Eurycope monodon, Mursch, Andre, Brenke, Nils & Wägele, Johann Wolfgang, 2008

Mursch, Andre, Brenke, Nils & Wägele, Johann Wolfgang, 2008, Results of the DIVA 1 Expedition of RV “ Meteor ” (Cruise M 48: 1): Three new species of Munnopsidae Sars, 1864 from abyssal depths of the Angola Basin (Crustacea: Isopoda: Asellota) *, Zootaxa 1866, pp. 493-539 : 495-509

publication ID	https://doi.org/ 10.5281/zenodo.183789
DOI	https://doi.org/10.5281/zenodo.5676886
persistent identifier	https://treatment.plazi.org/id/09748790-A205-7C5D-FF12-BC68A213FC90
treatment provided by	Plazi
scientific name	Eurycope monodon
status	sp. nov.

Treatment

Eurycope monodon View in CoL sp. nov.

Material examined

Holotype ( ZMH K 41791), male (2.14 mm), Angola Basin, 17 06.2’ S, 4 41.7’ E to 17 07.5’ S, 4 42.3’ E; Station No. 344, expedition M48:1 RV “ Meteor ”. Paratype ( ZMH K 41792), female (2.25 mm), same locality.

Additional material: 10 males, 10 females ( ZMH K 41793 K 41796)

Etymology

Named after Monodon monoceros Linné, 1758 (narwhal) referring to its long rostral seta.

Diagnosis

Eurycope with overhanging rostrum bearing a shallow frontal depression with a conspicuous long anteromedian spinelike seta. Lateral margins of head almost parallel, only slightly converging anteriorly. Each lateral side with 3 stout spinelike setae nearly forming a horizontal line. Pereonites of ambulosome equally shaped, caudally increasing in width. Pereonites of natasome decreasing in width from pereonite 5 to pereonite 7, pereonite 6 two thirds the length of the subequally long pereonites 5 and 7, the latter with straight posterior margin. Lateral edge of pleotelson straight in lateral view, caudal end not angled ventrally at insertion of uropods. Antenna 1 article 1 with flat distomedial lobe reaching two thirds of the following article’s length. Distolateral lobes of male pleopod 1 with large, cranially curved cusp.

Description of male holotype

Body ( Fig. 1 View FIGURE 1. E ): Longishly oval, slightly flattened dorsoventrally, length: width = 2.33. Body width evenly increasing from head to pereonite 5. Natasome with roundly triangulate pleotelson, slightly shorter than three quarters of body length. Body height between head and ambulosome almost constant; about 0.2 times body length, at caudal half of pereonite 5 increased (0.24 times body length), flattening posteriorly. Anterodorsal parts of head, tergites of pereonites 1 to 4 and all sternites showing fine texture of parallel cuticular grooves.

Head ( Fig. 1 View FIGURE 1. E ; Fig. 2 View FIGURE 2. E a): Length: width = 0.55, slightly narrower than pereonite 1, lateral sides with 3 stout spinelike setae nearly forming a horizontal line. Conspicuous anterolateral vault at base of antenna 2. Dorsal surface finely granular. Cuticular grooves on ventral and lateral surface, anterodorsally projecting onto rostrum. Rostrum length: width = 0.5, hanging over, tapering anteriorly, with shallow anteromedian depression. Anterolateral margin of rostrum in apical half with cuticular keel. Apex of rostrum with median seta 1.75 times as long as rostrum, anteriorly almost projecting to anterior tip of medial lobe of antenna 1 article 1. Frons clearly concave due to overhanging rostrum, ventrolateral margin with slightly projecting edge leading towards posterolateral margin of clypeus. Clypeus roughly halfcylindrical. Labrum and clypeus only separated by a fold. Clypeus length: labrum length = 0.4. Body width: cephalic width = 1.6.

Ambulosome ( Fig. 1 View FIGURE 1. E ): Width of pereonites increasing from first to fourth: 0.66, 0.72, 0.74, 0.78 times maximum body width. Lengths about equal (0.1–0.11 times of pereonite width). Each pereonite overlapping the preceding one. Anterior margin of pereonite 1 slightly concave, of pereonite 2 to pereonite 4 increasingly more convex. Surface with transversal cuticular grooves, parallel to anterior and lateral margins. Anterodorsal and dorsolateral surface finely granulated. Each anterolateral angle with short seta. Coxal lobes triangular, projecting anteriorly, with stout apical spinelike seta and up to 3 short lateral setae. Sternites more weakly sclerotized with more distinct cuticular grooves.

Natasome ( Fig. 1 View FIGURE 1. E ): Posterior margins of pereonites 5 and 6 overlapped by anterior margin of following tergite. Lateral margins in anterior half with up to 4 setae. Posterolateral angles decreasingly acute from pereonite 5 to 7, covered by margin of following pereonite. Pereonite 5 widest, length: width = 0.34, with convex anterior and concave posterior margin. Pereonite 6 and 7 length = 0.74 and 1.13 times length of pereonite 5, respectively, width 0.96 and 0.82 times width of pereonite 5, respectively. Pereonite 6 with margins as in pereonite 5, length: width = 0.26. Pereonite 7 length: width = 0.47. Anterior margin convex, posterior margin nearly straight. Anterior margin of pereonite 5 finely granulated. Coxae and sternites weakly sclerotized, with cuticular grooves. Coxae near posterolateral margin of sternite, without coxal lobes. Posterior margin of sternite of pereonite 7 medially with penes ( Wilson 1989) clearly visible as subtriangulate lobes caudally inserting in cavities in the base of fused pleopod 1.

Pleotelson ( Fig. 1 View FIGURE 1. E ; Fig. 8 View FIGURE 8. E a): 0.33 times body length, roundly triangular, almost as long as broad. Dorsoventrally flattened, width: depth = 2.24. Anterior margin almost straight, laterally slightly overlapping pereonite 7. A pair of dorsolateral tubercles of 0.05 times pleotelson width in diameter, distance to anterior margin of pleotelson 0.34 times pleotelson length, with central broom seta. Tubercles invisible in transmitted light, only detectable by central seta. Lateral margin without angle near insertion of uropods, caudal tip not bent ventrally. Distal two thirds of endopod of uropod visible in dorsal view. Lateroventral surface with cuticular grooves.

Antenna 1 ( Fig. 2 View FIGURE 2. E b) about one quarter of body length. Peduncular article 1 length: width = 1.06, approximately one third ofcephalic width. Medial lobe longer than lateral, dorsally granular, 3 apical spinelike setae. Lateral lobe with 1 spinelike and 1 short seta, 1 subapical spinelike seta. Peduncular article 2 cylindrical, inserting dorsally from distal third of first and half as long. 2.5 times longer than wide, distal margin with 9 setae. Peduncular article 3 two thirds as wide and half as long as second, with 2 small lateral spinelike setae. Flagellum 11jointed, first article half as long as peduncular article 3, distally with 1 long and 1 short seta. Following articles about a quarter narrower, the second with a short distoventral seta, ninth with 1 short distodorsal, tenth with 2 distolateral longer setae. Articles 3, 5, 8, 9 and 10 with 1 distal aesthetasc, article 11 with 2 aesthetascs and 1 apical broom seta.

Antenna 2 ( Fig. 2 View FIGURE 2. E c): Basalmost 4 peduncular articles preserved, width = width of antenna 1. Article 1 short, extended to rounded trapezoidal lobe, 1 subapical spinelike seta. Article 2 evenly cylindrical, laterally with 1 long and 2 short spinelike setae. Article 3 slightly longer than preceding articles together, anterior margin sloping. Distomedially 3 spinelike setae and 1 simple seta in a row. Lateral scale acute, triangular, frontally projecting 2 thirds of length of following article, lateral with 2 small setae. Article 4 0.25 times narrower in diameter, distal margin extended into dorsomedial and ventromedial lobe.

Mandibles ( Fig. 3 View FIGURE 3. E a–d; Fig. 4 a–c): 0.14 times body length, length: width = 1.8. 2 ventrolateral setae on left, 3 on right mandible, on a level with condyle. Palp ( Fig. 3 View FIGURE 3. E d; Fig. 4 a, b): 0.77 times as long as mandible body. Article 1 basally tapering, on left mandible with long subdistal seta. Article 2 1.5 times as long as first, slightly wider. Distal two thirds of lateral side with numerous short scale setae with 2 to 11 (mostly 5 to 6) short setulae. 3 large distal spinelike setae. Article 3 laterally flattened, apical half twisted clockwise in right, anticlockwise in left mandible. Medial surface with scale setae with 4 to 8 setulae. Ventral margin with row of 8 cleaning setae, subapically 3 strong onesidedly serrated spinelike setae, basal one 4 times longer than others. Incisor process ( Fig. 3 View FIGURE 3. E c; Fig. 4 a) on both mandibles with 4 sclerotized cusps, the second most ventral largest, second most dorsal cusp on left mandible shifted basally and inconspicuous, dorsalmost cusp on right mandible smallest. Lacinia mobilis ( Fig. 3 View FIGURE 3. E c) distally with a row of 7 cusps, increasingly larger from dorsal to ventral side. Spine row on left mandible with 2 short, stout setae and further proximally 2 longer, more slender onesidedly serrated stout setae with recurved distal third. Right spine row with 3 short and robust stout setae, first one with 4 apical teeth, further proximally 3 longer stout setae as on left mandible. Molar process ( Fig. 3 View FIGURE 3. E b; Fig. 4 c) with oval chewing area, slightly larger on right mandible and with more low tubercles. Left chewing area with 5 sensory cavities. Posterior margin of chewing area more prominent than anterior, with 4 plumose setae on each mandible, on right mandible with 9 cusps, the ventralmost largest, on left mandible 6 cusps. Condyle prominent, slightly shorter than molar process.

Paragnath ( Fig. 3 e View FIGURE 3. E ): Dorsoventrally flattened, unsclerotized, length: width = 0.71, with narrower pair of inner, wider and more flattened pair of outer lobes with convex lateral margins. Inner lobes 0.25 times shorter in length, halfcylindrical with rounded apices, distal third dorsally with scattered rows of fine setae. Outer lobes ventrally overlapping inner lobes, distal half of dorsal surface with outer area of sparse, fine setation and larger inner area with setae arranged in 4 to 5 transversal rows. Dorsal side with subapical outer row of 4 long setae, single stronger one at the margin, and inner row of 7 to 8 longer setae. Further proximal ridge with 10 longer setae. Lateral margin with 2 short stout setae on left and 1 on right side.

Maxilla 1 (Fig. 4 d–f): Outer endite length: width = 3.4, 1.5 times as long and twice as wide as inner, medial margin with 16, lateral margin in proximal half with 7 setae. Apex bluntly oblique, with 13 strong stout setae, 3 thereof twosidedly serrated in distal half, 2 others with subapical tooth. 2 simple setae proximodorsal to apex. Inner endite with ventral longitudinal row of 6, medial margin with 4, proximodorsal with 1 long seta. Apex bluntly coneshaped, with 4 setae and 3 stout setae, proximalmost stronger and approximately twice as long as others.

Maxilla 2 ( Fig. 5 View FIGURE 5. E a–d): Outer part of outer endite length> inner endite> inner part of outer endite. Inner endite apically rounded, dorsally with 31 setae. Apex with 4 onesidedly serrated stout setae, proximalmost longest and curved laterally. 11 setae of varying diameter. Both parts of outer endite 0.02 mm wide, apices blunted with small distodorsal lobe. Inner part with 6 proximal setae, 2 subapically on medial margin. Apex with 2 long and 2 shorter onesidedly serrated stout setae. Outer part of endite with 12 lateral setae, subapically on lateral margin 2 and on medial margin 3 setae. Apex with 3 onesidedly serrated stout setae.

Maxilliped ( Fig. 5 e View FIGURE 5. E –g): 0.18 times body length, coxa length: basis length = 0.26. Basis with lateral seam of fine setae, proximally beginning after the first third, distally reaching as far as insertion of palp. Medial margin bent dorsally, distal third with rounded, laterally pointing lobe with 3 setae. Endite spatulate with 2 clubshaped retinacula, distodorsally with 3 pairs of elongated tubercles and a more proximal transversal edge. Apex truncate at an angle of approximately 120 to medial margin, 4 ventral and 1 dorsal fan setae. Lateral margin rounded, 5 to 6 evenly distributed setae. Dorsal surface with subtriangular area of 29 setae, subapically as wide as endite, proximally narrower, dorsomedially reaching on a level with retinacula. Palp article 1 shortest, 1.2 times as wide as proximal end of basis. Lateral seam of setae continued, distally ending in larger seta. Distolateral angle with 1, lateral half with 2 ventrodistal setae. Article 2 largest, 3 times as long as article 1, distally increasing in width, distal margin truncate, almost straight. Lateral setae continuing on proximal 2 thirds of its length, ending in longer seta. 1 distolateral and 1 ventrolateral seta. Medial margin with 4 pappose setae with bald proximal third, demarcated by annulus. Article 3 nearly trapezoidal, with large distolateral seta. Medial margin up to distally rounded tip with 8 pappose setae as on article 2, but only half as long. Further laterally a longer simple seta. Ventral surface with 4 short setae. Article 4 yshaped due to distomedial lobe, proximally tapering. 2 lateral and 5 distomedial setae. Article 5 cylindrical, seemingly shifted laterally due to distolateral lobe of article 4, setose apices of both parallel to each other. 7 distal and subdistal setae. Epipodite length: width = 1.7, length: basis length = 1.48, broadly yshaped due to lateral lobe. Ventral surface with parallel cuticular grooves. Subdistally 1, laterally 4 setae. Lateral lobe rounded, in situ covering insertion of mandible.

Pereopods 1–4 ( Fig. 6 View FIGURE 6. E ): Uniformly baculiform walking legs. Total length pereopod 1: pereopod 2 = 0.79. Pereopod 1 basis 0.30, ischium 0.09, merus 0.06, carpus 0.31, propodus 0.17, dactylus 0.07 of pereopod 1 length. Basis elongated, sparsely setose, 2 ventral broom setae. Ischium with 2 setae. Merus distally broadening, with 8 setae. Carpus longest, slender, sparsely setose. Propodus with 1 dorsal and 6 distal setae. Dactylus evenly tapering, scytheshaped, ventrally curved, apex blunt, medial surface with 1 seta, further distally 2 shorter setae. Pereopod 2 basis 0.25, ischium 0.11, merus 0.05, carpus 0.27, propodus 0.21, dactylus 0.11 of pereopod 2 length. Basis with 1 preserved ventral broom seta, in proximal third 4 bases of broken off broom setae. Ischium with 8, merus with 10 setae. Carpus longest, more densely setose than on pereopod 1. Propodus more densely setose than on pereopod 1, distally with 6 long setae and 1 broom seta. Dactylus 2 times longer than pereopod 1 dactylus, Medially with 1 seta, laterally with opposing seta. Ventroproximally on medial side row of fine, short setae, further proximally ventral margin with 6 small teeth. Inconspicuous row of small teeth also on dorsal margin proximally of 2 long setae. Pereopod 3 and 4 of holotype and all other examined individuals unknown distally of basis.

Pereopods 5–7 ( Fig. 7 View FIGURE 7. E ): Basis cylindrical, stouter and shorter than on ambulatory pereopods. Distally broadening especially on pereopod 7, less distinct on pereopod 6. Pereopod 5 with long broom seta and 7 dorsal shorter, simple setae. Pereopod 6 with 6 simple setae and 1 broom seta. Pereopod 7 with 1 broom seta. Ischium cylindrical, on pereopod 5 as long and on pereopod 6 and 7 two thirds as long as basis. Pereopod 5 with 8, pereopod 6 and 7 with 5 long plumose setae. Merus cylindrical, half as long as ischium, dorsally rounded and broadest in distal third. Each pereopod with 1 dorsal swimming seta. Merus of pereopod 5 basally about two thirds as wide as ischium, 1 distal and 5 ventral setae, on pereopod 6 nearly as wide as ischium, with 5 ventral setae, on pereopod 7 half as wide, with 1 distoventral, 2 distolateral setae (1 broken off). Distal end of pereopod 6 and 7 at insertion of carpus with membranous seam. Carpus lengths P5 = P6 = P7, length: width = 1.14, 1.57, 1.27, laterally strongly flattened, dorsally convexly enlarged to semicircular shape, widest in basal half. Ventral margin less enlarged and almost straight, with membranous seam along nearly whole length. Swimming setae inserting on outer side of dorsal and ventral margin, dorsal ones up to 0.29 mm, at least twice as long as ventral ones. On pereopod 5 23 dorsal and 11 ventral swimming setae, on pereopod 6 20 and 10, on pereopod 7 26 and 12. Each with 2 spinelike setae dorsal of insertion of propodus, on pereopod 5 1 broom seta. Propodus length: width = 2, P5 propodus length: carpus length = 0.91, pereopod 7 propodus length: carpus length = 0.76, inserting slightly shifted to outer side of carpus, about two thirds as long and half as wide as carpus, laterally flattened, dorsal margin slightly and ventral margin more strongly convexly enlarged, widest in middle. Pereopod 5 with 14 dorsal and 11 ventral swimming setae. Pereopod 6 propodus unknown. Pereopod 7 with 13 dorsal and 10 ventral swimming setae. Ventral swimming setae slightly longer than dorsal, absent in proximal third of ventral margin. Dorsal and ventral of insertion of dactylus with 1 seta, on pereopod 5 with 1 broom seta. Dactylus lancetshaped, laterally flattened, about half as long as propodus, insertion slightly displaced to outer side of propodus. Short apical seta, on pereopod 7 additional spinelike seta. Pereopod 5 distal third with short dorsal seta, pereopod 7 subdistal quarter of dorsal margin serrated.

Pleopods ( Fig. 8 View FIGURE 8. E b–f; Fig. 9 View FIGURE 9. E a–c): Pleopod 1 and 2 inserting on a level with coxae of pereopod 7. Pleopod 1 ( Fig. 8 View FIGURE 8. E b, c) of both sides dorsally fused to sympodite, except for distal quarter. Suture visible along whole length of ventral side. Pleopod 1 0.27 times body length, about 3.5 times longer than wide. Dorsal side of each half elevated cuticular ledge, hanging over in its distal third, with fine, short setae. Further distally on each half a pair of shorter ledges on a level with inner lobe, enclosing a deepened groove, the lateral one with medially overhanging edge. Ventral side of this area on left half with 4, on right with 2 short setae. Distomedial lobes less than half as wide as proximal end of sympodite, with subtriangular tip and shallow, distoventral ridge, distolateral margin with 11 (3 ventral, 4 laterodorsal, 2 distodorsal and 2 distoventral) setae. Distolateral lobes shorter than distomedial lobes, narrow, pointed, ending in conspicuous 0.02 mm long, cranially curved cusp. Pleopod 2 with almost semicircular protopodite, 0.92 times pleopod 1 length. Length: width = 2.28, distal margin acute, slender. Proximolaterally 1 long, distolaterally 7 hemiplumose setae. Exopod rounded, unsclerotized, inserting dorsally in distal quarter of protopodite. Proximal half on caudal side with fine, dense setation. Endopod inserting from distal third of protopodite, bent between basal article and caudally pointing stylet. Stylet 0.5 times as long as protopodite, acute, sperm duct opening after basal third of stylet. Pleopod 3 0.74 times pleopod 1 length, with large lobiform endopod, length: width = 3, distally with 3 long plumose setae. Exopod 2jointed, width = 0.3 times endopod width, slightly exceeding endopod length. First article nearly 3 times as long as second, the latter lancetshaped and flattened, with strong apical seta. Margins of both articles framed by seam of fine setae, the longest on lateral margin. Pleopod 4 length: pleopod 1 length = 0.67, with large lobiform endopod, length: width = 2.11, without setation, exopod 0.3 times endopod width, singlejointed, evenly tapering to apex, lateral and medial margin with seam of fine setae. Apex with long plumose seta. Pleopod 5 length: pleopod 1 length = 0.65, length: width = 1.76, delicate, lobiform. Lateral margin rounded, medial straight, surface bald.

Uropods ( Fig. 2 View FIGURE 2. E d): Biramous, inserting ventrolaterally in shallow cavities in posterior quarter of pleotelson. Protopodite laterally slightly flattened, length: width = 1.4. 3 distal setae, largest as long as protopodite, distomedial at insertion of endopod. Both rami cylindrical with rounded apex, inserting distally on protopodite. Endopod length 1.6 times protopodite length, about 2.5 times as long and twice as wide as exopod, with subapical broom seta. Apex with 7 broom setae, 3 shorter simple setae and 2 spinelike setae. Exopod apex with 2 short and 2 long setae.

Description of female paratype ( Fig. 9 View FIGURE 9. E d, e; Fig. 19 View FIGURE 19. E h)

Length 2.25 mm, body as in male, rostrum with single anteromedial spinelike seta. Pleotelson as in male, dorsal tubercles present, central seta broken off. Sexual dimorphism only in antenna 1 and pleopods. Coxae of pereopods with fully developed oostegites. Antenna 1: Flagellum 5jointed, 1 aesthetasc on article 4 of flagellum. Pleopods: Operculum length: body length = 0.32, length: width = 1.51, boatshaped with sharp anteromedial keel, outline of operculum an angulate ellipsoid due to apex shifted further cranially, overlapping posterior margin of sternite 7. Posterior half decreasing in height, medial keel diminishing. Proximolaterally 1 hemiplumose seta. Caudal margin notched on a level with insertion of uropods, the latter uncovered. Cuticular grooves limited to area around these bulges and around medial keel.

Distribution

Southeastern Atlantic: Angola Basin at a depth of 5125–5410 m (22 20.0’ S, 3 18.3’ E to 22 20.2’ S, 3 18.4’ E, 5125–5144 m, station 318; 22 19.9’ S, 3 17.8’ E to 22 20.0’ S, 3 17.9’ E, 5126–5127 m, station 320; 18 19.4’ S, 4 39.7’ E to 18 20.8’ S, 4 38.6’ E, 5397–5398 m, station 338; 18 18.3’ S, 4 41.3’ E to 18 19.4’ S, 4 41,9’ E, 5395 m, station 340; 17 06.2’ S, 4 41.7’ E to 17 07.5’ S, 4 42.3’ E, 5415 m, station 344; 16 18.1’ S, 5 27.2’ E to 16 19.3’ S, 5 27.2’ E, 5387–5390 m, station 348; 16 14.3’ S, 5 26.8’ E to 16 14.9’ S, 5 26.7’ E, 5389 m, station 350 of expedition M48:1 RV “ Meteor ”).