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

Tytthocope longitelson sp. nov.

( Figs 10–15 )

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 ) 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 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 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 ) 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 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 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 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 ): 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 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 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 c) length 4.41 width, basis 4 (with oostegite, Fig. 13 d) length 4.57 width, length 1.05 basis 3 length.

Pereopods 5–7 ( Fig. 14 ): pereopod 5 ( Fig. 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 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 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 c) tapering distally to narrow tip, length 1.4 width. Pleopods 3–5 ( Fig. 15 ): Pleopod 3 ( Fig. 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 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 c) length 1.7 width.

Uropod ( Fig. 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 ), 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.

Figures

FIGURE 10. Tytthocope longitelson sp. nov. Holotype female (ZMH K- 44032). A, body, dorsal view. B, body, lateral view. C, pleotelson with operculum, ventral view. D, natasome, ventral view, pleotelson without operculum.

FIGURE 11. Tytthocope longitelson sp. nov. Holotype female (ZMH K- 44032). mandibles. A, right mandible with enlarged details of distal palp article and incisor. B, left mandible with enlarged details of distal palp article and incisor.

FIGURE 12. Tytthocope longitelson sp. nov. Holotype female (ZMH K- 44032). A, maxilla 2 with details of distal margins of lobes. B, maxilla 1 with details of distal margins of lobes. C, maxilliped, with detail of endite distal margin.

FIGURE 13. Tytthocope longitelson sp. nov. Holotype female (ZMH K- 44032). A, pereopod 1. B, pereopod 2. C, basis of pereopod 3. D, basis of pereopod 4.

FIGURE 14. Tytthocope longitelson sp. nov. Holotype female (ZMH K- 44032). A, pereopod 5. B, pereopod 6. C, pereopod 7.

FIGURE 15. Tytthocope longitelson sp. nov. Holotype female (ZMH K- 44032). A, pleopod 3. B, pleopod 4. C, pleopod 5. D, uropod. E, basis of antenna. F, antennula.

FIGURE 30. Total views of some species Tytthocope A, T. megalura (after Wilson & Hessler, 1981). B, T. fahrbachi. C, T. longitelson. D, T. sulcifrons. E, T. divae.