), and by dorsolateral infoldings on each side with cluster of fewer (five vs six) spines, more homogeneous in length ( Fig. 12E ). Lateral setae of superomedianum are basally much thicker ( Fig. 12F ) than slender normal setae in caudal position. All setae of superomedianum distally microserrated. Storage volume poorly filled with crustacean remains (mainly setae), a few very large mineral particles and very little masticated material. Midgut almost empty. Anal lobe distinct, weakly cuticularized (dashed line in Fig. 13C ).

THORAX. Basal plate of exopods 1–8 with minute knob at subrectangular disto-lateral edge. Dactylus of endopod 2 not reflexed; oriented about perpendicular to carpopropodus. Endopods 3–8 long and slender. Endopod 8 when stretched reaches anteriorly to tip of antennal scale, posteriorly to end of pleomere 6. Penes with ⅘ length of ischium 8.

PLEON. Length of pleomeres 1–5 is 0.6–0.7, 0.6, 0.5, 0.5–0.7 and 0.5–0.6 times length of pleomere 6, respectively, telson 1.1–1.2 times length of pleomere 6. Pleomere 6 shorter than combined pleomeres 4–5. Female pleopods increasing in length caudally. Exopods of male pleopods 1–5 subequal in length. Scutellum paracaudale triangular with narrowly blunt apex.

TAIL FAN ( Fig. 13C–F ). Exopod of uropods 1.5 times endopod length and 1.5–1.7 that of telson; endopod 0.9–1.0 length of telson. Exopod extends 0.3–0.4 times its length beyond endopod and 0.4–0.6 beyond telson. Statoliths composed of fluorite, diameter 0.18–0.29 mm (n = 5). Telson dissected in two specimens: both spines flanking pair of paramedian setae minute (0.05 mm) in adult male with BL 22.8 mm ( Fig. 13F ); only right paramedian spine that small in adult female with BL 27.8 mm, left spine five times that size, i.e., one third of adjacent large spine. Telson with a pair of paramedian subbasal fields (visualized as shadowed areas in Fig. 13C ) with 68–83 pores (n = 4; not all pores in focus in Fig. 13D ). Telson with 2–3 µm long triangular scales organized in groups of up to twenty, mostly about ten scales ( Fig. 13E ); groups together forming narrow longitudinal ribbon proceeding close to each lateral margin between ⅕ and ⅘ telson length from basis (visualized as shadowed lateral areas in Fig. 13C ).

NAUPLIOID LARVAE ( Fig. 13G–I ). Female with BL 27.3 mm carried 15 nauplioid larvae at substage N3. Body length of larvae 4.0– 4.6 mm. Nauplioid abdomen ends in furcal appendages, each armed with a fan of 18–22 spine-setae increasing in length distally (n = 5; Fig. 13I ). Tip of larval antennula with 9–12 mostly shorter spine-setae, not arranged in series (n = 5; Fig. 13H ). Remaining parts of body with smooth cuticle. Remaining features in Fig. 13G–I typical of stage of development.

Type locality and distribution

The type locality is the winter station (= Gauss Station) of the Deutsche Südpolar-Expedition 1901– 1903, coast of East Antarctica, 66°02ʹ S, 89°38ʹ E, depth 385 m. This circum-Antarctic species was reported by Petryashov (2006, 2014a) from 55– 78° S, depth 510–860 m and by San Vicente (2010) from 66– 75° S, depth 385– 547 m. The ANDEEP records are from Cape Basin, Weddell Abyssal Plain, NW Weddell Sea, Powell Basin, South Sandwich Trench and Drake Passage in the range of 41– 68° S, 10° E – 61° W, depth 1119–4931 m, thus representing strong latitudinal and bathymetric range extensions. Resulting total ranges 41– 78° S, 90° E anticlockwise to 61° W, depth 385–4931 m.

Figures

Fig. 11. Amblyops tattersalli Zimmer, 1914, adult males with BL of 27.7 mm (A), 22.8 mm (B–F) and adult female 27.3 mm (G). A. Cephalon, lateral view. B. Eyes expanded on slide, dorsal view. C–D. Details of B, showing spiniform scales on anterior margin (C) and on mid-dorsal face (D). E. Detail of B, showing tip of ocular papilla. F–G. Left antennular bursae in two specimens, dorsal view; note striated pad (F: sp) and bursa (G) filled with extraneous material. Abbreviations: ca = carapace; nc = nerve cord; op = ocular papilla; sp = striated pad; tb = toroidal bulge. A–B. Objects artificially separated from background.

Fig. 12. Foregut and midgut in Amblyops tattersalli Zimmer, 1914, adult male with BL of 22.8 mm. 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. Object artificially separated from background.

Fig. 13. Amblyops tattersalli Zimmer, 1914, adult male with BL of 22.8 mm (B–F), adult female 27.3 mm (A) and three of its nauplioid larvae (G–I). A. Disto-lateral angle of antennal scale, dorsal view. B. Pore group near caudal margin of carapace, dorsal view. C–F. Telson, dorsal view; details showing pore field close to caudal margin (D), groups of triangular scales along lateral margin (E) and pair of minute paramedian spines plus basal portion of setae on terminal margin (F). G. Nauplioid larva with BL of 4.6 mm, lateral view. H. Tip of antennula in another nauplioid, lateral view. I. Caudal furca in another nauplioid, dorsal view. Abbreviatios: a1 = antennula; a2 = antenna; cf = caudal furca; md = left mandible; tm = thoracomeres.

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. 22. Foregut in Amblyops bipapillatus sp. nov., holotype, adult female with BL of 16.7 mm (ZMH 64659). 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; pf = primary cardiac filter; sm = superomedianum; sp = storage space. A. Object artificially separated from background.