Bradyidius kurilokamchaticus, Markhaseva & Renz, 2021

Markhaseva, Elena L. & Renz, Jasmin, 2021, Description of three new species of Bradyidius (Copepoda: Calanoida), the new aetideids from the deep Pacific Ocean, with notes on the genera Bradyidius and Aetideopsis, Zootaxa 5004 (2), pp. 343-369 : 354-358

Bradyidius kurilokamchaticus sp. nov.

( Figs 7–9 )

Holotype. Adult female, dissected, body length 2.50 mm. SMF 37268/1-3 (slides) and 37269 (vial) (Senckenberg). Collected above the sea bed in the Pacific Ocean, Kurile-Kamchatka Trench at Sta. 2–10, 46° 14.76’ N 155° 32.81’ E, on 3 August 2012 by the KuramBio 1 expedition, Sonne cruise SO 223, at a depths of 4859 m.

Paratype. One adult female, partly dissected, body length 2.55 mm. ZIN, 91151. Collected above the sea bed in the Kurile-Kamchatka Trench at Sta. 9–12, 40°34.49’ N 150°59.85’ E on 24 August 2012 by the KuramBio 1 expedition, Sonne cruise SO 223, at a depth of 5399 m .

Additional material. One adult female in a very poor condition, dissected, body length 2.40 mm, same label data as for the holotype.

Description. Female. Body length 2.40–2.55 mm. Prosome 4.02 times as long as urosome ( Fig. 7A–B ). Rostrum two-pointed, not divergent in holotype ( Fig. 7C, E ), abnormal in paratype ( Fig. 7D, F ). Cephalosome and pedigerous somite 1 and pedigerous somites 4–5 incompletely separate; posterior corners prolonged into short points, reaching the posterior third of the genital double-somite ( Fig. 7A–B, G–J ). Urosome of 4 somites. Genital double-somite symmetrical, with lateral swellings in its anterior half (dorsal view) ( Fig. 7G–J ). Spermathecae narrow-elongate and oval (holotype), or oval-widened in the distal part ( Fig. 7G, I ). Caudal rami with 1 lateral seta, 1 ventral seta, and 4 terminal setae ( Fig. 7G–J ).

Antennule broken in all specimens, armature of the ancestral segment I as: 3s in holotype and 2s in paratype, armature of retained ancestral segments from II to XIV given after holotype and of ancestral segments XV–XVII after paratype as follows: II–IV–6s+1ae, V –2s+1ae, VI–2s, VII–2s+1ae, VIII and IX–2s each, X–XI–4s, XII and XIV–2?, XV–1s+1?, XVI–2s+1ae, XVII–1s+1?.

Antenna ( Fig. 8A ), after holotype, coxa with 1 seta, basis with 2 setae; exopod of 8 segments, setation formula 1,1-1-1, 1, 1, 1, 1, 1, and 3 setae, endopod segment 1 with 2 setae, endopod segment 2 with 7+7 setae.

Mandible ( Fig. 8B–C ), after holotype, gnathobase with 7 teeth; basis with 2 setae; exopod 5-segmented with 1, 1, 1, 1, and 2 setae; endopod segment 1 with 2 setae, segment 2 with 9+2 setae.

Maxillule, after holotype, praecoxal arthrite with 9 terminal spiniform setae, 4 posterior and 1 anterior setae, coxal endite with 5 setae; coxal epipodite with 7 long+2 short setae; proximal basal endite with 4 setae, tubercle is hardly visible, distal basal endite with 5 setae; endopod with 16 setae; exopod with 10 setae.

Maxilla, after types and additional specimens, praecoxal to basal endites with 3 setae each, all endites decorated with denticles; enditic-like lobe of proximal endopod segment with 3 setal elements, two thicker, spine-like; endopod in holotype with 8 (2+1+2+3) setae (setae partly broken), in paratype and in additional specimen with 9 setae (2+2+2+3).

Maxilliped, after holotype, syncoxa with 1 seta on proximal praecoxal endite, 2 setae on middle praecoxal endite and 3 setae on distal praecoxal endite; coxal lobe with 3 setae and conical tubercle with a deep notch. Basis with 3 setae. Endopod 6-segmented with 2, 4, 4, 3, 3+1, and 4 setae, first segment very small and fused to basis.

Legs. P1 ( Fig. 8D–F ), coxa with lateral spinules at the left leg in holotype and at the both legs in paratype, in holotype right coxa with projection ( Fig. 8D ), which might be an abnormality, left coxa in holotype and both coxae in paratype and additional specimen without projection; basis with medial distal seta curved with setules; endopod 1-segmented with lateral lobe, its lateral margin with spinules, anterior segment surface with distal spinules; exopod segment 1 with lateral setiform spine and segments 2 and 3 with 1 lateral spine each; lateral setiform spine of exopod segment 1 not reaching the base of exopod segment 2 lateral spine.

P2–P4 ( Fig. 9A–D ), P2–P4 coxa with 1 medial seta, at P2–P3 also with lateral spinules; basis without seta; endopod 2-segmented in P2, 3-segmented in P3–P4; posterior surface spinules present on P2 endopod segment 2; P3 endopod segments 2 and 3 and P4 endopod segments 1–3.

P5 absent.

Male unknown.

Type locality. 46° 14.76’ N 155° 32.81’ E

Etymology. The species name “ kurilokamchaticus ” refers to the type locality, in the Kurile-Kamchatka Trench.

Remarks. The new species Bradyidius kurilokamchaticus sp. nov. shares with B. curtus , B. pacificus and B. arnoldi a rostrum with nondivergent or parallel points while the rostrum has divergent points in the other congeners. The size of the new species (2.50–2.55 mm) is close to the size of B. curtus (2.80–2.90 mm), but B. kurilokamchaticus sp. nov. is smaller than B. pacificus (4.40–4.50 mm) and larger than B. arnoldi (1.67 mm). Additionally to the larger size, the new species is distinguished from B. arnoldi by the well-developed exopod segment 1 lateral setiform spine (vs lateral spine is rudimentary in B. arnoldi , see Fleminger,1957: figs. 1–13) and length of terminal spine of P2 exopod segment 3, which is as long as segment in B. kurilokamchaticus sp. nov (vs 1.5 times longer P2 exopod segment 3 in B. arnoldi ). Bradyidius kurilokamchaticus sp. nov. differs from B. curtus and B. pacificus in the armature of antenna exopod segment 1, that possesses 1 seta (vs seta absent in B. curtus and B. pacificus ), and from B. curtus also in the longer points of the prosome posterior corners, reaching the posterior third of the genital double-somite (vs points of posterior corners hardly extending the anterior third of the genital double-somite in B. curtus ) ( Fleminger, 1957; Markhaseva, 1996 and personal data herein).

Figures

FIGURE 7. Bradyidius kurilokamchaticus sp. nov. Female. A, habitus, dorsal view; B, habitus, lateral view; C, rostrum, lateral view; D, rostrum, lateral view; E, rostrum, ventral view; F, rostrum, ventral view, abnormal; G, posterior prosome and urosome, lateral view; H, urosome, dorsal view; I, posterior prosome and urosome, lateral view; J, posterior prosome and urosome, dorsal view. Scale bars: A–B 0.5 mm, C–H 0.1 mm. A–C, E, G–H, holotype, D, F, I–J, paratype.

FIGURE 8. Bradyidius kurilokamchaticus sp. nov. Female. A, antenna; B, mandible; C, mandible, gnathobase; D, P1; E, P1, exopod segment 1 lateral spine; F, P1, exopod segment 1 and exopod segment 2 lateral spines. Scale bars: 0.1 mm. A–E, holotype; F, paratype.

FIGURE 9. Bradyidius kurilokamchaticus sp. nov. Female, holotype. A, P2; B, P3; C, P4, terminal spine; D, P4, without terminal spine. Scale bars: 0.1 mm.