Rostrocalanus cognatus, Markhaseva & Schulz & Arbizu, 2008
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publication ID |
https://doi.org/ 10.1080/00222930802254771 |
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persistent identifier |
https://treatment.plazi.org/id/03A087E4-FF95-346B-FD91-3E2509E4692E |
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treatment provided by |
Felipe |
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scientific name |
Rostrocalanus cognatus |
| status |
sp. nov. |
Rostrocalanus cognatus sp. nov.
( Figures 4–6 View Figure 4 View Figure 5 View Figure 6 )
Material examined
Holotype. Adult female, dissected, body length 1.80 mm ( ZMH K-41626); tropical Atlantic, 22 ° 20 9 S, 003 ° 18 9 E, station 318, 9 July 2000, above the seabed at a depth of 5125 m. GoogleMaps
Paratypes. Three adult females, dissected, body length 1.75–1.90 mm ( ZMH K- 41627), 17 ° 06 9 S, 004 ° 42 9 E, station 344, 25 July 2000, above the seabed at a depth of 5415 m GoogleMaps . One adult female, undissected, in poor condition, body length 1.75 mm ( ZIN 91089), 18 ° 19 9 S, 004 ° 40 9 E, station 338, 22 July 2000, above the seabed at a depth of 5397 m GoogleMaps .
Description
Adult female, total length 1.75–1.90 mm; prosome 3.4–3.8 times as long as urosome. Rostrum ( Figure 4C, D View Figure 4 ) large, as rounded plate without filaments. Cephalosome ( Figure 4A, B View Figure 4 ) and pediger 1 fused, pedigers 4 and 5 incompletely separate; posterior corners ( Figure 4E, F, K–N View Figure 4 ) rounded in lateral view and extending approximately half way along genital double somite. Spermathecae ( Figure 4E–N View Figure 4 ) with distal part oval-shaped and directed anterodorsally. Genital double somite and urosome somites 2 and 3 with fringe of spinules on posterior border. Urosome and caudal rami with scattered spinules on dorsal, lateral and ventral sides. Caudal rami ( Figure 4G View Figure 4 ) with four terminal, one dorsolateral and one small ventral seta.
Antennule reaching posterior border of pediger 3. Antennule ( Figure 6A–C View Figure 6 ) of 24 free segments, armature as follows: I 3s, II–IV 6s+1ae, V 2s+1ae, VI 2s, VII 2s+1ae, VIII 2s, IX 2s+1ae; X–XI 4s+1ae, XII to XIII 1s each; XIV 2s+1ae, XV 1s, XVI 2s+1ae, XVII to XIX 1s each, XX 2s, XXI 1s+1ae, XXII to XXIII 1s each, XXIV to XXVI 2s each, XXVII–XXVIII incompletely separate with 2s and 3s+1ae respectively.
Antenna ( Figure 5A View Figure 5 ), coxa without seta, basis with one small vestigial seta; endopodal segment 1 with one seta, endopodal segment 2 with 13 setae; exopod seven-segmented with 0, 3, 1, 1, 1, 0 and 3 setae.
Mandible ( Figure 5B–E View Figure 5 ), gnathobase with keel, cutting edge with four to five teeth, one fork-like with three points; exopod of four segments with 1, 1, 1 and 1 seta; endopod segment 1 without seta, endopod segment 2 with six setae; basis with two setae, one very small.
Maxillule ( Figure 5F View Figure 5 ), praecoxal endite with nine terminal elements including four thick, long and three small and slender spines plus two setae proximally; coxal endite with two setae, coxal epipodite with three to four setae, or setae absent (left limb of holotype); proximal basal endite with two setae, distal basal endite fused to endopod and bearing five setae; exopod with five setae.
Maxilla ( Figure 5G View Figure 5 ), proximal praecoxal endite with one seta and small attenuation, distal with three setae; proximal and distal coxal endites with three setae each; proximal basal endite with four setae, endopod indistinctly threesegmented, with six long and slender, worm-like sensory setae.
Maxilliped ( Figure 6D View Figure 6 ), syncoxa without seta on proximal praecoxal endite, one seta on middle endite, and two setae on distal praecoxal endite; coxal endite with two setae; all setae of praecoxal endites poorly sclerotized but not aesthetasclike; basis with two medial setae; endopod five-segmented with 3, 2, 2, 3+1 and 4 setae.
P1 ( Figure 6E, F View Figure 6 ), basis without medial distal seta; endopod one-segmented with three medial and two terminal setae; lateral lobe poorly developed and ornamented with spinules along lateral margin; exopod three-segmented, segment 1 with lateral spine, segment 2 with lateral spine and medial seta, segment 3 with lateral spine, three medial setae and terminal spine. All lateral spines very long, with spine of segment 2 slightly longer than other.
P2 ( Figure 6G View Figure 6 ), coxa with medial seta; basis without spinules on posterior surface; endopod two-segmented, segment 1 with one medial seta, segment 2 with two medial, two terminal and one lateral setae and bearing spinules on posterior surface; exopod three-segmented, segments 1 and 2 with lateral spine and medial seta each, segment 3 with three lateral spines, four medial setae and terminal spine.
P3 ( Figure 6H View Figure 6 ), coxa with medial seta; basis without spinules on posterior surface; endopod three-segmented, segments 1 and 2 with one medial seta each, segment 3 with two medial, two terminal and one lateral setae; segment 3 with scattered spinules on posterior surface; exopod three-segmented, segments 1 and 2 with one lateral spine plus one medial seta each, segment 3 with three lateral spines, four medial setae and terminal spine.
P4 ( Figure 6J, K View Figure 6 ) with scattered spinules on posterior surface; coxa with medial seta; endopod three-segmented, segments 1 and 2 with one medial seta each, segment 3 with two medial, two terminal and one lateral setae; exopod three-segmented, segments 1 and 2 with lateral spine and medial seta each, segment 3 with three lateral spines, four medial setae and terminal spine.
P5 ( Figure 6L View Figure 6 ) uniramous, symmetrical, two-segmented; coxae without spinules; distal segment more than twice the length of coxa, with three spine-like unarticulated extensions terminally.
Male unknown.
Etymology
The specific name is derived from the Latin cognatus meaning similar, and refers to the general resemblance of this species to the type species of the new genus.
Remarks
Rostrocalanus cognatus differs from the type species by: (1) posterior corners rounded (vs pointed in R. peracutus ) and shorter than in R. peracutus ; (2) urosomites and caudal rami with scattered spinules on dorsal, lateral and ventral sides (without spinules in R. peracutus ); (3) setation of antennule segments XXVII–XXVIII: 5s+1ae (4s+1ae in R. peracutus ); (4) cutting edge of mandible bearing fork-like tooth with three points (with four points in R. peracutus ); (5) maxillule praecoxal endite with four thick and three small and slender spines (five thick spines and four soft aesthetasc-like setae in R. peracutus ); (6) maxillule exopod with five setae (six setae in R. peracutus ); (7) maxilla proximal praecoxal endite with one seta and small attenuation (one seta without attenuation in R. peracutus ); (7) P1 basis without medial distal seta (this seta present in R. peracutus ); (8) endopod lateral lobe poorly developed bearing spinules along lateral margin (lateral lobe well developed, rounded, bearing spinules on distolateral margin in R. peracutus ); (9) outer spine of P1 exopod segment 2 slightly longer than other spines of exopod (in R. peracutus spine on segment 2 intermediate); (10) basis of P2 and P3 without scattered spinules on posterior surface (present in R. peracutus ); (11) P5 coxa without spinules (only left coxa with spinules in R. peracutus ).
An additional single female of Rostrocalanus cf. cognatus was found in sample 016–10 collected by RV Polarstern during the ANDEEP III expedition at depths of 4469–4725 m (41 ° 08 9 S, 009 ° 56 9 E), collected on 26 January 2005. The precise affiliation to the species could not be verified because of its poor condition GoogleMaps .
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