Belonectes grasslei, 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 : 35-44

publication ID	https://doi.org/ 10.5281/zenodo.191112
DOI	https://doi.org/10.5281/zenodo.6214083
persistent identifier	https://treatment.plazi.org/id/03B78785-FF8A-8519-FF5C-512A1B3B2412
treatment provided by	Plazi
scientific name	Belonectes grasslei
status	sp. nov.

Treatment

Belonectes grasslei View in CoL sp. nov.

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

Material examined. Holotype. male (1.9 mm), ZMH K- 42034, ANDEEP III St. 78 – 9 – E, 22 February 2005, 71°09.52’ – 09.34’S, 14°00.76’ – 13°58.85’ W, 2149 m.

Allotype. Preparatory female (2.2 mm), ZMH K- 42035, same locality as holotype.

Paratypes. ZMH K-42036, juvenile male (1.4 mm) and juvenile female (1.3 mm), same data as holotype.

Etymology. The species is named in honor of the outstanding American marine biologist J. Frederick Grassle who always supported deep-sea research and is one of the founders of the Census of the Marine Life.

Description of male, holotype. Body ( Fig. 1 View FIGURE 1 ) length 2.5 width of pereonite 5, body height 0.31 of body length. Head length 0.6 width, length behind antennula insertion 0.7 antennula article 1 length; rostrum length 0.7 head length. Rostrum width between bases of antennulae subequal to length, width 2.6 antennula width. Cephalic keel weakly expressed, clypeus 1.6 as wide and 0.5 as long as labrum. Pereonite 1 almost as wide as head, shortest laterally, length 0.5 length of head behind antennula insertion; pereonites 2–4 slightly broader, laterally almost twice as long as pereonite 1, anterolateral margins of pereonites 1–4 and anterior projections of coxae acute. Natasome length 0.7 body length, width 1.3 width of head; pereonite 5 lateral length equal to lateral length of pereonites 6 and 7 together; pereonite 7 shortest. Lateral sutures between pereonites 5 and 6 relatively long: fused middle part about 0.5 of pereonite 5 width; ventral bump of posterior part of pereonite 5 with few setae. Pleotelson length 0.8 width, 0.3 body length, preanal ridge rounded terminally, bent posteriorly, length 0.25 pleotelson length, about twice as long as uropod protopod.

Antennula ( Fig. 5 View FIGURE 5 ) about 0.5 of body length; article 1 reaching mid-length of rostrum, length 1.4 width, with 1 dorsal broom seta, article 2 0.6 length and 0.4 width of article 1, with 3 distal broom setae; article 3 length 0.6 of article 2; article 4 length 0.5 article 3 length, article 5 slightly shorter than article 1, article 6 as long as article 4, following 34 articles length 0.5 article 6 length.

Antenna incomplete (broken off) on all specimens ( Fig. 5 View FIGURE 5 ): articles 1–4 subequal in size, scale on article 3 narrow, with distal seta.

Mandible ( Fig. 4 View FIGURE 4 ) pars incisiva with 4 cusps; lacinia mobilis of left mandible almost as long as pars incisiva, with 5 teeth; spine row with 7 and 8 spines on left and right mandibles respectively; condyle length 0.6 molar process length; palp length 1.2 mandibular body length, article 1 stout, with 2 setae, article 2 1.5 times as long as article 1, with 2 slender medial and 1 stout distal setae, article 3 with row of lateral setae and long distal seta.

Maxilla 1 ( Fig. 5 View FIGURE 5 ) 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. 5 View FIGURE 5 ) middle endite shortest, mesial endite longest, slightly narrower than lateral and middle endite together, with 6 strong and numerous slender distal setae lateral and middle endites with 2 long and 2 shorter distal setae each: shorter setae on middle endite of equal length, on lateral endite 1 seta just slightly shorter than 2 long setae and inner seta much smaller.

Maxilliped ( Fig. 5 View FIGURE 5 ) basis length 3 width, endite with 3 coupling hooks, distal margin slightly concave, with numerous simple slender setae and a few stout setae, lateral margin expanded, rounded; palp inserted after 0.6 length of basis, article 2 lateral margin slightly convex, length 1.5 length of medial margin; article 3 medial margin straight with several whip setae, medial length equal to lateral length of article 2; articles 3–5 subequal in length laterally, medial lobe of article 4 elongate, width 1.3 article 5 width, with 5 distal setae; article 5 with 1 lateral and 3 distal setae. Epipod length 3 times width, slightly shorter than basis, with fine distal setae.

Pereopods incomplete ( Fig.1 View FIGURE 1 B, C) see description for juvenile specimen below.

Pleopods ( Fig. 6 View FIGURE 6 ): Pleopod 1 length 3.4 midlength width, deeply keeled at midlength, depth 0.25 length, distal margin bent ventrally, medial lobes rounded, with 2 small setae each, lateral lobes nearly the same size more acute distally. Pleopod 2 protopod semicircular, length 1.4 width, lateral margin with 15 rather short plumose setae, stylet length 0.5 protopod length, sperm duct open at mid-length of stylet; exopod narrower than basal article of endopod, inserted on 0.15 of protopod length from distal margin. Pleopod 3 endopod length 1.4 width, distal plumose setae length less than half of endopod width; exopod 1.2 length and 0.4 width of endopod, distal article separated, length 0.6 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 ( Fig. 6 View FIGURE 6 ) 0.3 pleotelson length. Protopod length 1.1 width, slightly broadened distally; endopod length 2.1 protopod length, with 1 stout, and 1 simple distal seta; exopod 0.2 of endopod length and 0.3 width, with 2 stout, 1 broom and 3 simple distal setae.

Female ( Fig. 2 View FIGURE 2 ): Body similar to male, slightly broader, length 2.25 width of pereonite 5. Head length 0.5 width, rostrum length 0.8 head length. Rostrum width subequal to length, width 2.8 antennular basal article. Pereonite 1 almost as wide as head, shortest laterally and longest medially, pereonites 2–4 slightly broader and laterally almost twice as long as pereonite 1. Natasome length 0.7 body length, width 1.4 head width. Pleotelson length 0.9 width, 0.3 body length, preanal ridge shorter than in male, not bent, rounded terminally.

Antennula ( Fig. 2 View FIGURE 2 ) incomplete, article 1 length 1.3 width, with 1 dorsal broom seta and 1 small medial seta, article 2 0.5 length and 0.4 width of article 1, with 2 distal broom setae; article 3 length 0.5 of article 2.

Pleopods ( Fig. 2 View FIGURE 2 ): Pleopod 2 ( Fig. 2 View FIGURE 2 B, D) as long as wide, diamond-shaped in ventral view and conical in lateral view, covering anus, reaching apex of pleotelson, distal projection angled like pleotelson posterolateral margin, ventral tip of cone in midlength, height 0.6 length, distolateral margins with about 14 plumose setae on each side. Pleopod 3 endopod twice as long as protopod, length 1.2 width, distal plumose setae length 0.5 endopod width; exopod 1.3 length and 0.3 endopod width, distal article separated, length 0.5 basal article length. Pleopod 4 endopod length 1.4 width, exopod length 0.9 endopod length, distal plumose seta half as long as exopod. Pleopod 5 length 1.3 width.

Juveniles. In spite of the fact that both juvenile specimens have an operculum, shape and size of antennula and preanal ridge already indicate the future sex of the juveniles. The articles of the male antennula are stouter in comparison with those of the female, and the preanal ridge of the male is more pronounced.

Body ( Fig. 3 View FIGURE 3 ) length/width of pereonite 5 2.1 in female and 2.25 in male.

Antennula of juvenile male ( Fig. 3 View FIGURE 3 ) article 1 length 1.3 width, article 2 0.6 length and 0.5 width of article 1, with 2 distal broom setae; article 3 length 0.5 of article 2, article 4 length 0.6 article 3 length, article 5 as long as article 1 and as broad as article 2, article 6 as long as article 4, following 4 articles shorter than article 4, last two articles elongate, each with distal aestetasc. Antennula of juvenile female more slender than of male.

Pereopods 1–4 of juvenile male ( Fig. 7 View FIGURE 7 ): pereopod 1 length 0.8 body length, length ratios of ischium– dactylus to basis: 0.2, 0.15, 1.1, 0.8, 0.6; basis length 5.9 width, with sparse simple setae; ischium length 1.7 width, without setae; merus length 1.2 width, with 4 distal setae; carpus length 11.4 width, with 1 dorsal and 2 ventral setae; propodus length 9.6 width, without setae; claw length 0.2 dactylus length. Pereopod 2 the most stout and setose among ambulatory pereopods, length 1.25 pereopod 1 length, length ratios of ischium– dactylus to basis: 0.5, 0.2, 1.4, 1.1, 0.6; basis length 5.2 width, with 3 dorsal setae, ischium length 2.6 width, with 2 small ventral setae; merus length 1.7 width, with 3 distal setae; carpus length 14.8 width, with 7 ventral sensory spines and 4 dorsal setae; propodus length 13.8 width, with 7 ventral sensory spines and 1 stout and 1 distodorsal broom seta; dactylus length 11.0 width, claw length 0.2 dactylus length. Pereopod 3 length 1.15 pereopod 1 length, length ratios of ischium–dactylus to basis: 0.3, 0.2, 1.3, 0.9, 0.45; basis length 7.8 width, with 3 small ventral setae, 1 broom and 3 small dorsal setae; ischium length 2.0 width, merus length 1.7 width, carpus length 17.3 width, with 1 distodorsal seta; propodus length 12.0 width, with 4 ventral, 1 dorsal seta and 1 distodorsal broom seta; dactylus length 8.7 width, claw length 0.3 dactylus length. Pereopod 4 not complete, length ratios of ischium–carpus to basis: 0.3; 0.25, 1.3, basis length 6.0 width, with 1 dorsal broom seta and 1 simple seta; ischium length 2.3 width, with 2 small ventral setae; merus length 1.9 width, carpus length 11.8 width, with 6 ventral setae.

Pereopod 4 of juvenile female: length ratios of ischium–dactylus to basis: 0.4, 0.25, 1.2, 1.1, 0.7; basis length 5.3 width, with 2 broom and 4 small dorsal setae; ischium length 2.3 width with 4 ventral setae, merus length 1.9 width, with 1 distodorsal and 2 ventral setae; carpus length 17.4 width, with 1 dorsal and 4 ventral setae; propodus length 16.2 width, with 1 ventral 3 dorsal setae and 1 distodorsal broom seta; dactylus length 13.7 width, claw length 0.2 dactylus length.

Pereopods 5–7 ( Fig. 7 View FIGURE 7 ) of juvenile male: Pereopod 5 length 0.8 pereopod 1 length, length ratios of ischium–dactylus to basis: 1.05, 0.6, 1.8, 0.85, 0.8; basis length 2.3 width, with 2 small dorsal and 1 distoventral setae; ischium length 2.8 width, with 3 small ventral and 3 stout plumose dorsal setae; merus length 1.6 width, with 1 stout dorsal seta; carpus length 1.5 width, with 15 long dorsal and 5 shorter ventral plumose setae; propodus length 1.7 width, with 5 ventral and 6 dorsal plumose setae and 2 spine-like distodorsal setae; dactylus length 5.3 width, claw tiny. Pereopod 6 similar in shape to pereopod 5, but slightly larger, length 1.1 pereopod 5 length, length ratios of ischium–dactylus to basis: 0.95, 0.4, 1.5, 0.7, 0.6; basis length 2.8 width, with 1 small dorsal and 1 long distoventral seta; ischium length 3.3 times width, with 3 ventral setae; merus length 1.5 width; with dorsal stout seta and small ventral seta; carpus length 1.5 width, with 16 long and 1 stout simple dorsal setae and 6 ventral plumose setae; propodus length 1.5 width, with 5 ventral and 5 dorsal plumose setae and 2 spine-like distodorsal setae; dactylus length 4.1 width, claw tiny. Pereopod 7 not completely developed, length 0.4 pereopod 5 length, length ratios of ischium–dactylus to basis: 0.6, 0.5, 1.7, 1.1, 0.8; carpus length 1.6 width.

Remarks. B. grasslei sp. nov. differs from the two known species, B. parvus and B. latifrons by having longer sutures between pereonites 5 and 6, and a more conical shape of the female pleopod 2 with central position of the tip. B. grasslei sp. nov. is most similar to B. parvus . The differences from the latter are the following: in B. grasslei sp. nov. the triangular medial lobes of the distal margin of the male pleopod 1 are slightly longer than the lateral ones in contrast to the truncate medial lobes of B. parvus which are shorter than the lateral ones; the medial lobe of the maxilliped palp article 4 is slightly narrower than that in B. parvus .

Distribution. The species is only known from the type locality: the eastern slope of the Weddell Sea, 2149 m depth.