Dubinectes intermedius, Malyutina & Brandt, 2006

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 : 37-43

Dubinectes intermedius sp. nov.

( Figs 19–22 )

Eurycope acutitelson Menzies, 1962: 143 (partim).

Material examined

Holotype ( ZMH 41161), male (3.4 mm), ANDEEP III Stn. 110­ 8 March 2005 64°59.20’S, 43°02.05’W, 4698 m; paratypes ( ZMH 41162) manca female 2.1 mm, natasome of male 3.4 mm, the same locality.

Additional material.— 1 male, 2 females and 2 mancas (1.8 – 2.9 mm), which were together with 7 paratypes of D. acutitelson ( AMNH 12098 ): Biotrawl No 52, Vema­14­28, 28 March 1958, south­western flank of the Schmidt­Ott Rise southwest of Capetown, 41°03.5’S, 07°49’E, 4960 m .

Etymology

intermedius is referring to the position of the species, possessing characters that are intermediate between two other species.

Diagnosis

Rostrum only slightly longer than article 1 of antenna 1; natasome about 1.5 times anterior body part length; anterolateral margins of pereonites 6, 7 and pleotelson with limited anterodorsal extendion; posterior rim of pleotelson with rounded posteroventral process 0.35 times pleotelson length.

Description Body ( Fig. 19 ) length 2.6 times pereonite, 5 times width. Head length 0.7 times width; anterolateral margins with weak ledge, rostrum 0.7 times length of rest of head, concave distally; clypeus 2.1 times as broad and 0.5 times length of labrum.

Pereonite 4 about half the length of pereonite 1. Natasome 1.4 times anterior body part length; pereonite 7 0.8 times length of pereonite 5; pleotelson slightly longer than head, posteroventral projection 0.35 times pleotelson length, preanal ventral ridge low.

Antenna 1 of male ( Fig. 21 ) article 1 1.2 times width, setation: 3 broom dorsal setae, and 3 simple distomedial setae; article 2 0.5 times length of article 1, with 2 broom distal setae; article 3 almost equal in length to article 1, article 4 0.15 times length of article 3, with 1 broom and 1 simple distal setae, other 7 flagellar articles each with simple seta, last article with aesthetasc. Antenna 1 of female ( Fig. 20 ) article 2 length 0.65 times length of article 1, article 3 slightly shorter than article 1, flagellum of 5 articles last one with 1 aesthetasc and 5 setae.

Mandibles ( Fig. 20 ) incisor process with 3 weak cusps; lacinia mobilis of left mandible slender, 0.8 times length of incisor process, with 5 teeth; spine row with 3 and 4 spines respectively; palp article 2 1.9 times length of article 1, with 2 stout distal setae and small marginal setae.

Maxilliped ( Fig. 20 ) basis 2.1 times width, endite with 3 coupling hooks, distal margin with 3 large fan setae and numerous simple slender setae; palp article 2 lateral margin slightly convex, 1.3 times longer than straight medial margin; article 3 medial margin almost straight, 1.6 times longer than medial margin of article 2, with row of setulose setae; article 4 laterally 1.8 times length of articles 3, medial lobe half as the length of article 5, with 6 distal setae, article 5 with 7 distal setae. Epipod 1.2 times width, equal to length of basis, distal angle rectangular.

Pereopods ( Fig. 21 ): pereopod 1 0.3 times body length, length ratios of ischiumpropodus to basis: 0.5, 0.3, 0.9, 0.7, 0.2; basis with stout ventral setae and few small dorsal setae; merus with 5 stout ventral setae and distodorsal seta; carpus with 12 stout ventral and small simple distodorsal setae; propodus 0.5 times carpus width, with slender marginal setae. Pereopods 2–4 bases subequal in size, more than half basis 1 width, basis 3 slightly shorter than or equal to 2 and 4. Pereopod 2 length ratios of ischium­propodus to basis: 0.5, 0.3, 0.9, 0.75, 0.5; carpus with 13, stout ventral setae, 3 small dorsal setae, propodus with 7 stout ventral setae, 2 small dorsal setae and 7 long whip distal setae; pereopod 3 length ratios of ischium­propodus to basis: 0.5, 0.3, 0.95, 0.8, 0.45; carpus with 7 ventral and 9 small dorsal setae, propodus with 3 long ventral setae, 1 small dorsal seta and 7 long whip distal setae. Pereopod 5 length ratios of ischium­carpus to basis: 1.7, 0.8, 2.2; ischium with 7 plumose dorsal setae; carpus 1.3 times width; Pereopod 6 length ratios of ischium­dactylus to basis: 0.85, 0.4, 0.95, 0.8, 0.4; basis with 2 dorsal and 2 ventral setae; ischium with 6 long dorsal and 5 shorter ventral setae; merus with 3 ventral setae; carpus 1.1 times width; propodus 1.6 times width. Pereopod 7 length ratio of ischiumdactylus to basis: 1.0, 0.4, 1.2, 0.9, 0.55; basis with 3 ventral setae; ischium with 5 dorsal and 5 ventral setae; merus with 2 ventral setae; carpus 1.0 times width; propodus 1.9 times width.

Pleopods ( Fig. 22 ): pleopod 1 of male 2.6 times width, distal margin: lateral lobes 0.05 times length of total pleopod, each with acute lateral projections and several distal small setae; medial lobes almost as wide and 0.7 times length of lateral lobes, each with 3 small distal setae. Pleopod 2 of male protopod 1.6 times width, and equal in width to pleopod 1, with 4 lateral submarginal setae, stylet of endopod 2.2 times protopod length, exopod acute distally, medial hook equal in length to distal part. Pleopod 3 endopod 1.4 times width, exopod 1.1 times length of endopod, reaching its distal margin, basal article 0.4 times width of endopod, distal article 0.4 times length and 0.3 times width of basal article, with 1 distal simple seta and dense row of long hair­like lateral setae. Pleopod 4 endopod 1.3 times width, exopod 0.4 times width and 0.9 times length of endopod, with dense row of long hair­like lateral setae. Pleopod 5 endopod 1.4 times width.

Pleopod 2 of female ( Fig. 19f ) 0.8 times width.

Uropod ( Fig. 22 ) 0.3 times pleotelson length; protopod 2 times longer than broad, with 6 long whip setae on medial projection and several setae on distal half, endopod 0.4 times width and equal length of protopod, with with 1 broom and 7 simple distal setae; exopod 0.4 times endopod length, with 3 setae distally.

Remarks

D. intermedius sp. nov. takes a middle position between D. acutitelson and D. acutirostrum on one side and D. nodosus on the other. It is more similar to the latter in body shape, shape of the rostrum, and the natasome in dorsal view, but the new species has a stronger cuticle, a posteroventral projection on the posterior rim of the pleotelson, more projected anterolateral margins of pereonites 6, 7 and pleotelson than in D. nodosa . These characters make D. intermedius sp. nov. similar to D. acutitelson and D. acutirostrum , but they are not as well developed as in these species.

The relatively long posteroventral projection of the pleotelson was probably one reason why Menzies identified specimens of the new species as D. acutitelson , but the projection is not so strong and acute as in D. acutitelson and the range of the other characters, discussed above, helps to distinguish these species.

Distribution

South­eastern Atlantic: southern part of the Cape Basin at a depth 4960 m; western sector of the Southern Ocean: Weddell Sea at a depth 4698 m.

Figures

FIGURE 19. Dubinectes intermedius sp. nov. Male, holotype ZMH 41161, a, dorsal view; b, lateral view; c, head, frontal view; d, pleotelson ventral view; e, f, specimens which were together with the paratypes of D. acutitelson: e, immature male, dorsal view with attached pleotelson ventral and lateral views; f, female, dorsal view with attached pleotelson ventral and lateral views.

FIGURE 20. Dubinectes intermedius sp. nov. Immature female, paratype ZMH 41162, mouthparts and antenna 1.

FIGURE 21. Dubinectes intermedius sp. nov. Male, holotype ZMH 41161, pereopods and antenna 1.

FIGURE 22. Dubinectes intermedius sp. nov. Natasome of male, paratype ZMH 41162, pleopods and uropod.