Dactylamblyops benthophilus, Wittmann, 2024
publication ID |
https://doi.org/ 10.5852/ejt.2024.940.2577 |
publication LSID |
lsid:zoobank.org:pub:19DE5E4F-3A2C-41FF-A593-A4C74F7A9ABD |
DOI |
https://doi.org/10.5281/zenodo.12522114 |
persistent identifier |
https://treatment.plazi.org/id/986D4F91-F730-429C-9071-BC6015BE7D26 |
taxon LSID |
lsid:zoobank.org:act:986D4F91-F730-429C-9071-BC6015BE7D26 |
treatment provided by |
Plazi |
scientific name |
Dactylamblyops benthophilus |
status |
sp. nov. |
Dactylamblyops benthophilus sp. nov.
urn:lsid:zoobank.org:act:986D4F91-F730-429C-9071-BC6015BE7D26
Figs 3–8 View Fig View Fig View Fig View Fig View Fig View Fig
Dactylamblyops sp. A – Wittmann & Chevaldonné 2021: fig. 24c–d.
Diagnosis
Covers adults of both sexes. All features within limits of generic diagnosis. Carapace with triangular, distally broadly rounded rostrum covering only small portion of eyestalks. Eyes shortly set apart, pyriform to sub-conical, dorsoventrally compressed; sub-conical cornea with residual visual elements, cornea not divided by a ledge; ocular papilla near antero-mesial edge, length of papilla ⅒–⅕ cornea diameter, not extending beyond cornea. Antennal peduncle with oblique border between median and terminal segment. Scale with small terminal segment, scale length 4.4–5.5 times maximum width; scale extending 0.3–0.4 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. Mouthparts normal, labrum rostrally rounded. Thoracic endopods not subchelate. Females with three pairs of oostegites. Endopods of male pleopods 1–5 with 1, 13–14, 14, 13–14 and 12–13 segments, exopods with 13–14, 14, 14, 14 and 14 segments, respectively. No modified setae on pleopods of both sexes. Endopod of uropods with one minute spine on inner margin below statocyst. Telson elongate triangular with slightly sigmoid, continuously converging lateral margins, length 1.6–1.9 times maximum width near basis; proximal half with bare lateral margins, distal half of each lateral margin with 24–31 densely set spines increasing in length distally; apex with three large spines in continuous series with lateral spines, no small spine and no seta between large apical spines; telson with total of 51–64 spines. Differentiation from similar taxa given in ‘Discussion’.
Etymology
The species name is an adjective with Latinized masculine ending, underlining the more benthophilic habit compared with the sympatric, more pelagic congener D. hodgsoni .
Material examined
Holotype SOUTHERN OCEAN • 1 ♂ ad. ( BL = 22.6 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; ZMH 64669 View Materials . GoogleMaps
Paratypes SOUTHERN OCEAN • 2 ♀♀ ad. ( BL = 20.9–25.4 mm), 2 damaged juv.; same collection data as for holotype; ZMH 64672 View Materials GoogleMaps • 1 ♂ ad. ( BL = 19.9 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 supranet; ZMH 64673 View Materials GoogleMaps • 1 ♀ ad. (BL = 23.9 mm), 1 ♀ subad. (in 2 parts, BL = 16.0 mm); eastern Weddell Slope , Kapp Norvegia , ANDEEP-III station 078-10; 71°09.39ʹ S, 13°59.30ʹ W to 71°09.36ʹ S, 13°58.81ʹ W; depth 2156– 2147 m; 21 Feb. 2005; EBS epinet; ZMH 64675 View Materials GoogleMaps • 1 ♂ ad. (fragment, BL = 17.0 mm, on slides); same collection data as for preceding; ZMH 64674 View Materials GoogleMaps • 4 ♀♀ ad. ( BL = 17.8–24.0 mm), 1 ♂ ad. ( BL = 20.0 mm), 2 ♀♀ subad., 3 ♂♂ subad., 1 imm.; same collection data as for preceding except for occurrence in EBS supranet; ZMH 64677 View Materials GoogleMaps • 1 ♀ ad. ( BL = 21.8 mm, on slides); same collection data as for preceding; ZMH 64676 View Materials GoogleMaps • 1 ♂ ad. ( BL = 20.3 mm, on slides); 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 64670 View Materials GoogleMaps • 1 ♂ ad. ( BL = 24.4 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 supranet; ZMH 64671 View Materials GoogleMaps • 1 ♀ ad. ( BL = 19.3 mm), 1 ♂ subad. (damaged, BL ≈ 15 mm); Bellingshausen Sea , NW of Anvers Island, ANDEEP-III station 153-7; 63°19.31ʹ S, 64°36.94ʹ W to 63°19.15ʹ S, 64°37.18ʹ W; depth 2092–2118 m; 29 Mar. 2005; EBS supranet; ZMH 64678 View Materials GoogleMaps .
Other material
SOUTHERN OCEAN • 1 juv. ( BL = 6.7 mm); South Sandwich Trench , SE of Montagu Island, ANDEEP-II station 143-1; 58°44.69ʹ S, 25°10.27ʹ W to 58°44.49ʹ S, 25°10.47ʹ W; depth 773.9– 755.6 m; 25 Mar. 2002; EBS epinet GoogleMaps • 3 juv. ( BL = 4.8–6.9 mm); same collection data as for preceding except for occurrence in supranet GoogleMaps • 1 ♂ subad. ( BL = 17.3 mm), 1 imm. ( BL = 15.4 mm, in 2parts), 1juv.; NW Weddell Sea, ANDEEP-II station 132-2; 65°17.74ʹ S, 53°22.82ʹ W to 65°17.56ʹ S, 53°22.83ʹ W; depth 2086– 2086 m; 6 Mar. 2002; EBS supranet GoogleMaps • 1 ♀ subad. ( BL = 16.7 mm); 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 supranet GoogleMaps • 1 ♂ imm. ( BL = 12.1 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; recovered from sediment in web mug GoogleMaps • 1 ♀ imm. (BL = 7.9 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 GoogleMaps • 10 juv. ( BL = 4.8–7.9 mm); same collection data as for preceding except for occurrence in supranet GoogleMaps • 1 imm. (damaged, BL = 11.0 mm), 1 imm. (strongly damaged, BL ≈ 15 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 GoogleMaps • 1 juv. ( BL = 6.7 mm); Drake Passage , N of South Shetland Islands, ANDEEP-I station 105-7; 61°24.16ʹ S, 58°51.55ʹ W to 61°24.26ʹ S, 58°51.83ʹ W; depth 2297.9–2307.5 m; 12 Feb. 2002; EBS supranet GoogleMaps .
Type locality and distribution
The type locality is ANDEEP II station 141-10: South Sandwich Trench, E of Montagu Island, 58°25.08ʹ S, 25°00.77ʹ W to 58°24.93ʹ S, 25°00.95ʹ W, depth 2313– 2281 m. The species was recorded in most major parts of the W Antarctic examined, range 58– 71° S, 14– 65° W, depth 756–4805 m. It was captured in the supranet in 11 out of 14 successive mysid samples taken with a self-closing epibenthic sledge, suggesting a suprabenthic mode of life close above the deep-sea floor.
Description
Body length 17.8–25.4 mm (n = 9) in adult females, 17.0– 24.4 mm (n = 6) in adult males. Rostrum measures 2–3% of BL, carapace without rostrum 31–36%, thorax 37–44%, pleon without telson 46– 52% and telson 6–9%.
CARAPACE ( Figs 3A View Fig , 4D View Fig ). Normal, antero-lateral edges produced, broadly rounded ( Fig. 4D View Fig ). Cervical sulcus strong, cardial sulcus indistinct, posterior margin concave, terminal indentation broadly rounded. No pores seen (though not excluded). Carapace leaving ½–1½ thoracomeres mid-dorsally exposed.
EYES ( Figs 3A View Fig , 4D View Fig , 5F View Fig ). Ocular symphysis with unpaired, proximally trapeziform, distally triangular, apically rounded interocular lobe ( Fig. 4D View Fig ), in dorsal view mistakable with an anterior extension of rostrum. Eyestalks smooth all around, 0.7–0.9 times as long as terminal segment of antennular trunk. Cornea obliquely, laterally positioned on eyestalk ( Figs 3A View Fig , 4D View Fig ), kidney-shaped in dorsal view, apparent length 0.7–0.8 of total eye length, width 0.3–0.4. Cornea appears whitish in ethanol-preserved material. Its antero-posterior extension 1.0–1.2 times length of terminal segment of antennular trunk. Eye papilla ends in a toroid with pore in center ( Fig. 5F View Fig ). Organ of Bellonci present near ocular papilla.
ANTENNULA ( Figs 4A–B View Fig , 5A–E View Fig ). Antennular trunk measures 10–12% of BL. It extends half its length beyond eyes. Measured along dorsal midline, basal segment 0.3–0.4 of trunk length, median segment 0.1–0.2 and terminal segment 0.4–0.6. Length of basal segment 0.7–0.8 of width; mid-dorsally with deep antennular bursa ( Figs 4A View Fig , 5C–D View Fig ) leading down to a striated pad at bottom. Basal segment not produced at outer distal edge ( Fig. 4A View Fig ); no mid-ventral carina. Disto-median lobe ( Fig. 4B View Fig ) of terminal segment with three teeth increasing in size laterally, lobe disto-laterally with four barbed setae. Appendix masculina ( Figs 4A View Fig , 5A View Fig ) inserts ventrally near terminal margin of antennular trunk; appendix conical, apically rounded, 0.5–0.9 times as long as terminal segment of trunk, strongly setose. Female lobe ( Fig. 5B View Fig ) 0.3 times as long as terminal segment, well-developed, albeit less strongly setose. Wittmann & Chevaldonné (2021: fig. 24c–d) correctly figured this lobe as inserting ventrally but accidentally indicated it in text as inserting dorsally. Flagella large, width of outer flagellum measured near basis 1.3– 1.7 times width of inner flagellum. Basal portion of outer flagellum with ventral callynophore bearing broad row of densely set aesthetascs ( Fig. 5E View Fig ) in both sexes. Callynophore 0.6–0.7 times as long as terminal segment of antennular trunk.
ANTENNA ( Fig. 4C View Fig ). With smooth cuticle all around, not considering setae and disto-lateral tooth of antennal scale. Sympod 2-segmented, with large end sac of antennal gland. Sympod angular on disto-lateral edge, not forming a tooth-like projection. Antennal scale measures 16–20% of BL, 1.4–1.7 times as long as antennular trunk and 2.2–2.4 times as long as antennal peduncle. Scale 4.4–5.5 times as long as wide. Peduncle 3-segmented, its basal segment contributes 41–44% to total length, median segment 28–31% and terminal segment 27–29%.
LABRUM AND LABIUM ( Fig. 4E, G View Fig ). Labrum normal, rostrally forming a broad, rounded bulge; most caudal portions with strong lamellae and cover of scale-like fringes. Paired labia with stiff and normal setae, no spines, no teeth.
MANDIBLES ( Fig. 4F View Fig ). Palp 0.6–0.7 times as long as antennal scale. Palp not hispid, its basal segment without setae, remaining segments densely setose along mesial and lateral margins. Basal segment contributes 10–13%, median segment 49–54% and apical segment 37–40% to total palp length. Length of median segment 2.6–3.2 times maximum width; its mesial margin convex, lateral margin sigmoid. Length of apical segment 3.3–3.9 times maximum width. Masticatory part of mandibles normal, left and right mandibles alike: pars incisiva of both mandibles with 4–5 large teeth, and digitus mobilis with 5–9 teeth. Processus molaris with strong grinding lamellae not ending in teeth and with dense bundle of stiff bristles on proximal edge. Pars centralis of left mandible with series of 10–13 spines becoming more slender and with greater numbers of stiff bristles proximally, distalmost spine stout with few bristles. Pars centralis of right mandible with 6–9 slender, subequal spines bearing numerous stiff bristles.
GUT ( Fig. 6 View Fig ). Foregut with lateralia, infoldings and superomedianum of cardiac chamber densely covered by smooth, slender setae and spines. Lateralia anteriorly with dense series of slender, apically coronate, bluntly pronged spines ( Fig. 6B View Fig ) of various length and with slender, mostly blunt spines, in part with minute apical tooth ( Fig. 6C View Fig ). Posterior part of lateralia on each side of foregut with a complex of three unilaterally finely serrated spines arising from a common base ( Fig. 6D View Fig 2 View Fig ) and a second complex with four medium-sized plus at least three small spines of that kind ( Fig. 6D View Fig 1 View Fig ). Dorsolateral infoldings on each side with a pair of larger, unilaterally more coarsely serrated, bent spines ( Fig. 6E View Fig ). Content of five foreguts mainly masticated, unidentifiable organic material (detritus), mineral particles, foraminifera and one fragment of a polychaete larva. Telson with ventrally prominent anal lobe ( Fig. 6F–G View Fig , dashed line in Fig. 8G View Fig ). Lobe caudally bifid with thick cuticle, superficially resembling glutei separated by an intergluteal furrow ( Fig. 6G View Fig ).
MAXILLULA ( Fig. 4H View Fig ). Distal segment with 10–12 strong spines on transverse terminal margin, several spines subterminally serrated on outer margin. This segment subterminally with 7–10 setae bearing stiff barbs; total of 7–9 pores flanking outer (= most ventral = aboral) seta on both its sides. Endite of maxillula terminally with three large, distally spiny setae, on both sides accompanied by numerous less strong setae. As a striking feature, most proximal seta of endite long, slender and curved backward.
MAXILLA ( Fig. 7A View Fig ). Sympod with four mesial lobes, densely setose along their disto-mesial margins. Large proximal lobe with large, dense fan of simple setae. Only one large seta extends beyond this fan, on caudal face, at margin near distally neighboring lobe; this seta bears a dense unilateral series of stiff barbs along its distal half. It is proximally followed by loose series of 7–13 shorter, thin setae unilaterally microserrated at least on their distal half (these setae covered by fan in Fig. 7A View Fig ); this series extends over ⅔ of fan length. All four lobes with furry stripes of fine hairs on mesial portions of only caudal face; this is below drawing plane, thus stripes not visualized in Fig. 7A View Fig . Exopod of maxilla ends shortly before terminal margin of basal segment of palp. Exopod with total of 24–33 plumose setae all along lateral margin, subapically with only 0–1 seta on mesial margin; tip with 1–2 comparatively large setae; lateral margin with 19–26 intermediate-sized setae, subequal among each other, plus 3–5 large setae in most basal position. Mesial margin bare except, if any, for above-mentioned subapical seta. Maxillary palp with apical segment contributing 55–64% to palp length, no spines. Apical segment 1.6–1.8 times as long as maximum width. Basal segment less wide, subbasally with mesial bulge (endite) bearing 5–7 barbed, basally thick setae. Distal ¾ of apical segment all around with barbed setae except for a bare sector along central third of terminal margin. Mesial third of this segment with furs of tiny hairs on rostral and caudal faces (only rostral fur visualized in Fig. 7A View Fig ).
THORAX ( Figs 3C–D View Fig , 7B–K View Fig ). Intersegmental joints between sternites and sympod 2 with basally thick, all along barbed seta accompanied by five smaller barbed setae ( Fig. 7F View Fig ). Sympods 3–8 with one large seta accompanied by one smaller seta of that type ( Fig. 7H View Fig ). No such setae on sympod 1. Thoracic sternites to various extent covered by fur of minute hairs in both sexes (shaded areas in Fig. 7B View Fig ). Basal plates of thoracic exopods with smooth cuticle, length twice maximum width ( Fig. 7B View Fig ), plates widening distally up to ⅔ of length, plates with rectangular disto-lateral corner. Epipod 1 leaf-like, about as long as combined ischium, merus and carpus of endopod 1, no seta ( Fig. 7B View Fig ). Endopods with smooth cuticle, not considering setae and pores. Coxa of endopod 1 ( Fig. 7B View Fig ) with small mesial lobe apically bearing one barbed seta; basis with large, setose endite, remaining segments without endite; dactylus with field of about 40–60 pores, diameter <2 µm, on caudal face ( Fig. 7C, E View Fig ). Endopods 1–2 with six segments ( Fig. 7B, F View Fig ), remaining endopods with eight segments counting from basis to dactylus ( Fig. 7H View Fig ). Carpus 3–8 unsegmented; strongly oblique suture between carpus and propodus; less oblique, almost transverse suture between two segments of propodus ( Fig. 7H View Fig ). Dactyli 3–8 more slender than dactyli 1–2. Dactylus 1 with almost straight, subapically slightly serrated nail ( Fig. 7C–D View Fig ); dactylus 2 not reflexed; dactyli 2–8 with short, more slender, slightly bent, smooth nail ( Fig. 7G, I View Fig ). Endopod 3 extends shortly beyond antennular trunk when stretched anteriorly, endopod 8 to mandibles. Endopod 8 extends to pleomere 4 when stretched posteriorly. Penes ( Fig. 7K View Fig ) with subterminal ejaculatory opening, with setose, terminally rounded caudal lobe, and with non-setose, terminally rugose, triangular rostral lobe.
MARSUPIUM ( Fig. 7J View Fig ). Empty in all females of this material. Oostegite length increases by a factor of 2.8 from oostegite 1 to 3. Basal portions of dorsal margin without setae in oostegites 1–2 and from basal to subapical portions in oostegite 3. All oostegites with smooth cuticle, not considering setae. Their ventral and anterior margins plus part of posterior margin with dense series of barbed setae. Posterior parts of oostegites 1–3 on inner face with comparatively long setae microserrated on their distal half. Only oostegites 2–3 with numerous, on average shorter, slender smooth setae on outer face. These setae positioned all along ventral portions in large oostegite 3, and only in median to subapical portions on ventral fifth of oostegite 2.
PLEON ( Figs 3C–D View Fig , 8A–E View Fig ). Length of pleomeres 1–5 is 0.5–0.8, 0.6–0.8, 0.5–0.6, 0.4–0.6 and 0.5–0.7 times length of pleomere 6, respectively. Pleomere 6 shorter than combined length of pleomeres 4–5. Male pleopods with longitudinal series of setae on lateral (= rostral) face of sympod 1 ( Fig. 8A View Fig ), no setae on sympods 2–5 ( Fig. 8B View Fig ). Basal segment of endopod in all male pleopods with subrectangular, terminally rounded, setose pseudobranchial lobe; exopods of subequal size. Size of female pleopods increasing caudally. Female pleopod 1 with residual differentiation of pseudobranchial lobe (endopod), in pleopods 2–5 represented only by a short setose bulge. Scutellum paracaudale well rounded, sinusoid.
TAIL FAN ( Fig. 8F–I View Fig ). Telson, endopod and exopod of uropods are 1.0–1.2, 1.2–1.4 and 1.8–2.1 times length of sixth pleomere, respectively. Exopod of uropods ( Fig. 8F View Fig ) straight, 1.8–2.1 times as long as telson, endopod 1.1–1.5 times as long as telson and 0.7 times as long as exopod. Exopod extends 0.3–0.4 times its length beyond endopod and 0.5–0.6 times beyond telson; endopod extends 0.3 times its length beyond telson. Exopod with slightly convex, almost straight lateral margin and with weakly convex mesial margin. Both margins about parallel on proximal half, then converging up to truncate terminus with rounded edges. Margins of endopod converging in a V-shaped manner up to narrowly blunt terminus. Uropods ( Fig. 8F View Fig ) with smooth cuticle, not considering setae and single spine. Statoliths composed of fluorite, form sub-hemispherical with roughly plane fundus, as also found in other Erythropinae by Wittmann et al. (1993). Diameter 0.25–0.35 mm (n = 6), thickness ⅔ of diameter; no tegmen differentiated. Statolith formula 1 + 3 + (5–6) + (10–19) = (20–29) (n = 4). Telson ( Fig. 8G, I View Fig ) with pair of paramedian subbasal fields of 90–125 pores ( Fig. 8G–I View Fig ), pore diameters <3 µm. Telson with 2–7 µm long and 0.5–0.8 µm wide triangular scales (as in Fig. 36B View Fig ) organized in clusters of about 10–25 scales. Clusters together form a narrow longitudinal ribbon (nearly as in Fig. 19D View Fig but shorter and partly broader) proceeding close to each lateral margin along ⅓–⅔ of telson length from basis (shaded areas in Fig. 8G View Fig ).
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