Skogsbergiella tetrathrix, Chavtur, Vladimir G. & Keyser, Dietmar, 2015

Chavtur, Vladimir G. & Keyser, Dietmar, 2015, Benthic Ostracods of Skogsbergiella (Myodocopina: Cylindroleberididae) from the Southern Ocean, Zootaxa 4048 (4), pp. 508-522 : 510-516

Skogsbergiella tetrathrix sp. nov.

( Figs 2–6 )

Etymology. The specific name “ tetrathrix ” from Greek “tetra”- four, and “trix”- hair, refers to the 4 ventral setae on the comb of the fifth limb.

Material. One adult male.

Holotype. adult male, ZMH-K 41906, length 3.10 mm, appendages are mounted on a glass slide (ZMH-K 41906/1) and valves are preserved in alcohol (ZMH-K 41906/2), stored in the collection of the Zoological Museum in University of Hamburg, Germany.

Type locality. R. V. “Polarstern”, PS 61, ANT XIX/3, ANDEEP I cruise, ZMH-K 41910 – adult male (length 3.10 mm), Station 41-3-E, taken with an epibenthic sledge trawled from 59°21.97´S – 60°4.27´W, 2380 m to 59°22.55´S – 60°4.01´W, 2359 m, on 26 January, 2002.

Diagnosis of adult male. Carapace length 3.10 mm. List paralleling posterior margin with about 37 hyaline spines.

Mandible. Dorsal margin of basale with 5–6 setae. Exopodite about one-half length of dorsal margin of 1st endopodite segment.

Maxilla. Dorsal margin of basale with 1 proximal and 1 distal short setae.

Fifth limb. Comb only with 4 ventral setae (except exopodial seta).

Sixth limb. Anterior margin with 2 setae; posteroventral margin with 27 setae.

Seventh limb. Limb with 19 setae; opposing terminal combs with 12 teeth on each side.

Furca. Each lamella with 9 claws.

Lateral eyes. Absent

Description of adult male. Carapace ( Fig. 2 ). Length 3.10 mm. Carapace with posterior half of dorsal margin strongly tapered ( Figs. 2 A, B). Greatest height in anterior half (58%). About 50 setae scattered over infold of rostrum dorsal to list; total 27 setae on list and between list and dorsal margin of incisur; about 60 setae present on anteroventral infold ventral to incisur ( Fig. 2 C); list paralleling posterior margin with about 37 hyaline spines (Fig. D); setae between hyaline setae and processus between list and posterior margin difficult to distinguish (posterior infold covered with debris). About 8–10 setae forming cluster in dorso-posterior corner.

First antenna ( Figs 3 B–E, 4 A): 1st segment bare; 2nd segment with spines on ventral surface, 1 dorsal long spinous and 1 lateral short bare setae; 3rd segment with 6 spinous dorsal setae and 2 short recurved bare ventral setae; 4th segment with 1 long dorsal seta with short marginal spines and 2 short ventral setae; stout stem of sensory seta of 5th segment about twice as long as total 5th–8th segments and with numerous filaments; medial seta of 6th segment with short marginal spines and about as long as stem of 5th segment. Seventh segment: a-claw about onehalf length of seta on 6th segment; b-setae with more than 8 filaments (broken); c-seta with 28 filaments. Eight segment d- and e-setae bare; f-seta about 40% of length of c-seta and with 8 proximal and 1 distal filaments; g-seta with 11 proximal and 1 distal filaments.

FIGURE 5. Skogsbergiella tetrathrix sp. nov. (Adult male—ZMH-K 41906). A and B, dorsal margin of middle mandible; C and D, dorsal side of 2nd endopodite segment on mandible; E, maxilla; F and G, comb of fifth limb; H, anterior of sixth limb.

Second antenna ( Figs 4 B–D): Protopodite with short slender medial seta. Endopodite 3-segmented: 1st segment bare; 2nd segment with 2 bare short ventral setae; 3rd segment reflexed on 2nd and with bare long proximal seta and pointed tip with 8–9 ridges. Exopodite: 9th segment with 2 terminal minute spines on left limb ( Fig. 3 D) and without spines on right limb.

Mandible ( Figs 4 E, F, G; 5 A–D; 6 A): Coxal endite with 1 small seta at basis of endite; ventral margin of dorsal branch of coxal endite with 8 teeth. Basale: endite with 4 terminal spinous setae, distally with 4 tridentid setae with some marginal pairs of spines and 2 dwarf setae and proximally with a glandular peg and 1 tridentid seta; 1 tridentid seta on basale near endite; dorsal margin of basale with 2 long terminal setae, 0–1 midlength subterminal seta and 3 midlength midsetae. Exopodite about one-half length of dorsal margin of 1st endopodite segment and with 2 short bare subterminal setae. Endopodite: 1st segment with 3 long ventral setae, 2nd segment with 3 long terminal setae on ventral margin, dorsal margin with 3 fairly long proximal setae and stout spinous a-, b-, c- and d-setae, 1–2 short setae between a- and b-setae, 1 short lateral seta near b-seta, 2 long setae between b- and c-seta, 1 long seta between c- and d-setae and 1 long seta near base of d-seta; 3 rows of 3, 5–6, 7 setae present medially between b- and d-setae; 3rd segment as common for the genus.

Maxilla (Fig. 5 A): 1st and 2nd endites each with 3 long setae. Basale dorsally spinous: dorsal margin with 1 proximal and 1 distal short setae; ventral margin with 1 short proximal and 1 long spinous terminal setae; lateral side with 1 short proximal seta. Endopodite: anterior margin without seta, posterior margin with 1 long spinous terminal seta; end segment with 1 long spinous terminal seta.

Fifth limb (Figs 5 F, G): Epipodial appendage with 84 plumose setae on both limbs. Lateral side with long stout exopodite seta (extending slightly past end of comb) and 4 setae on ventral margin.

Sixth limb (fig. 6 B): Anterior margin with 1 upper and 1 lower setae; anteroventral corner with 2 setae; lateral flap without setae; posteroventral margin with 27 setae.

Seventh limb ( Figs 6 C, D): Limb with 19 setae, 14 proximal (7+8) and 4 terminal (2+2), each seta with 2–5 bells; opposing terminal combs with 12 spinous teeth on each side.

Caudal furca ( Fig. 6 E): Each lamella with 9 claws, 1st–7th claws and 8th– 9th claw-like setae.

Eyes ( Fig. 3 B): Lateral eyes absent. Medial eye well developed.

Upper lip ( Figs 3 B, F): Consisting of hirsute lobes, right lobe with 2 and left lobe with 1 soft short setae; lateral flap present on each side of mouth.

Copulatory organ ( Figs 6 E, F): Elongate, distally with 2 lobes, each with 6 setae.

Rod-shaped organ ( Figs 8 C, D): 2-segmented, fairly elongate and thick with rounded tip.

Comparisons. The new species is closely related to S. macrothrix Kornicker, 1975 but differs by greater size of carapace, 2-jointed rod-shaped organ, lesser number of teeth on combs of seventh limb and absence of lateral eyes ( Table 1 ).

Figures

FIGURE 2. Skogsbergiella tetrathrix sp. nov. (Adult male—ZMH-K 41906). A, left valve of carapace in interior view; B, right valve in lateral view; C, rostrum and anterior margin in interior view; D, posterior and postero-ventral margins in interior view; E, detail of ventral margin in interior view; F, central muscle scars.

FIGURE 3. Skogsbergiella tetrathrix sp. nov. (Adult male—ZMH-K 41906). A, rod-shaped organ; B, rod-shaped organ, first antenna, and upper lip; C and D, distal detail of first antenna; E, ventral margin of middle part of first antenna; F, detail of upper lip.

FIGURE 4. Skogsbergiella tetrathrix sp. nov. (Adult male—ZMH-K 41906). A, terminal setae of first antenna; B, left second antenna; C, endopodite of right second antenna; D, distal part of exopodite of second antenna; E, mandible (part, short setae not shown); F, basale endite and proximal part of basale on mandible; G, proximal tridentid seta near glandular opening on basale endite of mandible.

FIGURE 6. Skogsbergiella tetrathrix sp. nov. (Adult male—ZMH-K 41906). A, exopodite of mandible; B, sixth limb; C, seventh limb; D, distal part of seventh limb; E, furcal lamella and ventral half of copulatory organ; F, distal part of copulatory organ.

FIGURE 8. Skogsbergiella species A (Adult female—ZMH-K 41907). A and B, lateral eyes; C, rod-shaped organ; D, rodshaped organ, lateral and medial eyes, and first antenna (terminal setae on first antenna not shown); E, distal half of first antenna (distal and terminal setae not shown); F, second antenna (without 2 – 9 exopodite segments); G, exopodite of second antenna (without setae on 3 – 9 segments); H and I, distal part of exopodite on second antenna (with and without setae); J, detail of second antenna.