Tytthocope longitelson, 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 : 17-24

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.5696625
persistent identifier	https://treatment.plazi.org/id/03CBFA52-6F4C-4824-FF0D-D00EFD20F970
treatment provided by	Plazi
scientific name	Tytthocope longitelson
status	sp. nov.

Treatment

Tytthocope longitelson View in CoL sp. nov.

( Figs 10–15 View FIGURE 10 View FIGURE 11 View FIGURE 12 View FIGURE 13 View FIGURE 14 View FIGURE 15 )

Material examined. Holotype: ZMH K- 44032, non-ovigerous female 2.6 mm. ANDEEP III, RV Polarstern, EBS, st. 133-2, 16.03.2005, 62°46.73’S, 53°02.57’W, 1584 m.

Etymology. The name longitelson refers to the species of the genus with the longest pleotelson known.

Diagnosis. Rostrum with serrated high lateral keels. Antennula article 1 width third of rostrum width and length half of rostrum length. Pleotelson length 0.65 natasome length, posterior tip produced, triangular. Anterior margin of pereonite 5 and pleotelson raised. Pereonite 5 medial length 0.15 pleotelson length, 0.42 pereonite 6 length, pereonite 7 length 0.05 pleotelson length, 0.22 pereonite 6 medial length, half of pereonite 1 length. Maxilliped palp article 4 distomedial lobe slightly shorter than article 5.

Description of female, holotype. Body ( Fig. 10 View FIGURE 10 ) length 2.37 width of pereonite 4, body height 0.33 of body length. Cephalothorax length 0.42 width, length behind antennula insertion 0.63 antennula article 1 length; rostrum length 0.78 cephalothorax length. Rostrum with serrated high lateral keels, anterior margin grooved and sloping, length 1.83 antennula article 1 length, width between bases of antennulae 1.7 rostrum length, 3.1 antennula article 1 width. Clypeus 2.0 as wide and 0.5 as long as labrum. Pereonite 1 slightly shorter medially than pereonites 2–4, which are subequal in length. Anterolateral margins of coxae weakly projected in dorsal view of pereonites 2–4. Natasome length 0.65 body length, width 1.52 cephalon width, pereonites 5 and 6 anterolateral angle with long seta; pereonite 6 length 2.57 pereonite 5 length medially and 0.8 laterally, pereonite 7 length 0.44 pereonite 6 length laterally and 0.22 medially, posterolateral margins of pereonite 7 covered by anterolateral flanges of pleotelson. Pleonite 1 slightly shorter than pereonite 7. Pleotelson length 1.07 width, 0.43 body length, posterior tip produced, triangular, preanal ridge weakly developed. Anterior margin of pereonite 5 and pleotelson raised. Antennula ( Fig. 15 View FIGURE 15 f) tip broken off; article 1 length 1.14 width, article 2 length 1.38 width, 0.64 length and 0.46 width of article 1 with 1 distal broom seta; article 3 length 0.69 of article 2 length and width 0.42 article 2 width; article 4 length 0.47 article 3 length, article 5 slightly shorter than article 2, following 2 articles subequal in length to article 4.

Antenna ( Fig. 15 View FIGURE 15 e) broken off; article 1 small, triangular; articles 2 and 3 subequal in length, scale on article 3 triangular, length 0.3 article 4 length, with long distal seta; article 4 longest, with 1 small distal seta.

Mandibles ( Fig. 11 View FIGURE 11 ) incisor process with 4 cusps on right and 3 cups on left mandibles; lacinia mobilis of left mandible length 0.7 incisor process length, with 4 teeth; spine row with 7 and 9 spines on left and right mandibles respectively; molar process slightly shorter and almost as broad as incisor process, tapering with 2 long setae; condyle length 0.2 mandibular body length, subequal in length to palp article 1; palp slender, length 0.9 mandibular body length, article 2 length 2.5 article 1 length, with 2 stout distal setae, article 3 rather broad, with row of marginal serrated setae, 1 long setulated seta distally.

Maxilla 1 ( Fig. 12 View FIGURE 12 b) lateral endite width 1.45 mesial endite width, with small lateral setae and 12 distal spinelike setae, longest distolateral seta subequal in length to endite width, mesial endite with tuft of fine marginal setae, distal margin rounded with few more stout long setae.

Maxilla 2 ( Fig. 12 View FIGURE 12 a) middle endite shortest, lateral endite longest, mesial endite with 5 strong setulated setae and slender distomedial setae, lateral and middle endites with 2 long and 2 shorter distal setae each.

Maxilliped ( Fig. 12 View FIGURE 12 c) basis length 2.6 width, endite width 0.45 basis width, with 3 coupling hooks, distal margin obliquely cut, with 4 slender fan setae lateral margin rounded with simple slender setae; palp inserted after 0.48 length of basis, palp length 0.83 basis length, article 1 lateral length 3.1 medial length; article 2 width 1.16 basis width and 2.52 endite width, lateral length 1.7 medial length, lateral margin slightly convex with 7 setae, 1 seta distomedially, distolateral projection longer than article 3 laterally; article 3 width 0.87 article 2 width, medial margin rounded with fringe of setulae and 5 setae, medial length 5.4 lateral length and 1.13 article 2 medial length; article 4 with 1 distolateral seta, medial lobe length 0.75 article 5 length, with 2 distal setae; article 5 length subequal to lateral length of article 4, with 2 distal setae. Epipod length 2.85 width.

Pereopods 1–4 ( Fig. 13 View FIGURE 13 ): basis of pereopod 1 most slender, basis 2 broadest, slightly shorter than basis 1, basis 3 and 4 equal in width, basis 4 longest. Pereopod 1 ( Fig. 13 View FIGURE 13 a) length ratios of ischium-dactylus to basis: 0.38, 0.23, 0.85, 0.52, 0.22; basis length 5.05 width, with 2 dorsal small setae; ischium and merus 0.7-0.65 basis width, ischium with 1 ventral seta; merus with 1 distoventral seta; carpus slightly narrowing and curving midlength, length 10.7 width, with 2 dorsal small setae. Propodus with 2 dorsal and 2 distoventral setae, dactylar claws third of dactylus length, with 2 long setae proximally. Pereopod 2 ( Fig. 13 View FIGURE 13 b) length 1.63 pereopod 1 length, length ratios of ischium–dactylus to basis: 0.53, 0.48, 1.38, 1.59, 0.57; basis length 3.6 width, with 1 dorsal broom seta; ischium with 6 ventral setae; merus with 1 distodorsal and 1 distoventral setae; carpus length 6.74 width, with 4 ventral UB setae, 1 small UB seta and 2 small simple setae dorsally. Propodus length 12.5 width, width 0.6 carpus width, with 11 ventral UB setae, distoventral seta twice as long as the others, 3 dorsal simple setae and, distodorsal UB seta. Dactylar claws length 0.4 dactylus length. Pereopods 3 and 4 broken off; basis 3 ( Fig. 13 View FIGURE 13 c) length 4.41 width, basis 4 (with oostegite, Fig. 13 View FIGURE 13 d) length 4.57 width, length 1.05 basis 3 length.

Pereopods 5–7 ( Fig. 14 View FIGURE 14 ): pereopod 5 ( Fig. 14 View FIGURE 14 a) length 1.03 pereopod 1 length, length ratios of ischiumdactylus to basis: 1.0, 0.36, 1.38, 1.0, 0.45; basis with 3 small ventral setae and 1 long dorsal UB seta, ischium with 4 dorsal plumose setae, merus with1 distoventral UB seta; carpus length 1.26 width, with 26 dorsal and 10 ventral plumose setae, propodus length 1.5 width, with 12 dorsal and 10 ventral plumose setae, dorsal margin with serrate fringe of setulae distodorsally with 1 long stout UB seta and 1 broom seta, dactylus length 2.7 width, with serrate dorsal and distoventral margins. Pereopod 6 ( Fig. 14 View FIGURE 14 b) length 1.05 pereopod 5 length, basis slightly longer (1.25) than basis of pereopod 5, length ratios of ischium-dactylus to basis: 0.86, 0.28, 1.10, 0.80, 0.36; basis with 2 small ventral setae and 2 distoventral UB setae, merus without setae; carpus length 1.2 width, with 24 dorsal and 11 ventral plumose setae, propodus length 1.50 width, with 11 dorsal and 9 ventral plumose setae, distodorsal margin with 1 long stout UB seta and 1 broom seta, dactylus length 3.75 width, with serrate dorsal margin, 2 small distal setae. Pereopod 7 ( Fig. 14 View FIGURE 14 c) length 0.63 pereopod 6 length, length ratios of ischium–propodus to basis: 0.75, 0.32, 1.15, 0.73, 0.32; basis with 1 distoventral seta, ischium with 1 ventral and 2 dorsal plumose setae, carpus length 1.09 width, with 16 dorsal and 6 short ventral plumose setae, propodus length 1.75 width with 6 dorsal and 6 ventral plumose setae, dactylus length 2.3 width.

Pleopod 2 operculum ( Fig. 10 View FIGURE 10 c) tapering distally to narrow tip, length 1.4 width. Pleopods 3–5 ( Fig. 15 View FIGURE 15 ): Pleopod 3 ( Fig. 15 View FIGURE 15 a) endopod length 1.75 width, distal plumose setae length about third of endopod length; exopod length 1.65 endopod length, exopod width 0.40 endopod width, distal article length 0.45 proximal article length, with 2 plumose setae and small simple seta distally. Pleopod 4 ( Fig. 15 View FIGURE 15 b) endopod length 1.87 width, exopod subequal to endopod in length width 0.5 endopod width, distally with 1 plumose seta slightly longer than setae on pleopod 3. Pleopod 5 ( Fig. 15 View FIGURE 15 c) length 1.7 width.

Uropod ( Fig. 15 View FIGURE 15 d) 0.09 pleotelson length. Protopod as long as wide, with 1 distal seta; endopod length 1.9 protopod length, with 3 simple and 5 broom setae distally; exopod 0.6 of endopod length and 0.5 width, with 2 broom and 2 simple setae distally.

Remarks. Tytthocope longitelson sp. nov., T. megalura and T. fahrbachi sp. nov. are closely related. These all have a serrate rostral margin and a short pereonite 7. T. longitelson sp. nov. differs from the above mentioned two species due to the shape of its rostrum, which has a broad base and a relatively small article 1of the antennula. The new species is also different because of its short pereonite 5, which is as long as the ambulosomites, as well as its extremely short pereonite 7. The pleotelson of the new species is broader and longer than in the other species and has an acute posterior tip (compare Fig. 30 View FIGURE 30 ), a raised anteromedial margin of the pereonite 5 and the pleotelson. The maxilliped of the new species has an intermediate shape (compared to the two other species): article 3 has a more rounded distomedial margin, the medial margin of article 3 is less serrate in the new species compared to T. fahrbachi sp. nov., and the distomedial lobe of article 4 is longer than in the other two species. It has 3 coupling hooks like in T. megalura instead of 5 in T. fahrbachi sp. nov.

Distribution. The Weddell Sea, at 1584 m depth.