Metavargula adinothrix Kornicker, 1975

Chavtur, Vladimir G., Keyser, Dietmar & Bashmanov, Alexander G., 2010, First record and description of male of Metavargula adinothrix Kornicker, 1975 (Ostracoda: Myodocopina) from the Southern Ocean, Zootaxa 2434, pp. 33-46 : 43-45

Metavargula adinothrix Kornicker, 1975

( Figures 2–9 )

Metavargula adinothrix Kornicker, 1975: 131 –138, figs. 64–66, 68, 69.

Material. ZIM-K-41902, adult male, length 3.94 mm. Valves in micropalaeontological chamber, some

appendages in alcohol, remaining appendages on slide. R/V “Polarstern”, ANT XXII-3, St. 150–6–5,

61º49.14´S – 47º27.51´W to 61º48.53´S – 47º28.16´W, depth 1971.0 – 1999.0 m, Epibenthos sledge, 20 March

2005.

Additional material. R/V “Polarstern”, ANT XIX-3

Description of adult male. Carapace ( Figs. 2 , 3 , 4A). Length 3.95 mm. Greatest height about 55%. Oval with broadly rounded anterior, small incisur and developed rostrum. Posterior relatively elongate upsweeping caudal siphon with wide quadratic top. Caudal process with infold, broad and covered with tiny pores. List on infold in front of caudal process with pores and minute bristles. Surface of valves smooth but scale-like under high magnification.

First antenna (Figs. 4B, D; 5A). 1st and 2nd segments bare; 3rd and 4th segments each with one ventral and one dorsal bristle; sensory bristle of 5th segment with 12 long proximal paddle-like and 2 long distal slender bare filaments (each with terminal papilla), bifurcate tip, and about half length of g-bristle and somewhat more than 3 times length of a-bristle. Medial bristle on 6th segment subequal to length of its dorsal margin and bare. 7th segment: a-bristle bare and about twice as long as length of bristle on 6th segment, b-bristle somewhat less than 3 times as long as a-bristle and about 1/3 length of g-bristle with 4 filaments (proximal filament stout with bulbous proximal part followed by large sucker and small protuberance; 2nd and 3rd filaments near middle of bristle slender each with 2 small discs, 4th filament also slender but bare) and bifurcate tip; c-bristle (terminally broken) with 10 filaments (proximal filament similar to stout proximal filament of b-bristle but with somewhat less pronounced sucker, followed by 2 slender filaments each with 2 small discs, then bare filaments). 8th segment: d- and e-bristles somewhat longer than 60% of b-bristle, bare and with blunt tip; fbristle longer about 1.6 times than b-bristle, with 9 filaments (each with 4-5 spines) and bifurcate tip; g-bristle somewhat longer than f-bristle with 9 filaments (each with 4-5 spines) and bifurcate tip.

Second antenna (Figs. 4E–H; 5B,C). Protopodite with short bare medial bristle, subequal to length of exopodite and somewhat longer than its 1st segment. Endopodite weak, 2-segmented: 1st segment with 3 proximal (2 short and 1 long) and 1 distal long bristles, 2nd segment armed with long terminal filament. Exopodite: 1st segment barely shorter than total 2nd – 9th segments; bristle on 2nd segment with 7 – 10 distal spines on ventral margin (dorsal margin bare), about 70% length of 1st segment and 25% of bristle on 3rd segment, with bifurcate tip; bristles on 3rd to 9th segments with natatory setules and without spines; 9th segment with 3 long and 1 short bristles; segments 3rd to 9th with basal spines; basal spines smaller on proximal segments, but lateral spine on 9th segment smaller than basal spines of 7th and 8th segment.

Mandible (Figs. 5D–F; 6A–F). Coxale endite with 2 relatively stout terminal spines and tiny peg between them, short bristle and process present at basale on endite. Basale: dorsal margin with 1 distal and 2 terminal bristles; ventral margin with 1 a- and 1 b-bristles, 2 c-bristles (1 short distal and one midlength proximal) and 2 d-bristles (1 long distal and other midlength proximal). Exopodite slightly longer than dorsal margin of 1st endopodite segment, with 2 spinous bristles and pointed tip, dorso-distal part hirsute. Endopodite: ventral margin of 1st segment with 4 bristles, 2 long (1 plumose) and 2 short bare; ventral margin of 2nd segment with 2–3 groups of bristles having 1, 1 (only 1 on left limb) and 2 bristles, all short (medial bristles of terminal pair broad and with teeth along inner margin); dorsal margin of 2nd segment with 5 long, 2 medium length and 7–8 short bristles. End segment with 4 claws and 3 bristles (1 short, 1 medium length and 1 long).

Maxilla (Figs. 6G– I; 7A,B). Coxale with stout, relatively long, plumose bristle. Endite bristles not counted. Exopodite broad, with usual 3 bristles, 2 proximal plumose and 1 distal bare. Endopodite: cutting edge of 1st segment with 3 teeth, 2 alpha-bristles present (outer bristle longer and plumose, inner bristle bare) and 3 beta-bristles (2 short and 1 long, all with long spines along inner margin); 2nd segment with 3–4 a-, 3 b-, 1–2 c- and 1–2 d-bristles.

Fifth limb (Figs. 7C–E; 8A–C). Epipodial appendage deformed. Anterio-distal process of protopodite small and curved. Endite bristles not counted. Endopodite: main tooth of 1st segment consisting of usual 5 pectinate teeth and peg with proximal posterior bristle; 2nd segment with smooth anterior bristle and 15 bristles on margin adjacent to main tooth of 1st segment; inner lobe of 3rd segment with 3 bristles, shorter bristle hirsute, other 2 with or 1 spine; outer lobe with 1 bare bristle and 1 (outer) with setules; 4th plus 5th segments united without peg; 4th segment with 2–3 bristles, 5th with 2 bristles; inner surface of these segments covered with long setules.

Sixth limb (Figs. 6J; 8D; 9A). Epipodial appendage with 4 bristles (1–2 short), tiny process near base of proximal bristle and 2 proximal processes; 1st endite with 6 bristles, 2 terminal and 4 medial; 2nd endite with 5– 6 bristles, 2–3 terminal and 3 medial; 3rd and 4th endites each with 3 terminal bristles; end segment with 14 bristles, 2 posterior hirsute, others with long proximal setules, inner surface of all endites and end segment covered with setules.

Seventh limb (Fig. 8E). Terminal comb with about 5 long recurved teeth with digitate tips; elongate curved peg present opposite comb; teeth and peg annulate. Limb with distal group contains 16 distal bristles (7 ventral and 9 dorsal, each with 3–5 bells) and proximal group with 12 bristles (6 ventral and 6 dorsal, each with 2-4 bells).

Furca . Each lamella with 8 claws separated from lamella by suture; claws decrease in length posteriorly along lamella, each claw with teeth along posterior margin and with minute spines in row along anterior margin: a few minute spines present along anterior margin of each lamella.

Copulatory limbs ( Figs. 9 B–E). Each copulatory limb with 3 lobes. Finger-like lobe with 6–7 small teeth, shortest lobe with 12–13 bristles, longest lobe with stout recurved terminal process and with 4 proximal bristles.

Lateral eye. Eyes small, pigmented, with 4 ommatidia.

Medial eye (Fig. 5A). Eye large and pigmented.

Bellonci organ (Fig. 5A). Organ short and cylindrical.

Upper lip (Fig. 5A). Anterior part large, unpaired and with terminal glandular processes. Paired tusks relatively short (somewhat less than height of anterior part) with few glandular processes. Bulge posterior to tusks hirsute.

Anterior body (Fig. 5A). Straight and with very small anterior process; height subequal to height of anterior part of upper lip.

Comparisons. Male differs from female by smaller size and structure of infold of caudal siphon; by number, arming and size of bristles (and teeth on 5th and 7th limbs) on 1st and 2nd antennae, mandible and on 5th, 6th and 7th limbs; also by shape and height of upper lip and anterior body (table 2).

Distribution. This species is known only from the Southern Ocean. It has been collected in the Atlantic Sector of this ocean between 48ºS and 61ºS and from the Pacific Sector in area 48ºS–148ºE at the depth of 1790–1803 m ( Fig. 1 , table 1).

Carapace length 3.94 mm 5.22–6.31 mm

caudal siphon infold. with tiny pores with reticulate structure First antenna bristle of 5th limb with 12 proximal filaments with 9 proximal filaments

a-bristle of 7th segment about twice as long as bristle of 6th somewhat longer than bristle of 6th

segment segment.

c-bristle of 7th segment with 10 filaments with 9 filaments

Second antenna bristle on 2nd segment of with 7–10 distal spine spines along with 17 distal spines along ventral

exopodite ventral margin and without spines on margin and 7 proximal spines along

dorsal margin dorsal margin

Mandible Dorsal margin of 2nd with 5 long, 2 midlength and 7–8 with 6 long and 10 short bristles

endopodite segment short bristles

Maxilla 2nd endopodite segment with 3–4 a-, 3 b-, 1–2 c- and 1–2 d- with 4 a-, 3 b-, 4 c- and 3 d-bristles

bristles

Fifth limb main tooth on 1st endopodite with 5 pectinate teeth with 5 pectinate teeth changed after

segment Kornicker (pers. com. 2009)

2nd endopodite segment anterior bristle smooth anterior bristle plumose

Sixth limb epipodite with 4 bristles and proximal process with 10 bristles and without process

1st endite with 6 bristles with 4 bristles

2nd endite with 5–6 bristles with 6–8 bristles

end segment with 14 bristles with 18–19 bristles Seventh limb number bristles in distal group 16 (7+9) 27 (15+12).

(ventral+ dorsal margins)

number bristles in proximal 12 (6+6) 24 (11+13).

group (ventral+dorsal margins)

terminal comb 5 teeth with digital tip 11 teeth with usual tip

Upper lip tusks shorter than height of anterior part longer than height of anterior part Anterior body shape straight curved

height subequal to height of anterior part of higher than height of anterior part of

upper lip upper lip

anterior process small large

Figures

FIGURE 1. Location Map of Metavargula adinothrix.

FIGURE 2. Metavargula adinothrix (Male: ZIM – K – 41902). Right valve in lateral view. (The white shiny areas are parts of the shell glowing in the electron beam)

FIGURE 3. Metavargula adinothrix (Male: ZIM – K – 41902). A, detail of exterior surface in carapace; B, caudal process of left valve in inside view; C, pores on posterior list of left valve; D, pores on caudal process of inside view of left valve.

FIGURE 9. Metavargula adinothrix (Male: ZIM – K – 41902). A, sixth limb. Copulatory limbs: B, left and right limbs in lateral view; C, hook-like tip, D and E, smaller lobe of right and left limbs.