Philomedes orbicularis Brady, 1907

Chavtur, Vladimir G. & Keyser, Dietmar, 2016, Benthic myodocopid Ostracoda (Philomedidae) from the Southern Ocean, Zootaxa 4141 (1), pp. 1-70 : 50-54

Philomedes orbicularis Brady, 1907

( Figs. 32 , 33 )

1907 Philomedes orbicularis Brady : 4, pl. 1: Figs. 1–3 , 6–15 .

1912 Philomedes orbicularis Brady, 1907 —Müller,: 26 [key], 33.

1971 Philomedes orbicularis Brady, 1907 —Kornicker: 191, Fig. 16 .

1975 Philomedes orbicularis Brady, 1907 —Kornicker: 240–245, Figs. 131, 135 (map), 139–143; 1986 Philomedes orbicularis Brady, 1907 —Hartmann: 116–117.

1990 Philomedes orbicularis Brady, 1907 —Hartmann: 199.

1971 Philomedes trithrix Kornicker : 176, Figs. 6–12 .

1988 Philomedes cf. P. orbicularis Brady, 1907 —Hartmann: 142–143.

Studied material (coordinates, depth and sediment see Appendix). RV “Polarstern”, ANT XV/3, station 148: ZMH-K-42268—adult female (2.65 mm).

52th Russian Antarctic Expedition, station 12, sample 60: MIMB 18309—immature female (2.27 mm) and MIMB 18310—immature male (2.32 mm).

Station 12, sample 64: MIMB 18311—immature male (2.25 mm).

Station 12, sample 65: MIMB 18 308—adult female (2.80 mm).

Additional material. See Appendix.

Diagnosis of female ( Kornicker 1975, with additional remarks). Carapace: oval in lateral outline with minute caudal process often not visible in lateral view, surface with abundant short setules, length 2.27–2.80 mm.

First antenna: 2nd joint with 3 setae, 1 ventral, 1 lateral and 1 dorsal.

Second antenna: 1st joint of endopodite with 5 setae, 4 proximal and 1 distal; 2nd joint with 1 long and 1 short ventral setae and 1 long terminal seta.

Mandible: dorsal margin of basale with 4–5 setae, 2–3 near middle and 2 subterminal.

Sixth limb: epipodite with 3–4 setae.

Seventh limb: each limb with 32–43 setae, 2 pegs present on opposite terminal comb.

Caudal furca: each lamella with 11–13 claws, main claws short, stout, often with rounded tips.

Bellonci organ: 2-jointed, with pointed tip.

Lateral eye: minute, with 2–3 ommatidia or without well-defined ommatidia.

Anterior process (above upper lip): developed, slightly curved and with rounded tip.

Diagnosis of male. Carapace: length 2.45–2.71 mm.

First antenna: 2nd joint with 3 setae, 1 ventral, 1 lateral and 1 dorsal.

Second antenna: 1st joint of endopodite with 5 setae, 4 proximal and 1 distal; proximal seta of 3rd joint thin, about 1/3 (or shorter) of its length.

Mandible: dorsal margin of basale with 4 setae, 2 near middle and 2 subterminal; coxale endite present.

Sixth limb: epipodite with 3 setae.

Seventh limb: each limb with 29–31 setae; 3 pegs present on opposite terminal comb.

Caudal furca: each lamella with 9 or 10 claws.

Bellonci organ: 1-jointed, with rounded tip.

Anterior process (above upper lip): pointed projection present.

Supplementary description of adult female. Carapace ( Fig. 32 A–E). Length 2.27–2.80 mm (in literature: 2.34–2.65 mm). Infold on rostrum with 19–24 setae forming L-shaped row. Antero-ventral inside with 10–12 short setae and 10 striations ( Kornicker 1975: 12–15 and 8–9, respectively). Posterior infold with middle row of 3 spinelike setae ( Fig. 32 C, D). Surface of carapace with abundant short spines and rare setae ( Fig. 32 E).

First antenna ( Figs. 32 F, H; 33 A, B). Second joint with 3 spinous seta, 1 dorsal and 1 lateral midlong setae and 1 long ventral seta.

Second antenna ( Fig. 32 I–K). Endopodite: first joint with 5 setae, 4 proximal and 1 distal; subterminal seta of second joint with proximal knee ( Fig. 32 J) or normal type, ventral margin of this joint with 1 long and 1 midlength spinous setae.

Mandible ( Fig. 33 C–E). Basale: dorsal margin with 4–5 setae, 2–3 near middle and 2 subterminal; medial side with 6 setae, 3 pectinate and 3 usual type; lateral surface with 4 setae forming a row parallel to ventral margin; ventral margin with 2–3 distal setae. Endopodite: first joint with 4–5 ventral setae; dorsal margin of second joint with 3–4 setae in proximal group, 5–6 setae in distal group and 1 seta between these groups; ventral margin of second joint with 3 setae in subterminal group and 3 in terminal group.

Fifth limb. Epipodite with about 57 setae. Fourth and fifth joints fused, and in total with 6 setae.

Sixth limb. Endite I with 2 terminal and 1 medial setae, endite II with 3 terminal and 1 medial setae (with 3! medial setae on one limb in ZMH-K-42268 ANT XV/3 PS 10.02.98), endite III with 8–9 terminal and 1 medial setae, endite IV with 8 terminal and 1 medial setae, and end joint with 24–29 setae; 3 or 4 setae present in place of epipodial appendage.

Seventh limb ( Fig. 33 F–H). Each limb with 36–42 setae (32–43 in literature), 11 or 12 (4+7, 4+8 and 5+7) distal setae and 25–30 (11+14, 12+18 and 12+15) proximal setae; each seta with 3–7 bells. Terminal comb with teeth; 5–6 pegs (7–12 in literature) present on opposite comb.

Caudal furca ( Fig. 33 I). Limb with 12+12 or 11+13 claws.

Bellonci organ ( Fig. 32 F, G). Organ elongate, 2-jointed, longer than first joint of first antenna and with pointed tip.

Medial eye ( Fig. 32 F, G). Smooth.

Lateral eye ( Fig. 32 F). Minute.

Upper lip ( Fig. 32 F, G). Ventrally hirsute, terminally with several glandular processes.

Anterior process on body ( Fig. 32 F, G). Developed, elongate, curved or straight.

Supplementary description of A- 1 male. Carapace ( Fig. 33 K, L). Length 2.25–2.32 mm. Second antenna ( Fig. 33 M). Endopodite: first joint with 3 proximal and 1 distal setae; second joint with 1 long spinous seta and 1 bare and 1 spinous relatively short setae on ventral margin; third joint with 1 midlength dorsal and 2 short terminal setae.

Mandible. Basale: dorsal margin with 4 setae, 2 near middle and 2 subterminal; medial side with 3 setae, 1 pectinate and 2 normal type; lateral surface with 3 setae; ventral margin with 2 distal setae. Endopodite: first joint with 4 ventral setae; dorsal margin of second joint with 3 setae in proximal group, 5 setae in distal group and 1 seta between these groups.

Fifth limb. Fourth plus fifth joints with 6 setae.

Sixth limb. Endite I with 2 terminal and 1 medial setae, endite II with 3 terminal and 1 medial setae, endite III with 7 terminal and 1 medial setae, endite IV with 7–8 terminal and 1 medial setae, end joint with 17–18 setae; 1 or 2 setae present in place of epipodial appendage.

Seventh limb. Each limb with 26 setae, 6 (3+3) distal and 20 (6+14) proximal; each seta with 2–4 bells. Terminal comb with 6 teeth; 1 peg present on opposite comb.

Caudal furca. Limb with 3+3 claws.

Supplementary description of A- 1 female. Carapace. Length 2.27 mm.

Mandible. Basale: dorsal margin with 4 setae, 2 near middle and 2 subterminal, medial side with 6 setae, 3 pectinate and 3 normal type; lateral surface with 3 setae; ventral margin with 2 distal setae. Endopodite: first joint with 4–5 ventral setae; second joint similar to that of adult female.

Fifth limb. Fourth plus fifth joints with 5 setae in total.

Sixth limb. Endite I with 2 terminal and 1 medial setae, endite II with 3 terminal and 1 medial setae; endite III with 9 terminal and 1 medial setae; endite IV with 7 or 9 terminal and 1 medial setae; 1 or 2 setae present in place of epipodial appendage.

Seventh limb. Each limb with 34–40 setae, each seta with 1–4 bells. Terminal comb with 9 teeth; 2 pegs present on opposite comb.

Distribution and ecology. Circumantarctic sublitoral-bathyal species. It has been collected in the Scotia subregion of the Southern Ocean ( Kornicker 1971, 1975; Hartmann 1986, 1987a, 1988, 1990, 1991), vicinity of the Ross Sea ( Kornicker 1975), Prydz Bay and near of the Russian Polar station “Molodezhnaya” (present study) between 53° and 77°S ( Fig. 31 ), at the depths of 13 to 1000 m, in temperature range of 1.28° to -1.62°C, on hard and soft substrates: rock, stone, muddy sand, sandy mud, mud and also glass sponges.

Figures

FIGURE 1. Distribution map of species of the family Philomedidae in the Antarctic region and adjacent regions from literature and original data.

FIGURE 2. Distribution map of Scleroconcha gallardoi, S. tuberculata sp. nov., and S. species indet.

FIGURE 3. Scleroconcha tuberculata sp. nov. (Female: A, C—MIMB 18275; B, D, E, G—MIMB 18270; F—MIMB 18271; H, J—MIMB 18269; I, K—MIMB 18272). A, B—left valve of carapace in lateral and inside views; C—carapace in ventral view; D—detail of antero-ventral infold of left valve (marginal setae cut); E—detail of setae on left valve, lateral view; F – Idistal part of Bellonci organ; J, K—endopodite of 2 nd antenna.

FIGURE 6. Scleroconcha tuberculata sp. nov. (Female: A, C—MIMB 18271; B, D, H—MIMB 18272; E, F—MIMB 18269; G—MIMB 18270). A—exopodial joints 1 – 5 of 5 th limb; B – G—tip of 7 th limb; H—detail of caudal furca.

FIGURE 7. Scleroconcha tuberculata sp. nov. (Male: MIMB 18268). A, B—right and left valve of carapace in lateral view; C—carapace in ventral view; D—rostrum in lateral view; E—infold of rostrum; F—infold of rostrum and anterior detail of carapace; G—pits of middle right valve; H—upper lip, anterior process, medial eye and Bellonci organ; I—distal part of Bellonci organ; J—medial eye and base of Bellonci organ.

FIGURE 8. Scleroconcha tuberculata sp. nov. (Male: MIMB 18268). 2 nd antenna: A—exopodial joint 3 – 9 (setae not shown); B—exopodial joints 1 – 3; C, D—endopodite of left and right limb; E—detail of 3 rd endopodial joint; F— 1 st endopodial joint. Mandible: G, H—basale, exopodite (abnormal on left limb) and endopodite (setae shown only for basale); I—endite of coxale.

FIGURE 9. Scleroconcha tuberculata sp. nov. (Male: MIMB 18268). A, B—exopodite (abnormal on left limb), 1 st endopodial joint and detail of basale; C, D— 2 nd and 3 rd endopodial joints; E—tip of 7 th limb; F—detail of caudal furca; G—lateral eye.

FIGURE 10. Scleroconcha tuberculata sp. nov. (Immature male: A, D, I – L—MIMB 18273; B—MIMB 18274; C, E—ZMH- K- 42259; F—ZMH-K- 42260. Immature female: G, H—ZMH-K- 42261). A – C—left valves of carapace in lateral view; D – Gright valves in lateral view (for panel D ribs not shown); H—carapace in ventral view; I—upper lip, anterior process, medial eye and Bellonci organ; J, K—endopodite of 2 nd antenna; L—tip of 7 th limb.

FIGURE 11. Scleroconcha tuberculata sp. nov. (Immature female: A, B—ZMH-K- 42262; immature male: C – J—ZMH-K- 42259). A—left valve of carapace in lateral view; B—carapace in ventral view; C—infold of rostrum and detail of anterior margin; D, E—infold of caudal process of right valve; F— 1 st and 2 nd joints of 1 st antenna, medial eye and Bellonci organ; Gendopodite and details of protopodite and exopodite of 2 nd antenna; I, H—tip of 3 rd endopodial joint of 2 nd antenna; J—ventroproximal detail of mandible basale.

FIGURE 12. Scleroconcha gallardoi (Female: A, E—MIMB 18281; B, D, F, G— 18277; C—MIMB 18277; H – J—MIMB 18280; K—MIMB 18276). Carapace: A, D—right valve in lateral and inside view; B, C—left valve in lateral view; E, Gcarapace in ventral view; F—carapace in dorsal view; H—infold of rostrum; I—infold of anterior part; J—ornamentation and setae of middle valve in lateral view; K—upper lip and anterior process.

FIGURE 13. Scleroconcha gallardoi (Female: A, F—MIMB 18276; B, D, G, H—MIMB 18277; C, E—MIMB 18280). A— 1 st, 2 nd and 3 rd joint of 1 st antenna, medial eye and Bellonci organ; B—upper lip, anterior process, medial eye and Bellonci organ; C – F—endopodite of 2 nd antenna; G, H—basale, exopodite and 1 st endopodial joint of mandible.

FIGURE 14. Scleroconcha gallardoi (Immature female: A, C—MIMB 18282; immature male: B, D—MIMB 18283; female: E – G—MIMB 18279). A, B—right valve of carapace in lateral view; C, D—left valve in lateral view; E, F— 6 th limb (not all setae shown; abnormal end joint on panel F); G—abnormal joint of 6 th limb.

FIGURE 15. Scleroconcha gallardoi (Immature male: A – F, H, I—MIMB 18283; female: G—MIMB 18279), S. species (Juvenile: J—MIMB 18285). A—upper lip, anterior process, medial eye and Bellonci organ; B—distal part of Bellonci organ; C— 1 st and 2 nd joint of 1 st antenna (setae not shown) and lateral eye. 2 nd antenna: D—endopodite; E— 1 st and 2 nd endopodial joints; F— 2 nd and 3 rd joint. G – I—tip of 7 th limb. J—left valve of carapace.

FIGURE 16. Distribution map of Philomedes assimilis.

FIGURE 31. Distribution map of Philomedes orbicularis, P. rotunda and P. tetrathrix

FIGURE 32. Philomedes orbicularis (Female: A, C – E, G, I, K—MIMB 18308; B, F, H, J—ZMH-K- 42268). A, B—right valve of carapace in lateral and inside views; C, D—infold of caudal process of right and left valves; E—surface and setae in central area of right valve in lateral view; F, G—upper lip, anterior process, medial and lateral eyes (without eyes on Fig. G), Bellonci organ, 1 st and 2 nd joints of 1 st antenna; H— 2 nd joint of 1 st antenna; I – K—endopodite of 2 nd antenna.

FIGURE 33. Philomedes orbicularis (Female: A, C – G—MIMB 18308; B, H, I—ZMH-K- 42268. Immature female: J— MIMB 18309. Immature male: K, M—MIMB 18310; L—MIMB 18311). A— 1 st and 2 nd joints of 1 st antenna; B – D—exopodite, 1 st endopodial joint (ventral setae not shown) and its dorsal part (panels C and D) and dorsal surface of basale of mandible; Etip of mandibular exopodite; F – H—tip of 7 th limb; I—left lamella caudal furca; J – L—left valve; M—endopodite of 2 nd antenna.