Zosime carsteni, Pointner, 2017

Pointner, Karin, 2017, Description of two new species of Zosime (Copepoda: Harpacticoida: Zosimeidae), including remarks on its phylogeny and distribution on the Great Meteor Seamount plateau (North-east Atlantic Ocean), Journal of Natural History (J. Nat. Hist.) 51 (37 - 38), pp. 2283-2330 : 2288-2302

Zosime carsteni sp. nov.

( Figures 2 – 11 )

Type locality

Plateau of the GMS, subtropical north-eastern Atlantic (30.0°N, 28.5°W); sediment type: biogenic carbonate sediment, water depth: 284 – 339 m.

Type material

Holotype: female, #3-98-5, undissected, 1 slide, coll. no. SMF 37084/1 ; Paratype 1: male, #3-98-4, undissected, 1 slide, coll. no. SMF 37085/1 . Paratype 2: female, #2-92-4, dissected, mounted on 11 slides, coll. nos. SMF 37086/1 – 11 . Paratype 3: male, #3-98-6, dissected, mounted on 8 slides, coll. nos. SMF 37087/1 – 8 . Paratype 4: male, #8-102-4, dissected, mounted on 3 slides, coll. nos. SMF 37088/1 – 3 .

Etymology

Zosime carsteni sp. nov. is affectionately dedicated to Carsten Richter, Emden, Germany.

Description of female

Habitus ( Figure 2 (a,b)). Prosome clearly wider than urosome, dorso-ventrally compressed. Body length measured in dorsal view, from tip of rostrum to end of caudal rami and excluding setae, 551.6 – 697.6 µm (average: 595.4 µm, n = 8). P1-bearing somite fused with cephalosome to form cephalothorax, covered with several sensilla and small, round, irregularly distributed depressions (see inset in Figure 2 (a)). Rostrum fused to cephalothorax, rounded in dorsal view ( Figure 2 (a)), triangular in lateral view ( Figure 2 (b)). Postero-dorsal margins of all somites (except for anal somite) with cuticular processes of different size: cephalothorax, all prosomites and first urosomite with bigger processes than following urosomites. Anal somite not visible in dorsal view, covered by pseudoperculum of penultimate abdominal somite. Each somite with small number of setules and scales, three free prosomites with distal row of minute spines ventro-laterally. Urosomites two and three not fused in dorsal and lateral view, but in ventral view forming genital double-somite ( Figure 7 (b)). Pseudoperculum ( Figure 2 ) composed of several irregular cuticular extensions. Posterior margin of anal somite with small, lateral spinules visible in lateral view. Anal operculum absent.

Caudal ramus. As in male (see below).

Antennule ( Figure 3 ). Eight-segmented; first segment with one long slender and bipinnate seta and several spinules and setules along anterior margin; second segment with eight setae; third segment with one aesthetasc and 12 setae, aesthetasc fused at basis to large spinous seta, one tiny seta close to pedestal with aesthetasc; fourth segment with two setae; fifth segment with three setae; sixth segment with three setae (one broken), one long and flexible; seventh segment with two setae (both broken); eighth segment with one aesthetasc and seven setae, aesthetasc fused at basis with bipinnate seta. Setal formula: 1-1; 2-8; 3-11 + (1 + aesthetasc); 4-2; 5-3; 6-3; 7-2; 8-6 + (1 + aesthetasc).

Antenna. As in male (see below).

Mandible ( Figure 4 (b)). Gnathobase well developed with four teeth, one of which has two tips, and one short plumose seta. Basis with three apical plumose setae (one broken) and small setules along inner margin. Exopod reduced to small segment with one plumose seta. Endopod with one lateral and three apical plumose setae (one broken).

Maxillule ( Figure 4 (c,cʹ)). Praecoxa with eight stout pinnate spines, one small bare spine on inner edge of praecoxa, one minute bare seta among spines on anterior side, plus two long and slender setae on anterior side. Coxa apically with four slender setae (two bare, two plumose); coxal epipodite with one plumose seta (broken). Basis ( Figure 4 (c ʹ )) with seven setae (two broken), two plumose, others bare, and with minute spinules on inner margin. Both exopod and endopod one-segmented: exopod with three plumose setae and with small spinules on inner margin; endopod with six plumose setae (one broken).

Maxilla ( Figure 4 (d)). Syncoxa with three endites. Proximal (praecoxal) endite bilobed, with three setae on each lobe; proximal lobe with one bare and two pinnate setae, armed with several spinules; distal lobe with one pinnate and two bare setae. Middle coxal endite with three setae (two pinnate and one bare). Distal coxal endite with three setae (two bare and one pinnate but with bare tip). Basis with two claws, one bare and one serrated, and with three bare slender setae, one arising apically, one subapically, and one situated close to endopod. Endopod twosegmented: enp1 with two setae; enp2 with four setae, all setae slender and bare.

Maxilliped ( Figure 4 (e)). Syncoxa bare, about 1.5 times longer than wide. Basis with one plumose seta. Endopod with one long plumose seta apically and two small bare setae laterally.

P1–P4 ( Figures 5 (a,aʹ,b,bʹ) and 6(a,aʹ,b)). For setal formula see Table 2. Unless otherwise specified, setae plumose and flexible, spines with several overlapping, flat and blunt spinules along margins.

P1 ( Figure 5 (a,aʹ)). Coxa with several rows of spinules. Basis with one outer and one inner seta, armed with long setules on inner margin and several rows of spinules on anterior surface. Exopod three-segmented with spinules on outer margins of exp1 – 3: exp1 with one outer spine and long inner setules; exp2 ( Figure 5 (a ʹ )) with one outer spine and one inner seta; exp3 ( Figure 5 (a ʹ )) with three outer spines, two apical setae, and one inner seta. Endopod two-segmented: enp1 – 2 with outer spinules, inner margin without ornamentation ( Figure 5 (a)); enp1 with one inner seta; enp2 with one inner seta proximally located, with an outer central incision, one subapical seta and two apical elements, one outer spine and one setae.

P2–P4 ( Figures 5 (b,bʹ) and 6(a,aʹ,b)). Coxa with several rows of spinules. Basis with one outer seta, surrounded by minute spinules near its base in P4; basis with inner row of setules, with additional spinules on distal margin between exopod and endopod of P3 and P4. Exopod and endopod three-segmented, each segment more or less as wide as long. P2 exp1 with one outer spine, P3 and P4 exp1 with one outer spine and one inner seta. Exp2 with one outer spine and one inner seta. Exp3 with three lateral spines, two apical (outer margin of innermost pinnate, inner margin plumose), and two inner setae. Outer margin of exp1 – 3 with spinules; inner margin with setules in P2 – P4 exp1 – 2 and P2 exp3. Each segment of exopod with scattered scales on surface. Enp1 – 2 with one inner seta, P2 enp3 with one outer spine and two apical setae, P3 – P4 enp3 with one apical spine, two apical setae and one inner seta. P2 – P3 enp1 with long setules along outer margin; P2 enp2 – 3 with spinules (short and stout, rounded tip); P3 enp2 with setules, enp3 with spinules (slender, pointed tip); P4 enp1 bare, enp2 – 3 with setules. Inner margin of all endopodal segments bare. Intercoxal sclerite wide as in Figure 5 (b).

P5 ( Figure 7 (a)). Outer basal seta long, but still shortest of P5 setae, plumose and flexible, arising from small setophore. Exopod as long as wide, with four setae; three very long and heavily plumose (one broken), outermost seta distinctly smaller, bare and flexible, arising from small lateral projection. Exopod fused to baseoendopod but surface suture still visible anteriorly. Endopodal lobe reaching to half of exopod, with four very long heavily plumose setae, the innermost being shortest. Surface with several rows of scales. Inner margin with small setules distally.

P6 and genital field ( Figure 7 (b)). P6 consists of one plate with three small setae on each side; two setae plumose, innermost one smallest and bare. Copulatory pore covered by cuticular ridge.

Description of male

Habitus ( Figure 8 (a,b)) and most features as in female. Sexual dimorphism observed in body length, antennule, P2, P5 and P6. Body length 553.6 – 652.8 µm (average: 581.6 µm, n = 9).

Caudal ramus ( Figure 9 ). Almost square, about 1.1 – 1.4 times longer than maximum width (average: 1.3×, n = 8), covered with scales, proximal inner margin with spinules, with seven setae: seta I minute, placed lateroventrally about halfway down ramus length; seta II plumose, long and flexible, located at distal third of outer margin; seta III plumose, flexible, slightly longer than seta II; seta IV multipinnate, second longest; seta V distal part flexible, very long (longest); seta VI plumose, shorter than seta II; seta VII bare, tri-articulate at base and arising from minute pedestal, located near inner distal corner, slightly longer than seta II.

Antennule ( Figure 10 ). Subchirocer, seven-segmented, with geniculation between segments four and five: first segment with one plumose seta, several spines and spinules on inner margin; second segment with one long, plumose, flexible seta; third segment with 14 setae, two flexible and bare, one pinnate, rest plumose, seven proximal and seven arising apically from pedestal-like part of segment; fourth segment with one aesthetasc and 12 setae, aesthetasc fused at basis with one pinnate flexible seta; fifth segment with one seta (broken); sixth segment with four setae, of which one minute; seventh segment with one aesthetasc and seven setae, three with knotted basis. Setal formula: 1-1; 2-1; 3-14; 4-11 + (1 + aesthetasc); 5-1; 6-4; 7-6 + (1 + aesthetasc).

Antenna ( Figure 4 (a)). Coxa small and bare. Basis with two rows of setules and one abexopodal plumose seta. Exopod three-segmented: exp1 and 2 each with one lateral plumose seta; exp3 slightly longer than two preceding segments combined, with one plumose seta laterally and one plumose and one multipinnate seta apically. Endopod two-segmented: enp1 with one abexopodal plumose seta; enp2 with three pinnate setae laterally and six multipinnate setae apically, two outermost setae are shown to be spine-like, and another two long and slender. Enp2 also with several proximally and distally minute spinules.

P2 ( Figure 11 (a,aʹ)). Coxa with row of spinules on outer margin and row of minute spinules on inner margin anteriorly located. Basis with outer seta, long setules on inner margin and row of small spinules on anterior surface distally. Exp 1 with long and plumose inner seta and with additional spinules on surface, exp2 with pore close to outer spine, exp3 as in female. Enp1 with inner long and plumose seta. Enp2 as in female except for smaller spinules on outer margin and higher length to width ratio. Enp3 elongate, with one flexible plumose seta on inner margin; apical margin transformed into hook-like apophysis, with one tube-pore and outer margin with row of spinules.

P5 ( Figure 7 (d)). Reduced, fused to somite, left and right leg of P5 confluent. Outer basal seta long plumose and flexible, arising from setophore. Exopod fused to baseoendopod, with three marginal setae (two plumose and one smaller and bare) and one bare surface seta arising from short setophore between outer basal seta and outermost marginal seta. Endopodal lobe rudimentary, with two bare setae and row of minute spinules.

P6 ( Figure 7 (c)). Several scales on anterior surface and three setae; outer seta plumose; middle seta longest, plumose in proximal part, distal part bipinnate; innermost seta smallest, bare.

Intraspecific variability of Zosime carsteni sp. nov

In some male specimens of Zosime carsteni sp. nov., the P2 enp2/enp3 border is hardly detectable. Moreover, one male individual (paratype 3) was armed with two setae close to the apophysis and lacked the tube-pore on the left P2 enp3 ( Figure 11 (b)). This is regarded as an artefact, as all other males of Z. carsteni sp. nov. are armed with only one seta and one tube-pore close to the apophysis. Since it is identical with all other males in all other characters, it was attributed to Z. carsteni sp. nov. and included in the type series as an example of intraspecific variability.

Figures

Figure 2. Zosime carsteni sp. nov., female habitus (holotype): (a) dorsal view, rectangular inset showing detailed surface structure; (b) lateral view. Scale bar: 200 µm.

Figure 3. Zosime carsteni sp. nov., female antennule (paratype 2): general shape and setation of segments 1–8. Scale bar: 50 µm.

Figure 4. Zosime carsteni sp. nov.: (a) antenna (paratype 3, male); (b) mandible (paratype 2, female); (c) maxillule (paratype 2, female); (cʹ) basis of maxillule (paratype 2, female), * marks two broken setae in the background; (d) maxilla (paratype 2 female); (e) maxilliped (paratype 2, female). Scale bar: 50 µm.

Figure 5. Zosime carsteni sp. nov. (paratype 2, female): (a) left P1, anterior (outer basal seta reconstructed from right P1 of same paratype); (aʹ) P1 exp2–3, anterior; (b) female P2, posterior, intercoxal sclerite only partly shown; (bʹ) female P2 enp2–3. Scale bar: 50 µm.

Figure 6. Zosime carsteni sp. nov. (paratype 2, female): (a) P3, anterior; (aʹ), P3 exp2–3, anterior; (b) right P4 (outer basal seta reconstructed from left P4 of same paratype). Scale bar: 50 µm.

Figure 7. Zosime carsteni sp. nov.: (a) female P5 (paratype 2), anterior; (b) female P6 and genital field (paratype 2), ventral; (c) male P6 (paratype 3), anterior; (d) male P5 (paratype 3), anterior. Scale bars: 50 µm.

Figure 8. Zosime carsteni sp. nov., male habitus (paratype 1): (a) dorsal view, rectangular inset showing detailed surface structure; (b) lateral view. Scale bar: 200 µm.

Figure 9. Zosime carsteni sp. nov. (paratype 3): male pseudoperculum, anal somite and caudal rami, dorsal; caudal setae indicated by I–VII. Scale bar: 50 µm.

Figure 10. Zosime carsteni sp. nov., male antennule (paratype 3): general shape and setation of segments 1–7. Scale bar: 50 µm.

Figure 11. Zosime carsteni sp. nov., male: (a) P2 (paratype 4), anterior, arrow indicates tube-pore apically on enp3; (aʹ) P2 exp2–3 (paratype 4), anterior; (b) aberrant P2 endopod (paratype 3), with additional seta close to apophysis. Scale bar: 50 µm.