Philomedes orbicularis Brady 1907

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.