Macropyxis undetermined

Brandão, Simone N., 2010, Macrocyprididae (Ostracoda) from the Southern Ocean: taxonomic revision, macroecological patterns, and biogeographical implications, Zoological Journal of the Linnean Society 159 (3), pp. 567-672 : 600-604

MACROPYXIS CRONINI SP. NOV. ( FIGS 14 , 18 , 19 )

Etymology: In honour of Dr Thomas M. Cronin ( U. S. Geological Survey, USA).

Material: 5 live specimens.

Holotype: 1 A M ( SNB 0234 ) (soft parts in glass slide, valves in micropalaeontological slide), ANDEEP I, # 42-2-S, ZMH K-41373 .

Paratypes: 2 A F ( SNB 0233 , SNB 0236 ), 1 (A-1) ( SNB 0151 ), 1 (A-?2) ( SNB 0152 ), ANDEEP I, # 42-2- E+S, ZMH K-41374 .

Distribution ( Fig. 14 ): Recent. Western Scotia Basin, 3681–3690 m.

Valve measurements: Holotype, A M RV L 1.72 mm, H 0.66 mm, LV L 1.70 mm, H 0.59 mm. Paratypes, A F RV L 1.80–1.90 mm, H 0.75–0.77 mm.

Diagnosis: Carapace fairly small (for the genus). In lateral view, RV suboval (females) to elongate (males); with smoothly rounded dorsal margin, and fairly straight ventral margins; posterior margin relatively obtuse (for the genus), pointed at approximately 90°. Podomere IV of antenna II of (A-1) with two modified (= proximally bulbous) setae. Podomere IV of female appendage V with one medium-sized, ventral seta; podomere V with two medium-sized, subequal setae and one long, ventral seta. Right and left male appendage V fairly symmetrical; podomere II of male appendage V with two short, modified setae (= pegs) and one reduced seta; podomere III with one ventral, reduced seta and one distal, modified seta (= peg). Furca reduced, rods short and flexible, terminal setae longer than rod itself. Hemipenis subcircular, copulatory process short, thick, and curved at approximately 90°. Zenker’s organ with short central tube and large terminal bulb; vas deferens tightly coiled.

Description: Carapace fairly small (for the genus). In lateral view, RV suboval (females) to elongate (males); with smoothly rounded dorsal margin; fairly straight ventral margin; posterior margin relatively obtuse (for the genus), pointed at approximately 90°. LV elongate in lateral view; dorsal margin trisegmented, anterior segment concave in females, fairly straight in males; ventral margin sinuous; posterior margin pointed at 70–80°. Anterior zone of concrescence medium-sized, with ramified radial pore canals; posterior zone of concrescence thin, with straight radial pore canals. RV always larger than LV.

Antennae I and II robust, with relatively thick and short podomeres, setae, and claws. Podomere IV of antenna II slightly longer than wide. Mandible with one conical tooth and four tricuspidate teeth on the masticatory process; exopodite with one reduced seta and seven medium-sized setae. Vibratory plate of maxilla I with two strahlen and more than 20 feathered setae; ventral endite with two basal setae; other two endites without basal seta. Female appendage V relatively short and thick; podomere IV with one medium-sized, ventral seta; podomere V with two medium-sized, subequal setae and one long, ventral seta. Right and left male appendage V fairly symmetrical; podomere II of male appendage V with two short, modified setae (= pegs) and one reduced seta; podomere III curved at approximately 90°, with one ventral, reduced seta and one distal, modified seta. Podomere VI of appendage VI with two long, thin claws (ventral one slightly longer) and one short, ventral seta on distal margin. Appendage VII with thin and slender podomeres; podomere II with two long and one medium-sized setae. Furca reduced, rods short and flexible, with two to three proximal, reduced setae; distal setae thin and slender, longer than rod itself. Hemipenis subcircular, copulatory process short, thick and curved at approximately 90°. Zenker’s organ with short central tube and large terminal bulb; vas deferens tightly coiled.

Adult chaetotaxy: Antenna I 1, 2(0/.2), 3(.1/.1.), 4(.1/.1.), 5(.1/.1), 6(.1-2/.3), 7(0/0:3-4). Antenna II 1(0/0:1), 2(0/0:1), Exopodite (0/0:2,1r), 3(0/.6.1c,4), 4[female (.2./.2.1c,2)] [male (.2./.2.1c,2mod,1)], 5(0/.1c,1:4c,1), 6(0/0:2c,3s). Mandible 1(0/ 5t,+5.1.), 2(0/.0-2:1), Exopodite (0/0:1r,6-7), 3(0/2-3:2-3), 4(4-7/0:4), 5(.2c./ 0:1c,3-4). Maxilla I vibratory plate (2re,~20), palp 1(.1/0)+2(4/0), 3(0/0:6). Appendage V 1(0/0:1-3), Exopodite (0/0:7), [female 2, 3, 4(0/.1) 5(.1./0:2)]; [male 2(0/2mod,1), 3(0/.1r:1mod)]. Appendage VI 1(0/0:1-2), 2(.1.1.1/1), 3(.1/0), 4(.1/0), 5(1,1r/0) 6(0/0:1,2c). Appendage VII 1(.1/0), 2(.1.2./.1.) 3(.1/0), 4(.1/0), 5(.2/ 0), 6(0/0:2,1re). Furca 1(0/0:3r.1-2).

Remarks: Macropyxis cronini sp. nov. differs from other described Macropyxis species in: (1) Mx. cronini has less protruded posterior angle, and/or is more globulose, higher in relation to length than Mx. adunca , Mx. adrecta , Mx. amanda , Mx. antonbruunae , Mx. arta , Mx. audens , Mx. bathyalensis , Mx. improcera , Mx. kornickeri , Mx. longana , Mx. rhodana , Mx. similis , Mx. simulans , Mx. tenuicauda ; (2) Mx. adriatica presents a more rectilinear outline; (3) Mx. alanlordi sp. nov., Mx. kaesleri , Mx. kalbi , Mx. steinecki show conspicuously more sinuous outline, with more acute posterior angle; (4) Mx. thiedei is more subtriangular than Mx. cronini sp. nov.

The female and male valve outlines of Mx. cronini sp. nov. are very similar to Mx. amoena , Mx. eltaninae , Mx. andreseni , Mx. labutisi , Mx. sapeloensis , and Mx. sonneae . The outlines of the hemipenis of these last six species are conspicuously different (rectilinear or with a beak-like process, instead of subhemispherical) than that of Mx. cronini . Additionally, the terminal bulbs of the Zenker’s organ diverge between Mx. cronini (large), and the last four species (mediumsized). No illustration of the Zenker’s organ of Mx. amoena and Mx. eltaninae has been published.

Antenna I, maxilla I, appendage VI, and appendage VII of Macropyxis cronini sp. nov. are very similar to those of Mx. alanlordi sp. nov. Antenna II of Macropyxis cronini sp. nov. is very similar to those of Mx. sp. nov. 1, and the mandible of the former species is very similar to that of Macropyxis jeans sp. nov. Therefore, these appendages are only drawn for Mx. alanlordi , Mx. jeans , and Mx. sp. nov. 1.

MACROPYXIS GHARTMANNI SP. NOV. ( FIGS 14 , 20 , 27A–D, 27M )

Etymology: In honour of Prof. Dr Gerd Hartmann for his valuable contributions to the morphology, systematics, and zoogeography of Ostracoda.

Material: 2 live specimens.

Holotype: 1 A F ( SNB 0145 ) (soft parts in glass slide, valves in micropalaeontological slide), ANDEEP II, 133-3-E, ZMH K-41360 .

Paratype: 1 (A-1) ( SNB 0146 ) (valves in micropalaeontological slide, soft parts in glass slide), ANDEEP II , 133-3-E, ZMH K-41321 .

Distribution ( Fig. 14 ): Recent. North-western Weddell Sea, 1123 m.

Valve measurements: Holotype, A F RV L 2.10 mm, H 0.86 mm, LV L 2.08 mm, H 0.78 mm. Paratype (A-1) RV L 1.82 mm, H 0.72 mm.

Diagnosis: Carapace medium-sized (for the genus). In lateral view, valves elongate, subtriangular; RV with highly arched dorsal margin; posterior margin rounded at approximately 60–70°. Podomere IV of female appendage V with one long, ventral seta; podomere V with two long, subequal setae and one medium-sized, dorsal seta. Furca reduced, rods short and flexible, terminal setae longer than rod itself.

Description: Carapace medium-sized (for the genus). In lateral view, valves elongate, subtriangular; RV with highly arched dorsal margin; posterior margin rounded at approximately 60–70°; anterior margin narrowly rounded; ventral margin rounded anteriorly, and upswung, straight posteriorly; maximum height at mid-length. LV with trisegmented dorsal margin, but with inconspicuous angles between segments, anterior segment slightly concave; anterior margin narrowly rounded; posterior margin pointed rounded at approximately 45°; maximum height anterior to mid-length. Vestibules wide; anterior zone of concrescence fairly wide, with ramified radial pore canals; posterior zone of concrescence medium-sized, with mostly straight but also few ramified pore canals. RV always larger than LV.

Antenna I quite robust, with relatively thick and short podomeres and setae. Antenna II robust, with short and thick podomeres. Mandible with one conical tooth and four tricuspidate teeth on the masticatory process; exopodite with one reduced and six mediumsized setae. Vibratory plate of maxilla I with three strahlen and more than 19 feathered setae; ventral endite with two basal setae; other two endites without basal seta. Podomere II of female appendage V long; podomeres III to V short; podomere IV with one long, ventral seta; podomere V with two long, subequal setae and one medium-sized, dorsal seta. Podomere VI of appendage VI with two long, thin claws (ventral one longest) and one short, ventral seta on distal margin. Appendage VII with thin and slender podomeres; podomere II with three long setae. Furca reduced, rods short and flexible, with four proximal, reduced setae; distal setae thin and slender, longer than rod itself.

Adult chaetotaxy: Antenna I 1, 2(0/.2), 3(.1/.1.), 4(.1/.1.), 5(.1/.1), 6(.2/.3), 7(0/0:4). Antenna II 1(0/0:1), 2(0/0:1), Exopodite (0/0:2,1r), 3(0/5-6.1c,5), 4[female (.2./.2.1c,2)] 5(0/.1c,1:4c,1), 6(0/0:2c,3). Mandible 1(0/ 4t,+5:1), 2(0/.2:1), Exopodite (0/0:1r,5-6), 3(1/3-4:2), 4(7/0:4), 5(.2c./0:1c,4). Maxilla I vibratory plate (3re,~19), palp 1(.1-2/0)+2(4/0), 3(0/0:6). Appendage V 1(0/0:1-3), Exopodite (0/0:6), [female 2, 3, 4(0/.1) 5(.1./ 0:2)]. Appendage VI 1(0/0:2), 2(.1.1.1/1), 3(.1/0), 4(.1/ 0), 5(1,1r/0) 6(0/0:1,2c). Appendage VII 1(.1/0), 2(.1.2./.1.) 3(.1/0), 4(.1/0), 5(.2/0), 6(0/0:2,1re). Furca 1(0/ 0:4r.1).

Remarks: Macropyxis ghartmanni sp. nov. presents a set of characters that are diagnostic of different genera of Macrocyprididae (sensu Maddocks, 1990) : (1) subtriangular shape, with rounded (not acutely pointed) posterior margin (typical of Macroscapha and Macrocyprina ); (2) maxilla I with podomeres II and III fused (= palp podomeres I and II) (typical of Macrocypris, Macrocyprissa , Macromckenziea , Macropyxis ); (3) fairly reduced furca (typical of Macrocypris and Macropyxis ); and (4) (not stated by Maddocks, 1990, but observed in her drawings figs 29–31) podomeres IV and V of female appendage V (= podomeres III and IV of palp) with long setae (typical of Macropyxis ) instead of short claws (as in Macroscapha and Macrocyprina ). Herein Mx. ghartmanni was assigned to the genus Macropyxis because of its maxilla I, appendage V, and furca. Another species that present mixed characters – ‘ Mx. ’ thiedei from the Campbell Plateau (off New Zealand), tentatively assigned to the genus Macropyxis ( Jellinek & Swanson, 2003) – is very similar to Mx. ghartmanni , but the latter species presents (1) valves less high in relation to length (2) and slender furcae with longer and thinner rods and terminal setae.

As a result of its untypical subtriangular valve lateral outline, Mx. ghartmanni sp. nov. differ from almost all other described Macropyxis species (i.e. Mx. adrecta , Mx. adriatica , Mx. adunca , Mx. alanlordi sp. nov., Mx. amanda , Mx. amoena , Mx. andreseni , Mx. antonbruunae , Mx. arta , Mx. audens , Mx. bathyalensis , Mx. cronini sp. nov., Mx. eltaninae , Mx. improcera , Mx. kaesleri , Mx. kalbi , Mx. kornickeri , Mx. labutisi , Mx. longana , Mx. rhodana , Mx. sapeloensis , Mx. similis , Mx. simulans , Mx. sonneae , Mx. steinecki , Mx. tenuicauda ). All other Macropyxis species present more subparallel dorsal and ventral margins, and acutely pointed posterior margins.

The mandible of Macropyxis ghartmanni sp. nov. is very similar to that of Macropyxis jeans sp. nov.; therefore, this appendage is only drawn for the latter species.

Figures

Figure 14. Geographical distribution of Macropyxis and Macrosarisa species studied herein.

Figure 18. Valves and soft parts of Macropyxis cronini sp. nov. A, B, I–M, holotype adult male (SNB 0234, ZMH K-41373); C, D, N, paratype adult female (SNB 0236); E, F, paratype adult female (SNB 0233); G, H, paratype (A-1) (SNB 0151) (ZMH K-41374). A, C, E, G, right valve external view; B, D, F, H, left valve external view; I, J, hemipenis; K, Zenker’s organ; L, M, male appendage V; N, female appendage V. Scale bars: A–H = 500 Mm; I–N = 100 Mm.

Figure 19. Valves and soft parts of Macropyxis cronini sp. nov. A, B, E–G, paratype (A-1) (SNB 0151); C, D, paratype (A-?2) (SNB 0152) (ZMH K-41374). A, C, right valve external view; B, D, left valve external view; E, distal podomeres of antenna II; F, (A-1) appendage V; G, furca. Scale bars: A–D = 500 Mm; E, F = 100 Mm; G = 10 Mm.

Figure 20. Valves and soft parts of Macropyxis ghartmanni sp. nov. A–I, paratype (A-1) (SNB 0146, ZMH K-41321). A, right valve external view; B, left valve external view; C, antenna I; D, antenna II; E, distal, bulbous setae of podomere IV of antenna II; F, palp of maxilla I; G, appendage VI; H, appendage VII; I, furca. Scale bars: A, B = 500 Mm; C, D, G–I = 100 Mm; E, F = 50 Mm.

Figure 27. Valves and appendage VI of Macropyxis ghartmanni sp. nov., Macropyxis jeans sp. nov., Macropyxis parajeans sp. nov., and Macropyxis sp. nov. 1. Macropyxis ghartmanni sp. nov.: A, B, M, holotype adult female (SNB 0145, ZMH K-41360). C, D, paratype (A-1) (SNB 0146, ZMH K-41321). Macropyxis jeans sp. nov.: E, F, paratype (A-1) (SNB 0248, ZMH K-41378). Macropyxis parajeans sp. nov.: G, H, paratype (A-1) male (SNB 0232-DNA 40), I, J, paratype (A-2) (SNB 0247-DNA 116), (ZMH K-41381). Macropyxis sp. nov. 1: K, L, adult female (SNB 0208, ZMH K-41474). A, C, E, G, I, K, right valve external view; B, D, F, H, J, L, LV external view; M, podomere VI appendage VI. Scale bars: A–L = 500 Mm; M = 100 Mm.