Dactylamblyops murrayi W.M. Tattersall, 1939

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 : 7-9

Dactylamblyops murrayi W.M. Tattersall, 1939

Figs 1–2

Dactylamblyops murrayi W.M. Tattersall, 1939: 235–237 , figs 9–10 (Arabian Sea).

Dactylamblyops murrayi – Ii 1964: 289–293, figs 74–75 (detailed description, NW Pacific). — Pillai 1964: 3 (in list of Indian species); 1965: 1706–1707, fig. 53 (diagnosis, in key). — Murano 1971: 47 (in species list for Central Japan); 1981: 281–282, fig. 8 (supplementary description). — Ariani et al. 1993: table 1 (statolith structure). — Kazmi et al. 1999: 149, fig. 31 (in illustrated key to Arabian Sea species). — San Vicente & Cartes 2011: 464, table 2 (in key to species of Dactylamblyops , distribution). — Wittmann & Ariani 2019: suppl. (statolith composition, record). — Wittmann & Chevaldonné 2021: table 1 (morphology, sensory structures). — Mees & Meland 2024: Aphia-ID 226736 (accepted).

Diagnosis

Covers adults of both sexes. All features within limits of generic diagnosis. Carapace with broad triangular rostrum almost extending to distal margin of proximal segment of antennular trunk. Eyes shortly set apart, dorsoventrally compressed, cornea not divided by a ledge; ocular papilla with length ⅓–½ cornea diameter. Antennal peduncle with oblique border between median and terminal segment ( Fig. 1E ). Scale unsegmented, length 4–5 times maximum width; scale extending ⅕–⅓ of its length beyond antennular trunk; mesial margin setose, bare outer margin ending in a tooth. Setose terminal lobe of scale not projecting beyond disto-lateral tooth. Thoracic endopods not subchelate. Females with three pairs of oostegites. Male pleopods with endopods 2–5 and all exopods 10-segmented, no modified setae. Endopod of uropods with a single spine on inner margin below statocyst. Telson linguiform, with slightly sigmoid lateral margins, and with convex, continuously rounded terminal margin; length twice maximum width near basis. Proximal half of telson with bare lateral margins, distal half of each lateral margin with 18–32 densely set spines increasing in length distally. Terminal margin with three pairs of spines in continuous series with the lateral spines; no small spine between pair of large paramedian spines. Telson with total of 43–70 spines.

Material examined (non-type)

SOUTHERN OCEAN • 1 ♀ ad. (damaged, estimated BL ≈ 15.6 mm); NE Weddell Sea, Kosminski Fracture Zone deep, ANDEEP-II station 138-6; 62°58.09ʹ S, 27°54.54ʹ W to 62°58.02ʹ S, 27°54.25ʹ W; depth 4542.5– 4541.1 m; 17 Mar. 2002; EBS supranet.

Supplementary description

EYES ( Fig. 1A–D ). As in diagnosis. Eyes dorsoventrally compressed by a factor of 2.4, reaching beyond median segment of antennular trunk in obliquely lateral orientation. Eyes roughly pyriform in dorsal view but lens-shaped (bolster-shaped) in lateral view ( Fig. 1D ). Cornea transversely positioned distally on eyestalk. It contributes to about half of eye surface. Numerous, loosely set ( Fig. 1B ), imperfectly developed ommatidia reach surface. Eyestalk disto-laterally with large ocular papilla anteriorly extending beyond eye ( Fig. 1A ). Eye papilla ends in a toroid with pore in center ( Fig. 1C ). Organ of Bellonci near ocular papilla. Anterior margin of cephalon with subrostral, median process reaching only to proximal third of proximal segment of antennular trunk; this process wide-angled, distally bluntly rounded.

ANTENNAE ( Fig. 1E ). Antennula furnished with antennular bursa as in D. benthophilus sp. nov. Female lobe of D. murrayi with minute setae; this lobe smaller than that of D. benthophilus ( Fig. 5B ). Distal portions of antennal scale broken; its proximal fragment with setose mesial margin and bare lateral margin.

THORAX. Dorsal portions of thorax and carapace including rostrum broken.All thoracopods broken, only sympods and oostegites remaining. Presence of 1–2 long, thick, densely barbed setae on membranous joints between at least thoracic sternites 6–7 and their respective sympods.

MARSUPIUM ( Fig. 2A–C ). Formed by three pairs of setose oostegites strongly increasing in size caudally. Each oostegite of present specimen proximally with brush of essentially smooth setae, some of which are distally armed with a few minute stiff bristles. Only oostegites 2–3 with series of setae along lower and caudal margins, these setae with caudally increasing incidence and size of barbs. Inner face of each oostegite with one flagellate seta showing no suture between thick handle and long slender flagellum. Only oostegite 1 with an additional smaller seta of that kind subbasally on lower margin. Only oostegite 3 with ≈ 30 slender whip setae (suture present between handle and flagellum) loosely scattered over outer face near ventral and caudal margins.

PLEON. Contributes 52% and telson 16% to estimated total length of 15.6 mm in this damaged adult female. Pleomeres 1–5 are 0.6, 0.5, 0.5, 0.5 and 0.4 times as long as pleomere 6, respectively; this value is 1.2 for telson. Female pleopods unsegmented setose rods with pseudobranchial lobe; pleopod length increases caudally.

TAIL FAN ( Figs 1F , 2D ). Exopod of uropods 1.5–2.0 times as long as telson, endopod 1.1–1.5 times as long as telson. Statoliths composed of fluorite. Telson linguiform with converging, slightly sigmoid lateral margins. Proximal half of each lateral margin bare, distal half with ≈32 spines, estimated based on remnants of broken spines ( Fig. 1F ), spines on average increasing in length distally; most spines of terminal margin broken.

Type locality and distribution

The type locality by monotypy is the Indian Ocean, northern Arabian Sea, 23°02.5ʹ N, 64°15.9ʹ E, oblique tow in 1500–0 m (W.M. Tattersall 1939; coordinates in Sewell 1935). This species was reported by Ii (1964), Murano (1981) and Wittmann & Chevaldonné (2021) from the NW Pacific, deep waters off Japan, 28° N – 36° N, 129° E – 140° E, depth 480–1200 m. All other previously published references refer to materials from these localities. The present ANDEEP record from the Southern Ocean, NE Weddell Sea, 63° S, 28° W, depth 4541–4543 m, represents strong latitudinal and bathymetric extensions of the known range. The species, so far classified as panthalassic in meso- to bathypelagic depths, has now also been recorded from bathybenthic habitats.

Figures

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. 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. 5. Dactylamblyops benthophilus sp. nov., paratypes, adult males with BL of 20.3 mm (A, C, E: ZMH 64670), 17.0 mm (F: ZMH 64674) and adult female 21.8 mm (B, D: ZMH 64676). A. Appendix masculina, in dorsal view with focus on ventral face. B. Female lobe, ventrally on terminal segment of antennular trunk. C–D. Antennular bursa in median position at basal segment of antennular trunk, dorsal (C) and lateral (D) views. E. Longitudinal ribbon of setal bases (callynophore) on mesio-ventral face of lateral antennular flagellum, ventral view. F. Tip of ocular papilla, arrow points to toroidal bulge (tb).