Spinacopia dietkeyseri, Chavtur, Vladimir G., 2016

Chavtur, Vladimir G., 2016, Spinacopia dietkeyseri, a new species of Marine Ostracoda (Sarsiellidae: Myodocopina) from the Southern ocean, Zootaxa 4093 (3), pp. 391-406 : 393-404

Spinacopia dietkeyseri , new species

( Figs. 1–9 )

Etymology. The species is named in honor of ostracodologist Dietmar Keyser, University of Hamburg, Hamburg, Germany.

Holotype. ZMH K-41914, adult female, length 2.1 mm, appendages are mounted on slide (ZMH K-41914/1) and valves are preserved in ethanol (ZMH K-41914/2), stored in the collection of the Zoological Museum in the University of Hamburg (CeNak), Germany.

Type Locality. RV “Polarstern”, ANDEEP III, PS 67, ANT XXII/3, Stat. 150-6, epibenthic sledge trawled from 61°48.70’ S – 47°28.04’ W to 61°48.57’ S –47° 28.19 W, depth 1993–1996 m, 20.03.2005.

Paratypes. ZMH K-41915, adult female, 2.0 mm; ZMH K-41916, immature male, 1.7 mm; ZMH K-41917, immature male, 1.7 mm; 4 immature males—1.5, 1.72, 1.73 and 1.8 mm (all from the same sample as holotype).

Diagnosis of female. Adult female. Carapace: length 2.0– 2.1 mm, without radial ridges and nodes, posterodorsal bulge with a-setules and stepped ventral margin, surface pitted.

Mandible: coxale endite with bifurcate tip, U-shaped glandular opening on basale absent.

Maxilla: 1st, 2nd and 3rd endites with 6, 4 and 7 setae.

Fifth limb: 1st, 2nd, 3rd and 4th+5th exopodite segments with 4, 5, 5 and 6 setae.

Sixth limb: 1st, 2nd, 3rd and 4th endites wit 4, 4, 6 and 6 setae; end segment with 8–9 setae.

Seventh limb: Proximal group with 4 (2+2) setae; distal group with 5–6 (2+3 or 3+3) setae; each seta with 2 to 5 bells; terminus with opposing combs, each with 7 teeth.

Caudal furca: right lamella with 8 claws and left lamella with 9 claws. Claw 1 continuous with lamella; claw 3 weaker and shorter than claw 4.

Eyes: lateral eyes absent.

Rod-shaped organ: single-segmented, elongate and with rounded tip.

Description of adult female. Carapace ( Figs. 1–3 , 4 A–E). Length 2.0– 2.1 mm. Carapace oval in lateral view with greatest height near middle. Anterior margin with obtuse angle dorsal to minute indentation marking incisure ( Figs. 1 A, B, D; 3 A, F, G). Posterior carapace with short caudal process at middle of valve. Carapace widest postero-dorsally. Adult female with large postero-dorsal bulge; ventral margin bulge and stepped ( Fig. 3 B, C). Surface of carapace pitted ( Fig. 1 A, C). The a- setules abundant along anterior and ventral margins and scattered on lateral surfaces ( Fig. 3 A, F, G); short slender b- setules abundant along margins and on lateral surfaces (3 F, 4 C); surfaces of rostrum and caudal process covered by spines varying in size; ventral margin and lateral surface of postero-dorsal bulge bears g- setules with thickened tip ( Fig. 1 E). Infold ventral to incisor without seta near inner margin; list anterior to caudal process with 5 stout spinous setae dorsally and 4 smaller bare ones ventrally ( Figs. 2 A, D; 3 F, G); some small setae present along inner margin of postero-ventral section of infold ( Fig. 2 B).

First antenna (Figs. 4 F, 5 A). Dorsal margin of 2nd segment with distal minute spine and long spinous seta. Sparse clusters of spines on ventral margin of 2nd segment; 3rd and 4th segments not separated by suture. Seta of 5th segment about equal to total length of 2.–8. segment of this limb; 6th segment with one small medial seta; Seventh segment: a-seta about one-half of length of sensory seta of 5th segment; b-seta about same length as a-seta; c-seta about same length as sensory seta of 5th segment. Eight segment: d- and e-setae bare, slightly shorter than f-seta; f- and g-setae about same length as c-seta.

Second antenna ( Fig. 5 C–G). Protopodite bare, without medial seta. Endopodite 2-segmented: 1st segment with 3 short setae, 2nd segment on left limb with long spinous seta ( Fig. 5 F, G) and on right limb same as on left or with 1 long spinous and 1 short bare seta (Fig. D, E). Exopodite: distal margin of 1st segment with short recurved medial spine (Fig. 4 G).

Mandible ( Figs. 5 H, I; 6 A–F). Ventral margin of coxale spinous; coxale endite with bifurcate tip, small seta and long spines near base ( Fig. 6 D). Basale: dorsal margin with spine near middle and 2 spines subterminally; ventral margin with total of 8 setae, 3 in proximal group and 5 in distal group (proximal group with 2 short and 1 long setae, distal group with 4 short and 1 long setae); U-shaped glandular opening absent on lateral side. Exopodite with elongated blunt tip, ventral seta reaching about one-fifth length of dorsal margin of 1st endopodite segment ( Fig. 6 A, E, F). Endopodite: 1st segment with 2 medial spines near base of main ventral claw and minute spines forming 2 distal rows along anterior margin and on medial surface ( Fig. 6 A–C); 2nd segment with 2 spines slightly distal to middle of dorsal margin and small lateral spine near base of main ventral claw; 3rd segment with 0– 1 dorsal and 2 longer ventral spines near base of main claw.

Maxilla ( Fig. 6 G). Coxale with short anterior seta. Basale with seta near exopodite. Exopodite with 3 bare setae. Endites: 1st with 6 setae, 2nd with 4 and 3rd with 7 setae. Endopodite: 1st segment with spinous α- and ϐ-setae; 2nd segment with 2 spinous a-setae, bare c-seta and 5 pectinate terminal setae; distal inner margin of posterior terminal seta with closely spaced teeth forming row.

Fifth limb ( Fig. 7 A). Epipodial appendage with 42 plumose setae. Single endite with bare seta. Exopodite: 1st segment with 4 setae; 2nd segment with 5 setae, 3rd segment with 3 setae on inner lobe and 1 seta on outer lobe and 4th+5th segments with 6 setae; all segments hirsute.

Sixth limb (fig. 8 A). Limb hirsute. Four endites well defined: 1st and 2nd endites each with 4 setae, 3rd and 4th endite each with 6 setae. End segment with 3 groups of setae: anterior group with 5 setae, middle group with 1–2 setae and posterior group with 2 plumose setae.

Seventh limb ( Fig. 7 B). Proximal group with 4 (2+2) setae; distal group with 5–6 (2+3 or 3+3) setae; each seta with 2 to 5 bells and with marginal spines distally; terminus with opposing combs, each with 7 teeth.

Caudal furca ( Fig. 7 C, D). Right lamella with 8 claws and left lamella with 9 claws. Claw 1 continuous with lamella, remaining claws separated from lamella by suture; claw 3 weaker and shorter than claw 4. All claws slender and with pointed tip.

Eyes. Medial eye normal for genus. Lateral eyes absent.

Rod-shaped organ ( Fig. 5 A, B): 1-segmented, elongate and with rounded tip.

Description of immature male (instar IV). Carapace same as adult female. Length 1.50–1.80 mm.

First antenna ( Fig. 8 C, setae not shown) same as female.

Second antenna ( Fig. 6 E–G). Endopodite 3-segmented: 1st segment on dorsal margin with 3 short proximal setae and 2 minute subterminal spines; 2nd segment on dorsal margin with 1 midlength and 1 long proximal seta and short seta on middle; 3rd segment with 2 short terminal setae.

Mandible ( Fig. 9 A–C). Similar to adult female except: exopodite and 1st endopodite segment somewhat shorter.

Maxilla. Similar to adult female except: 2nd and 3rd endites with 3 and 5 setae respectively.

Fifth limb ( Fig. 9 E, D). Epipodial appendage with 40 plumose setae. Endite with seta. Exopodite: 1st and 3rd segments each with 3 setae, 2nd segment with 4 terminal setae and 1 proximal seta and 4+5 segments with 4 setae.

Sixth limb (9 F). Limb partly hirsute. Four endites well defined: 1st and 2nd endites each with 3 setae, 3rd with 5– 6 setae, 4th endites with 5 setae. End segment with 3 groups of setae: anterior group with 4 setae, middle group with 2 setae and posterior group with 2–3 plumose setae.

FIGURE 4. Spinacopia dietkeyseri sp. nov. (Adult female: A–E—ZMH K-41915; F—ZMH K-41914). A and B—infold of caudal process of carapace, C—surface of central area of carapace, D and E—muscle scars, F—terminal part of first antenna, G—1st exopodite segment of 2nd antenna.

Seventh limb lost.

Caudal furca. Each lamella with 6 claws. Claw 1 continuous with lamella, remaining claws separated from lamella by suture; claw 3 weaker and shorter than claw 4. All claws slender and with pointed tip.

Rod-shaped organ ( Fig. 8 C, D): 1-segmented, elongate and with slightly pointed tip.

Comparison. The new species is closely related to S. mastix Kornicker, 1975 but differs by ornamentation on surface of carapace and number of setae on maxilla, 5th, 6th and 7th limbs ( Table 2 ).

Distribution. The new species was collected in the Weddell Sea near the South Orkney Islands (61°48.70’ S – 47°28.04’ W to 61°48.57’ S –47° 28.19 W) at the depth range of 1993 to 1999 m.

The distribution of Spinacopia dietkeyseri n.sp. is in accordance with the known occurrence of Spinacopia in general. Until now, Kornicker (1975) and Hartmann (1992) found all members of this genus in waters of or near the Antarctic Convergence, with the exception of S. sandersi . This species was collected in the vicinity of Bermuda in deep water of 1150 m. Considering the fact that the swimming setae on the first antenna are rather short in this genus, is it a typical benthos organism. Also the stomach ingredients studied by Kornicker (1969) indicate that the food is mainly, if not exclusively, of benthic origin. This all could explain the occurrence of S. sandersi that far north in the Atlantic ocean. It is probably distributed towards the north by the cold water of the Antarctic bottom water mass. Why none of the other species of the genus has to date been found in the northern area might depend on their scarcity within samples collected at this depth.

Figures

FIGURE 1. Spinacopia dietkeyseri sp. nov. (Adult female: A, B and D—ZMH K- 41914; immature male: C, E and F—ZMH K- 41917). A—right valve of carapace in lateral view, B—left valve in inside view ,, C—carapace in antero-dorsal view, Drostrum in inside view, E and F—detail of postero-dorsal bulge on carapace.

FIGURE 2. Spinacopia dietkeyseri sp. nov. (Adult female: A – D—ZMH K- 41914). A—caudal process in inside view, Binner margin of infold anterior to caudal process, C—caudal process in outside view, D ─ caudal process in inside view.

FIGURE 3. Spinacopia dietkeyseri sp. nov. (Adult female: A – G—ZMH K- 41915). A—right valve in lateral view, Bcarapace in anterior view, C—carapace in ventral view, D—postero-dorsal view of carapace, E—postero-ventral view of open carapace, F—anterior area of carapace in outside view, G—anterior area of carapace in inside view.

FIGURE 5. Spinacopia dietkeyseri sp. nov. (Adult female: A – K—ZMH K- 41914). A—first antenna and rod-shaped organ, B—rod-shaped organ, C and D—left and right exo- and endopodite of second antenna, E—distal part of left endopodit of second antenna, F—distal part of right endopodit of second antenna, G—distal part of left endopodite of second antenna, H and I—basale segment of mandible.

FIGURE 6. Spinacopia dietkeyseri sp. nov. (Adult female: A – G—ZMH K- 41914). A—mandible, B and C— 1 st, 2 nd and 3 rd segments of mandible, D—coxale endite of mandible, E and F—exopodite of right and left mandible, G—maxilla.

FIGURE 7. Spinacopia dietkeyseri sp. nov. (Adult female: A – D—ZMH K- 41914). A— 5 th limb, B— 7 th limb, C and Dcaudal furca.

FIGURE 8. Spinacopia dietkeyseri sp. nov. (Adult female: A and B - ZMH K- 41914; immature male: C – G—ZMH K- 41916). A— 6 th limb, B—posterior part of body, C—first antenna (setae not shown) and rod-shaped organ, D—rod-shaped organ, Esecond antenna, F and G—endopodite of second antenna.

FIGURE 9. Spinacopia dietkeyseri sp. nov. (Immature male: A – F—ZMH K- 41916). A and B— 1 st endopodite segment of mandible, C—exopodite of mandible, D and E distal part of 5 th limb seen from different sides, F— 6 th limb,

Tables

TABLE 2. Comparison of characteristics of Spinacopia mastix Kornicker, 1975 and S. dietkeyseri n. sp. (adult females only).

Character	S. mastix	S. dietkeyseri sp. nov.
Carapace, length (mm)	2.26–2.36	2.0–2.1
height (mm)	1.83–1.91	1.80
posterodorsal bulge	f-setae on lateral surface and margin	g-setae with thickened tip on lateral surface and margin
Second antenna, long seta	placed distally	placed proximally on 2nd segment
Mandible, basale	U-shaped glandular opening present	U-shaped glandular opening absent
exopodite	thick	relatively thick
1st endopodite segment	1 minute seta near base of claw	2 minute setae near base of claw
Maxilla	1st, 2nd and 3rd endite with 6, 5 and 6 setae	1st, 2nd and 3rd endite with 6, 4 and 7 setae
Fifth limb, epipodite	44 plumose setae	42 plumose setae
exopodite segments	1st, 2nd, 3rd and 4th+5th with 3, 6, 4 and 6 setae	1st, 2nd, 3rd and 4th+5th with 4, 5, 5 and 6 setae
Sixth limb, endites	1st, 2nd, 3rd and 4th with3–4, 3, 4 and setae	1st, 2nd, 3rd and 4th with4, 4, 6 and 6 setae
terminal segment	with 9–10 setae	with 8–9 setae
Seventh limb, number of setae in proximal group	5–7 setae	4 setae
Rod-shaped organ	with bifurcate tip	with rounded tip
Discussion