Acanthocope eleganta, Malyutina, Marina & Brandt, Angelika, 2004

Malyutina, Marina & Brandt, Angelika, 2004, Acanthocopinae (Crustacea: Isopoda: Munnopsididae) from the Southern Ocean deep sea with the description of Acanthocope eleganta sp. nov., Zootaxa 550, pp. 1-20 : 4-11

Acanthocope eleganta sp. nov. ( Figs 2–5 )

Material examined: holotype, Ψ manca, stage 3 (5.9 mm), ANDEEP stn. 131–9, 65°18.55’S, 51°31.95’W, 2893–2894 m, northwest Weddell Sea, 6 March 2002, RV Polarstern ( ZMH K–40716).

Paratypes: 2 Ψ manca, stage 1 (2.9 and 2.7 mm), ANDEEP stn. 114—S, 61°43.54– 51’S, 60°44.21–43’W, 4482 m, northwest off Elephant Island, 17 February 2002, RV Polarstern ( ZMH K–40717); Ψ manca, stage 1 (2.5 mm), anterior part of manca, ANDEEP stn. 42–S, 59°40.30–32'S, 57°35.42–64’W, 3689 m, 27 January 2002, RV Polarstern ( ZMH K–40718).

Diagnosis: Coxal spine of pereopods 2–4 with broad base, slender, about as long as half width of pereonite; natasome about 4 times as long as anterior part of body; at least pereonites 5 and 6 with a pair of short anterodorsal spines and a long ventromedial spine each, anterolateral spines of pereonites 5 and 6 as long as and about twice as wide as coxal spines of pereopods 2–4 and twice as long as pereonites laterally; posterolateral spines of pleotelson slightly longer than anterolateral ones, curved, directed posteriorly, lateral margin in between lateral spines angular; terminal spine at least 0.6 times as long as pleotelson; preanal ventral process with short distolateral projections; uropod about half as long as terminal spine of pleotelson.

Description of the holotype: Body ( Fig. 2 ) 2.6 times as long as wide (greatest width of pereonite 5 with lateral spines), dorsal surface granulated, all lateral margins of body and spines with elongate transparent scale spinules, all body spines, especially terminal one with long setae; head 0.5 times as long as wide, with dorsal spinules and tubercles, lateral margins in dorsal view slightly convex, with spinule row; frontal margin sloping, smooth; interantennular distance 0.4 times as wide as head and twice as wide as antenna 1 basally, with serrated lateral margins.

Pereonite 1 0.9 times as wide as head; pereonites 1–4 slightly broadening and elongating from 1 to 4, pereonites 1 and 2 subequal in length, pereonite 4 longest; pereonites 1–4 anteriorly with a dorsomedial straight spine, directed upwards, spine on pereonite 1 slightly shorter, spines of pereonites 2–4 slightly longer than respective pereonite; lateral margins of pereonites 1–4 rounded, anterior margin with spinules; coxal spine of pereopods 2–4 subequal in length and in shape, as long as half of pereonite width, directed somewhat anteriorly.

Natasome 3.8 times as long as anterior body part; pereonites 5–7 decreasing in width and length from 5 to 7; anterolateral spines of pereonites 5 directed slightly anteriorly, those of pereonite 6 perpendicular to body axis, and of pereonite 7 posteriorly, spines of pereonites 5 and 6 twice as long as pereonite laterally and twice as wide as coxae of pereopods 2–4, spines of pereonite 7 not fully developed; pereonites 5 and 6 with a pair of short dorsal spines anteriorly, pereonite 7 only with a medial row of small spinules; ventral spines of pereonites 5 and 6 as long as lateral spines; pleotelson 1.8 times as long as wide, two pairs of lateral spines subequal in size, anterolateral pair directed slightly posteriorly, posterolateral pair curved more posteriorly, lateral margin in between angular; terminal spine from dorsal pore to tip 0.6 times as long as total pleotelson; dorsal surface with a slender anteromedial spine and weak narrow keel, bearing a row of spinules; preanal ventral process turned posteriorly, with projected posterolateral angles and rounded margin in between; 2 ventrally directed spines anterior to uropods insertion, visible in dorsal view, about half as long as uropod protopod.

Antenna 1 ( Fig. 2 ) 0.3 times as long as body, of 7 articles; article 1 2.3 times as long as wide, with many lateral spinules and dorsal acute tubercles, distal lobe tapering; article 2 slightly longer than distal lobe of article 1, widening distally, with distomedial broom seta; articles 3–7 0.7, 0.4, 1.6, 0.6 and 0.2 times as long as article 2, flagellar articles 6 and 7 with 1 aesthetasc each.

Antenna 2 ( Fig. 2 ) broken off after article 5; article 2 widest, with short distolateral and longer distomedial spines; article 3 slightly smaller than article 2, with 2 distal spines: lateral spine slender, almost as long as article and medial spine twice as long and wide as lateral one; article 4 0.7 times as long and wide as article 3; article 5 more than twice as long as articles 1–4 together, with 3 rows of marginal spinules.

Mandible ( Fig. 3 ) body with small spinules superiorly; both incisors with 4 cusps, lacinia mobilis of left mandible shorter than incisor, with 1 large proximal and 6 narrow distal teeth, spine row with 5 and 6 spines on left and right mandibles respectively, molar process distally with 3 small denticles; palp in holotype possibly broken off (of one article), in juvenile female palp of 3 articles, subequal in size, article 3 with 1 long and 1 short distal setae.

Hypopharynx ( Fig. 3 ) outer lobe 1.4 as long as wide, inner lobe 0.6 as long as outer, both with dense distal fine setae.

Maxilla 1 ( Fig. 3 ) mesial endite 0.6 times as wide as lateral endite, with 11 robust setae (2 of them serrated), and 1 simple short seta.

Maxilla 2 ( Fig. 3 ) mesial and middle endites subequal in length, lateral endite slightly longer; mesial endite with dense row distal setae, including 4 comb­like setae and 1 long setulated seta distomedially, middle and lateral endites with 4 distal long smooth setae.

Maxilliped ( Fig. 3 ) endite with 3 coupling hooks, distal margin concave, with 3 fansetae, 3 stout simple setae and numerous slender simple setae; palp article 2 almost as long as wide, slightly narrower than basis, laterally 1.8 times as long as medially, lateral margin expanded and rounded; article 3 0.7 times as wide as article 2, 1.1 times as long as article 2 medially and 0.2 laterally, with 7 rather long setulated setae on straight medial margin; article 4 twice as long as article 3 laterally, medial lobe as long and twice as wide as article 5, the lobe and article 5 with 4 simple distal setae each; lateral margin of basis, articles 1 and 2 with dense row of fine setae; epipod 3.7 times as long as wide, slightly shorter than basis, tip rounded distally, lateral margin projected medially.

Pereopods ( Figs 4 and 5 ) increasing in size from 1 to 4, pereopod 5 subequal in length to 3, pereopod 6 longest, 1.5 times as long as pereopod 1, pereopod 7 undeveloped; all pereopod bases subequal in length, basis of pereopod 5 shortest and broadest, all bases with marginal spinules, few broom setae on dorsal margin and small sparse marginal setae.

Pereopod 1 ( Fig. 4 ) ratios of lengths of ischium–dactylus to basis: 0.3, 0.2, 1.0, 0.6, 0.3, carpus and propodus with few small marginal simple setae, propodus with tuft of setulated distal setae.

Pereopod 2 ( Fig. 4 ) ratios of lengths of ischium–dactylus to basis: 0.3, 0.2, 0.9, 0.5, 0.6; carpus with 4 ventral robust setae on distal half and 1 on proximal half; propodus with 5 ventral robust setae, both articles with distodorsal tuft of a few whip setae and 1 broom seta.

Pereopod 3 ( Fig. 4 ) ratios of lengths of ischium–dactylus to basis: 0.3, 0.2, 1.1, 0.7, 0.6, carpus with 5 robust ventral setae on distal half, 2 robust setae on distal third and 3 whip setae proximally, propodus with 7 ventral robust setae and 7 simple dorsal setae, both the articles with distodorsal tuft of a few whip setae and one broom seta.

Pereopod 4 ( Fig. 4 ) ratios of lengths of ischium–dactylus to basis: 0.3, 0.2, 1.1, 0.9, 0.6, carpus with 7 ventral robust setae, propodus with 8 ventral robust setae, a few simple and 2 mediodorsal broom setae, 1 whip and 1 broom distodorsal seta.

Pereopods 5 and 6 similar, carpi with dorsal plumose setae almost twice as long as ventral, propodi as wide as bases, plumose setae on both margins of the same length, dorsal margin also with a few whip setae, dactyli with 2 long distodorsal setae and 2 short setae (one robust and one slender) on distoventral tip.

Pereopod 5 ( Fig. 5 ) ratios of lengths of ischium–dactylus to basis: 0.6, 0.3, 1.5, 1.1, 0.5, carpus 6 times as long as wide, 1.6 times as wide as basis, propodus 7 times as long as wide.

Pereopod 6 ( Fig. 5 ) ratios of lengths of ischium–dactylus to basis: 0.5, 0.2, 0.2, 1, 0.5, carpi 7.2 times as long as wide and 1.5 times as wide as basis, propodus 9 times as long as wide.

Pereopod 7 ( Fig. 4 ) not fully developed.

Pleopod 2 ( Fig. 2 b, c) 1.2 times as long as wide, margins with plumose setae, medial keel low, narrow, with spine on proximal third as long as ventral spines on pereonites 5 and 6, spine and keel with many small spinules.

Pleopod 3 ( Fig. 5 ) endopod 2.2 times as long as wide, with 3 distomedial plumose setae, exopod 0.3 times as wide and 1.3 times as long as endopod, with row of thin simple lateral setae, both articles subequal in width, apical article 0.5 times as long as basal one, with 6 distal plumose setae.

Pleopod 4 ( Fig. 5 ) endopod twice as long as wide, with acute distomedial tip, exopod a half as long and 0.2 times as wide as endopod, without seta.

Pleopod 5 ( Fig. 5 ) 1.8 times as long as wide.

Uropod ( Fig. 2 ) 0.3 times as long as pleotelson, about a half as long as terminal spine of pleotelson; protopod 11 times as long as wide, slightly broadening distally, with 1 lateral and a few distal setae; endopod 1.3 times as long and 0.7 as wide as protopod, with 1 lateral, 3 unequal bifid setae and 2 small setae distally; exopod tiny, with 3 distal setae.

Male: Not known.

Etymology: From the Latin elegans, alluding to the fine, perfect body shape; feminine.

Remarks: A. eleganta sp. nov. is similar to A. acutispina Beddard, 1885 from the abyssal of the southern Pacific near South America. The species share the slender coxal spines of pereopods 2–4, similar pleotelson shape with the posterolateral spines slightly curled posteriorly, and similar narrow last 3 pairs of pereopods. A. eleganta differs from A. acutispina in having the lateral margin of the pleotelson between the lateral spines angular, not straight as in A. acutispina , pereopod 1 not much shorter than pereopods 2–7 recorded for A. acutispina (which has pereopod 1 much shorter than pereopods 2–7), uropods almost half as long as the terminal spine of pleotelson ( A. acutispina has long uropods almost as long as the terminal spine). A. eleganta resembles also A. carinata Chardy, 1972 from the deep sea of the North Atlantic in the shape of the natasome, a pleotelson with a low, narrow dorsal keel, and the same relative size of uropods. A. eleganta differs from the latter in a more slender body, especially the natasome.

A. eleganta has ventral spines on pereonites 5 and 6. This character was noted before only for A. mendeleevi Malyutina, 1998 , but as these spines are fragile, they might have easily been broken off in other species.

Distribution: Antarctic, Southern Ocean, around the north part of Antarctic Peninsula, off Elephant Island and the northwestern Weddell Sea.

Figures

FIGURE 2. Acanthocope eleganta sp. nov. Ψ holotype, a, dorsal view; b, lateral view; c, pleotelson, ventral view; d, enlarged lateral spine of pereonite 5; antenna 1 and uropod.

FIGURE 3. Acanthocope eleganta sp. nov. Ψ holotype, mouth parts. Ψ paratype, mandibular palp.

FIGURE 4. Acanthocope eleganta sp. nov. Ψ holotype, pereopods 1 – 4 and 7.

FIGURE 5. Acanthocope eleganta sp. nov. Ψ holotype, pereopods 5 and 6, pleopods 3 – 5.