Eurycope crassiramis, Golovan, Olga A., 2008

Golovan, Olga A., 2008, Eurycope crassiramis sp. nov., a new species of Munnopsidae (Crustacea, Isopoda, Asellota) from the Weddell Sea, Southern Ocean *, Zootaxa 1866, pp. 540-554 : 541-552

publication ID	https://doi.org/ 10.5281/zenodo.183696
DOI	https://doi.org/10.5281/zenodo.6235174
persistent identifier	https://treatment.plazi.org/id/FD7587C4-FFF8-FFDC-42C3-FA0DFE02F864
treatment provided by	Plazi
scientific name	Eurycope crassiramis
status	sp. nov.

Treatment

Eurycope crassiramis View in CoL sp. nov.

( Figs 1–8 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 )

Material examined

Holotype: premature male (3.6 mm), ANDEEP III, Stn. 133 2, 16 March 2005, 62 46.73’– 62 46.33’S, 53 02.57’– 53 04.14’W, 1582 m ( ZMH K 41787).

Paratypes: 2 males (4.5 mm; 4.0 mm, preparatory); 3 females (3.3–3.6 mm); preparatory female with oostegites in early stages (3.6 mm); 35 juveniles (1.6–2.3 mm), same location as holotype ( ZMH K 41788).

Diagnosis

Cephalon and ambulosome length each about 0.1 body length, natasome 0.7–0.8 body length. Rostrum length 0.8–1.0 medial cephalic length, narrowing distally, anteriorly indented, overhang 0.1 length. Article 1 of antenna 1 with distomedial projection extending from 0.1–0.2 (female, immature male) to 0.5 (mature male) length beyond anterior tip of rostrum. Incisor of left mandible with 3 cusps, lacinia mobilis with 6 denticles, spine row with 6–7 setae. Male pleopod 1 distally angled downward at 45, with broad medial notch, distomedial lobes 0.8 length and 0.5 width of distolateral lobes, fringed with simple setae. Male pleopod 2 protopod with 11 lateral hemiplumose setae, distomedial edge slightly truncated; stylet length 0.7 protopod length. Operculum suboval, length 0.6 width, apex pointed, with seta, posterior margin flattened. Uropodal protopod not broadened medially, rami very broad: exopod length/width ratio 3.2–3.4, endopod length/width ratio 1.8–2.1.

Description (premature male, holotype)

Body wide, deep and vaulted, broadened at pereonites 5–6 ( Fig. 1 View FIGURE 1 A, B); length 2.2 width at pereonite 5; greatest height at pereonites 5–6 0.3 length. Cephalon ( Fig. 1 View FIGURE 1 C) width 2.6 length, length 0.1 body length, with concave posterior margin. Rostrum broad, narrowing distally, slightly overhanging frons, anteriorly indented, length 1.0 medial cephalic length, width at the most posterior extent of the rostral notch 0.1 cephalic width, width at the base of antennae 1 0.3 cephalic width, overhang 0.1 length. Cephalic keels small, each with 5 short stout setae. Frons subvertical. Postrostral lateral length 0.1 width; lateral spine blunt, triangular, 0.9 frons height, with 4 short setae. Pereon. Ambulosome short, less than 0.1 body length, natasome 0.8 body length. Pereonite 1 length 0.1 width, equal to postrostral cephalic length; pereonites 2–7 to pereonite 1 length ratios: 1.2, 1.0, 0.8, 6.0, 5.0, 8.4, length/width ratios: 0.1, 0.1, 0.1, 0.4, 0.3, 0.6. Lateral margins of pereonites 1–6 convex, of pereonite 7 slightly concave; anterior margins convex; pereonites 5–7 medioventral area convex, in pereonites 5 and 7 enlarged into angular projections, bearing plumose setae in pereonite 7, in pereonite 6 posteriorly depressed; ventrolateral area with cuticular ridges, pereonite 7 anteriorly of coxa with bulla, bearing single large seta. Coxae 1–4 subequal in length, length (including anterolateral processes) 3.0, 2.7, 3.2, 4.0 pereonites 1–4 length respectively, anterolateral process of coxa 1 extending beyond lateral antennal groove. Pleotelson length 0.3 body length, width 1.4 length, 1.0 pereonite 7 width; distal tip rounded, angled downward; posterior rim 0.2 pleotelson length.

Antenna 1 ( Fig. 1 View FIGURE 1 A, C) article 1 length equal to width, distomedial projection extending 0.2 of length beyond anterior tip of rostrum.

Mature male, paratype

Body ( Fig. 1 View FIGURE 1 E, F) length 2.1 width. Cephalon ( Fig. 1 View FIGURE 1 D) width 2.9 length, length 0.1 body length. Rostrum strongly narrowing distally, anterior notch deeper than in holotype, length 0.8 medial cephalic length, width at the most posterior extent of the rostral notch 0.08 cephalic width, width at the base of antennae 1 0.2 cephalic width, overhang 0.1 length. Frons subvertical, height 0.3 mouthfield depth. Labrum/clypeus length ratio 1.3. Postrostral lateral length 0.06 width.

Antenna 1 ( Fig 3 View FIGURE 3 A) article 1 length 1.2 width, distomedial projection extending 0.5 of length beyond anterior tip of rostrum, with 4 distal unequally bifid setae; article 2 length 1.5 width and 0.4 article 1 length, with 7 unequally bifid setae and some fine simple setae distally; article 3 length 2.3 width, subequal to article 2 length; flagellum 0.7 total length, with 41 articles, some articles with simple setae.

Antenna 2 ( Fig. 3 View FIGURE 3 B, C) articles 1–4 length/width ratios: 0.5, 1.4, 1.1, 0.8, articles 2–4 to article 1 length ratios: 1.4, 2.1, 1.6; article 2 with 2 lateral unequally bifid setae, article 3 with row of 13 unequally bifid setae; squama length 0.4 article 3 length, with 4 distal unequally bifid setae.

Mandibles ( Fig. 3 View FIGURE 3 D–F) incisor with 3 cusps, ventral cusp separated from 2 dorsal cusps by straight part of distal margin (bearing 1 small additional cusp on right mandible); lacinia mobilis of left mandible stout, 0.9 length of incisor, with 6 denticles, ventral denticle largest; spine row with 7 and 9 spines on left and right mandibles respectively; posterior margin of molar triturative surface with 6 and 5 setae on left and right mandibles respectively, dorsal margin extended. Palp article 2 0.5 mandibular body length, with sparse fine hairs and 3– 5 distolateral setae; article 1 0.4 article 2 length; article 3 curved, about 0.6 article 2 length, with about 9–12 cleaning setae.

Maxilla 1 ( Fig. 3 View FIGURE 3 G) lateral lobe length 3.1 width, width 2.1 mesial lobe width, medial margin with fine simple setae, distal margin with 9 robust serrated setae and 4 fine simple setae on distomedial angle. Mesial lobe length 3.8 width, medial margin with fine simple setae, distal margin with 8 fine simple setae and 1 long setulated seta on distomedial angle.

Maxilla 2 ( Fig. 3 View FIGURE 3 H) lateral lobe longest, length 5.0 width, with 2 long setulated setae and 4 fine simple setae. Middle lobe shortest, length 9.3 width, width 1.0 lateral lobe width, with 2 long setulated setae and some fine simple setae. Mesial lobe length about 5.0 width, width 2.0 lateral lobe width, distal margin with numerous fine simple setae.

Maxilliped ( Fig. 3 View FIGURE 3 I) basis length 2.3 width, endite length 1.8 width, extending beyond palp article 2 distal margin, with 4 retinaculae, distal margin with 6 fan setae and some simple slender setae, lateral and medial margins with dense fine simple setae. Palp articles 1 and 2 with distolateral angles produced into triangular lobes, article 1 lateral margin 2.6 medial margin length, width 0.7 basis width; article 2 lateral margin length 1.2 medial margin length and 1.7 article 1 lateral margin length, medial margin with 5 simple setae; article 3 medial margin convex, rounded, serrated, 3.2 lateral margin length and 0.7 article 2 lateral margin length, with 15 short simple setae, distal margin with few fine simple setae; article 4 lateral margin length 0.6 article 3 medial margin length, medial lobe length 0.8 lateral margin length, with 10 simple distal setae, article 5 length 1.2 article 4 length, with 5 simple setae; articles 1–5 length/width ratios: 0.7, 0.9, 0.7, 0.7, 2.9. Epipod trapezoid, length 1.6 width and 0.9 basis length, distomedial angle rounded, lateral projection broad, distal margin with 5 short setae, inserted in cuticular membrane.

Pereopod 1 ( Fig. 5 View FIGURE 5 A) basis to dactylus length/width ratios: 4.9, 3.7, 2.0, 7.5, 5.4, 4.0, ischium to dactylus versus basis length ratios: 0.4, 0.2, 0.9, 0.5, 0.1; basis with sparse small dorsal setae, 1 distoventral unequally bifid seta and some fine distal setae; ischium, merus and carpus with numerous long simple setae on ventral margin and 2 simple setae on dorsal angle, carpus with sparse, small dorsal setae; propodus with 1 long simple seta on ventral margin and numerous long simple setae distally; claws rounded apically, ventral claw slightly longer than dorsal, 1 seta inserting between claws.

Pereopod 2 ( Fig. 5 View FIGURE 5 B) basis to dactylus length/width ratios: 4.3, 4.0, 1.8, 8.0, 9.8, 10.0, ischium to dactylus versus basis length ratios: 0.7, 0.3, 1.3, 1.2, 0.7; ischium, merus, carpus and propodus ventral margin with sparse short simple setae, merus with 5 longer distoventral setae and 1 distodorsal unequally bifid seta; carpus with few short dorsal simple setae, 1 longer distodorsal simple seta and 1 distodorsal unequally bifid seta; propodus with 1 distodorsal and 1 distoventral unequally bifid seta; claws subequal in length, dorsal claw width about 2.0 ventral claw width, 1 seta inserting between claws.

Pereopod 3 ( Fig. 5 View FIGURE 5 C) dactylus missing; basis to propodus length/width ratios: 4.0, 4.6, 2.6, 10.4, 13.6, ischium to propodus versus basis length ratios: 0.7, 0.4, 1.4, 1.3; basis with sparse small simple setae; ischium with 9 ventral simple setae, 1 dorsal simple seta and 1 short distodorsal unequally bifid seta; merus with 1 ventral simple seta, 4 distoventral simple setae and 2 distodorsal unequally bifid setae; carpus with short simple setae on dorsal margin, 3 longer distodorsal setae and 2 distoventral unequally bifid setae; propodus ventral margin with short simple setae.

Pereopod 4 ( Fig. 5 View FIGURE 5 D) basis to dactylus length/width ratios: 4.8, 5.8, 2.6, 9.3, 15.3, 15.0, ischium to dactylus versus basis length ratios: 0.8, 0.4, 1.4, 1.4, 0.6; basis with 3 short distoventral unequally bifid setae; ischium ventral margin with sparse small simple setae; merus with 2 distodorsal unequally bifid setae; carpus with sparse small simple setae, 3 longer distodorsal simple setae, 2 distal unequally bifid setae and 1 distal broom seta; propodus with 1 simple distodorsal seta and 3 unequally bifid setae in distal third of ventral margin; claws subequal in length, slightly wider dorsally than ventrally, 1 seta inserting between claws.

Pereopod 5 ( Fig. 6 View FIGURE 6 A) propodus and dactylus missing; basis to carpus length/width ratios: 1.4, 2.4, 1.8, 1.3, ischium to carpus versus basis length ratios: 1.4, 0.8, 1.9; basis, ischium and merus with scales; basis ventrally with 2 simple setae and 1 unequally bifid seta; ischium dorsal margin with row of 11 plumose setae; merus with 1 dorsal plumose seta; carpus with 31 dorsal and 20 ventral submarginal plumose setae.

Pereopod 6 ( Fig. 6 View FIGURE 6 B) propodus and dactylus missing; basis to carpus length/width ratios: 1.5, 2.0, 1.8, 1.4, ischium to carpus versus basis length ratios: 1.2, 0.7, 1.8; basis, ischium and merus with scales; basis with 2 proximodorsal plumose setae, 3 long unequally bifid distoventral setae and 1 simple distoventral seta; ischium dorsal margin with row of 11 plumose setae, ventral margin with fine hairs and 3 distal unequally bifid setae; merus with fine hairs; carpus with 26 dorsal and 18 ventral submarginal plumose setae.

Pereopod 7 ( Fig. 6 View FIGURE 6 C) basis to dactylus length/width ratios: 1.4, 1.4, 1.6, 1.1, 2.3, 5.0, ischium to dactylus versus basis length ratios: 1.0; 0.7, 1.7, 1.6, 0.6; basis with 2 proximodorsal plumose setae and 3 unequally bifid distoventral setae; ischium dorsal margin with row of 5 plumose setae, ventral margin with 4 distal unequally bifid setae; merus with 1 dorsal unequally bifid seta; carpus with 32 dorsal and 18 ventral submarginal plumose setae and 2 short stout dorsal unequally bifid setae; propodus dorsal margin serrated, with 33 submarginal plumose setae, ventral margin vith 14 submarginal plumose setae and 1 distal broom seta; claw 0.2 dactylus length, acute, 1 seta inserting at base of claw.

Pleopod 1 ( Fig. 8 View FIGURE 8 A, B) sympod widest distally, length 2.5 greatest width, 0.2 length from distal tip angled downward at 45, with broad medial notch; ventral surface with 2 rows of 9 plumose setae each in middle third and 2 rows of 14 short simple setae each in distal third; distal lobes forming posteroventrally directed tube: distolateral lobes directed posteriorly, parallel to sympod axis, length 1.2 width; distomedial lobes directed posteroventrally, almost perpendicular to sympod axis, length 0.8 length of distolateral lobes, width 0.9 width of distolateral lobes, with about 10 simple setae on distal margin.

Pleopod 2 ( Fig. 8 View FIGURE 8 C) protopod length 1.2 width, with 11 lateral submarginal hemiplumose setae, distomedial edge sligthly truncated; endopod basal article length 2.7 width and 0.3 protopod length, stylet length 5.2 width and 0.7 protopod length; exopod posterolateral angle with tuft of long fine setae.

Pleopod 3 ( Fig. 8 View FIGURE 8 D) endopod cupped, lateral margin convex, length subequal width, with 3 distomedial plumose setae; exopod basal article length 1.7 width and 0.8 endopod length, distal article length 4.8 width and 0.7 basal article length.

Pleopod 4 ( Fig. 8 View FIGURE 8 E) endopod highly cupped, lateral margin convex, medial margin indented near distal tip, length 1.1 width; exopod basal article length 1.4 width and 0.7 endopod length, distal article length 3.6 width and 0.5 basal article length.

Pleopod 5 ( Fig. 8 View FIGURE 8 F) endopod highly cupped, margins convex, medial margin strongly indented near distal tip, length 0.8 width.

Uropod ( Fig. 8 View FIGURE 8 G) protopod length 0.8 width, distomedial angle slightly produced, truncated, distal margin with 18 unequally bifid setae, increasing in length and density toward distomedial angle; exopod length 3.4 width and 1.1 length of protopod, with 7 distal unequally bifid setae; endopod length equal exopod length, width 1.6 exopod width, with 2 broom setae and 13 unequally bifid distal setae.

Female, paratype

Body ( Fig. 2 View FIGURE 2 A, B) wider and higher than that of male, length 1.9 greatest width; greatest height 0.4 length. Cephalon ( Fig. 2 View FIGURE 2 C) length/width ratios the same as those of premature male (holotype). Pereon. Ambulosome slightly longer than that of male, length 0.14 body length, natasome 0.7 body length. Pereonites 2–7 to pereonite 1 length ratios: 1.6, 1.0, 1.2, 4.5, 4.3, 8.2. Coxae 1–4 length (including anterolateral processes) 2.7, 1.9, 3.0, 2.3 pereonites 1–4 length respectively, anterolateral process of coxa 1 almost reaching lateral antennal groove.

Antenna 1 ( Fig. 4 View FIGURE 4 A) articles 1–2 similar to those of premature male, article 1 distomedial projection extending 0.1 of length beyond anterior tip of rostrum; remaining articles missing.

Antenna 2 ( Fig. 4 View FIGURE 4 B) articles 1–4 length/width ratios: 0.6, 1.1, 1.4, 0.8, articles 2–4 to article 1 length ratios: 2.2, 3.3, 1.3.

Mandibles ( Fig. 4 View FIGURE 4 C, D) incisor similar to that of male, but between ventral and 2 dorsal cusps on right mandible 2 small additional cusps; spine row with 6 and 8 spines on left and right mandibles respectively; posterior margin of molar triturative surface with 3 setae. Palp article 2 length 0.7 mandibular body length, distally with fine setae; article 3 length about 0.4 article 2 length, with about 14 cleaning setae.

Remaining mouthparts ( Fig. 4 View FIGURE 4 E–G) similar to those of male.

Pereopods 1–4 ( Fig. 7 View FIGURE 7 A–D) generally more slender than those of male, with relatively longer basis and shorter ischium and dactylus (except pereopod 1, possessing relatively longer dactylus than that of male).

Basis to dactylus length/width ratios as follows: pereopod 1: 5.6, 2.9, 2.5, 9.0, 6.9, 5.3; pereopod 2: 5.4, 3.4, 2.0, 10.3, 10.0, 9.0; pereopod 3: 5.5, 3.7, 2.5, 9.0, 11.1, 7.5; pereopod 4: 6.3, 3.7, 2.6, 10.1, 16.3, 10.5. Ischium to dactylus versus basis length ratios as follows: pereopod 1: 0.4, 0.3, 0.9, 0.6, 0.2; pereopods 2 and 3: 0.5, 0.3, 1.1, 1.0, 0.4; pereopod 4: 0.4, 0.3, 1.0, 1.1, 0.4. Basis ventral margin with small unequally bifid setae that are numerous on pereopods 1–3 and sparse on pereopod 4; pereopod 1 ischium, merus and carpus with sparse simple setae.

Pereopods 5–7 ( Fig. 2 View FIGURE 2 B, 7E–G) basis slender and longer relative to that of male. Pereopod 5 basis and dactylus missing; ischium to propodus length/width ratios: 2.5, 1.6, 1.4, 2.2. Pereopod 6 propodus and dactylus missing; basis to carpus length/width ratios: 1.7, 1.7, 1.7, 1.5, ischium to carpus versus basis length ratios: 1.0, 0.6, 1.6. Pereopod 7 dactylus missing; basis to propodus length/width ratios: 2.0, 1.5, 1.6, 1.3, 2.1, ischium to propodus versus basis length ratios: 0.7; 0.4, 1.3, 1.3. Pereopod 7 basis without plumose setae; pereopods 5–7 ischium and carpus with less submarginal plumose setae than those of male (except pereopod 7 ischium): ischium dorsal margin bearing from 6–7 (on pereopods 5 and 7) to 9 (on pereopod 6) plumose setae; carpus bearing from 23–24 (on pereopods 5 and 6) to 31 (on pereopod 7) submarginal plumose setae near dorsal margin and 17–18 submarginal plumose setae near ventral margin. Propodus with 1 distodorsal long stout unequally bifid seta, dorsal margin with 28 submarginal plumose setae, ventral margin with 14 submarginal plumose setae.

Operculum ( Fig. 9 View FIGURE 9 A–C) in ventral view suboval, length 0.6 width, height 0.5 length; ventral surface with rounded keel, length 0.9 total length, apex pointed, at 0.1 of total length from distal tip, with seta (broken off in illustrated specimen); posterior margin flattened in lateral view, subvertical; lateral fields slightly curving ventrally, without marginal setae.

Pleopods 3–5 ( Fig. 9 View FIGURE 9 D–F) similar to those of male.

Uropod ( Fig. 9 View FIGURE 9 G) similar to that of male, but distomedial angle of protopod almost not produced, rounded, distal margin with about 14 unequally bifid setae; exopod with 5 distal unequally bifid setae; endopod with about 9 distal unequally bifid setae.

Etymology: Derived from the Latin crassus meaning thick and rami meaning branches, referring to the unusually broad uropodal rami.

Distribution: Known from the type locality only.

Remarks

The new species displays significant intraspecific variability of the rostral morphology and length of the first article of antenna 1 distomedial projection depending on sex and developmental stage. Juveniles possess a relatively broad and short rostrum and distomedial projection of the first article of antenna 1 ( Fig. 2 View FIGURE 2 D–I). They become elongated and narrower in the subsequent stages with the extreme state in mature males. Cephalic morphology of premature males resembles that of females.

E. crassiramis View in CoL sp. nov. mostly resembles E. gaussi Wolff, 1956 View in CoL . The latter species is known by holotype only from the Indian sector of the Southern Ocean (66 02’S, 89 38’E) where it was taken at shallower depth (385 m) ( Wolff 1956). Both species are rather similar in size, shape and length/width ratios of body and cephalon, including rostral characters. Uropods, the shape of male pleopod 2 and many antennal and mouthpart characters are nearly identical in these two species. E. crassiramis View in CoL can be distinguished from E. gaussi View in CoL in the following characters: the lacinia mobilis of the left mandible has 6 denticles, the spine row is composed of 6– 7 setae; the distolateral margin of the male pleopod 1 is broadly rounded and has no projecting corners.

E. crassiramis View in CoL can be easily distinguished from the remaining species of Eurycope View in CoL by the following: the short cephalon and ambulosome, each about 0.1 of the body length, the rostrum equal or subequal to medial cephalic length, the uropod with very broad rami and protopod not broadened medially, and the peculiar form of the male pleopod 1.