Emertonia ilse Mathiske & Veit-Köhler, 2021

Mathiske, Annabel, Thistle, David, Gheerardyn, Hendrik & Veit-Köhler, Gritta, 2021, Deep sea without limits-four new closely related species of Emertonia Wilson 1932 (Copepoda: Harpacticoida: Paramesochridae) show characters with a worldwide distribution, Zootaxa 5051 (1), pp. 443-486 : 455-463

Emertonia ilse Mathiske & Veit-Köhler sp. nov.

http://zoobank.org/ urn:lsid:zoobank.org:act:507DF461-3544-4F27-93C4-2E5A4F013E62

Type material. The examined specimens are registered and deposited in the Senckenberg Forschungsinstitut und Naturmuseum Frankfurt, Germany. All specimens of the type material were collected on the continental margin off Chile. Station numbers indicate “Expedition, station number, depth, core number, sediment horizon” .

Female holotype, SMF 37239 (adult female on 1 slide) : RV Sonne 156 C— PUCK, St. 7174, 1,222 m , R3 , 0–1 cm .

Male allotype, SMF 37240 (adult male on 1 slide) : RV Sonne 156 B— PUCK, St. 7167, 2,060 m , R1 , 0–1 cm .

Female paratype 1, SMF 37241 (adult female on 6 slides) : RV Sonne 156 C— PUCK, St. 7177A, 906 m , R4 , 0–1 cm .

Female paratype 2, SMF 37242 (adult female on 2 slides) : RV Sonne 156 B— PUCK, St. 7167, 2,060 m , R1 C, 0–1 cm .

Male paratype 3, SMF 37243 (adult male on 7 slides) : RV Sonne 156 C— PUCK, St. 7177B, 906 m , R3 , 0–1 cm .

Female paratype 4, SMF 37244 (adult female on 5 slides) : RV Sonne 156 C— PUCK, St. 7177C, 906 m , R4 , 0–1 cm .

Male paratype 5, SMF 37245 (adult male on 1 slide) : RV Sonne 156 C— PUCK, St. 7177A, 906 m , R3 , 0–1 cm .

Etymology. This species is dedicated to Ilse Veit-Köhler, mother of Gritta Veit-Köhler, who always encouraged her daughter’s love for nature and animals.

Description of female. Habitus ( Fig. 10A, B ). Total body length measured from anterior tip of rostrum to posterior margin of anal somite (holotype) 0.21 mm, including caudal rami 0.23 mm. Body cylindrical, slightly depressed dorsoventrally, with prosome slightly wider than urosome. Pedigerous somites bearing P2–P4 with middorsal backwardly directed protrusions arising from posterior margin. Pores present in small numbers, distributed dorsally and laterally on cephalothorax and most of free somites. Sensilla visible on cephalothorax and third pedigerous somite. Second and third prosomal somites dorsally ornamented with short row of microspinules. Entire posterior margin of first three urosomites ornamented with spinules. First urosomite with additional spinule row laterally. Fourth urosomite ventrolaterally with same-sized spinules as in preceding somites and minute spinules along entire posterior margin. Fourth urosomite forming thin, well developed pseudoperculum ( Fig. 10A, B ). Anal somite short with minute spinules ventrally and ventrolaterally along posterior margin ( Fig. 10B, C ).

Caudal rami of adult female ( Fig. 10C ) cylindrical, approximately three times longer than wide, with five setae: seta I absent; seta II slender, dorsally displaced; seta III slender with clearly visible inner structure, spine-like, situated dorsolaterally, near posterior end; seta IV shorter and more slender than III; seta V long and slender with clearly visible internal fracture plane, three pinnules in posterior half; seta VI absent; seta VII slender, arising from dorsal surface. Posterior margin of caudal rami with ventral spinule row.

Rostrum ( Fig. 11A ). Small, hyaline, not defined at base; not discernible in dorsal or lateral aspect.

Antennule ( Fig. 12A, B ). Eight-segmented. Armature formula:

I (0)

II (8) eight slender naked setae of different sizes, one of which minute

III (4) four naked setae

IV (1 + 2 aes) one naked seta and two aesthetascs

V (1) one long slender seta with one pinnule

VI (1) one slender naked seta

VII (3) three naked setae, one of which long

VIII [5 + (1 + aes) + aes] six slender setae, two aesthetascs, one of which fused at base with longest slender naked seta with one spinule

Antenna. See male ( Fig. 11B ).

Mandible ( Fig. 11D, E ). Coxa with slender elongate gnathobase ( Fig. 11D ); cutting edge with two large and four smaller teeth. Palp biramous ( Fig. 11E ). Basis asetose. Endopod two-segmented; proximal segment asetose, distal segment apically furnished with four naked, basally fused, slender setae. Exopod one-third length of endopod, one-segmented, with three apical setae.

Maxillule ( Fig. 11F, G ). Praecoxal arthrite with two juxtaposed slender setae on anterior surface. Inner margin of arthrite with five stout spines (two of which shorter than the others) and four additional setae (not all visible in Fig. 11G ). Coxal endite bearing three slender setae. Endite of basis armed with three slender naked setae. Endopod one-segmented, with three slender naked setae. Exopod missing.

Maxilla ( Fig. 11H ). Praecoxa and coxa fused forming syncoxa with three endites. No separation with basis visible. Proximal endite slightly bilobed, with slender, naked seta on either lobe. Middle endite with two slender, naked setae. Distal endite with two slender, naked setae. Allobasis with stout, naked, claw-like spine (no separation from allobasis visible) accompanied by two naked setae. Endopod two-segmented with one naked seta on proximal segment and three naked setae on distal one.

Maxilliped ( Fig. 11I ). Syncoxa and basis unarmed. Endopod one-segmented, with two small spines next to one long naked seta.

Swimming legs ( Fig. 13 ; Table 3). With rami characteristic for Emertonia species belonging to the andeep - group; intercoxal sclerites without ornamentation.

P1 ( Fig. 13A ). Coxa naked. Basis with row of short spinules along inner margin, one pinnate inner seta and one pinnate outer seta. Endopod slightly longer than exopod, both rami two-segmented and, except for exp1, armed with spinules on outer margin. Enp1 unarmed, enp2 terminally with one long inner seta bearing single pinnule, and one shorter, unipinnate, outer seta. Exp1 with one unipinnate outer spine. Exp2 with two unipinnate outer spines and two bipinnate apical setae.

P2–P4 ( Fig. 13B–D ). Surface of coxae naked. Bases of P2–P4 bearing one naked outer seta (accompanied by two spinules in P4). Three-segmented exopods slightly longer than endopods with spinules along outer margin (P2–P4) and terminally (P4). P2–P4 exp1 and exp2 with strong serrated spine; exp2 with two spinules along inner margin in P2, with one spinule situated on pronounced ledge in P3–P4. P2–P3 exp3 with four elements. P2 exp3 with two serrated outer spines and apically one long, naked, spine-like, outer seta and one long, inner seta with one pinnule. P3 exp3 as in P2, but spine-like terminal seta serrated at tip. P4 exp3 with two serrated spines (one short outer and one long terminal). Endopods P2–P3 one-segmented with spinules along outer margin, two short inner rows of fine spinules and an additional terminal spinule row. Endopod P2 bearing one long spinule, positioned on ledge and one subapically on inner margin. Endopods P2–P3 apically with long, rigid bipinnate seta. Endopod P4 two-segmented; armed with spinules along outer margin, one inner spinule on enp1 and several slender inner spinules on enp2; enp2 apically with one short naked, spine-like seta.

P5 ( Fig. 14A ). Baseoendopods fused forming medially cleft plate with naked outer basal seta on either side; completely separated from exopods; with slightly curved spinule rows situated near proximal outer margins. Endopodal lobes with paired halfmoon-shaped spinule rows around outer margins; with one large inner and one slightly smaller outer naked seta. Exopod with several spinules along inner margin and three naked spine-like setae, the innermost being shortest and the outer being the longest seta. The middle seta is more flexible, outwardly directed and situated on a protrusion.

P6 and genital field see Fig. 14B . Sixth pair of legs represented by small fused outgrowths bearing a minute spinous process on either side.

Description of male. Habitus ( Fig. 15 ). As in female but slightly larger and second and third urosomites not fused ( Fig. 15A, B ). Total body length measured from anterior tip of rostrum to posterior margin of anal somite (allotype) 0.23 mm, including caudal rami 0.25 mm. Only third prosomal somite dorsally ornamented with short row of microspinules. Mouthparts and swimming legs as in female, sexual dimorphism in antennule, P5, P6 and urosomal segmentation, in addition to slight differences in armature of caudal rami ( Fig. 15C : seta II very tiny on outer margin, no spinules along apical margin).

Antennule ( Fig. 16 ). Five-segmented. Segment I with spinule row along anterior margin, segment III relatively small, segment IV rounded and bulbous ( Fig. 16B, C ). Armature formula:

I (0)

II (4) four slender naked setae, one of which minute

III (2) two naked setae

IV (5 + aes) one slender naked, one minute and three spine-like ( Fig. 16C ) setae, and one aesthetasc

V (7 + aes) seven slender naked setae, one of which on anterior margin, and one aesthetasc

Antenna ( Fig. 11B ). Basis unarmed. Endopod two-segmented; enp1 with one short naked abexopodal seta; enp2 subapically with three spine-like naked setae, one of which small; apical margin of enp2 with five slender naked setae, two of which geniculate. Exopod one-segmented with one inner pinnate seta, apically with a spine adjacent to two setae of different sizes with transversally cut naked tips.

P5 ( Fig. 14C ). Baseoendopods fused medially; with naked outer basal seta; slightly curved spinule rows situated on either side of basal margin and along posterior margin on endopodal lobes. Exopod discrete at base; with with several spinules along inner margin and three naked setae, two of which spine-like, the innermost being shortest and the outer being the longest seta. The middle seta is flexible, situated on a protrusion and more outwardly directed.

P6 ( Fig. 14D ). Sixth leg represented by small, medially fused plates, each bearing one small, naked inner seta and one slightly larger, naked outer seta.

Figures

FIGURE 10. Emertonia ilse sp. nov. Female (holotype). A, habitus, dorsal view, arrow indicates inserting point of broken-off seta III; B, habitus, lateral view; C, caudal ramus, ventral view. Scale bars = a, b, 0.1 mm; c, 0.02 mm.

FIGURE 11. Emertonia ilse sp. nov. Female: A, rostrum (paratype 1); C, labrum (paratype 2); D, mandibular gnathobase (paratype 4); E, mandibular palp (paratype 4); F, maxillule, disarticulated (paratype 4); G, maxillule (paratype 4); H, maxilla (paratype 4); I, maxilliped (paratype 2). Male: B, antenna (paratype 3). Scale bar = 0.01 mm.Setae that are not clearly discernible indicated by *.

FIGURE 12. Emertonia ilse sp. nov. Female (paratype 1). A, antennule (armature omitted); B, disarticulated antennulary segments showing armature (paratype 1). Scale bar = 0.02 mm.

FIGURE 13. Emertonia ilse sp. nov. Female.A, P1 (paratype 3); B, P2 (paratype 1); C, P3 with intercoxal sclerite (paratype 1); D, P4 (paratype 1). Scale bar = 0.05 mm.

FIGURE 14. Emertonia ilse sp. nov. Female (paratype 1): A, P5; B, P6 and genital field. Male (paratype 3): C, P5; D, P6 (arrow indicates position of broken-off seta). Scale bar = 0.01 mm.

FIGURE 15. Emertonia ilse sp. nov. Male (allotype). A, habitus, dorsal view; B, habitus, lateral view; C, caudal ramus, ventral view. Scale bars = a, b, 0.1 mm; c, 0.02 mm.

FIGURE 16. Emertonia ilse sp. nov. Male (paratype 1).A, antennule (armature omitted); B, disarticulated antennulary segments showing armature. Scale bar = 0.02 mm.