Bythocypris praerenis Brandão, 2008, sp. nov.

Bythocypris praerenis sp. nov.

(Figs. 22–26)

Etymology. For its resemblance to B. reniformis Brady, 1880.

Material: 6 live specimens, 318 V. Holotype: 1 A F (SNB 0388), ANDEEP III # 133–2–E, ZMH K­ 41356. Paratypes: 1 A F (SNB 0387), 1 (A­1) (SNB 0209), 5 RV, 7 LV, 1 RLV, ANDEEP III # 133–2–E, ZMH K­ 41328; 23 RV, 26 LV, 20 RLV, 157 V, ANDEEP II, # 132–2–S, ZMH K­ 41329; 3 (A­1) (SNB 0275­ 7), 51 V, 2 RLV, ANDEEP II, # 133–3–E, ZMH K­ 41330; 2 RLV, 1 LV, ANDEEP II, # 133–3–S, ZMH K­ 41357.

Distribution. NW Weddell Sea, Southern Ocean (Atlantic Sector), 1123 to 2084 m.

FIGURE 22. Occurrence of Bythocypris reniformis informal group (published information) and Bythocypris praerenis sp. nov. Legend: — type locality of B. reniformis, from Brady (1880) and Puri and Hulings (1976); —other localities from Brady (1880); ♢— Briggs (1978); — Chapman (1941); — Dingle (2003); — Maddocks (1969); — Bythocypris praerenis sp. nov., ANDEEP II # 133; — Bythocypris praerenis sp. nov., ANDEEP II # 132.

Measurements (Fig. 23). Holotype, LV, L 1.60mm, H 0.77mm; RV, L 1.60mm, H 0.72mm. Paratypes, LV, A L 1.60–1.81mm, H 0.77–0.90mm; (A­1) L 1.32–1.44mm, H 0.64–0.71mm; (A­2) L 1.00– 1.14mm, H 0.53– 0.58mm; (A­3) L 0.84mm, H 0.44mm.

Diagnosis. Carapace very large, sub­reniform; maximum height anterior to mid­length; with numerous, straight, short marginal pore canals. Podomere VI of AII with 1 anterodorsal, tiny seta, 1 long claw, 1 medium­sized, posterodorsal, fused claw, and 2 medium­sized, posterodistal setae. Podomere IV of Md palp with 4 medium­sized setae and 3 medium­sized claws. Vibratory plate of Mx I with 7 strahlen and 25 feathered setae. Fu with 3 to 6 tiny, proximal setae and 3 medium­sized, finely feathered, distal setae. Genital lobe ovate­subtriangular, with a scoop­shaped internal process attached to short tube.

Description. Carapace very large, sub­reniform, maximum height anterior to mid­length, posterior angle obtuse. Lateral surface smooth. RV with anterodorsal margin straight, ventral margin concave. LV outline less sinuous, more evenly rounded, with arched dorsal margin. Calcified inner lamella wide; zone of concrescence fairly narrow, with numerous straight, short radial pore canals. Radial pore canals simple, with or without rim. Three anterior plus one posterior adductor muscle scars. In dorsal view, carapace elongate, maximum width at mid­length.

AI robust, with short and thick podomeres, with not very long setae; suture between podomeres II and II incomplete; chaetotaxy 1(0/0), 2(0/.1); 3(0/.1­2); 4(.1/0); 5(.2/.2); 6(.2/.2­3), 7(0/0:4­5). AII robust, with short and thick podomeres; exopodite with 1 short and 2 long setae; podomere VI with 1 anterodorsal, very short seta, 1 long claw, 1 medium­sized posterodorsal fused claw, and 2 medium­sized posterodistal setae; chaetotaxy 1(0/0: 2i), 2(1/0), Exopodite(0/0:3), 3(0/.3.2), 4(.2r,2./0), 5(.1.1c./.1r.1c,1), 6(1r,1c,2,1fc). Base of Md with 1 anterodorsal seta, masticatory process with 1 dorsal, bifurcate tooth, 4 trifurcate teeth, plus several short setae; exopodite with 1 very long and 2 long feathered setae; podomere IV of palp with 4 medium­sized setae and 3 medium­sized claws; chaetotaxy of palp 1(0/.1.: 1i), 2(.1.2./1: 1i), 3(.5./.1: 2i), 4(.2./0:3c,2). Vibratory plate of Mx I with 7 strahlen and around 25 setae; palp with 3 long, dorsal, setae 2 long, ventral setae and 1 distal, medium­sized, finely feathered claw. ApV robust, with short and thick podomeres; vibratory plate with 4 strahlen and 9 or 10 feathered setae; chaetotaxy 1(.1.2.2­3/0: 1i), 2(.2/0), 3(.1/0), 4(.1/0), 5(0/0:1r,1c,1r). Chaetotaxy of ApVI and VII 1 (.1.1.2/0), 2(.2/0), 3(.1/0), 4(.1/0), 5(0/0:1r,1c,1r). Fu with 3 to 6 tiny proximal setae, and 3 medium­sized feathered distal seta. One short seta between Fu rods. Genital lobe ovate­subtriangular, with scoop­shaped process attached to coiled tube.

Remarks. Bythocypris praerenis sp. nov. is similar to B. reniformis sensu Puri and Hulings, 1976, but the former species presents: (1) larger height to length ratio; (2) larger size (1.60 to 1.76mm instead of 1.09mm); (3) more concave ventral margin; (4) and wider calcified inner lamella, with straight, short marginal pore canals (instead of ramified).

The only three species of Bythocypris recorded from the high Antarctic region of the Southern Ocean (B. eltanina Maddocks, 1969, B. spiriscutica Maddocks, 1969 and B. promoza Maddocks, 1973) plus B. elongata Brady, 1880, B. mozambiquensis Maddocks, 1969, B. prolata Maddocks, 1969 are more subtriangular than B. praerenis. Bythocypris affins affins Brady, 1886 (sensu Brady & Norman 1889: 242, Fig.) is smaller and has a more rounded, less sinuous RV in lateral view, and is also wider, more ovate in dorsal view. Bythocypris affins madagascarensis Maddocks, 1969 is higher in relation to length with the maximum height of LV at midlength instead of conspicuously anterior to it.