Belonectes daytoni, Malyutina, Marina V. & Brandt, Angelika, 2009

Malyutina, Marina V. & Brandt, Angelika, 2009, Description of three new species of the deep-sea munnopsid genus Belonectes (Crustacea, Isopoda, Asellota) from the Weddell Sea, Southern Ocean, Zootaxa 2277, pp. 33-52 : 48-51

Belonectes daytoni sp. nov.

( Figs 11 – 13 )

Material examined. Holotype, male (2.1 mm) ( ZMH K- 42039), ANDEEP III St. 81 – 8 – S, 24 February 2005, 70°31.08’ – 32.23’S, 14°34.82’ – 14°34.90’W, 4382 m.

Etymology. The species is named after marine biologist, Dr. Paul Dayton for his important contributions to Southern Ocean benthic marine biology.

Description. Body ( Fig. 11 ) length 2.4 width of pereonite 5, body height 0.3 of body length. Head length 0.45 width, rostrum length 0.95 head length. Rostrum width subequal to length, and 1.6 antennula basal width. Cephalic keel weakly expressed, clypeus 1.6 as wide and 0.5 as long as labrum. Pereonite 1 almost as wide as head, length 3.5 head length behind antennula insertion; pereonites 2–4 slightly broader, almost twice as long as lateral margins and slightly shorter medially than pereonite 1, anterolateral margin of pereonites 1–4 acute in dorsal view; coxae anterior projection acute in dorsal view. Natasome length 0.75 body length, width 1.3 head width; pereonite 5 lateral length 0.9 lateral length of pereonites 6 and 7 together. Lateral sutures between pereonites 5 and 6 rather long: fused middle part 0.4 of pereonite 5 width. Pleotelson length 0.9 width, 0.3 body length, preanal ridge short, triangular, shorter than uropodal protopod.

Antennula incomplete ( Fig. 11 ) article 1 nearly reaching end of rostrum, length 1.3 width, with 2 small medial setae, article 2 0.4 length and 0.5 width of article 1, with 1 distal broom setae.

Antenna incomplete ( Fig. 11 ): articles 1–4 subequal in size, scale on article 3 small.

Left mandible ( Fig. 12 ): pars incisiva with 5 cusps; lacinia mobilis length 0.7 pars incisiva length, with 5 teeth; spine row with 7 spines; condyle length 0.6 molar process length; palp length 1.05 mandibular body length, article 1 without setae, article 2 length 1.5 article 1 length, with 1 stout distal seta, article 3 with row of lateral setae and long distal seta.

Maxilla 1 ( Fig. 12 ) lateral endite width 1.6 mesial endite width, with 12 distal spine-like setae, longest distolateral seta slightly longer than endite width.

Maxilla 2 ( Fig. 12 ) lateral endite with 2 long, 1 shorter and 1 small distal (most medial) setae, medial endite shortest, mesial endite longest, slightly narrower than both other endites together, with 7 strong and numerous slender distal setae.

Maxilliped ( Fig. 12 ) basis length 3.4 width, endite length 0.4 basis length, width 0.7 basis width, with 2 coupling hooks, distal margin narrow, slightly concave, with some simple slender setae and 3 stout fan setae; palp article 2 width 1.2 endite width, lateral margin slightly convex, length 1.4 medial margin length; article 3 subequal to article 2 in medial length and width, medial margin rounded, extended, with 8 setae; articles 3–5 subequal in length laterally, medial lobe of article 4 1.4 times longer and twice as broad as article 5, with 5 distal setae; article 5 with 1 lateral and 3 distal setae. Epipod length 3.4 width, 0.95 basis length, with fine distal setae.

Pleopods ( Fig. 13 ): Pleopod 1 length 2.9 width, deeply keeled in midlength, depth 0.2 length, distal margin: medial lobes rounded, with 4 small setae each, lateral lobes visibly longer than medial lobes, slightly acute distally. Pleopod 2 protopod length 1.8 width, distolateral part enlarged, bent dorsally with ventral keel, lateral margin with 8 rather short plumose setae, stylet length 0.5 protopod length, sperm duct opening at midlength of stylet; exopod slightly narrower than basal article of endopod, inserted on 0.3 of protopod length from distal margin. Pleopod 3 endopod length 1.4 width, distal plumose setae length about half of endopod width; exopod 1.1 length and 0.2 width of endopod, distal article length 0.7 basal article length. Pleopod 4 endopod length 1.6 width, exopod length 0.8 endopod length, distal plumose seta half as long as exopod. Pleopod 5 length 1.7 width.

Uropod not complete ( Fig. 11 ) Protopod length 1.1 width, slightly broadened distally; endopod broken, exopod 0.6 of protopod length, with 3 distal setae.

Remarks. Belonectes daytoni sp. nov. differs from other species of the genus by having a larger basal article of the antennula, which almost reaches the distal margin of the rostrum, and is 0.6 times as wide. The shape of the distal margin of the male pleopod 1 also distinguishes the new species: the medial lobes are rounded and shorter than the lateral lobes (in B. stoddarti the medial lobes are longer than the lateral ones, in B. grasslei they are more triangular and subequal to the lateral ones, in B. parvus the medial lobes are truncate and as long or shorter than the lateral ones, in the illustration of distal part of pleopod 1 of B. latifrons ( Menzies and George, 1972, p. 9.63) the lobes are not separated, probably of the same length. The shape of the pleopod 2 protopod is similar to that of B. stoddarti , but differs by a smaller distolateral lobe; the lateral plumose setae of the protopod are shorter and the exopod is relatively larger than in B. stoddarti . Article 3 of the maxilliped palp in B. daytoni sp. nov. has a more convex medial margin than that in B. stoddarti , and the medial lobe of article 4 is narrower than that in B. parvus .

Distribution. The species is only known from the type locality, the Weddell Sea, 4382 m depth.

Figures

FIGURE 11. Belonectes daytoni sp. nov., male, holotype, ZMH K- 42039: A, body dorsal views; B, body lateral view; C, anterior body part, ventral view; D, pleotelson, ventral view; E, F, G, pleotelson, different oblique views; H, head, lateral view, left antennula, dorsal view. Scale bar 0.1 mm.

FIGURE 12. Belonectes daytoni sp. nov., male, holotype, ZMH K- 42039: left mandible with enlarged parts, dorsal view, maxillae and maxilliped with enlarged parts, ventral view. Scale bar 0.1 mm.

FIGURE 13. Belonectes daytoni sp. nov., male, holotype, ZMH K- 42039: pleopods 1 – 5. Scale bar 0.1 mm.