Dubinectes acutitelson ( Menzies, 1962 )

Malyutina, Marina & Brandt, Angelika, 2006, A revaluation of the Eurycopinae (Crustacea, Isopoda, Munnopsidae) with a description of Dubinectes gen. nov. from the southern Atlantic deep sea, Zootaxa 1272 (1), pp. 1-44 : 16-19

Dubinectes acutitelson ( Menzies, 1962)

( Figs 5 and 6 )

Eurycope acutitelson Menzies, 1962: 143 , Figure 36 A – E.

Material examined

Holotype ( AMNH 12096 ), male (3.4 mm), allotype ( AMNH 12097 ), female (3.2 mm), paratypes ( AMNH 12098 ): 7 specimens (2.1 – 3.0 mm): Biotrawl No 52, Vema –14 – 28, 28 March 1958, south­western flank of the Schmidt­Ott Rise southwest of Cape Town, 41°03.5’S, 07°49’E, 4960 m.

Additional material from ANDEEP III.—Male natasome (2.5 mm) ( ZMH 41146), Stn. 16 – 10, 26 January 2005, 41°07.55’S, 09°55.94’W, 4720 m; 2 juveniles (2.4 and 1.9 mm), ( ZMH 41147) , Stn. 59­5, 14 February 2005, 67°30.75’S, 00°00.23’W, 4651 m; 1 damaged specimen (~ 4 mm) ( ZMH 41148), Stn. 88 – 8, 27 February 2005, 68°03.84’S, 20°31.39’W, 4928 m .

Diagnosis

Body with strong cuticule; rostrum thick, by volume dorsally, as long as four basal articles of antenna 2, with distal notch; head lateral ledge smooth; natasome approximately as long as anterior part of body; anterolateral margins of pereonites 6 and 7 and pleotelson greatly extended anterodorsally; posteroventral process of pleotelson thick, triangular, about half as long as pleotelson, uropod protopod angled at 90º, medial angle extended.

Redescription of holotype

Body length ( Fig. 5a – c ) 2.7 times width, height 0.8 times the width. Head length 0.7 times width; anterolateral ledge smooth; rostrum from tip to level of antennal sockets 1.5 times as long as remainder of head, with distal hollow; clypeus twice as broad and 0.4 times length of labrum.

Pereonite 1 as wide and long as head posterior to antennal sockets, pereonite 4 0.4 times length of pereonite 1. Natasome nearly as long as anterior body part. Pereonite 7 length 0.7 times length of pereonite 5; anterolateral margins of pereonites 6 and 7 and pleotelson greatly extended anterodorsally. Pleotelson length 0.7 times width, slightly longer than medial portion of head; posteroventral projection triangular, robust, 0.6 times length of pleotelson, preanal ridge with two projections near uropod insertions.

Antenna 1 ( Fig. 5a, b ) article 1 length 1.1 times width, distolateral projection reaching two third of article 2 with 2 or 3 broom setae dorsally and 3 simple setae distomedially; article 2 0.6 times length of article 1, with 2 or 3 broom distal setae; articles 3 as long as article 1, flagellum of 16 articles, article 4 (first flagellar article) length 0.1 times length of article 3, following articles subequal in length to article 4, some with aesthetasc.

Pereopod 2 ( Fig. 6 ): length ratios of ischium­propodus to basis: 0.55, 0.3, 1.1, 0.8; basis and ischium with sparse, small, simple setae, merus with 2 distodorsal simple setae and 1 small, simple ventral seta; carpus with 14 stout flagellate ventral and 5 small, simple dorsal setae; propodus with 6 stout, flagellate ventral setae and tuft of long, whip distal setae; dactylus broken off.

Pereopod 7 ( Fig. 6 ) about 0.5 times length of pereopod 2, length ratios of ischiumdactylus to basis: 1.0, 0.6, 1.2, 1.1, 0.7; ischium and merus each with 4 ventral plumose setae, carpus length 0.9 times width; propodus length 1.9 times width and 0.4 times width of carpus, both articles with distodorsal stout seta, dactylus longer than propodus width.

Pleopod 1 ( Fig. 6 ) length 2.1 times basal width; distolateral lobes length 0.1 pleopod length, each with 4 simple distal setae; distomedial lobes half as wide and 0.3 times length of distolateral lobes.

Pleopod 2 ( Fig. 6 ) protopod length 1.6 times width, with 4 lateral submarginal, plumose setae; stylet of endopod 1.6 times length of protopod; exopod medial hook as long as projected distal part.

Uropod ( Fig. 6 ) length 0.5 times length of pleotelson; protopod angled at 90º, distal part of equal length to proximal, medial angle projected, with 6 long, whip setae; endopod length 0.5 times width and 0.8 times length of protopod, with 1 broom and 6 whip distal setae; exopod length 0.42 times length and 0.5 times width of endopod, with 1 broom and 3 simple distal setae.

Female, paratypes. Similar to male ( Fig. 5d–h ), but body slightly stouter than in male, length 2.5 times width; antenna 1 shorter and from articles 2 more slender, pleopod 2 approximately as long as wide.

Remarks

This species is similar to D. acutirostrum sp. nov., see comparison under the description of D. acutirostrum . Both species differ from D. nodosus and D. intermedius sp. nov. in having strong, calcified body with long, thick anterior and posterior projections; stout, long rostrum and strong, long posteroventral process of pleotelson.

Distribution

South­eastern Atlantic, Cape Basin, depth 4720–4960 m; western sector of the Southern Ocean: Weddell Sea, depth 4651 – 4928 m.

Figures

FIGURE 5. Dubinectes acutitelson (Menzies, 1962). a–c, male, holotype, AMNH 12096; d–h, paratypes, AMNH 12097. a, f, g, body dorsal views; b, h, body lateral views, c, pleotelson oblique ventral view, d, e; head dorsal view, i, head, frontal view.

FIGURE 6. Dubinectes acutitelson (Menzies, 1962). Male, holotype, AMNH 12096. Pereopods 2 and 5; pleopods 1, 2 and uropod.