Oxyarcturus holoacanthus, Pereira & Roccatagliata & Doti, 2023
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publication ID |
https://dx.doi.org/10.3897/zse.99.106667 |
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publication LSID |
lsid:zoobank.org:pub:A22910A6-C10B-4D15-AE6A-2AA91A92A6CC |
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persistent identifier |
https://treatment.plazi.org/id/D7DE7D4E-1C60-4CD8-A180-808C9317B91F |
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taxon LSID |
lsid:zoobank.org:act:D7DE7D4E-1C60-4CD8-A180-808C9317B91F |
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treatment provided by |
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scientific name |
Oxyarcturus holoacanthus |
| status |
sp. nov. |
Oxyarcturus holoacanthus sp. nov.
Figs 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7 , 8 View Figure 8 , 9 View Figure 9 , 10 View Figure 10
Type material.
Holotype adult ♂ (30.7 mm). "Talud Continental III" expedition, Sta. 47 (38°06.58'S, 53°42.83'W), 2950 m, bottom otter trawl, 06 Sep. 2013, RV "Puerto Deseado", I. Chiesa & A. Martinez leg. MACN-In 44318.
Paratypes 4 adult ♂♂ (31.3-35.4 mm); 1 adult ♂ broken; 1 ovigerous ♀ (38.9 mm). Same data as holotype. MACN-In 44319.
Diagnosis.
Head with 2 long supraocular spines and 6 posterior supraocular spines. Eyes large (e/d ratio = 1.6). Pereonite 1 with 6 submedial, 2 sublateral and 4 lateral long spines. Pereonites 2-4 with 4 submedial, 2 sublateral and 2 lateral long spines. All four pereonites with additional small spines. Pereonites 5-7 with 2 submedial spines, and sublateral and lateral spines. All pleonites fused with the pleotelson, pleonite 1 indicated by transverse groove. Pleonites 1-3 with 2 submedial spines, and sublateral and lateral spines. Pleotelson, dorsal surface and lateral margins with long spines. Uropod, external surface of protopod with many short spines.
Description.
Adult male (habitus based on the holotype MACN-In 44318; appendages based on the paratype MACN-In 44319-a).
Body (Figs 1A, B View Figure 1 , 2A, B View Figure 2 ) cylindrical and geniculate. Head with 2 long supraocular spines, 6 long posterior supraocular spines, 2 long lateral spines. Eyes large (e/d ratio = 1.6). Pereonite 1 with 6 submedial, 2 sublateral and 4 lateral long spines. Pereonites 2-4 with 4 submedial, 2 sublateral and 2 lateral long spines. All four pereonites with additional small spines. Pereonites 5-7 with 2 submedial spines, and sublateral and lateral spines. All pleonites fused with pleotelson, pleonite 1 indicated by transverse groove. Pleonites 1-3 with 2 submedial spines, and sublateral and lateral spines; pleonite 3 with 2 long lateral spines. Pleotelson with 2 long caudolateral spines, and 1 short subterminal medial spine in between; dorsal surface with long spines; lateral margins with spines.
Antennula (Fig. 3A, B View Figure 3 ) peduncle of 3 articles; article 1 widest, with 1 feather-like seta distally, setules on both margins, and cuticular combs; article 2 longest, with 8 feather-like setae (some of them broken); article 3 0.79 × article 2 length, with 2 simple setae (broken). Flagellum of 3 articles; article 1 very short, ring-like and glabrous; article 2 longest, with 22 groups of 1-3 aesthetascs and 0-2 long simple setae each; article 3 minute, knob like, with 1 aesthetasc and 3 simple setae.
Antenna (Figs 1A, C View Figure 1 , 2A, B View Figure 2 , 3C View Figure 3 ) peduncle of 5 articles; article 1 short and wide, glabrous; article 2 subequal in width to article 1, with 3 distal spines and 5 simple setae on ventral margin; article 3 0.38 × article 5 length, with 2 distal spines and 8 simple setae; article 4 0.88 × article 5 length, with 2 distal spines; article 5 longest, with 1 distal spine. Flagellum of 8 articles, last article minute, claw-like (flagellum broken in the paratype drawn).
Mandibles (Fig. 3D, E View Figure 3 ) asymmetrical, without palp. Incisor processes with 4 strong sclerotized teeth. Molar processes with grinding surface and indented margins; right molar process narrower than left one, and with 9 setae on lower surface. Left lacinia mobilis with 3 rounded teeth and 1 stout serrate seta; right lacinia mobilis with 4 acute teeth and a few small setae.
Maxillula (Fig. 4A View Figure 4 ) lateral lobe with 10 stout setae distally. Mesial lobe with 3 setulate long setae distally (1 of them broken). Both lobes with simple setae marginally.
Maxilla (Fig. 4B View Figure 4 ) outer lobe with 6 serrate setae distally. Mesial lobe with 4 serrate setae distally. Inner lobe with 22-23 setulate setae distally. Surface and margins of outer, mesial and inner lobes covered with setules.
Maxilliped (Fig. 4C View Figure 4 ) basal endite short and broad, with 18 setulate setae on distal and lateral margins. Palp of 5 articles; article 1 0.4 × article 3 length, with 11 simple setae; article 2 0.6 × article 3 length, with 24-25 simple setae; article 3 longest, with 40 simple and serrulate setae on inner margin, and 4 long setae (3 of them broken) on outer distal angle; article 4 0.9 × article 3 length, with 30 simple and serrulate setae on inner margin, and 8 long simple and serrulate setae along outer margin; article 5 shortest, with 12 simple and serrulate setae. Epipod long, oval, surpassing distal margin of palp article 1, with few simple setae on ventral surface and inner margin. Basis and epipod, ventral surfaces with small setae and cuticular combs.
Pereopod I (Fig. 4D View Figure 4 ) shorter and stouter than pereopods II-IV. Basis short, with 1 short proximal spine (broken); ischium, merus and carpus 0.6, 0.4 and 0.3 × propodus length, respectively; propodus longest article; dactylus 0.6 × propodus length (excluding claws), with 2 distal claws, ventral claw 0.4 × dorsal claw length. Distal corner of basis and flexor margin of ischium with long simple setae. Flexor margins of merus to dactylus, and mesial face of propodus with serrulate setae (for sake of clarity, these latter setae were not drawn in Fig. 4D View Figure 4 ).
Pereopods II-IV (Fig. 5 View Figure 5 ) alike, pereopod IV longest. Bases gradually changing from short and smooth (pereopod II) to long and with spines (pereopod IV). Note: spines are broken or worn out in the specimen drawn. These spines are better preserved in the holotype (see Figs 1A View Figure 1 , 2A View Figure 2 ). Ischium, merus and carpus with 1 long distal spine (except on carpus of pereopod IV). Distal corner of flexor margin of basis and flexor margins of ischium to propodus with two rows of filter setae. Dactylus (excluding claws) 0.2-0.3 × propodus length, with 2 distal claws, ventral claw 0.4-0.6 × dorsal claw length (see Fig. 5C View Figure 5 ).
Pereopods V-VII (Fig. 6 View Figure 6 ) alike, shorter than pereopods II-IV, pereopod V longest (pereopod VI broken at merus level). Bases longest article, with spines and 0-4 feather-like setae on extensor margin. Note: spines are broken or worn out in the specimen drawn. These spines are better preserved in the holotype (see Figs 1A View Figure 1 , 2A View Figure 2 ). Ischium subequal in length to propodus; merus 0.4 × propodus length, with 1 distal spine and 10-16 spine-like setae on flexor margin; carpus 0.5 × propodus length, with 13-18 spine-like setae on flexor margin; propodus with 10 spine-like setae on flexor margin; dactylus (excluding claws) 0.8 × propodus length, with 2 simple setae on extensor margin and 2 distal claws, ventral claw 0.3 × dorsal claw length (see Fig. 6D View Figure 6 ). All articles with small setae scattered on extensor and flexor margins.
Penial plate (Figs 7A View Figure 7 , 8A View Figure 8 ) fused and elongated, tapering distally; distal end barely slit, with two lateral spoon-like projections (see details).
Pleopod I (Figs 7B View Figure 7 , 8B View Figure 8 ) protopod longer than those of remaining pleopods, with 9 coupling setae on inner margin, and 10 stout spines along outer margin. Endopod 1.1 × exopod length, inner and distal margins with 55 plumose setae; outer margin with many setules. Exopod, inner and distal margins with 33 plumose setae; outer margin with 49-50 short distally plumose setae (some of them arranged in a second row on posterior surface). Posterior surface groove narrowing distally, and ending on lateral margin, overlapped by a thin layer; groove slightly projected distally, followed by a group of tiny setae (see detail). All plumose setae shorter than rami.
Pleopod II (Fig. 9A View Figure 9 ) protopod quadrangular, with 6 coupling setae on inner margin. Endopod with 63 plumose setae marginally. Appendix masculina subequal in length to endopod, tapering distally, with a small, rounded expansion close to distal end (see detail). Exopod subequal in length to endopod, with 90 plumose setae marginally. All plumose setae shorter than rami.
Pleopods III-V (Fig. 9B-D View Figure 9 ) protopod with 0-2 plumose setae on inner margin. Endopod 0.8-1.0 × exopod length, with 2-30 plumose setae and some short simple setae. Exopod with distal setules.
Uropod (Fig. 9E, F View Figure 9 ) biramous. Protopod, external surface with 16 spines and many stunt tubercles; inner margin with 20 plumose setae (some broken). Endopod with 2 distal setae (both broken). Exopod 0.7 × endopod length, glabrous.
Adult female description (habitus and appendages based on paratype MACN-In 44319-b).
As adult male, except for:
Antennula (Fig. 10A View Figure 10 ) flagellum: article 1 with 3 feather-like setae; article 2 with 16 groups of 1-3 aesthetascs and 2 long simple setae each; article 3 with 2 aesthetascs, 1 feather-like seta (broken) and 2 simple setae.
Pleopod I (Fig. 10B View Figure 10 ) protopod longer than those of remaining pleopods, with 11 coupling setae on inner margin, and 10 stout spines on outer margin. Rami subequal in length. Endopod with 62 plumose setae marginally. Exopod with 79 plumose setae marginally. All plumose setae shorter than rami.
Pleopod II (Fig. 10C View Figure 10 ) protopod quadrangular, with 7 coupling setae on inner margin, and 4 plumose setae on outer margin (broken). Rami subequal. Endopod with 78 plumose setae marginally. Exopod with 86 plumose setae marginally. All plumose setae shorter than rami.
Etymology.
The specific epithet combines two Greek words holos = "entire, complete" and akantha = “spine”, referring to the many long and acute spines that cover the body surface of this species.
Distribution.
Only known from the Mar del Plata submarine canyon, off Buenos Aires Province, Argentina, at 2950 m depth (Fig. 11 View Figure 11 ).
Remarks.
Oxyarcturus holoacanthus sp. nov. is most similar to O. spinosus . Both species have a large number of long spines on body surface. Oxyarcturus holoacanthus sp. nov. can be distinguished from O. spinosus as follows: head with 6 posterior supraocular spines (2-4 posterior supraocular spines in O. spinosus ), pereonites 1-4 with 4-6 submedial spines (only 2 submedial spines in O. spinosus ), pereonites 5-7 and pleon with many long dorsal spines on both sexes (male with small tubercles and female with small spines in O. spinosus ).
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