Schornikovoecia eugenyi, a novel species and genus of deep benthopelagic halocyprids (Ostracoda, Myodocopa) from the North-west Pacific Author Chavtur, Vladimir G. Author Bashmanov, Alexander G. text Zootaxa 2018 2018-12-05 4527 2 197 210 journal article 27859 10.11646/zootaxa.4527.2.3 83e54f98-3c98-47fc-81bd-0996bcfbc974 1175-5326 2612104 3A906EF4-2712-4E8B-B5B3-94344B8E4EE8 Schornikovoecia eugenyi sp. nov. Chavtur, 2018 ( Figs. 2–8 ) Etymology. The species, like the genus, is named to honour of the famous late ostracodologist Eugeni Ivanovich Schornikov, who worked at the Institute of Marine Biology, Far Eastern Branch of Russian Academy Sciences, Russia . Holotype . MIMB 18357 /1 – adult female ( 3.91 mm ), appendages mounted on slide ( MIMB 18357 /1–1) and valves in alcohol ( MIMB 18357 /1–2). Deposition at the Collection of the Museum of National Scientific Center of Marine Biology, Russia . Type-locality . RV Sonne , St. 223/009–12; 40°34.49’– 40°34.28’N , 150°59.85’– 150°59.18’E ; 5399– 5392 m ; 24 August 2012 . Paratypes . MIMB 18357 /2 – adult female (4.0 mm) , RV Sonne , St. 223/001–11, 30 July 2012 ; MIMB 18357 / 3 – adult female ( 3.85 mm ) , RV Sonne , St. 223/007–10, 7 August 2012 ; MIMB 18357 /4 – adult male ( 4.02 mm ) , RV Sonne , St. 223/002–10, 3 August 2012 ; MIMB 18 357/5 – adult male ( 4.16 mm ) , RV Sonne , St. 223/007–10, 7 August 2012 . Description of female. Carapace ( Figs. 2 , 3 A–C). Length 3.76–4.0 mm ( holotype – 3.91 mm , paratype – 4.0 mm), height is about 44–45% of length. Antero-ventral and postero-ventral corners well-rounded, and dorsal margin nearly straight. Postero-dorsal corner of both valves armed with a sharp point, which carries four or five denticles. Large left and right asymmetrical glands have sclerotized capsules near their openings and are located beneath the postero-dorsal points. Along the posterior margin of each valve, a single row of dentate structures extends from immediately below the gland opening to the antero-ventral corner. These dentate structures diminish in size ventrally and have either straight or rounded tips. Each rostrum is large, straight, and pointed and projects about 18–19% of carapace length beyond the anterior margin. Rostral incisures extend beyond the anterior margins of the valves. Carapace sculpture looks like vertical and oblique rows of narrow, elongated “scales” covering all over the carapace surface (see Figs. 2 , 3A ). Frontal organ. Absent. First antenna ( Fig. 3D, E ). Elongate, consisting of five visible segments. As typical in the subfamily, dorsally, the fourth segment bears distally a large plumose seta and ventrally an oval cluster of sensory filaments consisting of numerous (perhaps 10–12) rows of about 25–30 filaments per row, in total of 250–300 filaments. Fifth segment is small but carries a principal seta and three shorter setae, which distally become so weak and flabby that they are hard to distinguish from cluster setae on fourth segment. Each first antenna with a row of long setules on ventral surface of second segment. First and second segments contain numerous small, dark pigment granules. Second antenna ( Fig. 3F, G ). Basal segment of endopodite bears distally two unequal setae, the longer of which has short setules. Second endopodite segment with three typical distal setae and three shorter filament-like setae located above. Mandible ( Fig. 4 A-D). Coxale with a strongly sclerotized knob-like articular process near the base of coxale endite. Coxale endite with nine blunt teeth on its tooth edge, of which the terminal four are barely visible. Proximal and distal tooth lists fused into a single list of 10 blunt teeth. Masticatory pad almost spherical: ventral half densely covered with short spines and dorsal surface with numerous minute flabby denticles. Basale endite with a row of six usual-form triangular teeth and similar outer tooth, a small tube-like seta (it leans on adjacent triangular tooth) and a short spine-like seta. Basale similar to that in male (see Fig. 7A ) with three dorso-distal plumose setae, one long bare seta near insertion of endopodite, a densely plumose seta on epipodial appendage, and three long and one short setae on basale endite. First endopodite segment with one disto-dorsal seta and three setae on ventral surface (one of them long and stout, and two other ones shorter and slimmer). Second segment lacks ventral setae but dorsally with a long distal claw-like seta and two slim shorter setae closely adjacent to its base. Third segment bears seven terminal setae: three long and stout ones and four shorter and more slender setae. Maxilla ( Fig. 4E, F ). Anterior margin of the first endopodite segment with group of four long setae near its base (all setae proximally armed with stiff setules set in pairs) and with single seta distally. Posterior edge with single basal seta (with double setules on its proximal half), and distally a group of five setae. All setae on first endopodite segment armed with setules that are long proximally and shorter distally, a total of 11 setae. Second segment with two claw-like setae and two pairs of typical setae. Fifth limb ( Fig. 5 A–C). Setae of the epipodial appendage arranged in groups of four (plus another that is short and slim), four and four plumose setae. Precoxa with three plumose setae. Coxale with 12 setae (five of which are plumose) and two claws. Basale ( Fig. 5A ) with nine typical setae and a cluster of seven moderately long slender setae placed distally on its dorsal surface, near the base of exopodite, represented by an extremely long and bare seta, that reaches almost tips of terminal setae ( Fig. 5C ). Proximal third of basale surface is covered with fine long setules. First endopodite segment has nine dorsal slender setae and three typical ventral setae. Ventral and proximodorsal surfaces of segment covered with fine long setules. Second segment has three claw-like terminal setae; central one is stronger and slightly longer than the dorsal and especially ventral setae. Sixth limb ( Fig. 5D, E ). Epipodial appendage with three groups of setae arranged in a pattern of six (plus another short and slim seta), five and five plumose setae. Precoxale and coxale with three setae each. Basale with five ventral setae and a lateral one. All 12 setae are plumose. Exopodite represented by extremely long, bare dorsodistal seta. First endopodite segment with five ventral setae and five dorsal setae. Second segment with two ventral and six dorsal setae. Limb surface covered with fine long setules. Similar to the fifth limb, terminal segment armed with three setae, of which the central one is stronger and slightly longer than dorsal and especially ventral setae. Seventh limb ( Fig. 5F, G ). Elongate and slender, with two terminal setae (one of them much longer than other). The lengths of shorter seta on the right and left seventh limbs are different. Caudal furca ( Fig. 5H, I ). Each lamella has eight slim and weak claws. First claw is six-jointed. Distance between 2 nd and 3 rd lamellae on caudal furca is different. There is a long unpaired seta behind the claws. FIGURE 2. Schornikovoecia eugenyi sp. nov. (Adult female: SO223/001-11, length 4.0 mm). A, carapace; B, sculpture pattern of carapace. FIGURE 3. Schornikovoecia eugenyi sp. nov. (Adult female: A, paratype MIMB 18357/2; B–G, holotype). A, right valve of carapace in lateral view; B and C, details of carapace: posterior dorsal corners in interior and exterior views; D, first antenna; E, distal part of first antenna; F, endopodite and first exopodite segment of second antenna; G, distal part of endopodite of second antenna. FIGURE 4. Sc hornikovoecia eugenyi sp. nov. (Adult female: A, B, D–F, holotype; C, paratype MIMB 18357/3). A and B, basal endite of mandible from inside and outside; C and D, coxal endite of mandible; E, maxilla (endites are not shown); F, proximal part of fifth limb. FIGURE 5. Schornikovoecia eugenyi sp. nov. (Adult female: A–I, holotype). A, basal segment of fifth limb; B, endopodite of fifth limb; C, endopodite of fifth limb (most setae are not shown, except for the longest one (vestige of the exopodite) on the basal segment and the terminal setae); D, sixth limb; E, precoxal endite of sixth limb; F and G, right and left seventh limbs; H and I, right lamella of caudal furca and part of left one. FIGURE 6. Schornikovoecia eugenyi sp. nov. (Adult male: A, B, D–F, H, J, paratype MIMB 18357/4; C, G, I, paratype MIMB 18357/5). A, left valve of carapace in lateral view; B, carapace in ventral view; C, first antenna; D, shaft of first antenna; E, distal part of first antenna; F and G, second and third (clasping organ) segments of endopodites of right and left second antenna; H, another view of right clasping organ (without setae); I, coxal endite of mandible; J, tooth edge and fused tooth lists of coxal endite of mandible. FIGURE 7. Schornikovoecia eugenyi sp. nov. (Adult male: A–D, paratype MIMB 18357/4; E, F, paratype MIMB 18357/5). A, mandible; B, masticatory pad of mandible coxale; C, sixth limb; D, precoxal endite of sixth limb; E, caudal furca (claws are broken) and copulatory appendage (without microglass). FIGURE 8. Schornikovoecia eugenyi sp. nov. Carapace of A-1 juvenile (3.03 mm) in ventral view (St. 223/008-12; see Table). Description of male. Carapace ( Fig. 6A, B ). Lengths are 4.02, 4.16 mm ( paratypes ), height is about 42% of length. Carapace details are similar to those of female. First antenna ( Fig. 6 C–E). Similar to that of female. As in female, first to fourth segments contain numerous black pigment granules. The ratio of lengths between first and second segments differ in the two imvestigated males ( Fig.6C, D ). Second antenna ( Fig. 6 F–H). Second endopodite segment bears two long setae distally (broken in both males) and two small slender pegs near the base of clasper. Another peg is located near the base of setae. Clasping organ formed by the third endopodite segment and its distal appendage, sharply curved back near its base. Three setae located at the base of the appendage are broken in both males. Right clasping organ large (see Figs 6F, H ), left one much smaller ( Fig. 6G ). Mandible ( Figs. 6I , J ; 7A, B ) and maxilla . Similar to those of female. Fifth limb. Similar to that of female, but cluster on the basale consists of five or six moderately long, slender setae (seven ones in the holotype ; see Fig. 4A ) and ventral surface of first endopodite segment bears seven or eight setae (nine in the holotype ; see Fig. 4B ). Sixth limb ( Fig. 7C, D ). Similar to that of female, but second endopodite segment with five dorsal setae (six ones in the holotype ; see Fig. 4D ). Terminal dorsal setae on third segment relatively longer than in female (see Fig. 4D ). Copulatory appendage ( Fig. 7E, F ). Elongate, almost straight, slim and rounded at the tip. No muscle bands visible. Caudal furca ( Fig. 7E ). The claws are broken. Distribution. The only member of the genus, Schornikovoecia eugenyi sp. nov. , was found in the northwestern Pacific between 40°–46°N, 150°–157°E at depths ranging from 4469 to 5419 m , and also in the Sea of Okhotsk in the area 48°N, 150°E at a depth of 3366 m (see Table 1 ).