Tytthocope divae, Malyutina, Marina V. & Brandt, Angelika, 2014

Malyutina, Marina V. & Brandt, Angelika, 2014, New species of the deep-sea munnopsid genus Tytthocope (Crustacea, Isopoda, Asellota) from the South Atlantic and the Southern Ocean, Zootaxa 3786 (1), pp. 1-43 : 24-34

publication ID	https://doi.org/ 10.11646/zootaxa.3786.1.1
publication LSID	lsid:zoobank.org:pub:2BB3C36D-3273-4DB4-9303-D1180571BCCF
DOI	https://doi.org/10.5281/zenodo.5696627
persistent identifier	https://treatment.plazi.org/id/03CBFA52-6F4B-4812-FF0D-D572FA4DFC0A
treatment provided by	Plazi
scientific name	Tytthocope divae
status	sp. nov.

Treatment

Tytthocope divae View in CoL sp.nov.

( Fig. 16–23 View FIGURE 16 View FIGURE 17 View FIGURE 18 View FIGURE 19 View FIGURE 20 View FIGURE 21 View FIGURE 22 View FIGURE 23 )

Material examined. Holotype: ZMH K- 43129, copulatory male 1.9 mm, DIVA III, RV Meteor, EBS, st. 532 EBS, 15 June 2009, 35°59.24’S, 49°00.86’W, 4605– 4507 m. Paratypes: ZMH K- 43130— 2 males (1.7 and 1.8 mm), 1 female about 1.9 mm (2 separated halves) from the same sample as the holotype; ZMH K- 43131—female with empty change on marsupium (2.0 mm), 4 females (1.6–2.1 mm), 4 males (1.5–1.8 mm, male 1.5 mm for dissection), EBS st. 533, 15 June 2009, 36°00.20’S, 49°01.96’W, 4602 m. ZMH K- 43131a, 3 females (1.45, 1.8, 2.5 mm), 6 males (1.4–1.8 mm), 1 juvenile (0.9 mm), EBS st. 534 EBS, 16 June 2009, 36°00.61’S, 49°01.54’W, 4608 m.

Etymology. The species name refers to the expedition DIVA (DIVersity of the abyssal Atlantic), during which the new species was collected.

Diagnosis. Rostrum without lateral keels, anterior margin with few small setae. Antennula article 1 width 0.6 rostrum width and length subequal to rostrum length. Pleotelson length subequal to width, third of body length; posterior tip rectangular and rounded. Pereonite 5 length 0.3 pleotelson length and 0.66 pereonite 6 length medially; pereonite 7 length 0.18 pleotelson length and 0.37 pereonite 6 length medially, subequal to pereonite 1 length. Maxilliped palp article 4 distomedial lobe as long and as broad as article 5. Male pleopod 1 with subparallel sides and rounded distal margin.

Description of male, holotype. Body ( Fig. 16 View FIGURE 16 ) length 2.36 width of pereonite 6, body height 0.35 of body length. Cephalothorax length 0.6 width, length behind antennula insertion 0.7 antennula article 1 length; rostrum length 0.55 cephalothorax length. Rostrum with weak lateral keels, anterior margin sloping, with few small setae, width between bases of antennulae subequal to rostrum length, and 1.8 antennula width. Clypeus 1.6 as wide and 0.5 as long as labrum. Anterolateral margins of coxae of pereonites 2–4 weakly projected in dorsal view. Natasome length 0.65 body length, width 1.63 cephalon width, lateral margins of natasome with scattered setae; pereonites 5 and 6 subequal in lateral length; pereonite 6 length 1.45 pereonite 5 length medially, pereonite 7 length 0.55 pereonite 6 length laterally and 0.37 medially, 0.18 pleotelson length, subequal to pereonite 1 length; pereonite 6 ventral bump protruded visibly more than equal protruded venter of pereonites 5 and 7. Pleotelson length 0.8 width, 0.31 body length, preanal ridge on lateral view almost as long as uropod.

Antennula of male ( Fig. 18 View FIGURE 18 d) length 0.55 of body length; article 1 length 1.3 width, with 1 broom seta; article 2 length 1.1 width, 0.55 length and 0.65 width of article 1 with 2 distal broom setae; article 3 length 0.5 article 2 length with 3 small simple distal setae; article 4 length 0.65 article 3 length; article 5 and following 21 articles subequal in length to article 4, most of them with aesthetascs.

Antenna ( Fig. 16 View FIGURE 16 a) length more than 1.26 body length (distal part of flagellum broken off); articles 1–4 subequal in size, length together equal to antennula articles 1–4 length, scale on article 3 triangular, with distal seta, article 4 with few distal setae; article 5 length 2.9 articles 1–4 length together, with dense row of dorsal setae; article 6 slightly narrower than article 5, length 1.08 article 5 length, with less dense setae than on article 5, flagellum with more than 24 articles.

Mandibles ( Fig. 18 View FIGURE 18 b,c) pars incisiva with 3 cusps on left and 4 cups on right mandibles; lacinia mobilis of left mandible almost as long as pars incisiva, with 5 teeth; spine row with 6 and 7 spines on left and right mandibles respectively; molar process as long as and almost twice as broad as incisor process, tapering with 4–5 distal teeth; condyle length 0.15 mandibular body length, equal to molar process length; palp length 0.85 mandibular body length, article 1 with 3 distal setae, article 2 length 1.75 article 1 length, with 2 stout distal setae and row of fine lateral setulae, article 3 with row of short marginal setae, 1 long setulated seta and 1 shorter simple seta distally.

Maxilliped ( Fig. 18 View FIGURE 18 a) basis length 2.95 width, endite slender, width 0.45 basis width, with 3 coupling hooks, distal margin slightly serrated, with 4 fan setae and several slender simple setae, lateral margin almost parallel to medial margin; palp inserted after 0.5 length of basis, article 1 lateral length 2.0 medial length; article 2 width 1.26 basis width and 2.75 endite width, lateral length 1.9 medial length, lateral margin slightly convex with 4 small setae, distolateral projection reaching mid-length of article 3 lateral margin; article 3 width 0.93 article 2 width, medial margin serrated with 5 setae, medial length 1.4 article 2 medial length, 1 seta laterally; article 4 with 2 lateral setae, medial lobe elongate equal in length to article 5, with 3 distal setae; article 5 length 1.7 article 4 lateral length, with 1 lateral seta and 4 distal setae. Epipod length 2.8 width.

Pereopods 1–4 ( Fig. 20 View FIGURE 20 ): basis of pereopod 1 most slender, basis of pereopod 3 broadest, basis 2 slightly longer than basis 1. Pereopod 1 ( Fig. 20 View FIGURE 20 a) length ratios of ischium-dactylus to basis: 0.4, 0.2, 0.9, 0.6, 0.3; basis length 6.9 width, with 6 dorsal and 6 small ventral setae; ischium and merus as wide as basis, ischium with 2 ventral and 2 dorsal setae; merus with 1 ventral and 2 dorsal setae; carpus narrowing distally, length 13.8 width, with 12 dorsal and 7 ventral small setae. Pereopods 2 and 3 broken off, basis 2 ( Fig. 20 View FIGURE 20 b) length 5.0 width, with 6 ventral and 7 dorsal setae, basis 3 ( Fig. 20 View FIGURE 20 c) length 4.4 width, with 7 ventral and 8 dorsal setae. Pereopod 4 ( Fig. 20 View FIGURE 20 d) length (without dactylus) 1.7 pereopod 1 length (without dactylus); length ratios of ischium-propodus to basis: 0.5, 0.2, 0.9, 0.6, 0.3.

Pereopods 5–7 ( Figs 21 View FIGURE 21 , 22 View FIGURE 22 ): pereopods 5 and 6 1.05 and 1.1 of pereopod 1 length respectively. Pereopod 5 ( Fig. 22 View FIGURE 22 d) slightly more stout, with shorter and broader basis and carpus, length ratios of ischium–dactylus to basis: 0.8, 0.25, 1.0, 0.7, 0.35, basis with 13 ventral small setae and 3 dorsal plumose setae, ischium with 2 dorsal plumose setae and 6 simple ventral setae, merus with distoventral unequally bifid seta; carpus length 1.15 width, with 22 dorsal and 11 ventral plumose setae, propodus length 1.7 width, with 11 dorsal and 12 ventral plumose setae, distodorsal and distoventral margins with 1 long stout UB and one broom seta each, dactylus length 2.6 width, with serrate dorsal and distoventral margins, 2 small distal setae. Pereopod 6 ( Fig. 21 View FIGURE 21 c) length 1.05 pereopod 5 length, basis slightly (1.1) longer, ischium slightly shorter (0.9) than these articles of pereopod 5, length ratios of ischium-dactylus to basis: 0.7, 0.17, 0.95, 0.7, 0.3; basis with 4 distoventral and 2 small proximodorsal setae, ischium with 2 simple ventral setae, merus with distoventral unequally bifid seta and 2 small ventral setae; carpus length 1.3 width, with 22 dorsal and 8 ventral plumose setae, propodus length 1.7 width, with 14 dorsal and 11 ventral plumose setae, distodorsal and distoventral margins each with 1 long stout UB seta and broom seta, dactylus length 2.8 width, with serrate dorsal margin, 2 small distal setae. Pereopod 7 ( Fig. 21 View FIGURE 21 d) length 0.6 pereopod 6 length, length ratios of ischium-propodus to basis: 0.6, 0.25, 1.0, 0.5, 0.25; carpus length 1.2 width, propodus length 1.6 width; ischium with 2 dorsal plumose setae, merus with distoventral UB seta, propodus with distodorsal UB seta.

Pleopod 1 ( Fig. 23 View FIGURE 23 a) with almost parallel sides and rounded distal margin, length 2.8 basal width, distal lobes almost not separated, medial lobes longer than lateral lobes, with 6 short setae each. Pleopod 2 ( Fig. 23 View FIGURE 23 b) protopod length 2.3 width, stylet length 0.6 protopod length; exopod hook narrower than basal part of endopod, inserted on 0.4 of protopod length from distal margin. Pleopod 3 ( Fig. 23 View FIGURE 23 c) endopod length 1.6 width, three distal plumose setae length about half of endopod length; exopod 1.5 length and 0.4 width of endopod, distal article separated, length 0.5 proximal article length, with 2 distal plumose setae, as long as endopod setae. Pleopod 4 ( Fig. 23 View FIGURE 23 d) endopod length 1.6 width, exopod 0.8 of endopod length and width, distal plumose seta as long as setae on pleopod 3.

Uropod ( Fig. 21 View FIGURE 21 b) 0.12 pleotelson length. Protopod length 0.8 width, slightly broadened distally; endopod length 1.8 protopod length, with 3 simple and 2 broom setae distally; exopod 0.6 of endopod length and 0.5 width, with 1 broom and 2 simple setae distally.

Female: Body similar to male ( Fig. 17 View FIGURE 17 a, b), but broader, length 2.1–1.9 width (ovigerous females with broader ambulosome). Cephalothorax length 0.5 width, rostrum length 0.8 cephalothorax length. Rostrum with a few distal setae, width 2.1 antennular basal article. Natasome length 0.7–body length, width 1.5–1.8 cephalon width. Pleotelson length 1.0 width, 0.34–0.37 body length.

Antennula ( Fig. 19 View FIGURE 19 a) smaller and more slender than in male, length 0.25 body length, article 1 length 1.2 width, with 1 dorsal broom seta, article 2 0.5 length and 0.4 width of article 1, with 1 distal UB seta and small simple seta distally; article 3 length 0.5 of article 2 with 2 simple distal setae, article 4 length 0.5 article 3 length with 1 broom seta; flagellum of 8 elongate articles, last 4 articles with aesthetascs.

Maxilla 1 ( Fig. 19 View FIGURE 19 c) lateral endite width 1.8 mesial endite width, with small lateral setae and 12 distal spinelike setae, longest distolateral seta length 1.3 endite width, mesial endite with marginal setae, distal margin acute with 2 long setae. Maxilla 2 ( Fig. 19 View FIGURE 19 b) middle endite shortest, lateral and mesial endites equal in length, mesial endite with 4 strong setulated and numerous slender distomedial setae, lateral and middle endites with 2 long and 2 shorter distal setae each. Maxilliped ( Fig. 19 View FIGURE 19 d) as in male.

Pleopod 2 ( Fig. 17 View FIGURE 17 c) length 1.18 width, with seta on tip. Pleopod 3 ( Fig. 22 View FIGURE 22 a) 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 length 0.5 basal article length. Pleopod 4 ( Fig. 22 View FIGURE 22 b) endopod length 1.4 width, exopod length 0.9 endopod length, distal plumose seta slightly longer than setae on pleopod 3. Pleopod 5 ( Fig. 22 View FIGURE 22 c) length 1.41 width.

Uropod ( Fig. 21 View FIGURE 21 a) 0.1 pleotelson length. Protopod length 0.85 width; endopod length 2.3 protopod length, with 3 simple and 2 broom setae distally; exopod 0.4 of endopod length and 0.5 width, with 1 broom and 2 simple setae distally.

Remarks. T. divae sp. nov. is similar to T. sulcifrons in having a rounded rostrum lacking the serrate lateral keels. Pereonite 7 of both species is relatively long in comparison to that of the T. megalura group of species. The differences of the new species from T. sulcifrons are the following: pleopod 1 of T. divae sp. nov. has almost parallel sides in contrast to the tapering pleopod 1 of T. sulcifrons ; the medial lobe of article 4 of the maxillipedal palp is subequal in length and width to article 5, the lobe in T. sulcifrons is longer and thicker than article 5.

Distribution. The species is only known from the type locality, the Argentine Basin, at the depths 4507–4608 m.