Synasterope pseudomystax, Chavtur, Vladimir G. & Keyser, Dietmar, 2016

Chavtur, Vladimir G. & Keyser, Dietmar, 2016, Description of new members of the family Cylindroleberididae (Ostracoda: Cylindroleberidoidea) from the Southern Ocean, Zootaxa 4137 (3), pp. 301-329 : 320-328

Synasterope pseudomystax sp. nov.

( Figs. 14–19 )

Etymology. The species name refers to the similarity to S. mystax Kornicker, 1975 .

Holotype. ZMH-K-45824, adult female, length 3.12 mm, appendages are mounted on slide (45824/1) and destroyed valves are preserved in 70 % ethanol (45824/2).

Type locality. R/V “Polarstern”, ANT XIX /3, PS 61, 2002: ZMH-K-45824—adult female (length 3.12 mm), Stat. 43-8-E, 60°26.48´S – 56°4.00´W to 60°27.18´S – 56°4.80´W, depth 3953.6-3962.4 m, 4 February 2002.

Paratype. R/V “Polarstern”, ANT XXII /3, PS 67, 2005:

Stat. 154-9-E: ZMH-K-41911—immature female (2.81 mm).

Material ( Fig. 20 ). R/V “Polarstern”, ANT XIX /3, PS 61, 2002:

Stat. 41-3: ZMH-K-45817 possible—juvenile (1.9 mm);

Stat. 42-2: ZMH-K-41911 possible—juvenile (1.6 mm);

Stat. 46-7: ZMH-K-45818 immature female and juvenile;

RV “Polarstern”, ANT XXII /3, PS 67, 2005:

Stat. 154-9: ZMH-K-41911– immature female (2.81 mm).

Description of adult female.

Carapace ( Figs. 14 and 15 ). Elongate with evenly rounded posterior margin. Length 3.12 mm. Greatest height in middle (44%). Infold behind rostrum with about 10 setae between list and outer margin; only 4 setae on rostral list; anterior infold with about 10 setae; posterior list with about 15 transparent setae and about 15 small setae between adjacent transparent setae. Infold between posterior list and posterior edge of carapace is poorly preserved.

First antenna ( Fig. 16 C–H). 1st joint with lateral terminal sclerotized knob on both outer and inner sides (fig. 16 D, E); 2nd joint with dorsal spinous seta; 3rd joint with very short bare ventral seta and 6 long spinous dorsal setae; 4th joint with 1 short bare and 1 long spinous seta, and 1 long spinous dorsal seta; sensory seta of 5th joint with 6 filaments ( Fig.16 C, I); seta of 6th joint somewhat longer than a-seta of 7th joint. 7th joint: c-seta with 3 long proximal and 1 short distal and 1 terminal filaments; b-, f-, and g-setae broken.

Second antenna ( Fig. 17 A–E). Protopodite with short slender medial seta. Endopodite 3-jointed; 3rd joint with long terminal seta. Exopodite joints without obvious spines.

Mandible ( Figs. 17 F–J, 18 A–D). Coxale endite broken and lost. Basale ( Fig. 18 C, D): endite with 3 terminal spinous setae, 3 triaenid setae, 2 dwarf setae and glandular peg; U-shaped margin depression and short dwarf seta present on basale proximal endite; dorsal margin on right limb with 1 and on left limb without midseta. Exopodite ( Fig. 17 F, H–J) reaching about one-half distance up dorsal margin of 1st endopodite joint, with hirsute tip and 2 short subterminal setae. Endopodite: 1st joint with 3 long spinous ventral setae; ventral margin of 2nd joint with 3 long spinous terminal setae, dorsal margin ( Fig. 18 A, B) with 1–3 proximal setae and stout spinous a-, b-, c- and dsetae; 1 short seta between a- and b-setae; 2 medial setae at margin between b- and c-setae; 5 medial setae forming oblique row between b- and c-setae; 1 long seta between c- and d-setae; 1 long seta near margin distal to d-seta; 3rd joint with pointed dorsal claw and 5 setae ( Fig. 17 G).

Maxilla ( Figs. 18 E, 19A). Epipodial appendage relatively long. Proximal endite with 4 long spinous setae and distal endite with 3 long spinous setae. Dorsal margin of basale with 1 short proximal and 1–2 distal setae; ventral margin with 1 short proximal seta and 1 long terminal seta. Endopodite: 1st joint with short dorsal seta and long ventral seta; 2nd joint with long terminal seta.

Fifth limb ( Fig. 19 B–D). Epipodial appendage with 74 plumose setae. Comb: with long exopodial seta, 3 setae near ventral margin and 6 terminal setae.

Sixth limb ( Fig. 19 E–G). Antero-dorsal corner without seta on medial surface; anterior margin with 1 upper seta; anterior tip without setae, lateral flap with 4 seta; postero-ventral margin with about 20 setae.

Seventh limb. Limb with 20–21 setae, proximal group with 9+7(8) setae and distal group with 2+2 setae.

Caudal furca. Each lamella with 9 claws and setae (1st– 7th claws and 8th and 9th setae).

Medial and lateral eyes ( Fig. 16 A). Medial eye bare, lateral eyes absent.

Rod-shaped organ ( Fig. 16 A, B). 1-jointed with rounded tip.

Description of immature female. Carapace ( Fig. 15 B). Length 2.80–2.81 mm. Similar to that of adult female except a somewhat higher? position of incisur and pattern of central adductor muscle scars.

First antenna, mandible (each limb with 1 midlength seta on dorsal margin on basale), maxilla etc. similar to that of female.

Caudal furca. Each lamella with 8 claws.

Comparison. This species is closely related to S. mystax Kornicker, 1975 but differs from it by size and structure of first and second antenna, mandible, maxilla, fifth and sixth limbs and rod-shaped organ ( Table 7 ).

Distribution. S. pseudomystax was collected from Antarctic waters between 59°–62° S and 56°–64° W at a depth of 2879–3962 m ( Fig. 20 ).

Composition. The genus Bathyleberis includes 8 species of which the following are known from the study area: B. monothrix Kornicker, 1975 , B. oculata Kornicker, 1975 , B. grossmani Kornicker, 1975 , B. babax Kornicker, 1996 (in Kornicker & Poore 1996) .

Distribution. Members of this genus live between 71° N ( Kornicker, 1988) and 61° S ( Kornicker, 1975) and a depth range of 2–4303 m.

1. Sensory seta of 1st antenna with 7 long terminal filaments, anterior margin of 6th limb with 6 or 7 setae....... B. grossmani

– Sensory seta of 1st antenna with 1 short proximal and 6 long terminal filaments, anterior margin of 6th limb with 1 or 2 setae.................................................................................................... 2

2. Lateral eye well developed with about 18 ommatidia; dorsal margin of mandibular basale with 3–4 midsetae...... B. oculata

– Lateral eye absent or, if present, without ommatidia; dorsal margin of mandibular basale with 1 midseta................. 3

3. Rod-shaped organ 1-jointed; anterior margin of 6th limb with 2 setae....................................... B. babax

– Rod-shaped organ 2-jointed; anterior margin of 6th limb with 1 setae.................................. B. monothrix

Figures

FIGURE 14. Synasterope pseudomystax sp. nov. (Immature female—ZMH-K- 41911). A—left valve of carapace in lateral view, B—right valve in inner view, C—rostrum in inner view, D—section of rostrum in inner view, E—anterior infold of right valve, F—posterior infold of right valve.

FIGURE 15. Synasterope pseudomystax sp. nov. (Adult female—ZMH-K- 45824: A, C, D; immature female ZMH-K- 41911). A, B—left valve in lateral view, C—posterior infold of left valve (flaplike setae of posterior list, and processes and setae near postero-ventral margin of valve not shown because of poor preservation), D—anterior infold of left valve.

FIGURE 16. Synasterope pseudomystax sp. nov. (Adult female—ZMH-K- 45824). A—medial eye and rod-shaped organ, Brod-shaped organ. C—first antenna: D— 2 nd segment and distal part of 1 st segment, E—distal margin of 1 st segment, F—ventral margin of 3 rd and 4 th segments, G— 7 th and 8 th segments, H— 8 th segment, I—seta on 5 th segment.

FIGURE 17. Synasterope pseudomystax sp. nov. (Adult female—ZMH-K- 45824). A—second antenna: B—terminal part of protopodite, C—distal part of 1 st and proximal part of 2 nd exopodite segments, D—terminal part of exopodite, E—endopodite. F—mandible (only stout setae on endopodite shown); G—distal part of mandible endopodite, H and I—dorsal part of basale and 1 st endopodite segment of mandible; J—exopodite of mandible.

FIGURE 18. Synasterope pseudomystax sp. nov. (Adult female—ZMH-K- 45824). A and B—dorsal part of 2 nd endopodite segment of mandible, C and D—ventral part of basale of mandible, E—maxilla.

FIGURE 19. Synasterope pseudomystax sp. nov. (Adult female—ZMH-K- 45824). A—distal half of maxilla, B— 5 th limb (setae on comb not shown), C— 5 th limb (exopodial seta on comb is broken), D—distal part of comb on 5 th limb, E— 6 th limb, F and G—anterior tip of 6 th limb.

FIGURE 20. Distribution of species of the genus Synasterope in the Antarctic area.

Tables

TABLE 7. The morphology comparison of Synasterope mystax Kornicker, 1975 and Synasterope pseudomystax sp. nov. (for adult females only)

Character	S. mystax (Kornicker 1975)	S. pseudomystax sp. nov. (herein)
Carapace length (mm)	2.50	3.12
height (mm and %)	1.32 and 53	1.40 and 44
setae on infold of rostrum	30	10
setae in rostral list	10	4
transparent setae on posterior list	28	15
setae between transparent setae	25	15
First antenna 1st segment	without terminal sclerotized knob	with terminal sclerotized knob on both outer and inner sides
Second antenna endopodite	1st segment equal to length of 2nd segment	1st segment shorter than 2nd segment
Mandible, basale spinous setae	4	3
triaenid setae	4	3
dwarf setae	1	2
additional dwarf seta	placed near basis of basale	placed on basis of basale
Maxilla terminal seta	with faint hairs	bare
setae on first endite	1 short and 3 long	4 long
Fifth limb epipodite	with 70 setae	with 74 setae
thin setae on comb	¹ neǝr bǝse of mǝin setǝ ǝnd 4–Ƽ neǝr ventrǝl mǝrgin	6 terminal and 3 near ventral margin
Sixth limb antero-dorsal corner	with minute seta on medial surface	without minute seta on medial surface
anterior side	with 1 upper and 1 lower seta	with 1 upper seta
anterior tip	with 4 setae	without setae
lateral flap	with 2 setae	with 4 setae
end segment	with 22–23 setǝe	with 20 setae
Rod-shaped organ	2-segmented	1-segmented
Genus BATHYLEBERIS Kornicker, 1975
Type-species. Bathyleberis grossmani Kornicker, 1975 .