Philomedes heptathrix Kornicker, 1975

Chavtur, Vladimir G. & Keyser, Dietmar, 2016, Benthic myodocopid Ostracoda (Philomedidae) from the Southern Ocean, Zootaxa 4141 (1), pp. 1-70: 37-45

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http://doi.org/10.11646/zootaxa.4141.1.1

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scientific name

Philomedes heptathrix Kornicker, 1975
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Philomedes heptathrix Kornicker, 1975 

( Figs. 24–27View FIGURE 24View FIGURE 25View FIGURE 26View FIGURE 27, 28View FIGURE 28: A –G, Plate 2View PLATE 2 E, F)

1975 Philomedes heptathrix Kornicker  : 248–255, Figs. 131, 135 (map), 147–150. 1971 Philomedes  species A—Kornicker,: 192, Fig. 17View FIGURE 17 (?).

Non 1990 Philomedes heptathrix Kornicker, 1975  —Hartmann: 199, Abb. 1.

Studied material (coordinates, depth and sediment see Appendix). 13 th Soviet (=Russian) Antarctic Expedition , Polar station “ Molodezhnaya ” cutting 1, station 3, sample 10: MIMB 18301View Materials —immature male (1.67mm). 

RV “Polarstern”, ANT XV/3, station 171: ZMH-K-42266 and 42267—2 adult females (1.95 and 1.77 mm).

52th Russian Antarctic Expedition, station 10, sample 54: MIMB 18297 and 18298—2 adult females (2.0– 1.90 mm).

Station 10, sample 56: MIMB 18 302—adult female (1.85 mm) and MIMB 18296—adult male (2.17 mm).

Station 12, sample 65: MIMB 18 300—adult female (1.87 mm).

Additional material. See Appendix.

Diagnosis of female ( Kornicker 1975, with additional remarks). Carapace: posterior rounded with narrow caudal process, length 1.60–2.02 mm.

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

Second antenna: 1st joint of endopodite with 7–9 setae, 5–6 proximal and 2–3 distal; 2nd joint with 1 long and 3 or 4 (very rarely) short ventral setae and 1 long recurved terminal seta.

Mandible: dorsal margin of basale with 6–7 setae, 4–5 near middle and 2 subterminal.

Sixth limb: epipodite with 3 setae.

Seventh limb: each limb with 9–13 setae, 4–5 distal and 5–8 proximal; 2–3 pegs present on opposite terminal comb.

Caudal furca: each lamella with 10 (or rarely 11) claws.

Bellonci organ: 1- or 2-jointed, with rounded tip.

Lateral eye: small with 2–3 divided ommatidia.

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

Diagnosis of male. Carapace: length 1.75–2.17 mm.

First antenna: 2nd joint with 2–3 setae, 1 ventral, 0–1 lateral and 1 dorsal.

Second antenna: 1st joint of endopodite with 5 setae, 4 proximal and 1 distal; proximal seta of 3rd joint about half of its length.

Mandible: dorsal margin of basale with 5–6 setae, 3–4 near middle and 2 subterminal; coxale endite present.

Sixth limb: epipodite with 3 setae.

Seventh limb: each limb with 10–12 setae, 5 distal and 5–7 proximal; 2 pegs present on opposite terminal comb.

Caudal furca: each lamella with 9–10 claws.

Bellonci organ: 2-jointed, with rounded tip.

Anterior process (above upper lip): small, with rounded tip.

Supplementary description of adult female. Carapace ( Figs. 24View FIGURE 24 A –G, I –M; 25 A, Plate 2View PLATE 2 E, F). Length 1.75– 2.02 mm ( Kornicker 1975: 1.60–1.85 mm). Infold on rostrum with 19–24 setae forming L-shaped row. Anteroventral inside with 20–28 short setae and 10–11 striations ( Kornicker 1975: 17 setae and 9–10 striations). Posterior infold with middle row of 5–11 short setae ( Kornicker 1975: 6 setae). Carapace smooth but with faint reticulations; sparse setae present on lateral surface ( Fig. 25View FIGURE 25 A).

First antenna ( Fig. 25View FIGURE 25 B, F). Second joint with 3 setae, 1 dorsal, 1 lateral and 1 ventral. Dorsal and ventral margins of first and second joints with long spines.

Second antenna ( Fig. 25View FIGURE 25 I –N). Endopodite: first joint with 7–9 setae, 5 (normal) or 6 (exception) proximal and 2 or 3 distal ( Kornicker 1975: only 2) setae. Ventral margin of second joint with 1 long and 3 (as exception 4) short setae.

Mandible ( Fig. 27View FIGURE 27 H, J). Basale: dorsal margin with 6–7 setae, 4–5 near middle and 2 subterminal setae; medial side with 6 setae, 3 pectinate and 3 normal type; lateral surface with 4–6 setae forming a row parallel to ventral margin; ventral margin with 3–4 distal setae. Endopodite: dorsal margin of second joint with 2 (as exception 1) setae in proximal group, 6 (as exception 4) setae in distal group and 1 seta between these groups, and ventral margin with 3 setae in subterminal and 3 in terminal groups.

Sixth limb ( Fig. 26View FIGURE 26 C –F). Endite I with 2 terminal and 1 medial setae; endite II with 3 terminal and 1 medial setae; endite III with 7–8 terminal and 1 medial setae; endite IV with 7–9 terminal and 1 medial setae; end joint with 21–28 setae; 3 setae present in place on epipodial appendage.

Seventh limb. Each limb with 10–13 setae ( Kornicker 1975: 9–12 setae), 4–5 distal (2+3 or 2+2) and 6–8 proximal (3+3, 3+4 or 4+4) setae; each seta with 3–5 bells. Terminal comb with 12–14 teeth ( Kornicker 1975: 13– 15 teeth); 2–3 pegs present on opposite comb.

Caudal furca. Limb with 10+10 or 10+11 claws.

Bellonci organ ( Fig. 25View FIGURE 25 B –D). Organ elongate, 1-jointed ( Kornicker, 1975: 2-jointed) and with rounded tip.

Upper lip ( Fig. 25View FIGURE 25 B, C, E). Lip with several glandular processes at tip.

Anterior process on body ( Fig. 25View FIGURE 25 B, C). Somewhat elongated, with rounded tip.

Supplementary description of adult male. Carapace ( Fig. 26View FIGURE 26 G –J). Length 2.17 mm ( Kornicker 1975: 1.75– 2.07 mm). Greatest height at posterior half. Rostrum broad. Infold on rostrum with 3–4 setae along vertical margin, and 12–16 setae paralleling anterior margin; 1 minute seta present on infold below rostrum; about 15–16 short setae ( Kornicker 1975: 12 setae) present in a row on antero-ventral infold; about 6 spine-like short setae present along posterior margin of infold of caudal process. Lateral surface of carapace with scattered short setae (with thick base).

First antenna ( Fig. 27View FIGURE 27 B, C). Second joint with 3 setae, 1 long spinous ventral, 1 lateral and 1 dorsal short bare setae. Sensory seta of fifth joint with slightly visible knee in middle ( Fig. 27View FIGURE 27 C) and 4 terminal filaments.

Second antenna ( Fig. 27View FIGURE 27 E, F). Endopodite: first joint with 5–6 setae, 4–5 proximal and 1 distal; second joint with 1 muscle band extending from dorso-median of its margin to the proximal margin of third joint ( Fig. 27View FIGURE 27 E). Proximal seta of third joint about half of its length.

Mandible ( Fig. 27View FIGURE 27 G, I, K). Coxale endite bifurcate with very short base. Basale: dorsal margin with 5–6 setae, 3–4 near middle and 2 subterminal (1 long and 1 short about half the length of dorsal margin of first endopodial joint); medial side with 6 setae, lateral surface with 4 setae forming a row parallel to ventral margin; ventral margin with 3 distal setae. Endopodite: first joint with 4–5 ventral setae ( Kornicker 1975: 3–4 setae); second joint similar to that of adult female.

Sixth limb. Endite I with 2 terminal and 1 medial setae, endite II with 4 terminal and 1 medial setae, endite III with 7 terminal and 1 medial setae, endite IV with 7 terminal and 1 medial setae, end joint with 18 setae; 3 setae present in place of epipodial appendage.

Seventh limb ( Fig. 28View FIGURE 28 G). Each limb with 11–12 setae, 5 (3+2) in distal group and 6–7 (3+3 or 3+4) in proximal group. Terminal comb with 10 teeth; 2 pegs present on opposite comb.

Caudal furca ( Fig. 28View FIGURE 28 C). Limb with 9+9 claws.

Copulatory appendage ( Fig. 28View FIGURE 28 B). Limb very short about 1/3 of length of lamella of furca or 1/2 length of its 1st claw.

Medial eye ( Fig. 27View FIGURE 27 A, B). Large and smooth.

Bellonci organ ( Fig. 27View FIGURE 27 A, B). Elongate, 2-jointed, with rounded tip and subequal in length or barely longer than first joint of first antenna.

Upper lip ( Fig. 27View FIGURE 27 B, D). Ventrally slightly hirsute. Tip with several glandular processes.

Anterior process on body ( Fig. 27View FIGURE 27 B). Reduced.

Description of A- 1 male. Carapace. Length 1.67 mm.

First antenna. Second joint with 4 spinous setae, 1 dorsal, 1 lateral and 2 ventral. Dorsal and ventral margins of first and second joints with long spines.

Second antenna ( Fig. 28View FIGURE 28 E, F). Endopodite: first joint with 3–4 proximal and 1 distal setae; second joint with 1 long and 3 short ventral setae; third joint with 1 medium-long dorsal and 2 short terminal setae.

Mandible. Basale: dorsal margin with 6 setae, 4 near middle and 2 subterminal; medial side with 6 setae; lateral surface with 4 setae forming a row parallel to ventral margin; ventral margin with 3 distal setae. Endopodite: first joint with 4 ventral setae; dorsal margin of second joint with 2 setae in proximal group, 6 setae in distal group and 1 seta between these groups, and ventral margin with 3 setae in subterminal and 3 in terminal groups.

Seventh limb. Each limb with 11–12 setae, 4–5 distal (2+2 or 2+3) and 7 proximal (3+4) setae; each seta with 3–4 bells. Terminal comb with 10 alate teeth; 2 pegs present on opposite comb.

Caudal furca. Limb with 9+9 claws.

Bellonci organ. Elongate, about as long as first joint of first antenna, without suture and with rounded tip.

Medial eye. Bare.

Remarks. Our specimen of male differs from Kornicker’s description (1975) by a different shape of carapace and smaller size of copulatory organ. Beside that, our A-1 male differs in having 2 ventral setae on the second joint of the first antenna.

Distribution and ecology. Circumantarctic sublitoral-upper bathyal species. It has been collected in the Weddell Sea ( Kornicker 1975; present study), in the vicinity of the Ross Sea ( Kornicker 1975), Prydz Bay and near the Russian Polar station “Molodezhnaya” (present study) and in the area 66°S and 69°W ( Hartmann 1990) between 66° and 77°S ( Fig. 23View FIGURE 23) at the depths of 15 to 570 m, on hard and soft substrates: rock, stone, gravel, sand, muddy sand.

MIMB

Museum of the Institute of Marine Biology